ALBERT

Description: 〈jats:title〉Abstract〈/jats:title〉〈jats:p〉Erosion of permafrost coasts due to climate warming releases large quantities of organic carbon (OC) into the Arctic Ocean. While burial of permafrost OC in marine sediments potentially limits degradation, resuspension of sediments in the nearshore zone potentially enhances degradation and greenhouse gas production, adding to the “permafrost carbon feedback.” Recent studies, focusing on bulk sediments, suggest that permafrost OC derived from coastal erosion is predominantly deposited close to shore. However, bulk approaches disregard sorting processes in the coastal zone, which strongly influence the OC distribution and fate. We studied soils and sediments along a transect from the fast‐eroding shoreline of Herschel Island—〈jats:italic〉Qikiqtaruk〈/jats:italic〉 (Yukon, Canada) to a depositional basin offshore. Sample material was fractionated by density (1.8 g cm〈jats:sup〉−3〈/jats:sup〉) and size (63 μm), separating loose OC from mineral‐associated OC. Each fraction was analyzed for element content (TOC, TN), carbon isotopes (δ〈jats:sup〉13〈/jats:sup〉C, Δ〈jats:sup〉14〈/jats:sup〉C), molecular biomarkers (〈jats:italic〉n〈/jats:italic〉‐alkanes, 〈jats:italic〉n〈/jats:italic〉‐alkanoic acids, lignin phenols, cutin acids), and mineral surface area. The OC partitioning between fractions changes considerably along the transect, highlighting the importance of hydrodynamic sorting in the nearshore zone. Additionally, OC and biomarker loadings decrease along the land‐ocean transect, indicating significant loss of OC during transport. However, molecular proxies for degradation show contrasting trends, suggesting that OC losses are not always well reflected in its degradation state. This study, using fraction partitioning that crosses land‐ocean boundaries in a way not done before, aids to disentangle sorting processes from degradation patterns, and provides quantitative insight into losses of thawed and eroded permafrost OC.〈/jats:p〉

Description: Tropospheric reactive bromine (Bry) influences the oxidation capacity of the atmosphere by acting as a sink for ozone and nitrogen oxides. Aerosol acidity plays a crucial role in Bry abundances through acid-catalyzed debromination from sea-salt-aerosol, the largest global source. Bromine concentrations in a Russian Arctic ice-core, Akademii Nauk, show a 3.5-fold increase from pre-industrial (PI) to the 1970s (peak acidity, PA), and decreased by half to 1999 (present day, PD). Ice-core acidity mirrors this trend, showing robust correlation with bromine, especially after 1940 (r = 0.9). Model simulations considering anthropogenic emission changes alone show that atmospheric acidity is the main driver of Bry changes, consistent with the observed relationship between acidity and bromine. The influence of atmospheric acidity on Bry should be considered in interpretation of ice-core bromine trends.

Description: The eruption of the Hunga Tonga‐Hunga Ha'apai volcano on 15 January 2022 was one of the most explosive eruptions of the last decades. The amount of water vapor injected into the stratosphere was unprecedented in the observational record, increasing the stratospheric water vapor burden by about 10%. Using model runs from the ATLAS chemistry and transport model and Microwave Limb Sounder (MLS) satellite observations, we show that while 20%–40% more water vapor than usual was entrained into the Antarctic polar vortex in 2023 as it formed, the direct chemical effect of the increased water vapor on Antarctic ozone depletion in June through October was minor (less than 4 DU). This is because low temperatures in the vortex, as occur every year in the Antarctic, limit water vapor to the saturation pressure and thus reset any anomalies through the process of dehydration before they can affect ozone loss.

Description: The availability of silicon (Si) in the ocean plays an important role in regulating biogeochemical and ecological processes. The Si budget of the Arctic Ocean appears balanced, with inputs equivalent to outputs, though it is unclear how a changing climate might aggravate this balance. In this study, we focus on Si cycling in Arctic coastal areas and continental shelf sediments to better constrain the Arctic Ocean Si budget. We provide the first estimate of amorphous Si (ASi) loading from erosion of coastal Yedoma deposits (30–90 Gmol yr−1), demonstrating comparable rates to particulate Si loading from rivers (10–90 Gmol yr−1). We found a positive relationship between surface sediment ASi and organic matter content on continental shelves. Combining these values with published Arctic shelf sediment properties and burial rates we estimate 70 Gmol Si yr−1 is buried on Arctic continental shelves, equivalent to 4.5% of all Si inputs to the Arctic Ocean. Sediment dissolved Si fluxes increased with distance from river mouths along cruise transects of shelf regions influenced by major rivers in the Laptev and East Siberian seas. On an annual basis, we estimate that Arctic shelf sediments recycle approximately up to twice as much DSi (680 Gmol Si) as is loaded from rivers (340–500 Gmol Si).

Description: The coastal ocean contributes to regulating atmospheric greenhouse gas concentrations by taking up carbon dioxide (CO2) and releasing nitrous oxide (N2O) and methane (CH4). In this second phase of the Regional Carbon Cycle Assessment and Processes (RECCAP2), we quantify global coastal ocean fluxes of CO2, N2O and CH4 using an ensemble of global gap-filled observation-based products and ocean biogeochemical models. The global coastal ocean is a net sink of CO2 in both observational products and models, but the magnitude of the median net global coastal uptake is ∼60% larger in models (−0.72 vs. −0.44 PgC year−1, 1998–2018, coastal ocean extending to 300 km offshore or 1,000 m isobath with area of 77 million km2). We attribute most of this model-product difference to the seasonality in sea surface CO2 partial pressure at mid- and high-latitudes, where models simulate stronger winter CO2 uptake. The coastal ocean CO2 sink has increased in the past decades but the available time-resolving observation-based products and models show large discrepancies in the magnitude of this increase. The global coastal ocean is a major source of N2O (+0.70 PgCO2-e year−1 in observational product and +0.54 PgCO2-e year−1 in model median) and CH4 (+0.21 PgCO2-e year−1 in observational product), which offsets a substantial proportion of the coastal CO2 uptake in the net radiative balance (30%–60% in CO2-equivalents), highlighting the importance of considering the three greenhouse gases when examining the influence of the coastal ocean on climate.

Description: Significant progress in permafrost carbon science made over the past decades include the identification of vast permafrost carbon stocks, the development of new pan‐Arctic permafrost maps, an increase in terrestrial measurement sites for CO〈jats:sub〉2〈/jats:sub〉 and methane fluxes, and important factors affecting carbon cycling, including vegetation changes, periods of soil freezing and thawing, wildfire, and other disturbance events. Process‐based modeling studies now include key elements of permafrost carbon cycling and advances in statistical modeling and inverse modeling enhance understanding of permafrost region C budgets. By combining existing data syntheses and model outputs, the permafrost region is likely a wetland methane source and small terrestrial ecosystem CO〈jats:sub〉2〈/jats:sub〉 sink with lower net CO〈jats:sub〉2〈/jats:sub〉 uptake toward higher latitudes, excluding wildfire emissions. For 2002–2014, the strongest CO〈jats:sub〉2〈/jats:sub〉 sink was located in western Canada (median: −52 g C m〈jats:sup〉−2〈/jats:sup〉 y〈jats:sup〉−1〈/jats:sup〉) and smallest sinks in Alaska, Canadian tundra, and Siberian tundra (medians: −5 to −9 g C m〈jats:sup〉−2〈/jats:sup〉 y〈jats:sup〉−1〈/jats:sup〉). Eurasian regions had the largest median wetland methane fluxes (16–18 g CH〈jats:sub〉4〈/jats:sub〉 m〈jats:sup〉−2〈/jats:sup〉 y〈jats:sup〉−1〈/jats:sup〉). Quantifying the regional scale carbon balance remains challenging because of high spatial and temporal variability and relatively low density of observations. More accurate permafrost region carbon fluxes require: (a) the development of better maps characterizing wetlands and dynamics of vegetation and disturbances, including abrupt permafrost thaw; (b) the establishment of new year‐round CO〈jats:sub〉2〈/jats:sub〉 and methane flux sites in underrepresented areas; and (c) improved models that better represent important permafrost carbon cycle dynamics, including non‐growing season emissions and disturbance effects.〈/jats:p〉

Description: 〈jats:title〉Abstract〈/jats:title〉〈jats:p〉Extensive investigation of continental rift systems has been fundamental for advancing the understanding of extensional tectonics and modes of formation of new ocean basins. However, current rift classification schemes do not account for conjugate end members formed by Large Igneous Province crust, referring to thick mafic crust, sometimes including continental fragments. Here, we investigate the rifting of William's Ridge (Kerguelen Plateau) and Broken Ridge, components of the Kerguelen Large Igneous Province now situated in the Southeast Indian Ocean, and incorporate these end members into the deformation migration concept for rifted margins. We use multichannel seismic reflection profiles and data from scientific drill cores acquired on both conjugate margins to propose, for the first time, a combined tectono‐stratigraphic framework. We interpret seismic patterns, tectonic features, and magnetic anomaly picks to determine an across‐strike structural domain classification. This interpretation considers the rift system overall to be “magma‐poor” despite being located proximal to the Kerguelen plume but suggests that syn‐rift interaction between the Kerguelen mantle plume and the lithospheric structure of William's Ridge and Broken Ridge has controlled the along‐strike segmentation of both conjugates. We integrate seismic reflection and bathymetric data to test the hypothesis of predominantly transform motion, between the Australian and Antarctic plates, in Late Cretaceous and Paleogene time.〈/jats:p〉

Description: 〈jats:title〉Abstract〈/jats:title〉〈jats:p〉Extensive investigation of continental rift systems has been fundamental for advancing the understanding of extensional tectonics and modes of formation of new ocean basins. However, current rift classification schemes do not account for conjugate end members formed by Large Igneous Province crust, referring to thick mafic crust, sometimes including continental fragments. Here, we investigate the rifting of William's Ridge (Kerguelen Plateau) and Broken Ridge, components of the Kerguelen Large Igneous Province now situated in the Southeast Indian Ocean, and incorporate these end members into the deformation migration concept for rifted margins. We use multichannel seismic reflection profiles and data from scientific drill cores acquired on both conjugate margins to propose, for the first time, a combined tectono‐stratigraphic framework. We interpret seismic patterns, tectonic features, and magnetic anomaly picks to determine an across‐strike structural domain classification. This interpretation considers the rift system overall to be “magma‐poor” despite being located proximal to the Kerguelen plume but suggests that syn‐rift interaction between the Kerguelen mantle plume and the lithospheric structure of William's Ridge and Broken Ridge has controlled the along‐strike segmentation of both conjugates. We integrate seismic reflection and bathymetric data to test the hypothesis of predominantly transform motion, between the Australian and Antarctic plates, in Late Cretaceous and Paleogene time.〈/jats:p〉

Description: Mineral dust accumulated on the ocean floor is an important archive for reconstructing past atmospheric circulation changes and climatological conditions in the source areas. Dust emitted from Southern Hemisphere dust sources is widely deposited over the oceans. However, there are few records of dust deposition over the open ocean, and a large need for extended geographical coverage exists. We present a large data set (134 surface sediment samples) of Late Holocene dust deposition from seafloor surface sediments covering the entire South Atlantic Ocean. Polymodal grain-size distributions of the lithogenic fraction indicate that the sediments are composed of multiple sediment components. By using end-member modeling, we attempt to disentangle the dust signal from non-aeolian sediments. Combined with 230Th-normalized lithogenic fluxes, we quantified the specific deposition fluxes for mineral dust, crrent-sorted sediments and ice-rafted debris (IRD). Although the method could not completely separate the different components in every region, it shows that dust deposition off the most prominent dust source for the South Atlantic Ocean—southern South America—amounts up to approximately 0.7 g cm−2 Kyr−1 and decreases downwind. Bottom-current-sorted sediments and IRD are mostly concentrated around the continental margins. The ratio of the coarse to fine dust end members reveals input from north African dust sources to the South Atlantic. The majority of the observations are in good agreement with new model simulations. This extensive and relevant data set of dust grain size and deposition fluxes to the South Atlantic could be used to calibrate and validate further model simulations.

Description: 〈jats:title〉Abstract〈/jats:title〉〈jats:p〉Extensive investigation of continental rift systems has been fundamental for advancing the understanding of extensional tectonics and modes of formation of new ocean basins. However, current rift classification schemes do not account for conjugate end members formed by Large Igneous Province crust, referring to thick mafic crust, sometimes including continental fragments. Here, we investigate the rifting of William's Ridge (Kerguelen Plateau) and Broken Ridge, components of the Kerguelen Large Igneous Province now situated in the Southeast Indian Ocean, and incorporate these end members into the deformation migration concept for rifted margins. We use multichannel seismic reflection profiles and data from scientific drill cores acquired on both conjugate margins to propose, for the first time, a combined tectono‐stratigraphic framework. We interpret seismic patterns, tectonic features, and magnetic anomaly picks to determine an across‐strike structural domain classification. This interpretation considers the rift system overall to be “magma‐poor” despite being located proximal to the Kerguelen plume but suggests that syn‐rift interaction between the Kerguelen mantle plume and the lithospheric structure of William's Ridge and Broken Ridge has controlled the along‐strike segmentation of both conjugates. We integrate seismic reflection and bathymetric data to test the hypothesis of predominantly transform motion, between the Australian and Antarctic plates, in Late Cretaceous and Paleogene time.〈/jats:p〉

Description: Since the 1980s various international directives and frameworks have acknowledged the potential of risk communication to foster community empowerment. However, to achieve empowerment, communication has to be effective. When it comes to natural disasters, such as earthquakes, science communication requires the involvement of communities as a whole, promoting bottom-up strategies and proactive engagement. In this light, we conducted a scoping review of scientific publications on seismic risk communication in Europe published between 2000 and 2022. We focused on how seismic risk communication has changed in that time span, looking for targeted approaches, tools, recipients and channels. Here we provide an overview of the results obtained from the analysis of 109 selected publications, also highlighting the importance of scientific communication as a transnational problem, due to the mobility of modern society. Our study reveals that seismic risk communication in Europe is becoming increasingly proactive, focusing on a bottom-up strategy that relies on youth to build the resilience of future generations. The potential for the community empowerment has been primarily addressed with seismic risk communication during the pre-crisis phase of the disaster, when risk awareness can be effectively raised. Social media are increasingly used to provide timely and actionable information in times of crisis, to engage citizens within a two-way risk communication model, in the pre-crisis time, and to provide scientific data for post-disaster processing. The future agenda of seismic risk communication in Europe should focus on building trust with the public, moving towards a three-way model of seismic risk communication and, even more importantly, taking action to curb the spread of fake news and their negative impact on disaster management. Last but not least, more efforts should be made to link practice and theory and explicitly build seismic risk communication on theoretical models.

Description: Published

Description: San Francisco, California, USA

Description: OS: Terza missione

Description: In mid-September 2021 there was a rapid increase in geophysical and geochemical parameters on the island of Vulcano, Italy, reaching alarming values. This phase of unrest aroused serious concern among Civil Protection, local authorities and the scientific community due to the risk of phreatomagmatic activity, with potentially serious repercussions on the inhabitants of the island and on visiting tourists. The beginning of the unrest was marked by a high occurrence rate of local micro-seismicity related to fluid dynamics within the shallower hydrothermal system (mainly Long Period and Very Long Period events); Volcano-Tectonic (VT) earthquakes increased in late October after most of the monitored parameters reached their climax. Afterwards, major episodes of VT activity were also recorded from March to April and at the end of the year 2022, when an earthquake of ML 4.6 occurred on December 4, SW of the island of Vulcano. Here, we analyze the VT earthquakes from January 2020 to December 2022, in terms of space-time distribution, energy release and focal mechanisms in the framework of the regional geodynamic context and in the light of the main characteristics of the seismic activity recorded in the Vulcano area over the past 36 years.

Description: Published

Description: San Francisco, California, USA

Description: OST3 Vicino alla faglia

Description: Understanding the material properties and physical conditions of basal ice is crucial for a comprehensive understanding of Antarctic ice‐sheet dynamics. Yet, direct data are sparse and difficult to acquire. Here, we employ ultra‐wideband radar to map high‐backscatter zones near the glacier bed within East Antarctica's Jutulstraumen drainage basin. Our backscatter analysis reveals that the basal ice in an area of ∼10,000 km² is composed of along‐flow oriented sediment‐laden basal ice units connected to the basal substrate, extending up to several hundred meters thick. Three‐dimensional thermomechanical modeling supports that these units form via basal freeze‐on of subglacial water that originated from further upstream. Our findings suggest that basal freeze‐on, and the entrainment and transport of subglacial material play a significant role in an accurate representation of material, physical, and rheological properties of the Antarctic ice sheet's basal ice, ultimately enhancing the accuracy and reliability of ice‐sheet modeling.

Description: Understanding the material properties and physical conditions of basal ice is crucial for a comprehensive understanding of Antarctic ice‐sheet dynamics. Yet, direct data are sparse and difficult to acquire. Here, we employ ultra‐wideband radar to map high‐backscatter zones near the glacier bed within East Antarctica's Jutulstraumen drainage basin. Our backscatter analysis reveals that the basal ice in an area of ∼10,000 km² is composed of along‐flow oriented sediment‐laden basal ice units connected to the basal substrate, extending up to several hundred meters thick. Three‐dimensional thermomechanical modeling supports that these units form via basal freeze‐on of subglacial water that originated from further upstream. Our findings suggest that basal freeze‐on, and the entrainment and transport of subglacial material play a significant role in an accurate representation of material, physical, and rheological properties of the Antarctic ice sheet's basal ice, ultimately enhancing the accuracy and reliability of ice‐sheet modeling.

Description: Understanding the material properties and physical conditions of basal ice is crucial for a comprehensive understanding of Antarctic ice‐sheet dynamics. Yet, direct data are sparse and difficult to acquire. Here, we employ ultra‐wideband radar to map high‐backscatter zones near the glacier bed within East Antarctica's Jutulstraumen drainage basin. Our backscatter analysis reveals that the basal ice in an area of ∼10,000 km² is composed of along‐flow oriented sediment‐laden basal ice units connected to the basal substrate, extending up to several hundred meters thick. Three‐dimensional thermomechanical modeling supports that these units form via basal freeze‐on of subglacial water that originated from further upstream. Our findings suggest that basal freeze‐on, and the entrainment and transport of subglacial material play a significant role in an accurate representation of material, physical, and rheological properties of the Antarctic ice sheet's basal ice, ultimately enhancing the accuracy and reliability of ice‐sheet modeling.

Description: 〈jats:title〉Abstract〈/jats:title〉〈jats:p〉Extensive investigation of continental rift systems has been fundamental for advancing the understanding of extensional tectonics and modes of formation of new ocean basins. However, current rift classification schemes do not account for conjugate end members formed by Large Igneous Province crust, referring to thick mafic crust, sometimes including continental fragments. Here, we investigate the rifting of William's Ridge (Kerguelen Plateau) and Broken Ridge, components of the Kerguelen Large Igneous Province now situated in the Southeast Indian Ocean, and incorporate these end members into the deformation migration concept for rifted margins. We use multichannel seismic reflection profiles and data from scientific drill cores acquired on both conjugate margins to propose, for the first time, a combined tectono‐stratigraphic framework. We interpret seismic patterns, tectonic features, and magnetic anomaly picks to determine an across‐strike structural domain classification. This interpretation considers the rift system overall to be “magma‐poor” despite being located proximal to the Kerguelen plume but suggests that syn‐rift interaction between the Kerguelen mantle plume and the lithospheric structure of William's Ridge and Broken Ridge has controlled the along‐strike segmentation of both conjugates. We integrate seismic reflection and bathymetric data to test the hypothesis of predominantly transform motion, between the Australian and Antarctic plates, in Late Cretaceous and Paleogene time.〈/jats:p〉

Description: We quantify sea ice concentration (SIC) changes related to synoptic cyclones separately for each month of the year in the Greenland, Barents and Kara Seas for 1979–2018. We find that these SIC changes can be statistically significant throughout the year. However, their strength varies from region to region and month to month, and their sign strongly depends on the considered time scale (before/during vs. after cyclone passages). Our results show that the annual cycle of cyclone impacts on SIC is related to varying cyclone intensity and traversed sea ice conditions. We further show that significant changes in these cyclone impacts have manifested in the last 40 years, with the strongest changes occurring in October and November. For these months, SIC decreases before/during cyclones have more than doubled in magnitude in the Barents and Kara Seas, while SIC increases following cyclones have weakened (intensified) in the Barents Sea (Kara Sea).

Description: Knowledge of Antarctica's sedimentary basins builds our understanding of the coupled evolution of tectonics, ice, ocean, and climate. Sedimentary basins have properties distinct from basement-dominated regions that impact ice-sheet dynamics, potentially influencing future ice-sheet change. Despite their importance, our knowledge of Antarctic sedimentary basins is restricted. Remoteness, the harsh environment, the overlying ice sheet, ice shelves, and sea ice all make fieldwork challenging. Nonetheless, in the past decade the geophysics community has made great progress in internationally coordinated data collection and compilation with parallel advances in data processing and analysis supporting a new insight into Antarctica's subglacial environment. Here, we summarize recent progress in understanding Antarctica's sedimentary basins. We review advances in the technical capability of radar, potential fields, seismic, and electromagnetic techniques to detect and characterize basins beneath ice and advances in integrated multi-data interpretation including machine-learning approaches. These new capabilities permit a continent-wide mapping of Antarctica's sedimentary basins and their characteristics, aiding definition of the tectonic development of the continent. Crucially, Antarctica's sedimentary basins interact with the overlying ice sheet through dynamic feedbacks that have the potential to contribute to rapid ice-sheet change. Looking ahead, future research directions include techniques to increase data coverage within logistical constraints, and resolving major knowledge gaps, including insufficient sampling of the ice-sheet bed and poor definition of subglacial basin structure and stratigraphy. Translating the knowledge of sedimentary basin processes into ice-sheet modeling studies is critical to underpin better capacity to predict future change.

Description: Given the role played by the historical and extensive coverage of sea ice concentration (SIC) observations in reconstructing the long‐term variability of Antarctic sea ice, and the limited attention given to model‐dependent parameters in current sea ice data assimilation studies, this study focuses on enhancing the performance of the Data Assimilation System for the Southern Ocean in assimilating SIC through optimizing the localization and observation error estimate, and two assimilation experiments were conducted from 1979 to 2018. By comparing the results with the sea ice extent of the Southern Ocean and the sea ice thickness in the Weddell Sea, it becomes evident that the experiment with optimizations outperforms that without optimizations due to achieving more reasonable error estimates. Investigating uncertainties of the sea ice volume anomaly modeling reveals the importance of the sea ice‐ocean interaction in the SIC assimilation, implying the necessity of assimilating more oceanic and sea‐ice observations.

Description: Molybdenum (Mo) is a trace element sensitive to oceanic redox conditions. The fidelity of sedimentary Mo as a paleoredox proxy of coeval seawater depends on the extent of Mo remobilization during postdepositional processes. Here we present the Mo content and isotope profiles for deep sediments from the Nankai Trough, Japan. The Mo signature suggests that these sediments have experienced extensive early diagenesis and hydrothermal alteration at depth. Iron (Fe)‐manganese (Mn) (oxyhydr)oxide alteration combined with Mo thiolation leads to a more than twenty‐fold enrichment of Mo within the sulfate reduction zone. Hydrothermal fluids and Mo adsorption onto Fe‐Mn (oxyhydr)oxides cause extremely negative Mo‐isotope values at the underthrust zone. These postdepositional Mo signals might be misinterpreted as expanded anoxia in the water column. Our findings highlight the importance of constraining postdepositional effects on Mo‐based proxies during paleoredox reconstruction.

Description: As a contribution to the Regional Carbon Cycle Assessment and Processes phase 2 (RECCAP2) project, we present synthesized estimates of Arctic Ocean sea-air CO2 fluxes and their uncertainties from surface ocean pCO2-observation products, ocean biogeochemical hindcast and data assimilation models, and atmospheric inversions. For the period of 1985–2018, the Arctic Ocean was a net sink of CO2 of 116 ± 4 TgC yr−1 in the pCO2 products, 92 ± 30 TgC yr−1 in the models, and 91 ± 21 TgC yr−1 in the atmospheric inversions. The CO2 uptake peaks in late summer and early autumn, and is low in winter when sea ice inhibits sea-air fluxes. The long-term mean CO2 uptake in the Arctic Ocean is primarily caused by steady-state fluxes of natural carbon (70% ± 15%), and enhanced by the atmospheric CO2 increase (19% ± 5%) and climate change (11% ± 18%). The annual mean CO2 uptake increased from 1985 to 2018 at a rate of 31 ± 13 TgC yr−1 dec−1 in the pCO2 products, 10 ± 4 TgC yr−1 dec−1 in the models, and 32 ± 16 TgC yr−1 dec−1 in the atmospheric inversions. Moreover, 77% ± 38% of the trend in the net CO2 uptake over time is caused by climate change, primarily due to rapid sea ice loss in recent years. Furthermore, true uncertainties may be larger than the given ensemble standard deviations due to common structural biases across all individual estimates.

Description: We assess the Southern Ocean CO2 uptake (1985–2018) using data sets gathered in the REgional Carbon Cycle Assessment and Processes Project Phase 2. The Southern Ocean acted as a sink for CO2 with close agreement between simulation results from global ocean biogeochemistry models (GOBMs, 0.75 ± 0.28 PgC yr−1) and pCO2-observation-based products (0.73 ± 0.07 PgC yr−1). This sink is only half that reported by RECCAP1 for the same region and timeframe. The present-day net uptake is to first order a response to rising atmospheric CO2, driving large amounts of anthropogenic CO2 (Cant) into the ocean, thereby overcompensating the loss of natural CO2 to the atmosphere. An apparent knowledge gap is the increase of the sink since 2000, with pCO2-products suggesting a growth that is more than twice as strong and uncertain as that of GOBMs (0.26 ± 0.06 and 0.11 ± 0.03 Pg C yr−1 decade−1, respectively). This is despite nearly identical pCO2 trends in GOBMs and pCO2-products when both products are compared only at the locations where pCO2 was measured. Seasonal analyses revealed agreement in driving processes in winter with uncertainty in the magnitude of outgassing, whereas discrepancies are more fundamental in summer, when GOBMs exhibit difficulties in simulating the effects of the non-thermal processes of biology and mixing/circulation. Ocean interior accumulation of Cant points to an underestimate of Cant uptake and storage in GOBMs. Future work needs to link surface fluxes and interior ocean transport, build long overdue systematic observation networks and push toward better process understanding of drivers of the carbon cycle.

Description: The seasonal cycle is the dominant mode of variability in the air-sea CO2 flux in most regions of the global ocean, yet discrepancies between different seasonality estimates are rather large. As part of the Regional Carbon Cycle Assessment and Processes Phase 2 project (RECCAP2), we synthesize surface ocean pCO2 and air-sea CO2 flux seasonality from models and observation-based estimates, focusing on both a present-day climatology and decadal changes between the 1980s and 2010s. Four main findings emerge: First, global ocean biogeochemistry models (GOBMs) and observation-based estimates (pCO2 products) of surface pCO2 seasonality disagree in amplitude and phase, primarily due to discrepancies in the seasonal variability in surface DIC. Second, the seasonal cycle in pCO2 has increased in amplitude over the last three decades in both pCO2 products and GOBMs. Third, decadal increases in pCO2 seasonal cycle amplitudes in subtropical biomes for both pCO2 products and GOBMs are driven by increasing DIC concentrations stemming from the uptake of anthropogenic CO2 (Cant). In subpolar and Southern Ocean biomes, however, the seasonality change for GOBMs is dominated by Cant invasion, whereas for pCO2 products an indeterminate combination of Cant invasion and climate change modulates the changes. Fourth, biome-aggregated decadal changes in the amplitude of pCO2 seasonal variability are largely detectable against both mapping uncertainty (reducible) and natural variability uncertainty (irreducible), but not at the gridpoint scale over much of the northern subpolar oceans and over the Southern Ocean, underscoring the importance of sustained high-quality seasonally resolved measurements over these regions.

Description: This contribution to the RECCAP2 (REgional Carbon Cycle Assessment and Processes) assessment analyzes the processes that determine the global ocean carbon sink, and its trends and variability over the period 1985–2018, using a combination of models and observation-based products. The mean sea-air CO2 flux from 1985 to 2018 is −1.6 ± 0.2 PgC yr−1 based on an ensemble of reconstructions of the history of sea surface pCO2 (pCO2 products). Models indicate that the dominant component of this flux is the net oceanic uptake of anthropogenic CO2, which is estimated at −2.1 ± 0.3 PgC yr−1 by an ensemble of ocean biogeochemical models, and −2.4 ± 0.1 PgC yr−1 by two ocean circulation inverse models. The ocean also degasses about 0.65 ± 0.3 PgC yr−1 of terrestrially derived CO2, but this process is not fully resolved by any of the models used here. From 2001 to 2018, the pCO2 products reconstruct a trend in the ocean carbon sink of −0.61 ± 0.12 PgC yr−1 decade−1, while biogeochemical models and inverse models diagnose an anthropogenic CO2-driven trend of −0.34 ± 0.06 and −0.41 ± 0.03 PgC yr−1 decade−1, respectively. This implies a climate-forced acceleration of the ocean carbon sink in recent decades, but there are still large uncertainties on the magnitude and cause of this trend. The interannual to decadal variability of the global carbon sink is mainly driven by climate variability, with the climate-driven variability exceeding the CO2-forced variability by 2–3 times. These results suggest that anthropogenic CO2 dominates the ocean CO2 sink, while climate-driven variability is potentially large but highly uncertain and not consistently captured across different methods.

Description: Comparing helicopter-borne surface temperature maps in winter and optical orthomosaics in summer from the year-long Multidisciplinary drifting Observatory for the Study of Arctic Climate expedition, we find a strong geometric correlation between warm anomalies in winter and melt pond location the following summer. Warm anomalies are associated with thinner snow and ice, that is, surface depression and refrozen leads, that allow for water accumulation during melt. Warm surface temperature anomalies in January were 0.3–2.5 K warmer on sea ice that later formed melt ponds. A one-dimensional steady-state thermodynamic model shows that the observed surface temperature differences are in line with the observed ice thickness and snow depth. We demonstrate the potential of seasonal prediction of summer melt pond location and coverage from winter surface temperature observations. A threshold-based classification achieves a correct classification for 41% of the melt ponds.

Description: We assessed the spatial and temporal variability of the Arctic Boundary Current (ABC) using seven oceanographic moorings, deployed across the continental slope north of Severnaya Zemlya in 2015–2018. Transports and individual water masses were quantified based on temperature and salinity recorders and current profilers. Our results were compared with observations from the northeast Svalbard and the central Laptev Sea continental slopes to evaluate the hydrographic transformation along the ABC pathway. The highest velocities (〉0.30 m s−1) of the ABC occurred at the upper continental slope and decreased offshore to below 0.03 m s−1 in the deep basin. The ABC showed seasonal variability with velocities two times higher in winter than in summer. Compared to upstream conditions in Svalbard, water mass distribution changed significantly within 20 km of the shelf edge due to mixing with- and intrusion of shelf waters. The ABC transported 4.15 ± 0.3 Sv in the depth range 50–1,000 m, where 0.88 ± 0.1, 1.5 ± 0.2, 0.61 ± 0.1 and 1.0 ± 0.15 Sv corresponded to Atlantic Water (AW), Dense Atlantic Water (DAW), Barents Sea Branch Water (BSBW) and Transformed Atlantic Water (TAW). 62–70% of transport was constrained to within 30–40 km of the shelf edge, and beyond 84 km, transport increases were estimated to be 0.54 Sv. Seasonality of TAW derived from local shelf-processes and advection of seasonal-variable Fram Strait waters, while BSBW transport variability was dominated by temperature changes with maximum transport coinciding with minimum temperatures. Further Barents Sea warming will likely reduce TAW and BSBW transport leading to warmer conditions along the ABC pathway.

Description: Atmospheric carbon dioxide concentrations (pCO2) beyond ice core records have been reconstructed from δ11B derived from planktic foraminifera found in equatorial sediment cores. Here, I applied a carbon cycle model over the Plio-Pleistocene to evaluate the assumptions leading to these numbers. During glacials times, simulated atmospheric pCO2 was unequilibrated with pCO2 in the equatorial surface ocean by up to 35 ppm while the δ11B-based approaches assume unchanged (quasi)equilibrium between both. In the Pliocene, δ11B-based estimates of surface ocean pH are lower in the Pacific than in the Atlantic resulting in higher calculated pCO2. This offset in pH between ocean basins is not supported by models. To calculate pCO2 in surface waters out of the δ11B-based pH some assumptions on either total alkalinity or dissolved inorganic carbon are necessary. However, the assumed values of these under-constrained variables were according to my results partly inconsistent with chemically possible combinations within the marine carbonate system. The model results show glacial/interglacial variability in total alkalinity of the order of 100 μmol/kg, which is rarely applied to proxy reconstructions. Simulated atmospheric pCO2 is tightly (r2 〉 0.9) related to equatorial surface-ocean pH, which can be used for consistency checks. Long-term trends in volcanic CO2 outgassing and the strength of the continental weathering fluxes are still unconstrained, allowing for a wide range of possible atmospheric pCO2 across the Plio-Pleistocene. Nevertheless, this carbon cycle analysis suggests that reported atmospheric pCO2 above 500 ppm in the Pliocene might, for various reasons, need to be revised to smaller numbers.

Description: Aquatic ecosystems play an important role in global methane cycling and many field studies have reported methane supersaturation in the oxic surface mixed layer (SML) of the ocean and in the epilimnion of lakes. The origin of methane formed under oxic condition is hotly debated and several pathways have recently been offered to explain the “methane paradox.” In this context, stable isotope measurements have been applied to constrain methane sources in supersaturated oxygenated waters. Here we present stable carbon isotope signatures for six widespread marine phytoplankton species, three haptophyte algae and three cyanobacteria, incubated under laboratory conditions. The observed isotopic patterns implicate that methane formed by phytoplankton might be clearly distinguished from methane produced by methanogenic archaea. Comparing results from phytoplankton experiments with isotopic data from field measurements, suggests that algal and cyanobacterial populations may contribute substantially to methane formation observed in the SML of oceans and lakes.

Description: 〈jats:title〉Abstract〈/jats:title〉〈jats:p〉Most viscous‐plastic sea ice models use the elliptical yield curve. This yield curve has a fundamental flaw: it excludes acute angles between deformation features at high resolution. Conceptually, the teardrop (TD) and parabolic lens (PL) yield curves offer an attractive alternative. These yield curves feature a non‐symmetrical shape, a Coulombic behavior for the low‐medium compressive stress, and a continuous transition to the ridging‐dominant mode, but their published formulation leads to negative or zero bulk and shear viscosities and, consequently, poor numerical convergence with stress states at times outside the yield curve. These issues are a consequence of the original assumption that the constitutive equations of the commonly used elliptical yield curve are also applicable to non‐symmetrical yield curves and yield curves with tensile strength. We derive a corrected formulation for the constitutive relations of the TD and PL yield curves. Results from simple uni‐axial loading experiments show that with the new formulation the numerical convergence of the solver improves and much smaller nonlinear residuals after a smaller number of total solver iterations can be reached, resulting in significant improvements in numerical efficiency and representation of the stress and deformation fields. The TD and PL yield curves lead to smaller angles of failure that better agree with observations. They are promising candidates to replace the elliptical yield curve in high‐resolution pan‐Arctic sea ice simulations.〈/jats:p〉

Description: Climate change in the Arctic has substantial impacts on human life and ecosystems both within and beyond the Arctic. Our analysis of CMIP6 simulations shows that some climate models project much larger Arctic climate change than other models, including changes in sea ice, ocean mixed layer, air-sea heat flux, and surface air temperature in wintertime. In particular, dramatic enhancement of Arctic Ocean convection down to a few hundred meters is projected in these models but not in others. Interestingly, these models employ the same ocean model family (NEMO) while the choice of models for the atmosphere and sea ice varies. The magnitude of Arctic climate change is proportional to the strength of the increase in poleward ocean heat transport, which is considerably higher in this group of models. Establishing the plausibility of this group of models with high Arctic climate sensitivity to anthropogenic forcing is imperative given the implied ramifications.

Description: Sea ice leads play an important role in energy exchange between the ocean and atmosphere in polar regions, and therefore must be considered in weather and climate models. As sea ice leads are not explicitly resolved in such models, lead-averaged surface heat flux is of considerable interest for the parameterization of energy exchange. Measurements and numerical studies have established that the lead-averaged surface heat flux depends not only on meteorological parameters, but also on lead width. Nonetheless, few studies to date have investigated the dependency of surface heat flux on lead width. Most findings on that dependency are based on observations with lead widths smaller than a few hundred meters, but leads can have widths from a few meters to several kilometers. In this parameter study, we present the results of three series of large-eddy simulations of turbulent exchange processes above leads. We varied the lead width and air temperature, as well as the roughness length. As this study focused on conditions without background wind, ice-breeze circulation occurred, and was the main driver of the adjustment of surface heat flux. A previous large-eddy simulation study with uncommonly large roughness length found that lead-averaged surface heat flux exhibited a distinct maximum at lead widths of about 3 km, while our results show the largest heat fluxes for the smallest leads simulated (lead width of 50 m). At more realistic roughness lengths, we observed monotonously increasing heat fluxes with increasing lead width. Further, new scaling laws for the ice-breeze circulation are proposed.

Description: The Arctic is warming much faster than the global average. This is known as Arctic Amplification and is caused by feedbacks in the local climate system. In this study, we explore a previously proposed hypothesis that an associated wind feedback in the Barents Sea could play an important role by increasing the warm water inflow into the Barents Sea. We find that the strong recent decrease in Barents Sea winter sea ice cover causes enhanced ocean-atmosphere heat flux and a local air temperature increase, thus a reduction in sea level pressure and a local cyclonic wind anomaly with eastward winds in the Barents Sea Opening. By investigating various reanalysis products and performing high-resolution perturbation experiments with the ocean and sea ice model FESOM2.1, we studied the impact of cyclonic atmospheric circulation changes on the warm Atlantic Water import into the Arctic via the Barents Sea and Fram Strait. We found that the observed wind changes do not significantly affect the warm water transport into the Barents Sea, which rejects the wind-feedback hypothesis. At the same time, the cyclonic wind anomalies in the Barents Sea increase the amount of Atlantic Water recirculating westwards in Fram Strait by a downslope shift of the West Spitsbergen Current, and thus reduce Atlantic Water reaching the Arctic basin via Fram Strait. The resulting warm-water anomaly in the Greenland Sea Gyre drives a local anticyclonic circulation anomaly.

Description: In the Fram Strait, mid-ocean ridge spreading is represented by the ultra-slow system of the Molloy Ridge, the Molloy Transform Fault and the Knipovich Ridge. Sediments on oceanic and continental crust are gas charged and there are several locations with documented seafloor seepage. Sedimentary faulting shows recent stress release in the sub-surface, but the drivers of stress change and its influence on fluid flow are not entirely understood. We present here the results of an 11-month-long ocean bottom seismometer survey conducted over the highly faulted sediment drift northwards from the Knipovich Ridge to monitor seismicity and infer the regional state of stress. We obtain a detailed earthquake catalog that improves the spatial resolution of mid-ocean ridge seismicity compared with published data. Seismicity at the Molloy Transform Fault is occurring southwards from the bathymetric imprint of the fault, as supported by a seismic profile. Earthquakes in the northern termination of the Knipovich Ridge extend eastwards from the ridge valley, which together with syn-rift faulting identified in seismic reflection data, suggests that a portion of the currently active spreading center is buried under sediments away from the bathymetric expression of the rift valley. This hints at the direct link between crustal rifting processes and faulting in shallow sediments. Two earthquakes occur close to the seepage system of the Vestnesa Ridge further north from the network. We suggest that deeper rift structures, reactivated by gravity and/or post-glacial subsidence, may lead to accommodation of stress through shallow extensional faults, therefore impacting seepage dynamics.

Description: Surface processes alter the water stable isotope signal of the surface snow after deposition. However, it remains an open question to which extent surface post-depositional processes should be considered when inferring past climate information from ice core records. Here, we present simulations for the Greenland Ice Sheet, combining outputs from two climate models with an isotope-enabled snowpack model. We show that surface vapor exchange and associated fractionation imprint a climate signal into the firn, resulting in an increase in the annual mean value of δ18O by +2.3‰ and a reduction in d-excess by −6.3‰. Further, implementing isotopic fractionation during surface vapor exchange improves the representation of the observed seasonal amplitude in δ18O from 65.0% to 100.2%. Our results stress that surface vapor exchange is important in the climate proxy signal formation and needs consideration when interpreting ice core climate records.

Description: We assessed the spatial and temporal variability of the Arctic Boundary Current (ABC) using seven oceanographic moorings, deployed across the continental slope north of Severnaya Zemlya in 2015–2018. Transports and individual water masses were quantified based on temperature and salinity recorders and current profilers. Our results were compared with observations from the northeast Svalbard and the central Laptev Sea continental slopes to evaluate the hydrographic transformation along the ABC pathway. The highest velocities (〉0.30 m s−1) of the ABC occurred at the upper continental slope and decreased offshore to below 0.03 m s−1 in the deep basin. The ABC showed seasonal variability with velocities two times higher in winter than in summer. Compared to upstream conditions in Svalbard, water mass distribution changed significantly within 20 km of the shelf edge due to mixing with- and intrusion of shelf waters. The ABC transported 4.15 ± 0.3 Sv in the depth range 50–1,000 m, where 0.88 ± 0.1, 1.5 ± 0.2, 0.61 ± 0.1 and 1.0 ± 0.15 Sv corresponded to Atlantic Water (AW), Dense Atlantic Water (DAW), Barents Sea Branch Water (BSBW) and Transformed Atlantic Water (TAW). 62–70% of transport was constrained to within 30–40 km of the shelf edge, and beyond 84 km, transport increases were estimated to be 0.54 Sv. Seasonality of TAW derived from local shelf-processes and advection of seasonal-variable Fram Strait waters, while BSBW transport variability was dominated by temperature changes with maximum transport coinciding with minimum temperatures. Further Barents Sea warming will likely reduce TAW and BSBW transport leading to warmer conditions along the ABC pathway.

Description: Snowpack emissions are recognized as an important source of gas-phase reactive bromine in the Arctic and are necessary to explain ozone depletion events in spring caused by the catalytic destruction of ozone by halogen radicals. Quantifying bromine emissions from snowpack is essential for interpretation of ice-core bromine. We present ice-core bromine records since the pre-industrial (1750 CE) from six Arctic locations and examine potential post-depositional loss of snowpack bromine using a global chemical transport model. Trend analysis of the ice-core records shows that only the high-latitude coastal Akademii Nauk (AN) ice core from the Russian Arctic preserves significant trends since pre-industrial times that are consistent with trends in sea ice extent and anthropogenic emissions from source regions. Model simulations suggest that recycling of reactive bromine on the snow skin layer (top 1 mm) results in 9–17% loss of deposited bromine across all six ice-core locations. Reactive bromine production from below the snow skin layer and within the snow photic zone is potentially more important, but the magnitude of this source is uncertain. Model simulations suggest that the AN core is most likely to preserve an atmospheric signal compared to five Greenland ice cores due to its high latitude location combined with a relatively high snow accumulation rate. Understanding the sources and amount of photochemically reactive snow bromide in the snow photic zone throughout the sunlit period in the high Arctic is essential for interpreting ice-core bromine, and warrants further lab studies and field observations at inland locations.

Description: Shells of the giant clam Tridacna can provide decade-long records of past environmental conditions via their geochemical composition and structurally through growth banding. Counting the daily bands can give an accurate internal age model with high temporal resolution, but daily banding is not always visually retrievable, especially in fossil specimens. We show that daily geochemical cycles (e.g., Mg/Ca) are resolvable via highly spatially resolved laser-ablation inductively coupled plasma mass spectrometry (LA-ICPMS; 3 \xc3\x97 33 \xce\xbcm laser slit) in our Miocene (\xe2\x88\xbc10 Ma) specimen, even in areas where daily banding is not visually discernible. By applying wavelet transformation on the measured daily geochemical cycles, we quantify varying daily growth rates throughout the shell. These growth rates are thus used to build an internal age model independent of optical daily band countability. Such an age model can be used to convert the measured elemental ratios from a function of distance to a function of time, which helps evaluate paleoenvironmental proxy data, for example, regarding the timing of sub-seasonal events. Furthermore, the quantification of daily growth rates across the shell facilitates the evaluation of (co)dependencies between growth rates and corresponding elemental compositions.

Description: The Himalayan mountain range produces one of the steepest and largest rainfall gradients on Earth, with 〉3 m/yr rainfall difference over a ∼100 km distance. The Indian Summer Monsoon (ISM) contributes more than 80% to the annual precipitation budget of the central Himalayas. The remaining 20% falls mainly during pre-ISM season. Understanding the seasonal cycle and the transfer pathways of moisture from precipitation to the rivers is crucial for constraining water availability in a warming climate. However, the partitioning of moisture into the different storage systems such as snow, glacier, and groundwater and their relative contribution to river discharge throughout the year remains under-constrained. Here, we present novel field data from the Kali Gandaki, a trans-Himalayan river, and use 4-year time series of river and rain water stable isotope composition (δ18O and δ2H values) as well as river discharge, satellite Global Precipitation Measurement amounts, and moisture source trajectories to constrain hydrological variability. We find that rainfall before the onset of the ISM is isotopically distinct and that ISM rain and groundwater have similar isotopic values. Our study lays the groundwork for using isotopic measurements to track changes in precipitation sources during the pre-ISM to ISM transition in this key region of orographic precipitation. Specifically, we highlight the role of pre-ISM precipitation, derived from the Gangetic plain, to define the seasonal river isotopic variability across the central Himalayas. Lastly, isotopic values across the catchment document the importance of a large well-mixed groundwater reservoir supplying river discharge, especially during the non-ISM season.

Description: The Himalayan mountain range produces one of the steepest and largest rainfall gradients on Earth, with 〉3 m/yr rainfall difference over a ∼100 km distance. The Indian Summer Monsoon (ISM) contributes more than 80% to the annual precipitation budget of the central Himalayas. The remaining 20% falls mainly during pre-ISM season. Understanding the seasonal cycle and the transfer pathways of moisture from precipitation to the rivers is crucial for constraining water availability in a warming climate. However, the partitioning of moisture into the different storage systems such as snow, glacier, and groundwater and their relative contribution to river discharge throughout the year remains under-constrained. Here, we present novel field data from the Kali Gandaki, a trans-Himalayan river, and use 4-year time series of river and rain water stable isotope composition (δ18O and δ2H values) as well as river discharge, satellite Global Precipitation Measurement amounts, and moisture source trajectories to constrain hydrological variability. We find that rainfall before the onset of the ISM is isotopically distinct and that ISM rain and groundwater have similar isotopic values. Our study lays the groundwork for using isotopic measurements to track changes in precipitation sources during the pre-ISM to ISM transition in this key region of orographic precipitation. Specifically, we highlight the role of pre-ISM precipitation, derived from the Gangetic plain, to define the seasonal river isotopic variability across the central Himalayas. Lastly, isotopic values across the catchment document the importance of a large well-mixed groundwater reservoir supplying river discharge, especially during the non-ISM season.

Description: Three recently published papers including Napier et al. (2022, https://doi.org/10.1029/2021PA004355) utilize novel microanalytical approaches with varved marine sediments to demonstrate the potential to reconstruct seasonal and inter-annual climate variability. Obtaining paleoclimate data at a resolution akin to the observational record is vitally important for improving our understanding of climate phenomena such as monsoons and modes of variability such as the El Niño Southern Oscillation, for which appraisals of past inter-annual variability is critical. The ability to generate seasonal and inter annual resolution sea surface temperature proxy time series spanning a thousand years or more is revolutionary and has the potential to fill gaps in our knowledge of climate variability. Although generally limited to sediments from regions with oxygen depleted bottom waters, there is great potential to integrate shorter seasonal resolution climate “snap shots” from other archives such as annually banded corals into composite time series. But as paleoceanographic data are used more by the observational and modeling fields, we make the case for conducting a thorough case-by-case assessment of the processes that influence the climate signal recovered from proxies, using careful replication to validate new approaches. Understanding or exploring the potential influence of processes which effectively filter the climate signal will lead to more quantitative paleoceanographic data that will better serve the broader climate science community.

Description: Radio Echo Sounding (RES) surveys conducted in May 2010 and April 2011 revealed a 2 km2 flat area with increased bed reflectivity at the base of Isunnguata Sermia at the western margin of the Greenland Ice Sheet. This flat reflector was located within a localized subglacial hydraulic potential (hydropotential) minimum, as part of a complex and elongated trough system. By analogy with comparable features in Antarctica, the initial interpretation of such a feature was a potential subglacial lake. In September 2013 a co-located seismic survey revealed a 1,750 m by 540 and 37 m thick stratified lens-shaped bedform at the base of a subglacial trough system. Amplitude Versus Angle (AVA) analysis yields a derived reflection coefficient R = 0.09 ± 0.14 indicative of consolidated sediments possibly overlain by dilatant till. The bed and flank on the northern side of the trough consist of unconsolidated, possibly water-bearing sediments with R = −0.10 ± 0.08, whereas on the southern side it consists of more consolidated material. We interpret the trough as a key component of the wider subglacial drainage network, for which the sediments on its northern side act as a localized water-storage reservoir. Given the observation of seasonally forming and rapidly draining supraglacial meltwater lakes in this area, we interpret the lens-shaped bedform as deposited by episodically ponding meltwater within the subglacial trough system. Our results highlight the importance of transient subglacial hydrological and sedimentological processes such as drainage events for the interaction of ice sheets and their substrates, to understand ice dynamics in a warming climate.

Description: Human activities have increasingly changed terrestrial particulate organic carbon (POC) export to the coastal ocean since the Industrial Age (19th century). However, the influence of human perturbations on the composition and flux of terrestrial biospheric and petrogenic POC sub-pools remains poorly constrained. Here, we examined 13C and 14C compositions of bulk POC and source-specific biomarkers (fatty acids, FA) from two nearshore sediment cores collected in the Pearl River-derived mudbelt, to determine the impacts of human perturbations of the Pearl River watershed on the burial of terrestrial POC in the coastal ocean over the last century. Our results show that although agricultural practices and deforestation during the 1930s–1950s increased C4 plant coverage in the watershed, the export fluxes of terrestrial biospheric and petrogenic POC remained rather unchanged; however, added perturbations since 1974, including increasing coal consumption, embankment and dam constructions caused massive export of both petrogenic POC and relatively fresh terrestrial biospheric POC from the river delta. Our data reveal that human activities substantially enhance the transfer of petrogenic POC and fresh biospheric POC to the coastal ocean after ca. 1974, with the latter process acting as an important sink for anthropogenic CO2.

Description: The greenhouse gas (GHG) balance of boreal peatlands in permafrost regions will be affected by climate change through disturbances such as permafrost thaw and wildfire. Although the future GHG balance of boreal peatlands including ponds is dominated by the exchange of both carbon dioxide (CO2) and methane (CH4), disturbance impacts on fluxes of the potent GHG nitrous oxide (N2O) could contribute to shifts in the net radiative balance. Here, we measured monthly (April to October) fluxes of N2O, CH4, and CO2 from three sites located across the sporadic and discontinuous permafrost zones of western Canada. Undisturbed permafrost peat plateaus acted as N2O sinks (−0.025 mg N2O m−2 d−1), but N2O uptake was lower from burned plateaus (−0.003 mg N2O m−2 d−1) and higher following permafrost thaw in the thermokarst bogs (−0.054 mg N2O m−2 d−1). The thermokarst bogs had below-ambient N2O soil gas concentrations, suggesting that denitrification consumed atmospheric N2O during reduction to dinitrogen. Atmospheric uptake of N2O in peat plateaus and thermokarst bogs increased with soil temperature and soil moisture, suggesting sensitivity of N2O consumption to further climate change. Four of five peatland ponds acted as N2O sinks (−0.018 mg N2O m−2 d−1), with no influence of thermokarst expansion. One pond with high nitrate concentrations had high N2O emissions (0.30 mg N2O m−2 d−1). Overall, our study suggests that the future net radiative balance of boreal peatlands will be dominated by impacts of wildfire and permafrost thaw on CH4 and CO2 fluxes, while the influence from N2O is minor.

Description: The strong cooling during the Last Glacial Maximum (LGM, 21 ka BP) provides a rigorous test of climate models' ability to simulate past and future climate changes. We force an atmospheric general circulation model with two recent global LGM sea surface temperature (SST) reconstructions, one suggesting a weak and the other a more pronounced cooling, and compare the simulated land surface temperatures (LSTs) to reconstructed data. Our results do not confirm either SST reconstruction. The cold SST data set leads to good agreement between simulated and observed LSTs at low latitudes, but is systematically too cold at mid-latitudes. The opposite is true for the warm SST data set. Differences between the simulated LSTs are caused by varying land surface albedos, which is lower for the warmer SST reconstruction. The inconsistency between reconstructed and simulated climate points to a potentially significant bias in the proxy reconstructions and/or the climate sensitivity of current climate models.

Description: A new version of the AWI Coupled Prediction System is developed based on the Alfred Wegener Institute Climate Model v3.0. Both the ocean and the atmosphere models are upgraded or replaced, reducing the computation time by a factor of 5 at a given resolution. This allowed us to increase the ensemble size from 12 to 30, maintaining a similar resolution in both model components. The online coupled data assimilation scheme now additionally utilizes sea-surface salinity and sea-level anomaly as well as temperature and salinity profile observations. Results from the data assimilation demonstrate that the sea-ice and ocean states are reasonably constrained. In particular, the temperature and salinity profile assimilation has mitigated systematic errors in the deeper ocean, although issues remain over polar regions where strong atmosphere-ocean-ice interaction occurs. One-year-long sea-ice forecasts initialized on 1 January, 1 April, 1 July and 1 October from 2003 to 2019 are described. To correct systematic forecast errors, sea-ice concentration from 2011 to 2019 is calibrated by trend-adjusted quantile mapping using the preceding forecasts from 2003 to 2010. The sea-ice edge raw forecast skill is within the range of operational global subseasonal-to-seasonal forecast systems, outperforming a climatological benchmark for about 2 weeks in the Arctic and about 3 weeks in the Antarctic. The calibration is much more effective in the Arctic: Calibrated sea-ice edge forecasts outperform climatology for about 45 days in the Arctic but only 27 days in the Antarctic. Both the raw and the calibrated forecast skill exhibit strong seasonal variations.

Description: In this study we assessed the representation of the sea surface salinity (SSS) and liquid freshwater content (LFWC) of the Arctic Ocean in the historical simulation of 31 CMIP6 models with comparison to 39 Coupled Model Intercomparison Project phase 5 (CMIP5) models, and investigated the projected changes in Arctic liquid and solid freshwater content and freshwater budget in scenarios with two different shared socioeconomic pathways (SSP2-4.5 and SSP5-8.5). No significant improvement was found in the SSS and LFWC simulation from CMIP5 to CMIP6, given the large model spreads in both CMIP phases. The overestimation of LFWC continues to be a common bias in CMIP6. In the historical simulation, the multi-model mean river runoff, net precipitation, Bering Strait and Barents Sea Opening (BSO) freshwater transports are 2,928 ± 1,068, 1,839 ± 3,424, 2,538 ± 1,009, and −636 ± 553 km3/year, respectively. In the last decade of the 21st century, CMIP6 MMM projects these budget terms to rise to 4,346 ± 1,484 km3/year (3,678 ± 1,255 km3/year), 3,866 ± 2,935 km3/year (3,145 ± 2,651 km3/year), 2,631 ± 1,119 km3/year (2,649 ± 1,141 km3/year) and 1,033 ± 1,496 km3/year (449 ± 1,222 km3/year) under SSP5-8.5 (SSP2-4.5). Arctic sea ice is expected to continue declining in the future, and sea ice meltwater flux is likely to decrease to about zero in the mid-21st century under both SSP2-4.5 and SSP5-8.5 scenarios. Liquid freshwater exiting Fram and Davis straits will be higher in the future, and the Fram Strait export will remain larger. The Arctic Ocean is projected to hold a total of 160,300 ± 62,330 km3 (141,590 ± 50,310 km3) liquid freshwater under SSP5-8.5 (SSP2-4.5) by 2100, about 60% (40%) more than its historical climatology.

Description: Based on the ERA5 reanalysis, we report on statistically significant impacts of transient cyclones on sea ice concentration (SIC) in the Atlantic sector of the Arctic Ocean in winter under “New Arctic” conditions (2000–2020). This includes a pattern of reduced SIC prior to and during cyclones for the whole study domain, while a regional difference between increased SIC in the Barents Sea and reduced SIC in the Greenland Sea is found as the net effect from 3 days prior to 5 days after the cyclone passage. Generally, locally low to medium SIC conditions combined with intense cyclones drive highest SIC changes. There are indications that both thermodynamic and dynamic effects contribute to the SIC changes, but a detailed quantification is required in future research. We provide evidence that cyclone impacts on SIC have amplified compared to the “Old Arctic” (1979–1999), particularly in the Barents Sea.

Description: Zooplankton plays a notable role in ocean biogeochemical cycles. However, it is often simulated as one generic group and top closure term in ocean biogeochemical models. This study presents the description of three zooplankton functional types (zPFTs, micro-, meso- and macrozooplankton) in the ocean biogeochemical model FESOM-REcoM. In the presented model, microzooplankton is a fast-growing herbivore group, mesozooplankton is another major consumer of phytoplankton, and macrozooplankton is a slow-growing group with a low temperature optimum. Meso- and macrozooplankton produce fast-sinking fecal pellets. With three zPFTs, the annual mean zooplankton biomass increases threefold to 210 Tg C. The new food web structure leads to a 25% increase in net primary production and a 10% decrease in export production globally. Consequently, the export ratio decreases from 17% to 12% in the model. The description of three zPFTs reduces model mismatches with observed dissolved inorganic nitrogen and chlorophyll concentrations in the South Pacific and the Arctic Ocean, respectively. Representation of three zPFTs also strongly affects phytoplankton phenology: Fast nutrient recycling by zooplankton sustains higher chlorophyll concentrations in summer and autumn. Additional zooplankton grazing delays the start of the phytoplankton bloom by 3 weeks and controls the magnitude of the bloom peak in the Southern Ocean. As a result, the system switches from a light-controlled Sverdrup system to a dilution-controlled Behrenfeld system. Overall, the results suggest that representation of multiple zPFTs is important to capture underlying processes that may shape the response of ecosystems and ecosystem services to on-going and future environmental change in model projections.

Description: In this study, we used stable isotopes of oxygen (δ18O), deuterium (δD), and dissolved inorganic carbon (δ13CDIC) in combination with temperature, salinity, oxygen, and nutrient concentrations to characterize the coastal (71°–78°W) and an oceanic (82°–98°W) water masses (SAAW—Subantarctic Surface Water; STW—Subtropical Water; ESSW—Equatorial Subsurface water; AAIW—Antarctic Intermediate Water; PDW—Pacific Deep Water) of the Southeast Pacific (SEP). The results show that δ18O and δD can be used to differentiate between SAAW-STW, SAAW-ESSW, and ESSW-AAIW. δ13CDIC signatures can be used to differentiate between STW-ESSW (oceanic section), SAAW-ESSW, ESSW-AAIW, and AAIW-PDW. Compared with the oceanic section, our new coastal section highlights differences in both the chemistry and geometry of water masses above 1,000 m. Previous paleoceanographic studies using marine sediments from the SEP continental margin used the present-day hydrological oceanic transect to compare against, as the coastal section was not sufficiently characterized. We suggest that our new results of the coastal section should be used for past characterizations of the SEP water masses that are usually based on continental margin sediment samples.

Description: The East Australian Current (EAC) is the western boundary current of the South Pacific Subtropical Gyre that transports warm tropical waters to higher southern latitudes and significantly impacts the climate of Australia and New Zealand. Modern observations show that the EAC has strengthened with rising global temperatures. However, little is known about the pre-industrial variability of the EAC and the forcing mechanisms. Planktic foraminifera Globigerinoides ruber (white) Mg/Ca-based sea surface temperature reconstructions offshore northeastern Australia between 15° and 26°S reveal an increase by ∼1.2°C after ∼1400 CE. We infer that the increase in temperature is related to a stronger EAC heat transport that is likely driven by a strengthening of the Southern Hemisphere subtropical gyre circulation due to a progressive shift of the Southern annular mode toward its positive phase and of El Niño-Southern Oscillation toward more El Niño-like conditions.

Description: The climate signal imprinted in the snow isotopic composition allows to infer past climate variability from ice core stable water isotope records. The concurrent evolution of vapor and surface snow isotopic composition between precipitation events indicates that post-depositional atmosphere-snow humidity exchange influences the snow and hence the ice core isotope signal. To date, however, this is not accounted for in paeleoclimate reconstructions from isotope records. Here we show that vapor-snow exchange explains 36% of the summertime day-to-day δ18O variability of the surface snow between precipitation events, and 53% of the δD variability. Through observations from the Greenland Ice Sheet and accompanying modeling we demonstrate that vapor-snow exchange introduces a warm bias on the summertime snow isotope value relevant for ice core records. In case of long-term variability in atmosphere-snow exchange the relevance for the ice core signal is also variable and thus paleoclimate reconstructions from isotope records should be revisited.

Description: Statistical analysis of reanalysis and observed data reveals that high dust surface mass concentration in northern Greenland is associated with a Pacific Decadal Oscillation like pattern in its negative phase in the North Pacific as well as with La Niña conditions in the tropical Pacific region. The sea surface temperature anomalies in the Pacific realm resemble the Interdecadal Pacific Oscillation (IPO). The associated atmospheric circulation pattern, in the form of a wave-train from the North Pacific to the Eurasian continent, favors enhanced dust uptake and transport toward the northern Greenland. Similar patterns are associated with a low-resolution stacked record of five Ca2+ ice cores, that is, ngt03C93.2 (B16), ngt14C93.2 (B18), ngt27C94.2 (B21), GISP2−B, and NEEM-2011-S1, from northern Greenland, a proxy for regional dust concentration, during the last 400 years. We argue that northern Greenland ice core dust records could be used as proxies for the IPO and related teleconnections.

Description: We propose to make the damping time scale, which governs the decay of pseudo-elastic waves in the Elastic Viscous Plastic (EVP) sea-ice solvers, independent of the external time step and large enough to warrant numerical stability for a moderate number of internal time steps. A necessary condition is that the forcing on sea ice varies slowly on the damping time scale, in which case an EVP solution may still approach a Viscous Plastic one, but on a time scale longer than a single external time step. In this case, the EVP method becomes very close to the recently proposed modified EVP (mEVP) method in terms of stability and simulated behavior. In a simple test case dealing with sea ice breaking under the forcing of a moving cyclone, the EVP method with an enlarged damping time scale can simulate linear kinematic features which are very similar to those from the traditional EVP implementation, although a much smaller number of internal time steps is used. There is more difference in sea-ice thickness and linear kinematic features simulated in a realistic Arctic configuration between using the traditional and our suggested choices of EVP damping time scales, but it is minor considering model uncertainties associated with choices of many other parameters in sea-ice models.

Description: The North Atlantic Basin is a major sink for atmospheric carbon dioxide (CO2) due in part to the extensive plankton blooms which form there supported by nutrients supplied by the three-dimensional ocean circulation. Hence, changes in ocean circulation and/or stratification may influence primary production and biological carbon export. In this study, we assess this possibility by evaluating inorganic nutrient budgets for 2004 and 2010 in the North Atlantic based on observations from the transatlantic A05-24.5°N and the Greenland-Portugal OVIDE hydrographic sections, to which we applied a box inverse model to solve the circulation and estimate the across-section nutrient transports. Full water column nutrient budgets were split into upper and lower meridional overturning circulation (MOC) limbs. According to our results, anomalous circulation in early 2010, linked to extreme negative NAO conditions, led to an enhanced northward advection of more nutrient-rich waters by the upper overturning limb, which resulted in a significant nitrate and phosphate convergence north of 24.5°N. Combined with heaving of the isopycnals, this anomalous circulation event in 2010 favored an enhancement of the nutrient consumption (5.7 ± 4.1 kmol-P s−1) and associated biological CO2 uptake (0.25 ± 0.18 Pg-C yr−1, upper-bound estimate), which represents a 50% of the mean annual sea–air CO2 flux in the region. Our results also suggest a transient state of deep silicate divergence in both years. Both results are indicative of a MOC-driven modulation of the biological carbon uptake (by the upper MOC limb) and nutrient inventories (by the lower MOC limb) in the North Atlantic.

Description: The presence of clouds in the Arctic regulates the surface energy budget (SEB) over the sea-ice surface and the ice-free ocean. Following several previous field campaigns, the cloud-radiation relationship, including cloud vertical structure and phase, has been elucidated; however, modeling of this relationship has matured slowly. In recognition of the recent decline in the Arctic sea-ice extent, representation of the cloud system in numerical models should consider the effects of areas covered by sea ice and ice-free areas. Using an in situ stationary meteorological observation data set obtained over the ice-free Arctic Ocean by the Japanese Research Vessel Mirai (September 2014), coordinated evaluation of six regional climate models (RCMs) with nine model runs was performed by focusing on clouds and the SEB. The most remarkable findings were as follows: (1) reduced occurrence of unstable stratification with low-level cloud water in all models in comparison to the observations, (2) significant differences in cloud water representations between single- and double-moment cloud schemes, (3) extensive differences in partitioning of hydrometeors including solid/liquid precipitation, and (4) pronounced lower-tropospheric air temperature biases. These issues are considered as the main sources of SEB uncertainty over ice-free areas of the Arctic Ocean. The results from a coupled RCM imply that the SEB is constrained by both the atmosphere and the ocean (and sea ice) with considerable feedback. Coordinated improvement of both stand-alone atmospheric and coupled RCMs would promote a more comprehensive and improved understanding of the Arctic air-ice-sea coupled system.

Description: Bedforms of Thwaites Glacier, West Antarctica both record and affect ice flow, as shown by geophysical data and simple models. Thwaites Glacier flows across the tectonic fabric of the West Antarctic rift system with its bedrock highs and sedimentary basins. Swath radar and seismic surveys of the glacier bed have revealed soft-sediment flutes 100 m or more high extending 15 km or more across basins downglacier from bedrock highs. Flutes end at prominent hard-bedded moats on stoss sides of the next topographic highs. We use simple models to show that ice flow against topography increases pressure between ice and till upglacier along the bed over a distance that scales with the topography. In this basal zone of high pressure, ice-contact water would be excluded, thus increasing basal drag by increasing ice-till coupling and till flux, removing till to allow bedrock erosion that creates moats. Till carried across highlands would then be deposited in lee-side positions forming bedforms that prograde downglacier over time, and that remain soft on top through feedbacks that match till-deformational fluxes from well upglacier of the topography. The bedforms of the part of Thwaites surveyed here are prominent because ice flow has persisted over a long time on this geological setting, not because ice flow is anomalous. Bedform development likely has caused evolution of ice flow over time as till and lubricating water were redistributed, moats were eroded and bedforms grew.

Description: Ocean models at eddy-permitting resolution are generally overdissipative, damping the intensity of the mesoscale eddy field. To reduce overdissipation, we propose a simplified, kinematic energy backscatter parametrization built into the viscosity operator in conjunction with a new flow-dependent coefficient of viscosity based on nearest neighbor velocity differences. The new scheme mitigates excessive dissipation of energy and improves global ocean simulations at eddy-permitting resolution. We find that kinematic backscatter substantially raises simulated eddy kinetic energy, similar to an alternative, previously proposed dynamic backscatter parametrization. While dynamic backscatter is scale aware and energetically more consistent, its implementation is more complex. Furthermore, it turns out to be computationally more expensive, as it applies, among other things, an additional prognostic subgrid energy equation. The kinematic backscatter proposed here, by contrast, comes at no additional computational cost, following the principle of simplicity. Our primary focus is the discretization on triangular unstructured meshes with cell placement of velocities (an analog of B-grids), as employed by the Finite-volumE Sea ice-Ocean Model (FESOM2). The kinematic backscatter scheme with the new viscosity coefficient is implemented in FESOM2 and tested in the simplified geometry of a zonally reentrant channel as well as in a global ocean simulation on a 1/4° mesh. This first version of the new kinematic backscatter needs to be tuned to the specific resolution regime of the simulation. However, the tuning relies on a single parameter, emphasizing the overall practicality of the approach.

Description: Climate change in the Arctic leads to permafrost degradation and to associated changes infreshwater geochemistry. There is a limited understanding of how disturbances such as active layerdetachments or retrogressive thaw slumps impact water quality on a catchment scale. This study investigateshow permafrost degradation affects concentrations of dissolved organic carbon (DOC), total dissolvedsolids (TDS), suspended sediment, and stable water isotopes in adjacent Low Arctic watersheds. Weincorporated data on disturbance between 1952 and 2015, as well as sporadic runoff and geochemistry dataof streams nearby. Our results show that the total disturbed area decreased by 41% between 1952 and 2015,whereas the total number of disturbances increased by 66% in all six catchments. The spatial variabilityof hydrochemical parameters is linked to catchment properties and not necessarily reflected at the outflow.Degrading ice‐wedge polygons were found to increase DOC concentrations upstream in Ice Creek West,whereas hydrologically connected disturbances were linked to increases in TDS and suspended sediment.Although we found a great spatial variability of hydrochemical concentrations along the paired watershed,there was a linear relationship between catchment size and daily DOC, total dissolved nitrogen, and TDSfluxes for all six streams. Suspended sedimentflux on the contrary did not show a clear relationship as onehydrologically connected retrogressive thaw slump impacted the overallflux in one of the streams.Understanding the spatial variability of water quality will help to model the lateral geochemicalfluxes fromArctic catchments

Description: Coeval changes in atmospheric CO2 and 14C contents during the last deglaciation are often attributed to ocean circulation changes that released carbon stored in the deep ocean during the Last Glacial Maximum (LGM). Work is being done to generate records that allow for the identification of the exact mechanisms leading to the accumulation and release of carbon from the oceanic reservoir, but these mechanisms are still the subject of debate. Here we present foraminifera 14C data from five cores in a transect across the Chilean continental margin between ~540 and ~3,100 m depth spanning the last 20,000 years. Our data reveal that during the LGM, waters at ~2,000 m were 50% to 80% more depleted in Δ14C than waters at ~1,500 m when compared to modern values, consistent with the hypothesis of a glacial deep ocean carbon reservoir that was isolated from the atmosphere. During the deglaciation, our intermediate water records reveal homogenization in the Δ14C values between ~800 and ~1,500 m from ~16.5–14.5 ka cal BP to ~14–12 ka cal BP, which we interpret as deeper penetration of Antarctic Intermediate Water. While many questions still remain, this process could aid the ventilation of the deep ocean at the beginning of the deglaciation, contributing to the observed ~40 ppm rise in atmospheric pCO2.

Description: Just like people are often divided into two opposing categories—early birds and night owls, introverts and extroverts—meteorologists designate two main types of storms. Storms that form through organized convection are long-lived, cover a large area, generate and accumulate more clusters of clouds with time, take place in environments with large-scale circulation, and are triggered by uplifting air from a passing front or low-pressure system. Meanwhile, storms that form through unorganized convection are triggered by a temperature anomaly or change near Earth’s surface, take place in environments without large-scale circulation, and are more chaotic and unpredictable. Of the two types, organized convection is better understood and more ubiquitous, especially in the tropics. But meteorologists still have much to learn about convective organization to better understand and predict the behavior of storms. Here Becker et al. investigated the impact of convective organization on entrainment—a process in which warm, buoyant parcels of air become saturated with moisture; form cumulus clouds; and mix with cooler, drier parcels of air. This causes some cloud droplets to evaporate, cooling down the clouds and making them less buoyant. At this point, either the clouds can dissipate into a popcorn-like formation—which is called unaggregated convection—or other cumulus clouds in the vicinity will pile onto them, forming a larger cloud cluster (aggregated convection). Using a numerical model developed by the Max Planck Institute for Meteorology and the German Weather Service, the team created two simulations of convectional organization over a 312,000-square-kilometer grid with 1-kilometer spacing. One simulation started out with unaggregated convection that remained unaggregated throughout. The other simulated the same conditions but started out with aggregated convection and stayed fully aggregated throughout the simulation. The team found that in the lower levels of the troposphere, where our weather occurs, the rate of entrainment is higher when convection is aggregated. This is due to increased turbulence caused by updrafts. Meanwhile, more buoyancy is maintained during aggregated convection because of a moist layer, or shell, surrounding the convective cluster. The researchers advise that future modeling of convective organization should include simulations of this moist shell. This study sheds light on how convective systems interact with their environments and their behavior (whether by aggregating or dissipating) as they move farther skyward. ( Geophysical Research Letters , https://doi.org/10.1002/2017GL076640, 2018) —Sarah Witman, Freelance Writer

Description: Joseph B. Walsh. Credit: Benjamin Bennett Joseph B. “Joe” Walsh died on 30 August 2017 at the age of 86 in Adamsville, R.I., where he had lived for many years. Joe was well known in the rock mechanics community, although perhaps underappreciated outside it. The influence of his work is, nonetheless, broad and profound. Seismologists who interpret high velocities of compressional waves compared with those of shear waves (high Vp / Vs ratios) as indicators of high pore pressures, oil explorers who recognize oil and gas zones in tomographic images, and geophysicists identifying high permeability and water content from electrical conductivity measurements all rely on Joe’s foundational work. The reason is because these scientists are not so much measuring the properties of the rock as measuring the influence of its cracks. Joe, in a series of classic papers in the 1960s and 1970s, did the fundamental work establishing the profound effect of cracks on the elastic and transport properties of rock. By recognizing this influence, Joe was able to provide, for example, rational explanations for relationships between the constitutive relations for permeability and for electrical resistivity, to predict how increasing effective pressure changes permeability, and to understand the influence of surface roughness on joint transmissivity or the coefficient of friction. Whole fields of study are based on those beginnings. Early Career Joseph B. Walsh was born in Utica, N.Y., the son of Joseph B. and Ann (née Bowman) Walsh. He grew up in upstate New York before moving to Massachusetts to attend the Massachusetts Institute of Technology (MIT), from which between 1952 and 1958 he received bachelor’s, master’s, and doctor of science degrees in mechanical engineering. His D.Sc. work yielded a paper with Frank McClintock in which they developed what became known as the modified Griffith theory for brittle fracture in compression. After graduating from MIT, Joe spent 2 years in industry, including a stint with a consulting company in Stockholm. This job morphed into a globe-circling trip in a VW bug, ending with Joe in California, substantially poorer financially but much richer in experience. Returning to Massachusetts, he applied his skills in solid mechanics as an engineer at the Woods Hole Oceanographic Institution, where he was responsible for the design of the pressure hull for the pioneering submersible Alvin . Joe joined the Geology and Geophysics (later Earth, Atmospheric and Planetary Sciences) Department at MIT in 1963, beginning a 25-year collaboration with W. F. Brace. It was a very fruitful combination: Joe did the theory, and Bill did the experiments. The Walsh-Brace period was one of rapid development in rock mechanics on many fronts. A host of graduate students and postdocs (including most of us) were trained under their guidance, many of whom went on to productive research careers in academia and industry. Theory Grounded in Reality Joe’s papers are both succinct and eloquent. He identified the most pertinent elements of each problem and focused his analysis exclusively on those aspects. His chosen tools were pencil, paper, and the fundamental principles of mechanics. Joe arrived at work each day impeccably attired in coat, tie, and slacks. Sitting at his desk, he would dive into his cool mathematical treatments, seemingly abstract but always securely attached to reality. As a result of his training with McClintock, Argon, and others in MIT’s Mechanical Engineering Department, Joe always tested his work with experimental or observational data, thus providing a perfect interface with Brace’s group. A Taste for Conversation and Rugby At lunchtime, he could be found at a local diner, talking to machinists, custodians, or academics.Despite his analytical proclivity, Joe was not detached socially. To all who knew him, he was a quiet, unassuming man with a wry sense of humor. He liked people and had catholic tastes in his choice of company. At lunchtime, he could be found at a local diner, talking to machinists, custodians, or academics. In the evening, he might dine at one of several classic private social clubs in the Back Bay. His gentle demeanor gave no clue that in his younger years he was an avid rugby player and the founding director of the U.S. Rugby Foundation. Joe was equally at ease bantering with a surly waitress or securing a large donation for the rugby foundation from an influential industrial magnate. A Very Active Retirement Joe retired from MIT in 1986 and settled in Rhode Island. In “retirement,” Joe continued to conduct theoretical studies of fluid flow in fractured rocks and of rock friction. He was appointed visiting scholar in the Department of Earth, Environmental and Planetary Sciences at Brown University in 1999, and he continued in that capacity until his passing, having been reappointed only a few months before. Joe eagerly mined experimental rock friction data at Brown, which he used as a starting point for his analyses. Armed with his famous and formidable yellow legal pad and No. 2 pencil, Joe worked closely with experimentalists at Brown and elsewhere to establish a physical basis for rate and state friction laws. In addition to scientific interactions, Joe also educated younger scientists at Brown by his example about the importance of a proper lunch, the joys of poetry (Joe could, and did, recite many poems from memory), and the meaning of savoir faire. Joe continued his scientific work up to the time of his death. American Geophysical Union president Ralph Cicerone congratulates Joseph Walsh on being named an AGU Fellow in 1993. Credit: AGU Joe’s work often took him overseas: He served as a visiting scientist at the University of Cambridge in England; the University of Edinburgh, Scotland; and the South African Chamber of Mines in Johannesburg. Although his name is not a household word outside the rock mechanics community, Joe has been well recognized for his accomplishments. In 2007, he received the Rock Mechanics Research Award, in 2000 he was honored as a Life Fellow at the University of Cambridge, and in 1993 he was named a Fellow by the American Geophysical Union. —Christopher H. Scholz (email: scholz@ldeo.columbia.edu), Lamont-Doherty Earth Observatory, Columbia University, Palisades, N.Y.; David L. Goldsby, Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia; and Yves Bernabé and Brian Evans, Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge

Description: Declining water quality in inland and coastal systems has become, and will continue to be, a major environmental, social, and economic problem as human populations increase, agricultural activities expand, and climate change effects on hydrological cycles and extreme events become more pronounced. Providing government and nongovernment groups with timely observations on the time and location of anomalous water quality conditions can lead to more informed decisions about the use, management, and protection of water resources. By observing the color of the water, satellite sensors provide information on the concentrations of the constituents that give rise to these colors. These constituents include chlorophyll a (the primary photosynthetic pigment in phytoplankton), total suspended solids (an indicator of sediments and other insoluble material), and dissolved organic matter. Other environmentally relevant optical characteristics include turbidity and water clarity. Varieties of physical and biological phenomena can be inferred from space. This map pinpoints potential biogeochemical hot spots that require further investigations through field sampling. (left) A Landsat 8 true-color image of Boston Harbor, Mass., alongside (right) the corresponding near-surface turbidity map produced via NASA’s Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) Data Analysis System (SeaDAS). Warmer colors represent higher turbidity. The area in the top right of both images is Massachusetts Bay. Credit: NASA Goddard Space Flight Center A 1-day workshop at NASA’s Goddard Space Flight Center introduced the concept and potential capabilities of a satellite-based, near-real-time water quality monitoring tool. This tool will complement existing field monitoring programs by automatically alerting water resource and ecosystem managers to potentially hazardous water quality conditions, resulting in more timely and informed decision-making. The workshop aimed to identify the next steps toward making a satellite-based, near-real-time water quality monitoring system a reality with input and guidance from end users.The workshop brought together more than 340 environmental specialists, economists, scientists, industry representatives, and legal advisors from state and federal agencies and the private sector. The primary requirements that workshop attendees identified for developing this warning system include automated, near-real-time processing of Landsat-Sentinel imagery, the development of robust anomaly detection algorithms, and support for ongoing implementation and calibration and validation efforts. The workshop further aimed to identify the next steps toward making such a near-real-time system a reality with input and guidance from end users. The workshop featured a series of short presentations on the perspectives of end users on the potential value of satellite data for water quality monitoring. These presentations covered a broad range of topics, including monitoring harmful algal blooms in California, Utah, Oklahoma, Oregon, and Florida; identifying sites for aquacultures in New England; and concerns about pipeline leaks contaminating waterways. Other talks highlighted the need for improved satellite technology (e.g., hyperspectral missions) with sunglint mitigation strategies in the future to enable more precise and accurate estimations of water quality conditions from space. The NASA Goddard team is currently developing a prototype system for select regions to evaluate the performance of such an expedited service.The NASA Goddard team is currently developing a prototype system for select regions (e.g., Florida’s Indian River Lagoon, Lake Mead, and Oregon reservoirs) to evaluate the performance of such an expedited service. The team, in collaboration with water authorities, will initiate algorithm development, prototyping, testing, and implementation of the system. All presentations are available on the meeting’s website. The Water Quality Workshop was sponsored by the NASA Goddard Applied Sciences office. We thank Steve R. Greb, Richard Stumpf, Maria Tzortziou, and Jeremy P. Werdell for serving on the organizing committee. —Nima Pahlevan (email: nima.pahlevan@nasa.gov; @nima_pahlevan), NASA, Greenbelt, Md.; also at Science Systems and Applications, Inc., Greenbelt, Md.; Steve G. Ackleson, Naval Research Laboratory, Washington, D. C.; and Blake A. Shaeffer, U.S. Environmental Protection Agency, Research Triangle Park, N.C.

Description: Caves may be dark and eerie, but now they are a little less mysterious. That is, at least, when it comes to what happens to the atmospheric methane that enters the caves. Researchers recently completed the most extensive published study to date of methane concentrations in karst caves. Cave environments are a global sink for methane, they assert, but other scientists have voiced some reservations about that claim. Scientists conducting those initial explorations expected to find higher methane concentrations inside the caves than in the surrounding atmosphere, but they found the opposite.Karst terrains, such as caves, sinkholes, and other formations pockmarked by internal voids, form when soluble rocks such as limestone erode. The most widespread karst caves form when carbon dioxide dissolves in surface waters, creating carbonic acid that disintegrates the limestone. Caves and other karst environments underlie about 14% of Earth’s land, and it’s not well known how this terrestrial subsurface interacts with the atmosphere, said independent biogeochemist Kevin Webster of Tucson, Ariz., who led the new study and was formerly with the University of Arizona in Tucson. Methane is a potent greenhouse gas, and its concentration in the atmosphere is increasing. Scientists are tracing methane’s sources and sinks to help them understand the rate and expected amount of the gas’s accumulation in our planet’s atmosphere. Within the past decade, investigators started measuring methane levels in a few caves and associated karst landscapes. The scientists conducting those initial explorations expected to find higher methane concentrations inside the caves than in the surrounding atmosphere, but they found the opposite, according to Webster. Giuseppe Etiope measures the flux of methane from a cave surface in Kentucky. Credit: Agnieszka Drobniak To find out if methane depletion is unique to only a handful of caves, Webster and his colleagues recently measured the air inside 33 karst caves in the United States and 3 caves in New Zealand, essentially tripling the known data set. From May 2012 to September 2016, they measured methane concentrations, as well as ratios of stable carbon and hydrogen isotopes in the methane. Supporting measurements provided information on the cave air residence times and mixing processes. Thirty-five, or 97%, of the tested caves had methane concentrations lower than those in the outside atmosphere in at least one measurement location, the researchers report in the 1 March issue of Earth and Planetary Science Letters ( EPSL ). Methane Eaters So what’s happening to the methane? Earlier karst cave studies that initially observed the methane depletion proposed two main hypotheses: Methane is oxidized by ions and radicals from the radioactive decay of radon, or methane is consumed by methane-eating microorganisms. However, the researchers doing those studies couldn’t conduct all the measurements needed to distinguish between the two, Webster noted, whereas he and his colleagues made special provisions to collect the essential data. The researchers found the isotopic signature of methanotrophic bacteria, which led them to conclude that those bacteria were the cause of the methane loss.For instance, he and his team report in the EPSL paper, which was first published online on 8 January, that they measured the hydrogen isotope ratios of their methane samples, which had not been done previously in these cave environments, according to Webster. To be able to do so, Webster told Eos , the scientists custom built an inlet for a gas chromatograph–isotope ratio mass spectrometer and used the inlet to preconcentrate the methane. “Preconcentration is necessary because methane is at such low abundance in air” and even less abundant in cave air, Webster explained. Ultimately, the researchers found the isotopic signature of methanotrophic bacteria, which led them to conclude that those bacteria were the cause of the methane loss. The scientists’ novel approach also helped them to solve another mystery. It turns out that the team observed at least two sources of methane entering some of the caves: The main source was the atmosphere outside of the cave, but a minor contribution also came from two different microbial biochemistries. “That was very surprising,” said Webster, given that researchers have previously observed such processes co-occurring only in lake or fen environments. David Mattey, an isotope geochemist at Royal Holloway, University of London, in the United Kingdom, saluted the advance of using hydrogen isotopes to fingerprint different methanogenic sources. Mattey, an original proposer of the microbial depletion pathway who was not involved with the new cave study, noted that the findings by Webster and his team confirm his earlier work. To eliminate contamination, Arndt Schimmelmann fills a plastic bag with cave air to remove any air from external sources prior to collecting a cave air sample in a glass sampling container. Credit: Agnieszka Drobniak Global Sink The fact that nearly all of the studied caves consumed methane suggests to Webster that caves in general do the same. “There is nothing unusual about methane consumption in caves or the minor processes of methane production we observed,” he said. On the basis of their measurements, he and his coauthors contend in their paper that karst environments reduce methane’s atmospheric concentrations worldwide. Because the microbial sources of methane were minor, those emissions did little to offset the net loss of methane in the caves. The next step is to figure out how large the losses are, Webster said. Mattey needs more evidence. “You have to be careful claiming that it might have a global impact,” he said, “because it’s very, very difficult to upscale it from just one or two measurements.” He advised more long-term monitoring as well as reaching a better understanding of fluxes and how the caves are connected to the atmosphere. —Laura G. Shields (lgshields@gmail.com; @LauraGShields), Science Communication Program Graduate Student, University of California, Santa Cruz

Description: Like river canyons, steep-sided submarine channels are effective transportation systems capable of carrying billions of tons of sediment across distances of hundreds of kilometers. Although previous studies have shown that helical (spiraling) flow around meander bends plays an important role in transporting sediment in rivers, a lack of field measurements from deep-ocean turbidity currents has led to competing models describing their motion around curves. To settle this controversy, Azpiroz-Zabala et al. present the first deep-ocean measurements of turbidity currents around a submarine channel bend. Using an acoustic Doppler current profiler anchored downstream of a meander at a depth of 2,000 meters in Congo Canyon, the team acquired the velocity-depth profiles of 10 flows that occurred between December 2009 and March 2010. Surprisingly, despite having variable thicknesses ranging from 16 to 75 meters and durations lasting from 8 hours to 10 days, nearly all of the turbidity currents displayed the same helical flow structure. It consisted of two stacked cells rotating in opposite directions, with the bottom cell revolving in the direction opposite to helical flows observed in rivers. These results are consistent with models of other types of stratified flows and support the hypothesis that the same mechanism that forms circulation cells in other geophysical flows (such as rivers and saline flows)—the interaction of competing pressure gradients—also applies to turbidity currents. These difficult-to-obtain measurements show that the type of circulation a large-scale flow will exhibit depends upon the extent to which the current is stratified. The resulting helical flow causes the sediment to slosh from side to side, to gather at the inner bend, or to be continuously overturned. In combination with fluid turbulence, these processes keep sediment in suspension across long distances and thus play a crucial role in the ability of turbidity currents to transport enormous amounts of sediment from the continental shelf all the way to the deep-ocean floor. ( Geophysical Research Letters , https://doi.org/10.1002/2017GL075721, 2017) —Terri Cook, Freelance Writer

Description: A new scorecard that rates members of Congress on how they voted on environmental issues found that 46 Republican senators scored a 0% in 2017. The average score for all Republican senators was 1%, according to the League of Conservation Voters (LCV), a nonprofit environmental group based in Washington, D. C., that released the scorecard on Monday. This is the lowest average score for Republican senators since LCV began tracking this issue in 1970, according to the group. In contrast, 2e7 Democratic senators earned a 100% on the scorecard, with Democrats averaging 93%. The low Republican average score means that those senators “voted against the environment and public health at every opportunity,” the LCV report states. On the House side, 124 Republicans received a zero, with House GOP members overall receiving an average score of 5%. Among House Democrats, 84 earned a 100% score, and House Democrats overall earned a 94% average score. “The Republican-led Congress repeatedly refused to stand up to President Trump’s extreme antienvironmental agenda and his attacks on our air, water, land, wildlife.”“At the federal level, 2017 was an unmitigated disaster for the environment and public health, with President Trump and his cabinet quickly becoming the most antienvironmental administration in our nation’s history,” Tiernan Sittenfeld, LCV’s senior vice president for government affairs, said at a briefing on Monday to release the report. “The Republican-led Congress repeatedly refused to stand up to President Trump’s extreme antienvironmental agenda and his attacks on our air, water, land, wildlife. This is particularly shameful in a year when climate change–fueled hurricanes and wildfires caused so much devastation. Fortunately, Senate Democrats, led by Sen. Schumer”—the Senate minority leader from New York—“maintained a green firewall of defense to block any egregious events throughout 2017.” Votes That Were Counted The report graded members of Congress on the basis of specific votes that LCV and other environmental and conservation organizations determined were key indicators. On the Senate side, members were scored on how they voted in 19 instances. These included eight votes to confirm the administration’s cabinet or subcabinet nominees, whom the report labeled as “historically anti-environmental.” Among them was Environmental Protection Agency administrator Scott Pruitt. The report said that Pruitt “has aggressively gutted the agency from the inside.” Other votes counted in the scorecard were the recent tax bill that opens the Arctic National Wildlife Refuge to fossil fuel development and legislation that would threaten drinking water and public lands. An environmental voting scorecard issued by the League of Conservation Voters shows a sharp drop in Senate Republican scores between 2016 and 2017. Credit: League of Conservation Voters Sen. Whitehouse said that the low scores for Republicans in both houses “very clearly show a party that has been completely captured by the polluting industries.”In the Senate, “what this year’s results show is a dramatic crash on the Republican side of the aisle, which is in many respects a very sad testament to what has become of the GOP,” Sen. Sheldon Whitehouse (D-R.I.) said at the briefing. Only 14 Senate Republicans scored zero in 2016 compared with the 46 who did in 2017. House numbers were fairly stable, with 122 House members receiving a zero in 2016 compared with 124 with that score in 2017. Whitehouse said that the low scores for Republicans in both houses “very clearly show a party that has been completely captured by the polluting industries.” At least one Republican senator, Thad Cochran of Mississippi, paid little regard to his LCV grade of zero. “As a lifelong Republican, Sen. Cochran tends not to score highly with liberal activist groups,” a spokesperson for the senator told Eos . “Senator Cochran’s career reflects a careful understanding of the importance of protecting and preserving our nation’s natural resources. He has a strong record of making decisions on environmental issues that are in the best interests of Mississippi and our nation, and supporting legislation and policies that promote cooperative conservation programs.” Looking at Votes by Climate Caucus Members For House members, LCV graded 35 votes on issues related to public lands, climate change, water resources, clean air, deregulation of environmental rules, and other environment-relevant topics. The average environmental voting record for House Republicans falls far below that for Democrats, according to the League of Conservation Voters. Credit: League of Conservation Voters Republican House members who belong to the bipartisan Climate Solutions Caucus averaged a 16% score, which is more than 3 times higher than the overall Republican average, according to the report. However, the report concluded that members of the caucus, which was founded in 2016 to explore policy options on climate change, need to do more. “Joining the caucus can be an important step, but it’s simply not enough,” the report states. “We need these Republican members to vote for climate action, to lead on real solutions, and to push their colleagues and party leadership to do better.” “We don’t think the scorecard accurately captures the emerging work being done by the caucus to develop bipartisan solutions to climate change.”The head of a group that has worked closely with the caucus said the scorecard is valuable but that it does not provide the whole picture about the importance of the caucus. “We think the scorecard plays the essential role of providing pressure on members of Congress to do better on environmental issues, especially climate change. However, we don’t think the scorecard accurately captures the emerging work being done by the caucus to develop bipartisan solutions to climate change,” Mark Reynolds, executive director of the Citizens’ Climate Lobby (CCL), said in a statement provided to Eos . The lobby is a grassroots advocacy organization based in Coronado, Calif., that focuses on national policies to address climate change. A CCL analysis published on Wednesday found that 15 of the 34 caucus members who are Republicans improved their environmental voting scores since joining the caucus, despite the fact that only 5 of the 35 tracked votes are “climate-relevant.” “Much is happening behind the scenes, thanks to the caucus, and we think patience will eventually be rewarded with major legislation to address climate change,” Reynolds added. —Randy Showstack (@RandyShowstack), Staff Writer

Description: Earth system models contain dozens if not hundreds of parameters that are not easily definable or accurately tunable over most of the Earth, meaning these models do not fulfill their true potential as tools for simulating or predicting weather and climate. Ricciuto et al. [2018] extend the mathematical technique called Polynomial Chaos (PC), a method to determine uncertainty in dynamical systems, with a new Bayesian compressive sensing (BCS) algorithm to applications at very high dimensions like those found in complex Earth system models. Interesting applications, such as sensitivity analysis, parameter optimization and distribution estimation are possible. With the help of PC-BCS, the sensitivity indices within models can be directly computed, and is demonstrated to be a more effective means of optimizing the land surface parameters of the Energy Exascale Earth System Model (E3SM). Citation: Ricciuto, D., Sargsyan, K., & Thornton, P. [2018]. The impact of parametric uncertainties on biogeochemistry in the E3SM land model. Journal of Advances in Modeling Earth Systems , 10. https://doi.org/10.1002/2017MS000962 —Paul A. Dirmeyer, Editor, JAMES

Description: Rooftop gardens. Seedlings sprouting on windowsills. The clucking of chickens in a metropolitan backyard. These and more are small harbingers of the expansion of urban agriculture around the world. More than half of the world’s population lives in cities, a figure that the United Nations expects to increase to 67% by 2050—yet urbanized land makes up just 1% of the Earth’s surface. Because of this, urban planners are working to make cities more resilient, habitable, and adaptable to change. In a new paper, Clinton et al. have developed a framework to estimate the environmental benefits of urban agriculture on a global scale—current and future. The team envisions a scenario in which over the next few decades, cities around the world adopt intensive efforts to expand urban agriculture. Using Google Earth Engine, a free platform for processing global satellite data, the researchers analyzed data sets on population, urban landscapes, meteorology, terrain, and food and agriculture. They developed national estimates for the entire globe of ecosystem services provided by urban agriculture, finding that existing vegetation in urban areas provides the equivalent of about $33 billion each year. In more specific terms, the team estimates that urban agriculture, if deployed across all available vacant land, rooftops, and building façades, could produce 100–180 million tons of food, save about 14–15 billion kilowatt hours of energy, sequester 100,000–170,000 tons of nitrogen, and offset roughly 2 trillion cubic feet of storm runoff each year. Projected out, the researchers estimate that dramatically increasing urban agriculture efforts around the globe has the potential to positively influence food production, nitrogen fixation, energy savings, pollination, climate regulation, soil formation, and the biological control of pests, services that are worth, as a whole, as much as $160 billion. The team’s findings show that urban agriculture has the ability to improve food security and ecosystem health on a global scale. Although its impacts vary from country to country, the results are promising. This study is a thorough look at the importance of urban agriculture, especially in the face of global climate change and unsustainable urban development practices around the world. ( Earth’s Future , https://doi.org/10.1002/2017EF000536, 2018) —Sarah Witman, Freelance Writer

Description: In 2017, more than 200 students participated in the Virtual Poster Showcase (VPS), a program of the American Geophysical Union (AGU) that is designed to help students share research without traveling to an in-person conference. This program has been continually advancing in size and scope since it was created in 2013. Embellishments added last year helped to scale up the program as well as to add value for participants.Four embellishments added to VPS in 2017 helped to scale up the program as well as to add value for the student participants and their faculty and research advisers. A year ago, two high school instructors helped pilot the participation of 21 groups of high school juniors and seniors in VPS. Some of these students stated that they expected the experience to strengthen their college applications. A university instructor incorporated VPS into the curriculum of her spring graduate course in science communication. This meant that all aspects of the VPS process (abstract submission, poster creation, a video presentation of the student’s project, participation in a peer evaluation component, and responses to feedback from professionals serving as judges) were considered for the students’ final grades in the course. As part of a partnership between AGU and the American Geosciences Institute, all 447 VPS abstracts from 2015 onward are now available and searchable within GeoRef, the world’s largest database of geoscience abstracts. A geographic information system (GIS) map of all VPS participants, their abstracts, and the location of each lead author’s institution has been created to share the abstracts with the entire Earth and space science community. This GIS visualization is a project between University of Texas at El Paso professor Raed Aldouri and his GIS class. The link will be publicized in the coming weeks after all the 2017 abstracts have been added to the GIS. Global Participation In 2017, VPS offered spring and fall showcases that have continued to draw students from around the globe. For the third year in a row, the fall showcase attracted U.S. undergraduate students who had completed summer research programs known as Research Experience for Undergraduates (REUs). The National Science Foundation funds those programs nationwide. VPS is not just for those in the United States or just for undergraduate students. Nearly half of the participants in VPS’s 2017 events were graduate students from around the world. Overall, VPS’s non-U.S. participants in 2017 came from 15 countries and five continents. Building Student Confidence Taking part in the Virtual Poster Showcase continues to increase students’ confidence levels in preparing and presenting posters.Taking part in the Virtual Poster Showcase continues to increase students’ experience with preparing and presenting research. Nearly four out of five students in the 2017 showcases reported a boost in confidence in their poster preparation and presentation skills. Survey respondents also said that having a VPS abstract will ultimately help them in the next steps of their careers. During the two VPS events in 2017, presentations featured a wide array of research that spanned many subdisciplines within the Earth and space sciences, from environmental degradation caused by zinc smelting to modeling solar wind parameters in the Martian atmosphere. The first-place winners of the spring and fall showcases are listed below. Information about other winners can be found on the Virtual Poster Showcase recognition page. Spring 2017 winners: Graduate showcase: Babak Jalalzadeh Fard, Northeastern University, “Effective mitigation and adaptation strategies for public health impacts of heatwaves for Brookline, MA” Undergraduate showcase: Jacob Smith, Clemson University, “The effect of atmospheric CO2 on the chemical weathering of silicate minerals as measured by cation flux in the vadose zone” High school showcase: Hannah Kim, Thomas Jefferson High School for Science and Technology, “The effect of disease resistance on the bacterial community of the fecal microbiome of Crassostrea virginica ” Fall 2017 winners: Graduate showcase: Ruadhan Magee, University of Queensland, Australia, “Magma dynamics recorded in clinopyroxene megacrysts: Investigating the destructive 1669 eruption of Mount Etna” Undergraduate showcase: Caitlin Hoeber, San Jose State University, “Spatial and temporal effects on diversity of Monterey Bay’s microbiome” Each first-place winner of the graduate and undergraduate showcases will receive a travel grant to attend the 2018 AGU Fall Meeting in Washington, D. C., along with complimentary meeting registration. Spring Showcase Open for Abstracts Register and submit your abstracts today.The 2018 spring showcase is accepting abstracts until Tuesday, 13 March, 11:59 p.m. Eastern Time. VPS offers an excellent means for students to share their research and get valuable feedback from their peers and professionals in the Earth and space sciences. Register and submit your abstracts today at http://vps.agu.org, or message vps@agu.org to learn more about how you can participate in future showcases. To everyone who helped make VPS a continued success this past year, AGU’s Virtual Poster Showcase staff offers its heartfelt thanks. It is only through the generous volunteerism of professionals who sign up as VPS judges and through the VPS program’s collaborations with other professional societies and individuals within the scientific community that the VPS program can continue to strive toward AGU’s mission of advancing Earth and space science. —Pranoti M. Asher (email: pasher@agu.org), Manager, Higher Education, AGU; and Nathaniel Janick, Career Services Coordinator, AGU

Description: The 2017 hurricane season was especially severe in the Northern Hemisphere. When Hurricane Harvey hit Houston, Texas, in August, so much water fell on the city that the ground sank beneath the weight of it. Hurricane Irma followed closely on its heels, and Puerto Rico is still reeling from Hurricane Maria, which swept through in late September. There is no doubt that swiftly and accurately measuring hurricane conditions to predict their behavior before landfall could safeguard lives—and lifesaving infrastructure. With this goal in mind, Foti et al. demonstrate a new satellite remote sensing technique that uses reflected GPS signals to measure ocean wind speeds during hurricanes. The Global Navigation Satellite System–Reflectometry (GNSS-R) technique takes measurements of Earth surface conditions by reading GPS signals after they bounce off Earth’s surface. This method can sense many surface properties like ocean roughness, wind speed, soil moisture, and sea ice. A previous study used this technique to record hurricane winds from an aircraft, but the new research shows that the same technique also works from satellite altitudes to sense ocean surface roughness in hurricane wind conditions. To prove that the technique was sensitive enough to be used from space, the researchers used data from a GNSS Receiver Remote Sensing Instrument mounted onto a satellite 635 kilometers above the ocean. For this study, the scientists used data collected between May 2015 and October 2016, during which time Hurricane Joaquin, Hurricane Jimena, and Typhoon Chan-hom occurred. The researchers compared the GNSS-R satellite measurements with data from other sources, including tropical cyclone best track data from the National Oceanic and Atmospheric Administration’s National Centers for Environmental Information; two climate reanalysis products; and a spaceborne scatterometer, a tool that uses microwave radar to measure winds near the surface of the ocean. They found that the GNSS-R satellite data successfully sensed wind speed conditions in each hurricane compared with these other data sources. They also captured rapid changes in wind speed that occur around the eye of the cyclone, which did not appear to be affected by any data loss, like what can be caused by heavy precipitation in other satellite data. There are still uncertainties, however. The wind speed algorithm the scientists used was developed for low to moderate winds, below 67 miles per hour (30 meters per second). As a result, the authors conclude that the GNSS-R technique needs further validation at high wind speeds. Although the GNSS-R technique could improve wind speed measurements and hurricane research in the future, the scientists conclude that more work needs to be done to develop the technique and improve the accuracy of the high wind speeds it measures. ( Geophysical Research Letters , https://doi.org/10.1002/2017GL076166, 2017) —Alexandra Branscombe

Description: A congressional panel yesterday heard testimonies about the impact of and fight against sexual harassment in the sciences. Four women prominent and successful in their fields spoke about the need to reform not just the laws but also a harmful culture that considers such behaviors permissible and fosters systemic inequity. The entire scientific community, especially those in leadership positions, must strive to change a culture that treats harassment as commonplace.“We talk a lot about getting more women in the sciences,” said Rep. Suzanne Bonamici (D-Ore.), but “we need to be able to keep them there when they get there.” Bonamici sits on the Subcommittee on Research and Technology of the House Committee on Science, Space, and Technology, which held the hearing. According to the witnesses, antiharassment policies must grow more comprehensive and include more input from experts; findings and procedures require greater transparency, and violations must provoke tangible consequences. Overall, the entire scientific community, especially those in leadership positions, must strive to change a culture that treats harassment as commonplace, they said. “We cannot afford to lose another brilliant scientist because she did not feel safe in her lab,” said Rep. Daniel Lipinski (D-Ill.), ranking member of the subcommittee. Clarity, Transparency, and Informed Policy Making No standard harassment policy prevails at American universities and research institutions, nor is there a consistent definition of what actions constitute harassment, some witnesses noted. The four witnesses who testified before the House Subcommittee on Research and Technology on 27 February. From left to right are Rhonda Davis, Kathryn Clancy, Kristina Larsen, and Chris McEntee. Credit: House Committee on Science, Space, and Technology Kathryn Clancy, an associate professor of anthropology at the University of Illinois at Urbana-Champaign, explained that antiharassment policies need to be explicit about acceptable and unacceptable behaviors, easily accessible to all, and taught as part of standard workplace training. They also need to address the problems actually occurring in that workplace, said Clancy, who conducts research on workplace climate in the sciences. “We need to do a lot more of the hard work, not just slapping on a policy and saying ‘OK, sexual harassment is fixed,’” Clancy said. Scientific institutions should ask themselves, “What is the culture at our organization, and is this the culture that we want?” she added. Attorney Kristina Larsen told the subcommittee that many antiharassment policies focus mainly on legality and the potential for litigation, instead of addressing more prevalent, but technically legal, smaller harassments. Larsen represents women and underrepresented minorities in science, technology, engineering, and mathematics (STEM) fields who are facing discrimination, harassment, and retaliation. “Don’t write a zero-tolerance policy until you’re really clear on what you’re not tolerating,” she advised in her testimony. We need to base policies on “the conduct that is actually damaging” to victims and not worry “about whether it is legal or illegal under the law,” she said. Fieldwork Amplifies Problems Field research conducted far from a formal academic environment increases the need to have clear and explicit ethical policies and codes of conduct, said Chris McEntee, executive director and CEO of the American Geophysical Union, publisher of Eos . “A very small number of people, who were actually harassed, even knew what the reporting mechanism was” at field sites.“The Earth and space sciences typically involve remote field settings,” she noted in her testimony. “When coupled with a male-dominated environment and power structure, these situations can amplify the problem.” Clancy highlighted that field research brings added uncertainty about antiharassment policies. “In field sciences, we found that the majority of our respondents were not aware of a code of conduct or sexual harassment policy for their field site. And [only] a very small number of people, who were actually harassed, even knew what the reporting mechanism was,” she said. Principal investigators, supervisors, and field site directors should develop and enforce implicit and explicit codes of conduct and bear responsibility for them, she added. Making Consequences for Harassers Real Witnesses and members of Congress at the hearing lauded the National Science Foundation (NSF) for its 8 February decision requiring grant-seeking universities to maintain clear antiharassment policies and to report policy violations to NSF. “No taxpayer dollars should be awarded to a university researcher who engages in harassment and inappropriate behavior toward a colleague or student under their charge,” Rep. Lamar Smith (R-Texas), who chairs the House Committee on Science, Space, and Technology, said during yesterday’s hearing. Subcommittee chairwoman Barbara Comstock (left) speaks with witness Rhonda Davis of NSF (right) after the hearing. Credit: Kimberly M. S. Cartier Rhonda Davis, head of NSF’s Office of Diversity and Inclusion, who also testified at the hearing, noted that NSF’s new guidelines were prompted by the fact that American universities do not have a universal ethics policy regarding sexual or other types of harassment or any requirement for universities to develop such policies beyond the scope of federal protections, like Title IX. Consistent and visible enforcement of antiharassment policy will help mitigate the harassment “epidemic,” said Clancy, citing her research. “Across workplaces, it’s consistent that if you have consequences…you do see less harassment in those workplaces,” she explained. The fear of backlash for reporting harassment falls on the targets of harassment, not the harassers, said McEntee, who encouraged sanctions against harassers for violating ethics policies. “People don’t change because they feel the light; people change because they feel the heat.”“People don’t change because they feel the light; people change because they feel the heat,” said Larsen. “And there is no heat in academics….We have a problem with enforcement.” Davis said that NSF’s new policy includes independent and anonymous avenues for anyone, including students, to report harassment directly to NSF, which may reduce the fear of backlash. Culture Change Needed All of the witnesses called for culture change in the scientific community, where, they said, harassment is allowed to persist and is deemed tolerable. “Let’s move away from a culture of compliance and towards a culture of change,” Clancy said, by “focusing on the behaviors we want to see.” “I see you, and I think of you, and I thank you for getting up every day, and I derive strength from you.”Clancy and McEntee called for more well informed training in how to recognize harassing and harmful behavior and how to safely diffuse a situation from the outside. This type of bystander intervention, especially from those in leadership positions, they explained, would have a twofold effect: first, showing the harasser that such behavior is not acceptable or tolerated in the workplace and, second, demonstrating that vulnerable persons are visible, heard, and supported by those with the power to effect change. Speaking directly to victims of sexual harassment, Clancy added, “I see you, and I think of you, and I thank you for getting up every day, and I derive strength from you. I hope you know how much you mean to those of us who do this work.” —Kimberly M. S. Cartier (@AstroKimCartier), News Writing and Production Intern

Description: New details released yesterday about the administration’s $7.47 billion funding request for the National Science Foundation (NSF) for fiscal year (FY) 2019 show that proposed budgets related to the geosciences are slated for two of the three biggest monetary and percentage increases among the agency’s major funding accounts. The Directorate for Geosciences (GEO) requests $853 million, a 3.3% increase above the FY 2017 spending level. The Office of Polar Programs, which operates as part of GEO, gets a 14.3% boost, bringing its requested funding to $534.5 million. This assumes that Congress goes along with the White House’s request. The budget request “would allow NSF to build on the important work done by our directorates within individual fields by encouraging convergence among different disciplines in science and engineering.”Only the budget for NSF’s Office of Integrative Activities fares better among the agency’s major accounts. The office’s $537 million requested budget, a 27.7% increase, includes funding for midscale research infrastructure and for several new areas known as “convergence accelerators,” which are initiatives to leverage resources across the agency to support innovative science. This information (see Table 1) updates earlier budget materials released by NSF on 12 February. The budget request “would allow NSF to build on the important work done by our directorates within individual fields by encouraging convergence among different disciplines in science and engineering and collaboration with partners in different disciplines in science and engineering and collaboration with partners in different sectors,” NSF director France Córdova said in a statement. “Investments that incorporate such an approach will accelerate U.S. innovation.” Table 1. National Science Foundation’s FY 2019 Budget Request to Congressa   FY 2017 Actualb FY 2019 Requestb Changeb Percentage Change Research and Related Activities 6,006.5 6,150.7 144.2 2.4 Geosciences (GEO) 825.6 853.0 27.4 3.3 Office of Polar Programs (OPP) 467.9 534.5 66.7 14.3 Biological Sciences (BIO) 742.2 738.2 −4.1 −0.5 Computer and Information Science and Engineering (CISE) 935.9 925.4 −10.5 −1.1 Engineering (ENG) 930.9 921.4 −9.5 −1.0 Mathematical and Physical Sciences (MPS) 1,362.4 1,345.3 −17.1 −1.3 Social, Behavioral, and Economic Sciences (SBE) 270.9 246.2 −24.7 –9.1 Office of International Science and Engineering (OISE) 49.0 48.5 −0.5 −0.9 Integrative Activities (IA) 420.3 536.7 116.5 27.7 U.S. Arctic Research Commission 1.4 1.4 0.0 −0.7 Education and Human Resources 873.4 873.4 0.0 0.0 Major Research Equipment and Facilities Construction 222.8 94.7 −128.1 −57.5 Agency Operations and Award Management 382.1 333.6 −48.4 −12.7 National Science Board 4.3 4.3 0.1 1.2 Office of Inspector General 15.1 15.4 0.3 1.7 Total, NSF 7,504.1 7,472.0 −32.1 −0.4 aSources: “National Science Foundation FY 2019 Budget Request to Congress” and “Summary Table.” bValues in millions of U.S. dollars, rounded to the nearest $0.1 million. A Look at the Geosciences Budget In the FY 2019 request, funding for the geosciences does well overall, although some divisions within GEO decline about 6% (see Table 2). “GEO supports the [budget] request and is confident that it will allow significant advancement of knowledge about how the Earth works” and in other specific programs, GEO directorate head William Easterling told Eos. However, “with an overall NSF budget that is flat from FY17, and with the priorities of investing in [other NSF initiatives], some reductions in other areas are inevitable.” As part of a whopping 37.4% increase, GEO’s Division of Integrative and Collaborative Education and Research would receive $30 million to fund the Navigating the New Arctic (NNA) program. NNA would establish an observing network “to document and understand the Arctic’s rapid biological, physical, chemical, and social changes,” according to NSF budget documents. The agency’s proposed budget includes funding for 10 “big ideas,” which are programs at the frontiers of science and engineering that the agency has selected for investment.NSF calls NNA a “big idea.” In all, the agency’s proposed budget includes funding for its 10 big ideas, which are programs at the frontiers of science and engineering that the agency has selected for investment. In addition to NNA, GEO programs contribute to several other big ideas funded by other agency divisions: Harnessing the Data Revolution for 21st Century Science and Education (funded at $30 million), Understanding the Rules of Life ($30 million), and INCLUDES (Inclusion across the Nation of Communities of Learners of Underrepresented Discoverers in Engineering and Science; $20 million). “Virtually all areas of research supported by GEO are needed to advance the Big Ideas (NNA and others) and so we see broad opportunities for the Geosciences community within those investments,” Easterling told Eos . Table 2. Directorate for Geosciences Budget Request for FY 2019 a FY 2017 Actualb Revised FY 2019 Requestb Changeb Percentage Change Atmospheric and Geospace Sciences (AGS) 253 239 −14 −5.6 Earth Sciences (EAR) 179 169 −10 −5.5 Integrative and Collaborative Education and Research (ICER) 76 105 29 37.4 Ocean Sciences (OCE) 317 340 23 7.2 Total 826 853 27 3.3 aSources: “National Science Foundation FY 2019 Budget Request to Congress” and “Directorate for Geosciences.” bValues in millions of U.S. dollars, rounded to the nearest million. In a budget proposed to go up 7.2%, GEO’s Division of Ocean Sciences (OCE) receives $174.8 million for infrastructure and $40 million for the Ocean Observatories Initiative. The ocean sciences also will benefit from a $28.7 million request for the $255.6 million Regional Class Research Vessel project, which is included in NSF’s Major Research Equipment and Facilities Construction funding account. However, the envisioned FY 2019 funding supports construction of only two of three regional class research vessels for which Congress appropriated money in FY 2017. “In FY 2017, [Public Law] 115-31 appropriated $121.88 million in funding to facilitate the planning and construction of three vessels. In the context of the President’s overall fiscal goals intended to maintain spending restraint, this Budget Request supports construction of the two vessels,” NSF budget documents note. Easterling expressed satisfaction with the proposed GEO budget despite some expected belt-tightening in certain areas. The proposal “will allow investments in NSF’s Big Ideas to begin, and it will allow important investments in research infrastructure through the start of modernization of McMurdo Station and through commitment to a second Regional Class Research Vessel for modernizing the academic fleet,” Easterling said. Polar Funding The Antarctic infrastructure project is “a necessity for maintaining U.S. scientific and geopolitical eminence across the continent of Antarctica.”For its Office of Polar Programs (OPP), the NSF funding proposal includes $420.2 million for infrastructure, an increase of 21.3%. That includes $103.7 million in FY 2019 for the Antarctic Infrastructure Modernization for Science (AIMS) construction project. In the budget document, the agency describes the $355 million project, which will modernize major facilities at McMurdo Station, as “a necessity for maintaining U.S. scientific and geopolitical eminence across the continent of Antarctica.” OPP director Kelly Falkner told Eos that “we would be delighted to take [on] the long-needed, major overhaul of McMurdo Station to set the [U.S. Antarctic Program] on a more robust, sustainable pathway.” —Randy Showstack (@RandyShowstack), Staff Writer

Description: Jules Verne’s adventure novels Five Weeks in a Balloon and Around the World in 80 Days highlighted some of the great technological advances of the late 19th century that revolutionized travel and captured the imagination of the public [ Verne, 1863, 1873]. Among those inspired by the novels was Nellie Bly, an American journalist for the New York World , who set off in November 1889 to complete a journey by rail and steamship, following Verne’s imagined path around the world in a record 72 days [ Bly, 1890] (Figure 1). Fig. 1. In 1889–1890, real-life New York World reporter Nellie Bly completed Jules Verne’s imagined path (shown here) around the world in slightly less than Verne’s “80 days.” Neither Bly’s journey nor Verne’s Around the World in 80 Days actually involved balloon travel, but Verne’s book drew on his previous novel Five Weeks in a Balloon. The earlier novel inspired the idea of incorporating balloon travel for one leg of the trip in the 1956 movie Around the World in 80 Days that has become a beloved misconception about Verne’s later book. Credit: Roke/Wikimedia Commons CC BY-SA 3.0 Bly’s accounts demonstrated how new technology, such as the transcountry railroads in the United States and India and the Suez Canal, brought exotic destinations within reach. The revolutionary development of submarine cables and the electric telegraph allowed Bly to keep her editors, and the larger connected world, aware of her progress in near-real time. The France-U.S. collaborative Stratéole 2 project is planning its own series of balloon trips, which will circle the world near the equator for 80 days (more or less), as did these fictional and factual 19th century adventurers, demonstrating new technology and sending new observations from the voyage back via satellite. Drifting with the Winds Scientists with the Stratéole 2 project will release superpressure balloons, designed to drift in the lower stratosphere, from the Seychelles islands in the Indian Ocean (Figure 2). Superpressure balloons contain a fixed amount of helium sealed inside an envelope that does not stretch. This type of balloon is not fully inflated when it is launched, but it expands to its full volume as it rises to an altitude where the gas density inside the balloon matches the density of the surrounding air and where it drifts with the wind. Fig. 2. Early test flights of the French National Center for Space Studies superpressure balloon system during February–May 2010 followed a tropical route. The flight durations of the three balloons were 92, 78, and (yes!) 80 days. The traces of the balloon paths show some wave structure, and the balloon paths reversed direction when the quasi-biennial oscillation, a periodic east–west oscillating feature in tropical lower stratospheric winds, changed phase. Credit: A. Hertzog Each balloon will carry as many as four instruments. As they collect their high-accuracy measurements of meteorological variables, chemical tracers, clouds, and aerosols, their horizontal motions are nearly identical to those of the surrounding air mass. These measurements will advance our knowledge and understanding of cirrus clouds, aerosols, and equatorial waves in the tropical tropopause layer (TTL; the transition region between the troposphere and the stratosphere) and in the lower stratosphere. Shown here is a fully inflated superpressure balloon in the lab at the French National Center for Space Studies (CNES). Credit: Philippe Cocquerez, CNES The Stratéole 2 research program will begin with a five-balloon technology validation campaign in Northern Hemisphere (boreal) fall–winter 2018–2019, followed by 20 balloon flights in boreal fall–winter 2020–2021. In the second campaign, 10 balloons will fly at an altitude near 20 kilometers, just above the TTL, and another 10 will fly near 18 kilometers, within the TTL. From past experience, we expect each balloon to fly for more than 2 months. Typically, a balloon will fly for about 84 days before chaotic atmospheric motions or interactions with Rossby waves push it outside of the deep tropics. A final 20-balloon campaign in 2023–2024 will drift in the opposite direction because of the shifting phase of the quasi-biennial oscillation (QBO), a dominant, periodic east–west oscillating feature in tropical lower stratospheric winds. Challenges Aloft The Stratéole 2 campaign targets the TTL, the primary entry point for tropospheric air into the stratosphere. As air slowly ascends across the TTL, the coldest temperatures encountered at the cold point tropopause (CPT) freeze water vapor into ice crystals. The formation of ice crystals dehydrates the air and regulates the amount of humidity reaching the global stratosphere, giving the TTL an outsized importance considering its geographic extent. The ice crystals form thin cirrus clouds, which have a global impact on the balance between incoming solar radiation and radiation reflected back into space at tropical latitudes. Water vapor and cirrus feedbacks are extremely important in climate system models. The underlying processes that control the formation and sublimation (direct conversion of ice crystals to water vapor) of these clouds remain strongly debated. These processes involve the interplay of deep convection, microphysics, aerosols, wave-induced temperature variations with timescales ranging from minutes to weeks, and the balance of forces driving large-scale slow ascent of air in the tropics. The superposition of wave-induced fluctuations on the average upwelling motion forces the temperatures in the TTL to extreme values at the CPT—less than –94°C at times and well below those expected from radiative equilibrium. These same waves also drive the QBO, which has an important long-range indirect influence on high-latitude seasonal forecasts. The waves, generated by convection below, transport momentum vertically across the TTL and drive QBO wind variations as the momentum dissipates in the stratosphere. Satellite and in situ observations can track the wind reversals of the QBO, but most general circulation models cannot replicate the QBO using current methods. This shortcoming is due to a combination of inadequate spatial resolution and a lack of small-scale wave drag applied at the subgrid scale. Even when models do simulate the QBO, doubts remain on the contribution from various families of waves with different scales and frequencies. As a result, even models that internally generate a QBO were unable to forecast the anomalous disruption of the oscillation that occurred in February 2016 [ Osprey et al., 2016]. Science Objectives This superpressure balloon, shown here at launch, is not fully inflated. As it rises, the volume of helium sealed inside increases until the spherical balloon is fully inflated, giving the balloon a fixed density. Once the balloon has reached the atmospheric level where the air has the same density, it drifts with the wind, providing accurate wind measurements. Credit: Philippe Cocquerez, CNES The overarching objectives of Stratéole 2 are to explore processes that control the transfer of trace gases and momentum between the equatorial upper troposphere and lower stratosphere. The instruments will provide fine-scale measurements of water vapor, temperature, and aerosol/ice at the balloon gondola and also within several kilometers below flight level, documenting air composition and investigating the formation of cirrus in the upper TTL. The balloons also provide unique measurements of equatorial waves over the full spectrum from high-frequency buoyancy waves to planetary-scale equatorial waves, providing information needed to improve representation of these waves in climate models. Stratéole 2 balloons will sample the whole equatorial band from 20°S to 15°N, thus complementing the widespread (but limited-resolution) spaceborne observations and the high-resolution (but geographically restricted) airborne and ground-based measurements from previous field missions. Past balloon campaign measurements sampling the Antarctic stratospheric vortex [see Podglajen et al., 2016] have been used to make accurate estimates of wave momentum fluxes as well as to explain springtime stratospheric ozone loss rates; we expect similar successes with our current campaigns. Stratéole 2 balloon flights will collect measurements over oceanic areas that are otherwise devoid of any stratospheric wind measurements.Other Stratéole 2 science objectives include contributions to operational meteorology and satellite validation. Wind analyses and forecasts have notably large errors in the tropics because sparse tropical wind measurements cannot be modeled in a straightforward way through their dynamical relation to temperature, as they are at higher latitudes. Thus, reducing these errors requires a higher density of measurements. Stratéole 2 balloon flights will address this data shortage by providing unprecedented, accurate wind observations in the equatorial regions of the upper troposphere and lower stratosphere. In particular, the project will collect measurements over oceanic areas that are otherwise devoid of any stratospheric wind measurements. The data will also contribute to the validation of Atmospheric Dynamics Mission Aeolus (ADM-Aeolus) wind products. An innovative European Space Agency mission, ADM-Aeolus, due to be launched in September 2018, is designed to perform the first spaceborne wind lidar measurements, providing unprecedented global coverage. The ensemble of Stratéole 2 instrumentation includes in situ measurements of pressure, temperature, and winds every 30 seconds and less frequently sampled observations of ozone, aerosols, water vapor, and carbon dioxide, plus remotely sensed cloud structure from microlidar and directional radiative fluxes. Instruments providing profiles will include GPS radio occultation receivers that measure temperature profiles to the side of the balloons. Novel reel-down devices suspended as far as 2 kilometers directly below the balloons will also provide profiles to explore the fine-scale distribution of temperature, aerosol/ice, and humidity. Capturing temperature variations in high-resolution profiles, in particular, from the unique balloon platform, is an approach that will provide new insight into equatorial wave processes. Measuring ozone in combination with water vapor and carbon dioxide enables us to discover correlations among these tracers that describe transport processes at the top of the TTL, including convective overshoots that rapidly transport air from the surface into the TTL. Data Dissemination Within 12 months of the end of each balloon campaign, the Stratéole 2 data set will be freely available to the scientific community.The Stratéole 2 data policy is in compliance with World Meteorological Organization (WMO) Resolution 40 (WMO Cg-XII) on the policy and practice for the exchange of meteorological and related data and products. Within 12 months of the end of each balloon campaign, the Stratéole 2 data set will be freely available to the scientific community through the Stratéole 2 Data Archive Center (S2DAC), which is scheduled to launch its website in July 2018. S2DAC will collect and make available the balloon observations and associated ground-based and satellite data, reanalyses, and model outputs. The S2DAC includes a primary, full repository at the Dynamic Meteorology Laboratory (LMD) in France and a secondary mirror site at the Laboratory for Atmospheric and Space Physics (LASP) in Boulder, Colo., in the United States. In addition, during the balloon campaigns, a subset of the Stratéole 2 data set, specifically flight-level winds, will be disseminated on the Global Telecommunication System for their assimilation in numerical weather prediction systems. We invite and encourage the use of Stratéole 2 data by the broader scientific community, and potential users can watch for future campaign updates on the project website. Up, Up, and Away In the spirit of Verne’s imagined use of new technologies and Bly’s real-world application of those technologies to explore the world, the Stratéole 2 campaign will scientifically explore the tropical tropopause and lower stratosphere from a long-duration superpressure balloon platform. The use of multiple balloons will permit extensive exploration of the finely layered features and unique processes occurring in this remote part of the atmosphere. With the involvement of the broader scientific community, analyses of the Stratéole 2 measurements hold promise to provide a new and deeper understanding of these processes and the connections of this region to global chemistry, dynamics, and climate variability. Acknowledgments Major funding for the Stratéole 2 campaign is provided by France’s National Center for Space Studies (CNES) and National Center for Scientific Research (CNRS), as well as the U.S. National Science Foundation (NSF).

Description: Many of the natural disasters that make the news headlines are related to extreme or unusual weather events. In an open-access article recently published in Reviews in Geophysics , Steptoe et al. [2018] examine extreme atmospheric hazards effecting different countries and regions around the world, and their connections with the global climate system. The editor asked the authors to explain more about these hazards and describe how scientific insights can be used by governments, communities and corporations involved in disaster risk reduction. What do you mean by “extreme atmospheric hazards”? Extreme atmospheric hazards are high impact weather events, typically judged by human or financial losses, caused by processes occurring in the Earth’s atmosphere. The atmospheric processes responsible for extreme events are themselves often influenced by some other large-scale component of the Earth’s atmosphere-ocean system, such as ocean-wide changes to sea-surface temperatures. Why is it important to understand regional extreme atmospheric events in the wider context of large scale atmosphere-ocean processes? In atmospheric science, the links that connect large scale changes in the atmosphere or ocean (such as widespread changes in temperature or humidity in an ocean basin) with localized hazards relating to regional weather conditions (such as extremes of rainfall or temperature) are collectively referred to as teleconnections. Most local extreme events may be related to temporal changes in the large scale dynamics of the climate system. Large scale changes are predicted by weather and climate models more skillfully than local extremes so understanding the link is vital to understanding impacts. There are many different kinds of teleconnection, typically named after the geographic location in which they are observed. Because any one teleconnection may influence weather conditions in multiple remote locations, understanding the interplay between regional extremes and teleconnections helps us to understand how different extreme hazards occurring in widely separate locations can have a common origin. In our review, we examined 16 different regional hazards and their interplay with eight different teleconnections. Connections between 10 key drivers of global weather and climate (acronyms around left of circle in bold) and 16 regional extreme weather events (right). Credit: Steptoe et al., 2018, Figure 3 Can you give a specific example of a regional atmospheric hazard and its connection to global teleconnections? In our review, we find that rainfall over China shares the most connections with global drivers. We summarized academic papers that have identified links to six teleconnections including large scale atmosphere-ocean processes in both Northern and Southern Hemispheres. The regional hazard with the strongest single linkage to a teleconnection are windstorms over Europe, and their connection to the North Atlantic Oscillation (NAO). The NAO describes a varying pattern in surface pressure across the North Atlantic. For European windstorms, the NAO pattern has a strong steering effect on winds high in the atmosphere, which in turn influences the path stormy weather takes as it approaches Europe. Which is the most significant process that influences multiple hazards across different regions at the same time. Our investigation finds that El Niño–Southern Oscillation (ENSO) influence 15 regional hazards. ENSO describes variations in sea-surface temperatures in the equatorial Pacific. In some cases, this connection is relatively well understood (for example, the way it influences rainfall over South Africa) and in other cases work is still being carried out to better understand the connection (such as its influence on Mexican rainfall). How does a scientific understanding of these teleconnections help to understand the risks and prepare for extreme events? Extreme events are the occasions that pose the greatest risk to communities and livelihoods. Hence, understanding the sorts of climatic situations where extremes events are more likely to happen represents one important facet of disaster risk management. By understanding the teleconnections and their associated hazards, it becomes possible to develop mitigation methods tailored to, and in advance of, potential risks. For example, the relationship between rainfall in South and Southeast Asia is driven by connections with the Indian Ocean Dipole (IOD) and ENSO. Understanding this complex relationship may offer a predictive insight into rainfall and potential hazards, such as flood or drought, for the coming season. This predictive insight in one aspect the scientific community can contribute to in order to enable advanced planning to mitigate against potential risks. How may these insights influence organizations to better plan for, and respond to, multi-hazard risks? Atmospheric science makes an important contribution to understanding hazard risk in areas such as California which is susceptible to wildfires. Credit: U.S. Forest Service International policies reflect the growing understanding of atmospheric hazards and their interconnectivity. Throughout the UN Sendai Framework for Disaster Risk Reduction 2015 – 2030, multi-hazard resilience is a consistent theme, reflected in guidance towards “inclusive and risk-informed” decision making and in the context of managing disaster risk effectively. In practice, these insights have contributed to multi-hazard approaches being adopted in early warning systems across the globe. The Regional Integrated Multi-Hazard Early Warning System for Africa and Asia (RIMES) provides monitoring and data services to local tsunami centers and national meteorological services, as well partnering with research organizations on projects implementing early warning systems in-country, such as early flood warning in Bangladesh. For private sector groups, such as the insurance industry, knowledge of the relationship between teleconnections and hazards can be vitally important when underwriting exposure, as it may increase their risk of multi-hazard losses across different regions. —Hamish Steptoe, Met Office, UK; email: hamish.steptoe@metoffice.gov.uk; Sarah Jones, JBA Risk Management, UK; and Helen Fox, Office for National Statistics, UK

Description: Environmental remediation efforts in low- and middle-income countries have yet to be evaluated for their cost effectiveness. To address this gap we calculate a cost per Disability Adjusted Life Year (DALY) averted following the environmental remediation of the former lead smelter and adjoining residential areas in Paraiso de Dios, Haina, the Dominican Republic, executed from 2009 to 2010. The remediation had the effect of lowering surface soil lead concentrations to below 100 mg/kg and measured geometric mean blood lead levels (BLLs) from 20.6 μg/dL to 5.34 ug/dL. Because BLLs for the entire impacted population were not available, we use environmental data to calculate the resulting disease burden. We find that before the intervention 176 people were exposed to elevated environmental lead levels at Paraiso de Dios resulting in mean BLLs of 24.97 (95% CI: 24.45–25.5) in children (0–7 years old) and 13.98 μg/dL (95% CI: 13.03–15) in adults. We calculate that without the intervention these exposures would have resulted in 133 to 1,096 DALYs and that all of these were averted at a cost of USD 392 to 3,238, depending on assumptions made. We use a societal perspective, meaning that we include all costs regardless of by whom they were incurred and estimate costs in 2009 USD. Lead remediation in low- and middle-income countries is cost effective according to World Health Organization thresholds. Further research is required to compare the approach detailed here with other public health interventions.

Description: Rotavirus is the most common cause of diarrheal disease among children under 5. Especially in South Asia, rotavirus remains the leading cause of mortality in children due to diarrhea. As climatic extremes and safe water availability significantly influence diarrheal disease impacts in human populations, hydroclimatic information can be a potential tool for disease preparedness. In this study, we conducted a multivariate temporal and spatial assessment of 34 climate indices calculated from ground and satellite Earth observations to examine the role of temperature and rainfall extremes on the seasonality of rotavirus transmission in Bangladesh. We extracted rainfall data from the Global Precipitation Measurement and temperature data from the Moderate Resolution Imaging Spectroradiometer sensors to validate the analyses and explore the potential of a satellite-based seasonal forecasting model. Our analyses found that the number of rainy days and nighttime temperature range from 16°C to 21°C are particularly influential on the winter transmission cycle of rotavirus. The lower number of wet days with suitable cold temperatures for an extended time accelerates the onset and intensity of the outbreaks. Temporal analysis over Dhaka also suggested that water logging during monsoon precipitation influences rotavirus outbreaks during a summer transmission cycle. The proposed model shows lag components, which allowed us to forecast the disease outbreaks 1 to 2 months in advance. The satellite data-driven forecasts also effectively captured the increased vulnerability of dry-cold regions of the country, compared to the wet-warm regions.

Description: New dam construction is known to exacerbate malaria transmission in Africa as the vectors of malaria— Anopheles mosquitoes—use bodies of water as breeding sites. Precise environmental mechanisms of how reservoirs exacerbate malaria transmission are yet to be identified. Understanding of these mechanisms should lead to a better assessment of the impacts of dam construction and to new prevention strategies. Combining extensive multi-year field surveys around the Koka Reservoir in Ethiopia and rigorous model development and simulation studies, environmental mechanisms of malaria transmission around the reservoir were examined. Most comprehensive and detailed malaria transmission model, HYDREMATS, was applied to a village adjacent to the reservoir. Significant contributions to the dynamics of malaria transmission are shaped by wind profile, marginal pools, temperature, and shoreline locations. Wind speed and wind direction influence Anopheles populations and malaria transmission during the major and secondary mosquito seasons. During the secondary mosquito season, a noticeable influence was also attributed to marginal pools. Temperature was found to play an important role, not so much in Anopheles population dynamics, but in malaria transmission dynamics. Change in shoreline locations drives malaria transmission dynamics, with closer shoreline locations to the village making malaria transmission more likely. Identified environmental mechanisms help in predicting malaria transmission seasons and in developing village relocation strategies upon dam construction to minimize the risk of malaria.

Description: No abstract is available for this article.

Description: Valley fever is endemic to the southwestern United States. Humans contract this fungal disease by inhaling spores of Coccidioides spp. Changes in the environment can influence the abundance and dispersal of Coccidioides spp., causing fluctuations in valley fever incidence. We combined county-level case records from state health agencies to create a regional valley fever database for the southwestern United States, including Arizona, California, Nevada, New Mexico, and Utah. We used this data set to explore how environmental factors influenced the spatial pattern and temporal dynamics of valley fever incidence during 2000–2015. We compiled climate and environmental geospatial data sets from multiple sources to compare with valley fever incidence. These variables included air temperature, precipitation, soil moisture, surface dust concentration, normalized difference vegetation index, and cropland area. We found that valley fever incidence was greater in areas with warmer air temperatures and drier soils. The mean annual cycle of incidence varied throughout the southwestern United States and peaked following periods of low precipitation and soil moisture. From year-to-year, however, autumn incidence was higher following cooler, wetter, and productive springs in the San Joaquin Valley of California. In southcentral Arizona, incidence increased significantly through time. By 2015, incidence in this region was more than double the rate in the San Joaquin Valley. Our analysis provides a framework for interpreting the influence of climate change on valley fever incidence dynamics. Our results may allow the U.S. Centers for Disease Control and Prevention to improve their estimates of the spatial pattern and intensity of valley fever endemicity.

Description: Much concern has been raised about the increasing threat to air quality and human health due to ammonia (NH 3 ) emissions from agricultural systems, which is associated with the enrichment of reactive nitrogen (N) in southern Asia (SA), home of more than 60% the world's population (i.e., the people of West, central, East, South, and Southeast Asia). Southern Asia consumed more than half of the global synthetic N fertilizer and was the dominant region for livestock waste production since 2004. Excessive N application could lead to a rapid increase of NH 3 in the atmosphere, resulting in severe air and water pollution in this region. However, there is still a lack of accurate estimates of NH 3 emissions from agricultural systems. In this study, we simulated the agricultural NH 3 fluxes in SA by coupling the Bidirectional NH 3 exchange module (Bi-NH 3 ) from the Community Multi-scale Air Quality model with the Dynamic Land Ecosystem Model. Our results indicated that NH 3 emissions were 21.3 ± 3.9 Tg N yr −1 from SA agricultural systems with a rapidly increasing rate of ~0.3 Tg N yr −2 during 1961−2014. Among the emission sources, 10.8 Tg N yr −1 was released from synthetic N fertilizer use, and 10.4 ± 3.9 Tg N yr −1 was released from manure production in 2014. Ammonia emissions from China and India together accounted for 64% of the total amount in SA during 2000−2014. Our results imply that the increased NH 3 emissions associated with high N inputs to croplands would likely be a significant threat to the environment and human health unless mitigation efforts are applied to reduce these emissions.

Description: While there have been substantial efforts to quantify the health burden of exposure to PM 2.5 from solid fuel use (SFU), the sensitivity of mortality estimates to uncertainties in input parameters has not been quantified. Moreover, previous studies separate mortality from household and ambient air pollution. In this study, we develop a new estimate of mortality attributable to SFU due to the joint exposure from household and ambient PM 2.5 pollution and perform a variance-based sensitivity analysis on mortality attributable to SFU. In the joint exposure calculation, we estimate 2.81 (95% confidence interval: 2.48–3.28) million premature deaths in 2015 attributed to PM 2.5 from SFU, which is 580,000 (18%) fewer deaths than would be calculated by summing separate household and ambient mortality calculations. Regarding the sources of uncertainties in these estimates, in China, India, and Latin America, we find that 53–56% of the uncertainty in mortality attributable to SFU is due to uncertainty in the percent of the population using solid fuels and 42–50% from the concentration-response function. In sub-Saharan Africa, baseline mortality rate (72%) and the concentration-response function (33%) dominate the uncertainty space. Conversely, the sum of the variance contributed by ambient and household PM 2.5 exposure ranges between 15 and 38% across all regions (the percentages do not sum to 100% as some uncertainty is shared between parameters). Our findings suggest that future studies should focus on more precise quantification of solid fuel use and the concentration-response relationship to PM 2.5 , as well as mortality rates in Africa.

Description: New analyses are revealing the scale of pollution on global health, with a disproportionate share of the impact borne by lower-income nations, minority and marginalized individuals. Common themes emerge on the drivers of this pollution impact, including a lack of regulation and its enforcement, research and expertise development, and innovative funding mechanisms for mitigation. Creative approaches need to be developed and applied to address and overcome these obstacles. The existing “business as usual” modus operandi continues to externalize human health costs related to pollution, which exerts a negative influence on global environmental health.

Description: Dengue is the most important human arboviral disease in Singapore. We classified residential areas into low-rise and high-rise housing and investigated the influence of urban drainage on the distribution of dengue incidence and outdoor breeding at neighborhood and country scales. In Geylang area (August 2014 to August 2015), dengue incidence was higher in a subarea of low-rise housing compared to high-rise one, averaging 26.7 (standard error, SE = 4.83) versus 2.43 (SE = 0.67) per 1,000 people. Outdoor breeding drains of Aedes aegypti have clustered in the low-rise housing subarea. The pupal density per population was higher in the low-rise blocks versus high-rise ones, 246 (SE = 69.08) and 35.4 (SE = 25.49) per 1,000 people, respectively. The density of urban drainage network in the low-rise blocks is double that in the high-rise ones, averaging 0.05 (SE = 0.0032) versus 0.025 (SE = 0.00245) per meter. Further, a holistic analysis at a country-scale has confirmed the role of urban hydrology in shaping dengue distribution in Singapore. Dengue incidence (2013–2015) is proportional to the fractions of the area (or population) of low-rise housing. The drainage density in low-rise housing is 4 times that corresponding estimate in high-rise areas, 2.59 and 0.68 per meter, respectively. Public housing in agglomerations of high-rise buildings could have a positive impact on dengue if this urban planning comes at the expense of low-rise housing. City planners in endemic regions should consider the density of drainage networks for both the prevention of flooding and the breeding of mosquitoes.

Description: Communities in Australia's Murray-Darling Basin face the challenge of trying to achieve social, economic and environmental sustainability; but experience entrenched conflict about the best way to achieve a sustainable future, especially for small rural communities. Integral ecology is a philosophical concept that seeks to address community, economic, social and environmental sustainability simultaneously. Its inclusive processes are designed to reduce stakeholder conflict. However, to date the application of the integral ecology concept has been largely qualitative in nature. This study developed a quantitative integral ecology framework, and applied this framework to a case study of the Riverina, in the Murray-Darling Basin. Seventy-seven community-focused initiatives were assessed, ranked and quantified. The majority of the community-focused ranked initiatives did not exhibit all aspects of integral ecology. Initiatives typically prioritized either i) economic and community development or ii) environmental health; rarely both together. The integral ecology framework developed here enables recommendations on future community initiatives and may provide a pathway for community leaders and other policy-makers to more readily apply integral ecology objectives. Further research refining the framework's operationalization, application and implementation to a wider-scale may enhance communities’ capacity to develop and grow sustainably.

Description: The 2015 Paris Agreement aims to limit global warming to well below 2 K above pre-industrial levels, and to pursue efforts to limit global warming to 1.5 K, in order to avert dangerous climate change. However, current greenhouse gas emissions targets are more compatible with scenarios exhibiting end-of-century global warming of 2.6 - 3.1 K, in clear contradiction to the 1.5 K target. In this study, we use a global climate model to investigate the climatic impacts of using solar geoengineering by stratospheric aerosol injection to stabilize global-mean temperature at 1.5 K for the duration of the 21 st century against 3 scenarios spanning the range of plausible greenhouse gas mitigation pathways (RCP2.6, RCP4.5, RCP8.5). In addition to stabilizing global mean temperature and offsetting both Arctic sea-ice loss and thermosteric sea-level rise, we find that solar geoengineering could effectively counteract enhancements to the frequency of extreme storms in the North Atlantic and heatwaves in Europe, but would be less effective at counteracting hydrological changes in the Amazon basin and North Atlantic storm track displacement. In summary, solar geoengineering may reduce global mean impacts but is an imperfect solution at the regional level, where the effects of climate change are experienced. Our results should galvanize research into the regionality of climate responses to solar geoengineering.

Description: Even if global warming is kept below +2°C, European agriculture will be significantly impacted. Soil degradation may amplify these impacts substantially and thus hamper crop production further. We quantify biophysical consequences and bracket uncertainty of +2°C warming on calories supply from ten major crops and vulnerability to soil degradation in Europe using crop modelling. The Environmental Policy Integrated Climate (EPIC) model together with regional climate projections from the European branch of the Coordinated Regional Downscaling Experiment (EURO-CORDEX) were used for this purpose. A robustly positive calorie yield change was estimated for the EU Member States except for some regions in Southern and South-Eastern Europe. The mean impacts range from +30 Gcal ha –1 in the north, through +25 and +20 Gcal ha –1 in Western and Eastern Europe, respectively, to +10 Gcal ha –1 in the south if soil degradation and heat impacts are not accounted for. Elevated CO 2 and increased temperature are the dominant drivers of the simulated yield changes in high-input agricultural systems. The growth stimulus due to elevated CO 2 may offset potentially negative yield impacts of temperature increase by +2°C in most of Europe. Soil degradation causes a calorie vulnerability ranging from 0 to 80 Gcal ha –1 due to insufficient compensation for nutrient depletion and this might undermine climate benefits in many regions, if not prevented by adaptation measures, especially in Eastern and North-Eastern Europe. Uncertainties due to future potentials for crop intensification are about two to fifty times higher than climate change impacts.

Description: Systemic threats to food-energy-environment-water systems require national policy responses. Yet complete control of these complex systems is impossible and attempts to mitigate systemic risks can generate unexpected feedback effects. Perverse outcomes from national policy can emerge from the diverse responses of decision-makers across different levels and scales of resource governance. Participatory risk assessment processes can help planners to understand sub-national dynamics and ensure that policies do not undermine the resilience of social-ecological systems and infrastructure networks. Researchers can play an important role in participatory processes as both technical specialists and brokers of stakeholder knowledge on the feedbacks generated by systemic risks and policy decisions. Here, we evaluate the use of causal modeling and participatory risk assessment to develop national policy on systemic water risks. We present an application of the Risks and Options Assessment for Decision-Making (ROAD) process to a district of Vietnam where national agricultural water reforms are being piloted. The methods and results of this project provide general insights about how to support resilient decision-making, including the transfer of knowledge across administrative levels, identification of feedback effects, and the effective implementation of risk assessment processes.

Description: As global average sea-level rises in the early part of this century there is great interest in how much global and local sea level will change in the forthcoming decades. The Paris Climate Agreement's proposed temperature thresholds of 1.5 °C and 2 °C have directed the research community to ask what differences occur in the climate system for these two states. We have developed a novel approach to combine climate model outputs that follow specific temperature pathways to make probabilistic projections of sea-level in a 1.5 °C and 2 °C world. We find median global sea-level projections for 1.5 °C and 2 °C temperature pathways of 44 cm and 50 cm respectively. The 90% uncertainty ranges (5-95%) are both around 48 cm by 2100. In addition, we take an alternative approach to estimate the contribution from ice sheets by using a semi-empirical global sea-level model. Here we find median projections of 58 cm and 68 cm for 1.5 °C and 2 °C temperature pathways. The 90% uncertainty ranges are 67 cm and 82 cm respectively. Regional projections show similar patterns for both temperature pathways, though differences vary between the median projections (2-10 cm) and 95 th percentile (5-20 cm) for the bulk of oceans using process-based approach and 10-15 cm (median) and 15-25 cm (95th percentile) using the semi-empirical approach.

Description: To contribute to a quantitative comparison of climate engineering (CE) methods, we assess atmosphere-, ocean-, and land-based CE measures with respect to Earth system effects consistently within one comprehensive model. We use the Max Planck Institute Earth System Model (MPI-ESM) with prognostic carbon cycle to compare solar radiation management (SRM) by stratospheric sulfur injection and two carbon dioxide removal methods: afforestation and ocean alkalinization. The CE model experiments are designed to offset the effect of fossil-fuel burning on global mean surface air temperature under the RCP8.5 scenario to follow or get closer to the RCP4.5 scenario. Our results show the importance of feedbacks in the CE effects. For example, as a response to SRM the land carbon uptake is enhanced by 92 Gt by the year 2100 compared to the reference RCP8.5 scenario due to reduced soil respiration thus reducing atmospheric CO 2 . Furthermore, we show that normalizations allow for a better comparability of different CE methods. For example, we find that due to compensating processes such as biogeophysical effects of afforestation more carbon needs to be removed from the atmosphere by afforestation than by alkalinization to reach the same global warming reduction. Overall, we illustrate how different CE methods affect the components of the Earth system, we identify challenges arising in a CE comparison, and thereby contribute to developing a framework for a comparative assessment of CE.

Description: Anthropogenic land use and land cover change, including local environmental disturbances, moderate rates of wind-driven soil erosion and dust emission. These human-dust cycle interactions impact ecosystems and agricultural production, air quality, human health, biogeochemical cycles, and climate. While the impacts of land use activities and land management on aeolian processes can be profound, the interactions are often complex and assessments of anthropogenic dust loads at all scales remain highly uncertain. Here, we critically review the drivers of anthropogenic dust emission and current evaluation approaches. We then identify and describe opportunities to: (1) develop new conceptual frameworks and interdisciplinary approaches that draw on ecological state-and-transition models to improve the accuracy and relevance of assessments of anthropogenic dust emissions; (2) improve model fidelity and capacity for change detection to quantify anthropogenic impacts on aeolian processes; and (3) enhance field research and monitoring networks to support dust model applications to evaluate the impacts of disturbance processes on local to global-scale wind erosion and dust emissions.

Description: Methane accounts for 20% of the global warming caused by greenhouse gases, and wastewater is a major anthropogenic source of methane. Based on the Intergovernmental Panel on Climate Change (IPCC) greenhouse gas inventory guidelines and current research findings, we calculated the amount of methane emissions from 2000 to 2014 that originated from wastewater from different provinces in China. Methane emissions from wastewater increased from 1349.01 Gg to 3430.03 Gg from 2000 to 2014, and the mean annual increase was 167.69 Gg. The methane emissions from industrial wastewater treated by wastewater treatment plants (E It ) accounted for the highest proportion of emissions. We also estimated the future trend of industrial wastewater methane emissions using the artificial neural network model. A comparison of the emissions for the years 2020, 2010 and 2000 showed an increasing trend in methane emissions in China and a spatial transition of industrial wastewater emissions from eastern and southern regions to central and southwestern regions and from coastal regions to inland regions. These changes were caused by changes in economics, demographics and relevant policies.