ALBERT

Description: Mantle-derived noble gases in volcanic gases are powerful tracers of terrestrial volatile evolution, as they contain mixtures of both primordial (from Earth's accretion) and secondary (e.g., radiogenic) isotope signals that characterize the composition of deep Earth. However, volcanic gases emitted through subaerial hydrothermal systems also contain contributions from shallow reservoirs (groundwater, crust, atmosphere). Deconvolving deep and shallow source signals is critical for robust interpretations of mantle-derived signals. Here, we use a novel dynamic mass spectrometry technique to measure argon, krypton, and xenon isotopes in volcanic gas with ultrahigh precision. Data from Iceland, Germany, United States (Yellowstone, Salton Sea), Costa Rica, and Chile show that subsurface isotope fractionation within hydrothermal systems is a globally pervasive and previously unrecognized process causing substantial nonradiogenic Ar-Kr-Xe isotope variations. Quantitatively accounting for this process is vital for accurately interpreting mantle-derived volatile (e.g., noble gas and nitrogen) signals, with profound implications for our understanding of terrestrial volatile evolution.

Description: Published

Description: eadg2566

Description: OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametrici

Description: JCR Journal

Description: TR17-08, a marine sedimentary core (14.6 m), was collected during 2017 from the Edisto Inlet (Ross Sea, Antarctica), a small fjord near Cape Hallett. The core is characterized by expanded laminated sedimentary sequences making it suitable for studying submillennial processes during the Early Holocene. By studying different well-known foraminifera species (Globocassidulina biora, G. subglobosa, Trifarina angulosa, Nonionella iridea, Epistominella exigua, Stainforthia feylingi, Miliammina arenacea, Paratrochammina bartrami and Portatrochammina antarctica), we were able to identify five different foraminiferal assemblages over the last ∼ 2000 years BP. Comparison with diatom assemblages and other geochemical proxies retrieved from nearby sediment cores in the Edisto Inlet (BAY05-20 and HLF17-1) made it possible to distinguish three different phases characterized by different environmental settings: (1) a seasonal phase (from 2012 to 1486 years BP) characterized by the dominance of calcareous species, indicating a seasonal opening of the inlet by more frequent events of melting of the sea-ice cover during the austral summer and, in general, a higher-productivity, more open and energetic environment; (2) a transitional phase (from 1486 to 696 years BP) during which the fjord experienced less extensive sea-ice melting, enhanced oxygen-poor conditions and carbonate dissolution conditions, indicated by the shifts from calcareous-dominated association to agglutinated-dominated association probably due to a freshwater input from the retreat of three local glaciers at the start of this period; and (3) a cooler phase (from 696 years BP to present) during which the sedimentation rate decreased and few to no foraminiferal specimens were present, indicating ephemeral openings or a more prolonged cover of the sea ice during the austral summer, affecting the nutrient supply and the sedimentation regime.

Description: Published

Description: 95–115

Description: OSA2: Evoluzione climatica: effetti e loro mitigazione

Description: JCR Journal

Description: Perturbations in stratospheric aerosol due to explosive volcanic eruptions are a primary contributor to natural climate variability. Observations of stratospheric aerosol are available for the past decades, and information from ice cores has been used to derive estimates of stratospheric sulfur injections and aerosol optical depth over the Holocene (approximately 10 000 BP to present) and into the last glacial period, extending back to 60 000 BP. Tephra records of past volcanism, compared to ice cores, are less complete but extend much further into the past. To support model studies of the potential impacts of explosive volcanism on climate variability across timescales, we present here an ensemble reconstruction of volcanic stratospheric sulfur injection (VSSI) over the last 140 000 years that is based primarily on terrestrial and marine tephra records. VSSI values are computed as a simple function of eruption magnitude based on VSSI estimates from ice cores and satellite observations for identified eruptions. To correct for the incompleteness of the tephra record, we include stochastically generated synthetic eruptions assuming a constant background eruption frequency from the ice core Holocene record. While the reconstruction often differs from ice core estimates for specific eruptions due to uncertainties in the data used and reconstruction method, it shows good agreement with an ice-core-based VSSI reconstruction in terms of millennial-scale cumulative VSSI variations over the Holocene. The PalVol reconstruction provides a new basis to test the contributions of forced vs. unforced natural variability to the spectrum of climate and the mechanisms leading to abrupt transitions in the palaeoclimate record with low- to high-complexity climate models. The PalVol volcanic forcing reconstruction is available at https://doi.org/10.26050/WDCC/PalVolv1 (Toohey and Schindlbeck-Belo, 2023).

Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in LeClerc, H., Tompsett, G., Paulsen, A., McKenna, A., Niles, S., Reddy, C., Nelson, R., Cheng, F., Teixeira, A., & Timko, M. Hydroxyapatite catalyzed hydrothermal liquefaction transforms food waste from an environmental liability to renewable fuel. IScience, 25(9), (2022): 104916, https://doi.org/10.1016/j.isci.2022.104916.

Description: Food waste is an abundant and inexpensive resource for the production of renewable fuels. Biocrude yields obtained from hydrothermal liquefaction (HTL) of food waste can be boosted using hydroxyapatite (HAP) as an inexpensive and abundant catalyst. Combining HAP with an inexpensive homogeneous base increased biocrude yield from 14 ± 1 to 37 ± 3%, resulting in the recovery of 49 ± 2% of the energy contained in the food waste feed. Detailed product analysis revealed the importance of fatty-acid oligomerization during biocrude formation, highlighting the role of acid-base catalysts in promoting condensation reactions. Economic and environmental analysis found that the new technology has the potential to reduce US greenhouse gas emissions by 2.6% while producing renewable diesel with a minimum fuel selling price of $1.06/GGE. HAP can play a role in transforming food waste from a liability to a renewable fuel.

Description: This work was funded by the DOE Bioenergy Technology Office (DE-EE0008513), a DOE DBIR (DE-SC0015784) and the MassCEC. The authors thank WenWen Yao, Department of Environmental Science at WPI, for TOC analysis, Mainstream Engineering for heating value characterization of the oil and solid samples, Wei Fan for assistance in obtaining SEM images and, Julia Martin and Ronald Grimm for their assistance in collecting XPS data, and Jeffrey R. Page for his assistance with oil upgrading and analysis. HOL was partially funded for this work by NSF Graduate Research Fellowship award number 2038257. A portion of this work was performed at the National High Magnetic Field Laboratory Ion Cyclotron Resonance user facility, which is supported by the NSF Division of Materials Research and Division of Chemistry through DMR 16-44779 and the State of Florida.

Description: Abstract. Clouds are assumed to play an important role in the Arctic amplification process. This motivated a detailed investigation of cloud processes, including radiative and turbulent fluxes. Data from the aircraft campaign ACLOUD were analyzed with a focus on the mean and turbulent structure of the cloudy boundary layer over the Fram Strait marginal sea ice zone in late spring and early summer 2017. Vertical profiles of turbulence moments are presented from contrasting atmospheric boundary layers (ABLs) from 4 d. They differ by the magnitude of wind speed, boundary-layer height, stability, the strength of the cloud-top radiative cooling and the number of cloud layers. Turbulence statistics up to third-order moments are presented, which were obtained from horizontal-level flights and from slanted profiles. It is shown that both of these flight patterns complement each other and form a data set that resolves the vertical structure of the ABL turbulence well. The comparison of the 4 d shows that especially during weak wind, even in shallow Arctic ABLs with mixing ratios below 3 g kg-1, cloud-top cooling can serve as a main source of turbulent kinetic energy (TKE).Well-mixed ABLs are generated where TKE is increased and vertical velocity variance shows pronounced maxima in the cloud layer. Negative vertical velocity skewness points then to upside-down convection. Turbulent heat fluxes are directed upward in the cloud layer as a result of cold downdrafts. In two cases with single-layer stratocumulus, turbulent transport of heat flux and of temperature variance are both negative in the cloud layer, suggesting an important role of large eddies. In contrast, in a case with weak cloud-top cooling, these quantities are positive in the ABL due to the heating from the surface. Based on observations and results of a mixed-layer model it is shown that the maxima of turbulent fluxes are, however, smaller than the jump of the net terrestrial radiation flux across the upper part of a cloud due to the (i) shallowness of the mixed layer and (ii) the presence of a downward entrainment heat flux. The mixed-layer model also shows that the buoyancy production of TKE is substantially smaller in stratocumulus over the Arctic sea ice compared to subtropics due to a smaller surface moisture flux and smaller decrease in specific humidity (or even humidity inversions) right above the cloud top. In a case of strong wind, wind shear shapes the ABL turbulent structure, especially over rough sea ice, despite the presence of a strong cloud-top cooling. In the presence of mid-level clouds, cloud-top radiative cooling and thus also TKE in the lowermost cloud layer are strongly reduced, and the ABL turbulent structure becomes governed by stability, i.e., by the surface–air temperature difference and wind speed. A comparison of slightly unstable and weakly stable cases shows a strong reduction of TKE due to increased stability even though the absolute value of wind speed was similar. In summary, the presented study documents vertical profiles of the ABL turbulence with a high resolution in a wide range of conditions. It can serve as a basis for turbulence closure evaluation and process studies in Arctic clouds.

Description: Springtime Arctic mixed-phase convection over open water in the Fram Strait as observed during the recent ACLOUD (Arctic CLoud Observations Using airborne measurements during polar Day) field campaign is simulated at turbulence-resolving resolutions. The first objective is to assess the skill of large-eddy simulation (LES) in reproducing the observed mixed-phase convection. The second goal is to then use the model to investigate how aerosol modulates the way in which turbulent mixing and clouds transform the low-level air mass. The focus lies on the low-level thermal structure and lapse rate, the heating efficiency of turbulent entrainment, and the low-level energy budget. A composite case is constructed based on data collected by two research aircraft on 18 June 2017. Simulations are evaluated against independent datasets, showing that the observed thermodynamic, cloudy, and turbulent states are well reproduced. Sensitivity tests on cloud condensation nuclei (CCN) concentration are then performed, covering a broad range between pristine polar and polluted continental values. We find a significant response in the resolved mixed-phase convection, which is in line with previous LES studies. An increased CCN substantially enhances the depth of convection and liquid cloud amount, accompanied by reduced surface precipitation. Initializing with the in situ CCN data yields the best agreement with the cloud and turbulence observations, a result that prioritizes its measurement during field campaigns for supporting high-resolution modeling efforts. A deeper analysis reveals that CCN significantly increases the efficiency of radiatively driven entrainment in warming the boundary layer. The marked strengthening of the thermal inversion plays a key role in this effect. The low-level heat budget shifts from surface driven to radiatively driven. This response is accompanied by a substantial reduction in the surface energy budget, featuring a weakened flow of solar radiation into the ocean. Results are interpreted in the context of air–sea interactions, air mass transformations, and climate feedbacks at high latitudes.

Description: The presence of reactive bromine in polar regions is a widespread phenomenon that plays an important role in the photochemistry of the Arctic and Antarctic lower troposphere, including the destruction of ozone, the disturbance of radical cycles, and the oxidation of gaseous elemental mercury. The chemical mechanisms leading to the heterogeneous release of gaseous bromine compounds from saline surfaces are in principle well understood. There are, however, substantial uncertainties about the contribution of different potential sources to the release of reactive bromine, such as sea ice, brine, aerosols, and the snow surface, as well as about the seasonal and diurnal variation and the vertical distribution of reactive bromine. Here we use continuous long-term measurements of the vertical distribution of bromine monoxide (BrO) and aerosols at the two Antarctic sites Neumayer (NM) and Arrival Heights (AH), covering the periods of 2003–2021 and 2012–2021, respectively, to investigate how chemical and physical parameters affect the abundance of BrO. We find the strongest correlation between BrO and aerosol extinction (R=0.56 for NM and R=0.28 for AH during spring), suggesting that the heterogeneous release of Br2 from saline airborne particles (blowing snow and aerosols) is a dominant source for reactive bromine. Positive correlations between BrO and contact time of air masses, both with sea ice and the Antarctic ice sheet, suggest that reactive bromine is not only emitted by the sea ice surface but by the snowpack on the ice shelf and in the coastal regions of Antarctica. In addition, the open ocean appears to represent a source for reactive bromine during late summer and autumn when the sea ice extent is at its minimum. A source–receptor analysis based on back trajectories and sea ice maps shows that main source regions for BrO at NM are the Weddell Sea and the Filchner–Ronne Ice Shelf, as well as coastal polynyas where sea ice is newly formed. A strong morning peak in BrO frequently occurring during summer and that is particularly strong during autumn suggests a night-time build-up of Br2 by heterogeneous reaction of ozone on the saline snowpack in the vicinity of the measurement sites. We furthermore show that BrO can be sustained for at least 3 d while travelling across the Antarctic continent in the absence of any saline surfaces that could serve as a source for reactive bromine.

Description: Stable water isotopologues of snow, firn and ice cores provide valuable information on past climate variations. Yet single profiles are generally not suitable for robust climate reconstructions. Stratigraphic noise, introduced by the irregular deposition, wind-driven erosion and redistribution of snow, impacts the utility of high-resolution isotope records, especially in low-Accumulation areas. However, it is currently unknown how stratigraphic noise differs across the East Antarctic Plateau and how it is affected by local environmental conditions. Here, we assess the amount and structure of stratigraphic noise at seven sites along a 120 km transect on the plateau of Dronning Maud Land, East Antarctica. Replicated oxygen isotope records of 1 m length were used to estimate signal-To-noise ratios as a measure of stratigraphic noise at sites characterised by different accumulation rates (43-64 mm w.e. a-1), snow surface roughnesses and slope inclinations. While we found a high level of stratigraphic noise at all sites, there was also considerable variation between sites. At sastrugi-dominated sites, greater stratigraphic noise coincided with stronger surface roughnesses, steeper slopes and lower accumulation rates, probably related to increased wind speeds. These results provide a first step to modelling stratigraphic noise and might guide site selection and sampling strategies for future expeditions to improve high-resolution climate reconstructions from low-Accumulation regions.

Description: Bacterial populations face the constant threat of viral predation exerted by bacteriophages (‘phages’). In response, bacteria have evolved a wide range of defense mechanisms against phage challenges. Yet the vast majority of antiphage defense systems described until now are mediated by proteins or RNA complexes acting at the single-cell level. Here, we review small molecule-based defense strategies against phage infection, with a focus on the antiphage molecules described recently. Importantly, inhibition of phage infection by excreted small molecules has the potential to protect entire bacterial communities, highlighting the ecological significance of these antiphage strategies. Considering the immense repertoire of bacterial metabolites, we envision that the list of antiphage small molecules will be further expanded in the future.

Description: Scenarios—which account for the costs of and interactions among different mitigation options—show that we will need to remove hundreds of gigatons of carbon dioxide (CO2) from the atmosphere over the course of the century to limit warming to well below 2°C, make efforts to limit it to 1.5°C, and ensure the sustained well-being of our planet. Yet at present, only 2 Gt is being removed per year, and nearly all of it is from forestry—only 0.1% is from novel forms of carbon removal. This commentary shows that the deployment of novel CO2 removal (CDR) over the next decade, its formative phase, is likely to be consequential in determining whether CDR will be available at scale and in time to reach net-zero CO2 emissions consistent with the Paris Agreement’s temperature goal.

Description: Changes in Southern Ocean export production have broad biogeochemical and climatic implications. Specifically, iron fertilization likely increased subantarctic nutrient utilization and enhanced the efficiency of the biological pump during glacials. However, past export production in the subantarctic Southeast Pacific is poorly documented, and its connection to Fe fertilization, potentially related to Patagonian Ice Sheet dynamics is unknown. We report on biological productivity changes over the past 400 ka, based on a combination of 230Thxs-normalized and stratigraphy-based mass accumulation rates of biogenic barium, organic carbon, biogenic opal, and calcium carbonate as indicators of paleo-export production in a sediment core upstream of the Drake Passage. In addition, we use fluxes of iron and lithogenic material as proxies for terrigenous matter, and thus potential micronutrient supply. Stratigraphy-based mass accumulation rates are strongly influenced by bottom-current dynamics, which result in variable sediment focussing or winnowing at our site. Carbonate is virtually absent in the core, except during peak interglacial intervals of the Holocene, and Marine Isotope Stages (MIS) 5 and 11, likely caused by transient decreases in carbonate dissolution. All other proxies suggest that export production increased during most glacial periods, coinciding with high iron fluxes. Such augmented glacial iron fluxes at the core site were most likely derived from glaciogenic input from the Patagonian Ice Sheet promoting the growth of phytoplankton. Additionally, glacial export production peaks are also consistent with northward shifts of the Subantarctic and Polar Fronts, which positioned our site south of the Subantarctic Front and closer to silicic acid-rich waters of the Polar Frontal Zone, as well as a with a decrease in the diatom utilization of Si relative to nitrate under Fe-replete conditions. However, glacial export production near the Drake Passage was lower than in the Atlantic and Indian sectors of the Southern Ocean, which may relate to complete consumption of silicic acid in the study area. Our results underline the importance of micro-nutrient fertilization through lateral terrigenous input from South America rather than aeolian transport, and exemplify the role of frontal shifts and nutrient limitation for past productivity changes in the Pacific entrance to the Drake Passage.

Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Tian, Y., Liu, X., Li, J., Deng, Y., DeGiorgis, J. A., Zhou, S., Caratenuto, A., Minus, M. L., Wan, Y., Xiao, G., & Zheng, Y. Farm-waste-derived recyclable photothermal evaporator. Cell Reports Physical Science, 2(9), (2021): 100549, https://doi.org/10.1016./j.xcrp.2021.100549

Description: Interfacial solar steam generation is emerging as a promising technique for efficient desalination. Although increasing efforts have been made, challenges exist for achieving a balance among a plethora of performance indicators—for example, rapid evaporation, durability, low-cost deployment, and salt rejection. Here, we demonstrate that carbonized manure can convert 98% of sunlight into heat, and the strong capillarity of porous carbon fibers networks pumps sufficient water to evaporation interfaces. Salt diffusion within microchannels enables quick salt drainage to the bulk seawater to prevent salt accumulation. With these advantages, this biomass-derived evaporator is demonstrated to feature a high evaporation rate of 2.81 kg m−2 h−1 under 1 sun with broad robustness to acidity and alkalinity. These advantages, together with facial deployment, offer an approach for converting farm waste to energy with high efficiency and easy implementation, which is particularly well suited for developing regions.

Description: This project is supported by the National Science Foundation through grant no. CBET-1941743. This project is based upon work supported in part by the National Science Foundation under EPSCoR Cooperative Agreement no. OIA-1655221.

Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Liu, C.-Z., Dick, H. J. B., Mitchell, R. N., Wei, W., Zhang, Z.-Y., Hofmann, A. W., Yang, J.-F., & Li, Y. Archean cratonic mantle recycled at a mid-ocean ridge. Science Advances, 8(22), (2022): eabn6749, https://doi.org/10.1126/sciadv.abn6749.

Description: Basalts and mantle peridotites of mid-ocean ridges are thought to sample Earth’s upper mantle. Osmium isotopes of abyssal peridotites uniquely preserve melt extraction events throughout Earth history, but existing records only indicate ages up to ~2 billion years (Ga) ago. Thus, the memory of the suspected large volumes of mantle lithosphere that existed in Archean time (〉2.5 Ga) has apparently been lost somehow. We report abyssal peridotites with melt-depletion ages up to 2.8 Ga, documented by extremely unradiogenic 187Os/188Os ratios (to as low as 0.1095) and refractory major elements that compositionally resemble the deep keels of Archean cratons. These oceanic rocks were thus derived from the once-extensive Archean continental keels that have been dislodged and recycled back into the mantle, the feasibility of which we confirm with numerical modeling. This unexpected connection between young oceanic and ancient continental lithosphere indicates an underappreciated degree of compositional recycling over time.

Description: This study was financially supported by the National Science Fund for Distinguished Young Scholars 42025201 (to C.-Z.L.), the National Key Research and Development Project of China 2020YFA0714801 (to C.-Z.L.), the Strategic Priority Research Program of the Chinese Academy of Sciences XDA13010106 (to C.-Z.L.), the Strategic Priority Research Program of the Chinese Academy of Sciences XDB42020301 (to C.-Z.L.), and NSF grants 2114652 and 1657983 (to H.J.B.D.).

Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Stolp, Z. D., Kulkarni, M., Liu, Y., Zhu, C., Jalisi, A., Lin, S., Casadevall, A., Cunningham, K. W., Pineda, F. J., Teng, X., & Hardwick, J. M. Yeast cell death pathway requiring AP-3 vesicle trafficking leads to vacuole/lysosome membrane permeabilization. Cell Reports, 39(2), (2022): 110647, https://doi.org/10.1016/j.celrep.2022.110647.

Description: Unicellular eukaryotes have been suggested as undergoing self-inflicted destruction. However, molecular details are sparse compared with the mechanisms of programmed/regulated cell death known for human cells and animal models. Here, we report a molecular cell death pathway in Saccharomyces cerevisiae leading to vacuole/lysosome membrane permeabilization. Following a transient cell death stimulus, yeast cells die slowly over several hours, consistent with an ongoing molecular dying process. A genome-wide screen for death-promoting factors identified all subunits of the AP-3 complex, a vesicle trafficking adapter known to transport and install newly synthesized proteins on the vacuole/lysosome membrane. To promote cell death, AP-3 requires its Arf1-GTPase-dependent vesicle trafficking function and the kinase Yck3, which is selectively transported to the vacuole membrane by AP-3. Video microscopy revealed a sequence of events where vacuole permeability precedes the loss of plasma membrane integrity. AP-3-dependent death appears to be conserved in the human pathogenic yeast Cryptococcus neoformans.

Description: Funding sources: National Institutes of Health, United States grants AI144373 and NS127076 (J.M.H.), AI115016 and AI153414 (K.W.C.), and AI052733, AI152078, and HL059842 (A.C.); National Natural Science Foundation of China 31970550; and the Priority Academic Program Development of the Jiangsu Higher Education Institutes (X.T.).

Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Zhang, Y., Gazel, E., Gaetani, G. A., & Klein, F. Serpentinite-derived slab fluids control the oxidation state of the subarc mantle. Science Advances, 7(48), (2021): eabj2515, https://doi.org/10.1126/sciadv.abj2515.

Description: Recent geochemical evidence confirms the oxidized nature of arc magmas, but the underlying processes that regulate the redox state of the subarc mantle remain yet to be determined. We established a link between deep subduction-related fluids derived from dehydration of serpentinite ± altered oceanic crust (AOC) using B isotopes and B/Nb as fluid proxies, and the oxidized nature of arc magmas as indicated by Cu enrichment during magma evolution and V/Yb. Our results suggest that arc magmas derived from source regions influenced by a greater serpentinite (±AOC) fluid component record higher oxygen fugacity. The incorporation of this component into the subarc mantle is controlled by the subduction system’s thermodynamic conditions and geometry. Our results suggest that the redox state of the subarc mantle is not homogeneous globally: Primitive arc magmas associated with flat, warm subduction are less oxidized overall than those generated in steep, cold subduction zones.

Description: Y.Z. acknowledges funding from the National Science Foundation of China (91958213), the Chinese Academy of Sciences (XDB42020402), and the Shandong Provincial Natural Science Foundation, China (ZR2020QD068). This study was supported in part by the U.S. National Science Foundation NSF EAR 1826673 to E.G. and G.A.G. and OCE 1756349 to E.G.

Description: Most tropical corals live in symbiosis with Symbiodiniaceae algae whose photosynthetic production of oxygen (O2) may lead to excess O2 in the diffusive boundary layer (DBL) above the coral surface. When flow is low, cilia-induced mixing of the coral DBL is vital to remove excess O2 and prevent oxidative stress that may lead to coral bleaching and mortality. Here, we combined particle image velocimetry using O2-sensitive nanoparticles (sensPIV) with chlorophyll (Chla)-sensitive hyperspectral imaging to visualize the microscale distribution and dynamics of ciliary flows and O2 in the coral DBL in relation to the distribution of Symbiodiniaceae Chla in the tissue of the reef building coral, Porites lutea. Curiously, we found an inverse relation between O2 in the DBL and Chla in the underlying tissue, with patches of high O2 in the DBL above low Chla in the underlying tissue surrounding the polyp mouth areas and pockets of low O2 concentrations in the DBL above high Chla in the coenosarc tissue connecting neighboring polyps. The spatial segregation of Chla and O2 is related to ciliary-induced flows, causing a lateral redistribution of O2 in the DBL. In a 2D transport-reaction model of the coral DBL, we show that the enhanced O2 transport allocates parts of the O2 surplus to areas containing less chla, which minimizes oxidative stress. Cilary flows thus confer a spatially complex mass transfer in the coral DBL, which may play an important role in mitigating oxidative stress and bleaching in corals.

Description: We developed a new version of the Alfred Wegener Institute Climate Model (AWI-CM3), which has higher skills in representing the observed climatology and better computational efficiency than its predecessors. Its ocean component FESOM2 has the multi-resolution functionality typical for unstructured-mesh models while still featuring a scalability and efficiency similar to regular-grid models. The atmospheric component OpenIFS (CY43R3) enables the use of latest developments in the numerical weather prediction community in climate sciences. In this paper we describe the coupling of the model components and evaluate the model performance on a variable resolution (25–125 km) ocean mesh and a 61 km atmosphere grid, which serves as a reference and starting point for other on-going research activities with AWI-CM3. This includes the exploration of high and variable resolution, the development of a full Earth System Model as well as the creation of a new sea ice prediction system. At this early development stage and with the given coarse to medium resolutions, the model already features above CMIP6-average skills in representing the climatology and competitive model throughput. Finally we identify remaining biases and suggest further improvements to be made to the model.

Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Freeman, D. H., & Ward, C. P. Sunlight-driven dissolution is a major fate of oil at sea. Science Advances, 8(7), (2022): eabl7605, https://doi.org/10.1126/sciadv.abl7605.

Description: Oxygenation reactions initiated by sunlight can transform insoluble components of crude oil at sea into water-soluble products, a process called photo-dissolution. First reported a half century ago, photo-dissolution has never been included in spill models because key parameters required for rate modeling were unknown, including the wavelength and photon dose dependence. Here, we experimentally quantified photo-dissolution as a function of wavelength and photon dose, making possible a sensitivity analysis of environmental variables in hypothetical spill scenarios and a mass balance assessment for the 2010 Deepwater Horizon (DwH) spill. The sensitivity analysis revealed that rates were most sensitive to oil slick thickness, season/latitude, and wavelength and less sensitive to photon dose. We estimate that 3 to 17% (best estimate 8%) of DwH surface oil was subject to photo-dissolution, comparable in magnitude to other widely recognized fate processes. Our findings invite a critical reevaluation of surface oil budgets for both DwH and future spills at sea.

Description: This work was supported by the Fisheries and Oceans Canada Multi-Partner Research Initiative award to C.P.W. (project #1.06), the NSF Graduate Research Fellowship awarded to D.H.F. (award #174530), and NSF-OCE grant #1841092 to C.P.W.

Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Peng, Q., Xie, S.-P., Wang, D., Huang, R. X., Chen, G., Shu, Y., Shi, J.-R., & Liu, W. Surface warming-induced global acceleration of upper ocean currents. Science Advances, 8(16), (2022): eabj8394, https://doi.org/10.1126/sciadv.abj8394.

Description: How the ocean circulation changes in a warming climate is an important but poorly understood problem. Using a global ocean model, we decompose the problem into distinct responses to changes in sea surface temperature, salinity, and wind. Our results show that the surface warming effect, a robust feature of anthropogenic climate change, dominates and accelerates the upper ocean currents in 77% of the global ocean. Specifically, the increased vertical stratification intensifies the upper subtropical gyres and equatorial currents by shoaling these systems, while the differential warming between the Southern Ocean upwelling zone and the region to the north accelerates surface zonal currents in the Southern Ocean. In comparison, the wind stress and surface salinity changes affect regional current systems. Our study points a way forward for investigating ocean circulation change and evaluating the uncertainty.

Description: Q.P. is supported by the National Natural Science Foundation of China (42005035), the Science and Technology Planning Project of Guangzhou (202102020935), and the Independent Research Project Program of State Key Laboratory of Tropical Oceanography (LTOZZ2102). D.W. is supported by the National Natural Science Foundation of China (92158204), and the Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) (311020004). S.-P.X. is supported by the National Science Foundation (AGS-1934392). Y.S. is supported by the National Key Research and Development Program of China (2016YFC1401702). G.C. is supported by National Natural Science Foundation of China (41822602). The numerical simulation is supported by the High-Performance Computing Division and HPC managers of W. Zhou and D. Sui in the South China Sea Institute of Oceanology.

Description: Arctic river deltas and deltaic near-shore zones represent important land–ocean transition zones influencing sediment dynamics and nutrient fluxes from permafrost-affected terrestrial ecosystems into the coastal Arctic Ocean. To accurately model fluvial carbon and freshwater export from rapidly changing river catchments as well as assess impacts of future change on the Arctic shelf and coastal ecosystems, we need to understand the sea floor characteristics and topographic variety of the coastal zones. To date, digital bathymetrical data from the poorly accessible, shallow, and large areas of the eastern Siberian Arctic shelves are sparse. We have digitized bathymetrical information for nearly 75 000 locations from large-scale (1:25 000–1:500 000) current and historical nautical maps of the Lena Delta and the Kolyma Gulf region in northeastern Siberia. We present the first detailed and seamless digital models of coastal zone bathymetry for both delta and gulf regions in 50 and 200 m spatial resolution. We validated the resulting bathymetry layers using a combination of our own water depth measurements and a collection of available depth measurements, which showed a strong correlation (r〉0.9). Our bathymetrical models will serve as an input for a high-resolution coupled hydrodynamic–ecosystem model to better quantify fluvial and coastal carbon fluxes to the Arctic Ocean, but they may be useful for a range of other studies related to Arctic delta and near-shore dynamics such as modeling of submarine permafrost, near-shore sea ice, or shelf sediment transport. The new digital high-resolution bathymetry products are available on the PANGAEA data set repository for the Lena Delta (https://doi.org/10.1594/PANGAEA.934045; Fuchs et al., 2021a) and Kolyma Gulf region (https://doi.org/10.1594/PANGAEA.934049; Fuchs et al., 2021b), respectively. Likewise, the depth validation data are available on PANGAEA as well (https://doi.org/10.1594/PANGAEA.933187; Fuchs et al., 2021c).

Description: Data from the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition allowed us to investigate the temporal dynamics of snowfall, snow accumulation and erosion in great detail for almost the whole accumulation season (November 2019 to May 2020). We computed cumulative snow water equivalent (SWE) over the sea ice based on snow depth and density retrievals from a SnowMicroPen and approximately weekly measured snow depths along fixed transect paths. We used the derived SWE from the snow cover to compare with precipitation sensors installed during MOSAiC. The data were also compared with ERA5 reanalysis snowfall rates for the drift track. We found an accumulated snow mass of 38 m SWE between the end of October 2019 and end of April 2020. The initial SWE over first-year ice relative to second-year ice increased from 50 % to 90 % by end of the investigation period. Further, we found that the Vaisala Present Weather Detector 22, an optical precipitation sensor, and installed on a railing on the top deck of research vessel Polarstern, was least affected by blowing snow and showed good agreements with SWE retrievals along the transect. On the contrary, the OTT Pluvio2 pluviometer and the OTT Parsivel2 laser disdrometer were largely affected by wind and blowing snow, leading to too high measured precipitation rates. These are largely reduced when eliminating drifting snow periods in the comparison. ERA5 reveals good timing of the snowfall events and good agreement with ground measurements with an overestimation tendency. Retrieved snowfall from the ship-based Ka-band ARM zenith radar shows good agreements with SWE of the snow cover and differences comparable to those of ERA5. Based on the results, we suggest the Ka-band radar-derived snowfall as an upper limit and the present weather detector on RV Polarstern as a lower limit of a cumulative snowfall range. Based on these findings, we suggest a cumulative snowfall of 72 to 107 m and a precipitation mass loss of the snow cover due to erosion and sublimation as between 47 % and 68 %, for the time period between 31 October 2019 and 26 April 2020. Extending this period beyond available snow cover measurements, we suggest a cumulative snowfall of 98-114 m.

Description: Metabolic interactions between auxotrophs and prototrophs in microbial communities are understudied. Yu et al. showed how intracellular as well as intercellular metabolism affects community fitness in the absence and presence of abiotic stress, that is, drugs.

Description: The Global Ocean Data Analysis Project (GLODAP) is a synthesis effort providing regular compilations of surface-to-bottom ocean biogeochemical bottle data, with an emphasis on seawater inorganic carbon chemistry and related variables determined through chemical analysis of seawater samples. GLODAPv2.2022 is an update of the previous version, GLODAPv2.2021 (Lauvset et al., 2021). The major changes are as follows: data from 96 new cruises were added, data coverage was extended until 2021, and for the first time we performed secondary quality control on all sulphur hexafluoride (SF6) data. In addition, a number of changes were made to data included in GLODAPv2.2021. These changes affect specifically the SF6 data, which are now subjected to secondary quality control, and carbon data measured onboard the RV Knorr in the Indian Ocean in 1994–1995 which are now adjusted using CRM measurements made at the time. GLODAPv2.2022 includes measurements from almost 1.4 million water samples from the global oceans collected on 1085 cruises. The data for the now 13 GLODAP core variables (salinity, oxygen, nitrate, silicate, phosphate, dissolved inorganic carbon, total alkalinity, pH, CFC-11, CFC-12, CFC-113, CCl4, and SF6) have undergone extensive quality control with a focus on systematic evaluation of bias. The data are available in two formats: (i) as submitted by the data originator but converted to World Ocean Circulation Experiment (WOCE) exchange format and (ii) as a merged data product with adjustments applied to minimize bias. For the present annual update, adjustments for the 96 new cruises were derived by comparing those data with the data from the 989 quality controlled cruises in the GLODAPv2.2021 data product using crossover analysis. SF6 data from all cruises were evaluated by comparison with CFC-12 data measured on the same cruises. For nutrients and ocean carbon dioxide (CO2) chemistry comparisons to estimates based on empirical algorithms provided additional context for adjustment decisions. The adjustments that we applied are intended to remove potential biases from errors related to measurement, calibration, and data handling practices without removing known or likely time trends or variations in the variables evaluated. The compiled and adjusted data product is believed to be consistent to better than 0.005 in salinity, 1 % in oxygen, 2 % in nitrate, 2 % in silicate, 2 % in phosphate, 4 μmol kg-1 in dissolved inorganic carbon, 4 μmol kg-1 in total alkalinity, 0.01–0.02 in pH (depending on region), and 5 % in the halogenated transient tracers. The other variables included in the compilation, such as isotopic tracers and discrete CO2 fugacity (fCO2), were not subjected to bias comparison or adjustments.

Description: The diagnosis of the conservation state of monumental structures from constraints to the spatial distribution of their physical properties on shallow and inner materials represents one of the key objectives in the application of non-invasive techniques. In situ, CRP and 3D ultrasonic tomography can provide an effective coverage of stone materials in space and time. The intrinsic characteristics of the materials that make up a monumental structure and affect the two properties (i.e., reflectivity, longitudinal velocity) through the above methods substantially differ. Consequently, the content of their information is mainly complementary rather than redundant. In this study we present the integrated application of different non-destructive techniques i.e., Close Range Photogrammetry (CRP), and low frequency (24 KHz) ultrasonic tomography complemented by petrographycal analysis based essentially on Optical Microscopy (OM). This integrated methodology has been applied to a Carrara marble column of the Basilica of San Saturnino, in Byzantine-Proto-Romanesque style, which is part of the Paleo Christian complex of the V-VI century. This complex also includes the adjacent Christian necropolis in the square of San Cosimo in the city of Cagliari, Sardinia, Italy. The column under study is made of bare material dating back probably to the first century A.D., it was subjected to various traumas due to disassembly and transport to the site, including damage caused by the close blast of a WWII fragmentation bomb. High resolution 3D modelling of the studied artifact was computed starting from the integration of proximal sensing techniques such as CRP based on Structure from Motion (SfM), with which information about the geometrical anomalies and reflectivity of the investigated marble column surface was obtained. On the other hand, the inner parts of the studied body were successfully inspected in a non-invasive way by computing the velocity pattern of the ultrasonic signal through the investigated materials using 3D ultrasonic tomography. This technique gives information on the elastic properties of the material related with mechanical properties and a number of factors, such as presence of fractures, voids, and flaws. Extracting information on such factors from the elastic wave velocity using 3D tomography provides a non-invasive approach to analyse the property changes of the inner material of the ancient column. The integrated application of in situ CRP and ultrasonic techniques provides a full 3D high resolution model of the investigated artifact. This model enhanced by the knowledge of the petrographic characteristics of the materials, improves the diagnostic process and affords reliable information on the state of conservation of the materials used in the construction processes of the studied monumental structure. The integrated use of the non-destructive techniques described above also provides suitable data for a possible restoration and future preservation.

Description: Copernicus

Description: Published

Description: On line

Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica

Description: Originating from the boreal forest and often transported over large distances, driftwood characterises many Arctic coastlines. Here we present a combined assessment of radiocarbon (14C) and dendrochronological (ring width) age estimates of driftwood samples to constrain the progradation of two Holocene beach-ridge systems near the Lena Delta in the Siberian Arctic (Laptev Sea). Our data show that the 14C ages obtained on syndepositional driftwood from beach deposits yield surprisingly coherent chronologies for the coastal evolution of the field sites. The dendrochronological analysis of wood from modern driftlines revealed the origin and recent delivery of the wood from the Lena River catchments. This finding suggests that the duration transport lies within the uncertainty of state-of-the-art 14C dating and thus substantiates the validity of age indication obtained from driftwood. This observation will help to better understand changes in similar coastal environments, and to improve our knowledge about the response of coastal systems to past climate and sea-level changes.

Description: Earth system and climate modelling involves the simulation of processes on a wide range of scales and within and across various compartments of the Earth system. In practice, component models are often developed independently by different research groups, adapted by others to their special interests and then combined using a dedicated coupling software. This procedure not only leads to a strongly growing number of available versions of model components and coupled setups but also to model- and high-performance computing (HPC)-system-dependent ways of obtaining, configuring, building and operating them. Therefore, implementing these Earth system models (ESMs) can be challenging and extremely time consuming, especially for less experienced modellers or scientists aiming to use different ESMs as in the case of intercomparison projects. To assist researchers and modellers by reducing avoidable complexity, we developed the ESM-Tools software, which provides a standard way for downloading, configuring, compiling, running and monitoring different models on a variety of HPC systems. It should be noted that ESM-Tools is not a coupling software itself but a workflow and infrastructure management tool to provide access to increase usability of already existing components and coupled setups. As coupled ESMs are technically the more challenging tasks, we will focus on coupled setups, always implying that stand-alone models can benefit in the same way. With ESM-Tools, the user is only required to provide a short script consisting of only the experiment-specific definitions, while the software executes all the phases of a simulation in the correct order. The software, which is well documented and easy to install and use, currently supports four ocean models, three atmosphere models, two biogeochemistry models, an ice sheet model, an isostatic adjustment model, a hydrology model and a land-surface model. Compared to previous versions, ESM-Tools has lately been entirely recoded in a high-level programming language (Python) and provides researchers with an even more user-friendly interface for Earth system modelling. ESM-Tools was developed within the framework of the Advanced Earth System Model Capacity project, supported by the Helmholtz Association.

Description: Numerous studies have addressed the possible existence of large floating ice sheets in the glacial Arctic Ocean from theoretical, modelling, or seafloor morphology perspectives. Here, we add evidence from the sediment record that support the existence of such freshwater ice caps in certain intervals, and we discuss their implications for possible non-linear and rapid behaviour of such a system in the high latitudes. We present sedimentary activities of 230Th together with 234U/238U ratios, the concentrations of manganese, sulphur and calcium in the context of lithological information and records of microfossils and their isotope composition. New analyses (PS51/038, PS72/396) and a re-analysis of existing marine sediment records (PS1533, PS1235, PS2185, PS2200, amongst others) in view of the naturally occurring radionuclide 230Thex and, where available, 10Be from the Arctic Ocean and the Nordic Seas reveal the widespread occurrence of intervals with a specific geochemical signature. The pattern of these parameters in a pan-Arctic view can best be explained when assuming the repeated presence of freshwater in frozen and liquid form across large parts of the Arctic Ocean and the Nordic Seas. Based on the sedimentary evidence and known environmental constraints at the time, we develop a glacial scenario that explains how these ice sheets, together with eustatic sea-level changes, may have affected the past oceanography of the Arctic Ocean in a fundamental way that must have led to a drastic and non-linear response to external forcing. This concept offers a possibility to explain and to some extent reconcile contrasting age models for the Late Pleistocene in the Arctic Ocean. Our view, if adopted, offers a coherent dating approach across the Arctic Ocean and the Nordic Seas, linked to events outside the Arctic.

Description: The modeling of paleoclimate, using physically based tools, is increasingly seen as a strong out-of-sample test of the models that are used for the projection of future climate changes. New to the Coupled Model Intercomparison Project (CMIP6) is the Tier 1 Last Interglacial experiment for 127 000 years ago (lig127k), designed to address the climate responses to stronger orbital forcing than the midHolocene experiment, using the same state-of-the-art models as for the future and following a common experimental protocol. Here we present a first analysis of a multi-model ensemble of 17 climate models, all of which have completed the CMIP6 DECK (Diagnostic, Evaluation and Characterization of Klima) experiments. The equilibrium climate sensitivity (ECS) of these models varies from 1.8 to 5.6 ∘C. The seasonal character of the insolation anomalies results in strong summer warming over the Northern Hemisphere continents in the lig127k ensemble as compared to the CMIP6 piControl and much-reduced minimum sea ice in the Arctic. The multi-model results indicate enhanced summer monsoonal precipitation in the Northern Hemisphere and reductions in the Southern Hemisphere. These responses are greater in the lig127k than the CMIP6 midHolocene simulations as expected from the larger insolation anomalies at 127 than 6 ka. New synthesis for surface temperature and precipitation, targeted for 127 ka, have been developed for comparison to the multi-model ensemble. The lig127k model ensemble and data reconstructions are in good agreement for summer temperature anomalies over Canada, Scandinavia, and the North Atlantic and for precipitation over the Northern Hemisphere continents. The model–data comparisons and mismatches point to further study of the sensitivity of the simulations to uncertainties in the boundary conditions and of the uncertainties and sparse coverage in current proxy reconstructions. The CMIP6–Paleoclimate Modeling Intercomparison Project (PMIP4) lig127k simulations, in combination with the proxy record, improve our confidence in future projections of monsoons, surface temperature, and Arctic sea ice, thus providing a key target for model evaluation and optimization.

Description: In order to investigate the impact of spatial resolution on the discrepancy between simulated δ18O and observed δ18O in Greenland ice cores, regional climate simulations are performed with the isotope-enabled regional climate model (RCM) COSMO_iso. For this purpose, isotope-enabled general circulation model (GCM) simulations with the ECHAM5-wiso general circulation model (GCM) under present-day conditions and the MPI-ESM-wiso GCM under mid-Holocene conditions are dynamically downscaled with COSMO_iso for the Arctic region. The capability of COSMO_iso to reproduce observed isotopic ratios in Greenland ice cores for these two periods is investigated by comparing the simulation results to measured δ18O ratios from snow pit samples, Global Network of Isotopes in Precipitation (GNIP) stations and ice cores. To our knowledge, this is the first time that a mid-Holocene isotope-enabled RCM simulation is performed for the Arctic region. Under present-day conditions, a dynamical downscaling of ECHAM5-wiso (1.1◦ × 1.1◦) with COSMO_iso to a spatial resolution of 50km improves the agreement with the measured δ18O ratios for 14 of 19 observational data sets. A further increase in the spatial resolution to 7km does not yield substantial improvements except for the coastal areas with its complex terrain. For the mid-Holocene, a fully coupled MPI-ESM-wiso time slice simulation is downscaled with COSMO_iso to a spatial resolution of 50km. In the mid-Holocene, MPI-ESM-wiso already agrees well with observations in Greenland and a downscaling with COSMO_iso does not further improve the model–data agreement. Despite this lack of improvement in model biases, the study shows that in both periods, observed δ18O values at measurement sites constitute isotope ratios which are mainly within the subgrid-scale variability of the global ECHAM5-wiso and MPI-ESM-wiso simulation results. The correct δ18O ratios are consequently not resolved in the GCM simulation results and need to be extracted by a refinement with an RCM. In this context, the RCM simulations provide a spatial δ18O distribution by which the effects of local uncertainties can be taken into account in the comparison between point measurements and model outputs. Thus, an isotope-enabled GCM–RCM model chain with realistically implemented fractionating processes constitutes a useful supplement to reconstruct regional paleo-climate conditions during the mid-Holocene in Greenland. Such model chains might also be applied to reveal the full potential of GCMs in other regions and climate periods, in which large deviations relative to observed isotope ratios are simulated.

Description: Proxy climate records are an invaluable source of information about the earth’s climate prior to the instrumental record. The temporal- and spatial-coverage of records continues to increase, however, these records of past climate are associated with significant uncertainties due to non-climate processes that influence the recorded and measured proxy values. Generally, these uncertainties are timescale-dependent and correlated in time. Accounting for structure in the errors is essential to providing realistic error estimates for smoothed or stacked records, detection of anomalies and identifying trends, but this structure is seldom accounted for. In the first of these companion articles we outlined a theoretical framework for handling proxy uncertainties by deriving the power spectrum of proxy error components from which it is possible to obtain timescale-dependent error estimates. Here in part II, we demonstrate the practical application of this theoretical framework using the example of marine sediment cores. We consider how to obtain estimates for the required parameters and give examples of the application of this approach for typical marine sediment proxy records. Our new approach of estimating and providing timescale-dependent proxy errors overcomes the limitations of simplistic single value error estimates. We aim to provide the conceptual basis for a more quantitative use of paleo-records for applications such as model-data comparison, regional and global synthesis of past climate states and data assimilation.

Description: The mid-Pliocene warm period (mPWP; ∼3.2 million years ago) is seen as the most recent time period characterized by a warm climate state, with similar to modern geography and ∼400 ppmv atmospheric CO2 concentration, and is therefore often considered an interesting analogue for near-future climate projections. Paleoenvironmental reconstructions indicate higher surface temperatures, decreasing tropical deserts, and a more humid climate in West Africa characterized by a strengthened West African Monsoon (WAM). Using model results from the second phase of the Pliocene Modelling Intercomparison Project (PlioMIP2) ensemble, we analyse changes of the WAM rainfall during the mPWP by comparing them with the control simulations for the pre-industrial period. The ensemble shows a robust increase in the summer rainfall over West Africa and the Sahara region, with an average increase of 2.5 mm/d, contrasted by a rainfall decrease over the equatorial Atlantic. An anomalous warming of the Sahara and deepening of the Saharan Heat Low, seen in 〉90 % of the models, leads to a strengthening of the WAM and an increased monsoonal flow into the continent. A similar warming of the Sahara is seen in future projections using both phase 3 and 5 of the Coupled Model Intercomparison Project (CMIP3 and CMIP5). Though previous studies of future projections indicate a west–east drying–wetting contrast over the Sahel, PlioMIP2 simulations indicate a uniform rainfall increase in that region in warm climates characterized by increasing greenhouse gas forcing. We note that this effect will further depend on the long-term response of the vegetation to the CO2 forcing.

Description: The mid-Pliocene warm period (3.264–3.025 Ma) is the most recent geological period during which atmospheric CO2 levels were similar to recent historical values (∼400 ppm). Several proxy reconstructions for the mid-Pliocene show highly reduced zonal sea surface temperature (SST) gradients in the tropical Pacific Ocean, indicating an El Niño-like mean state. However, past modelling studies do not show these highly reduced gradients. Efforts to understand mid-Pliocene climate dynamics have led to the Pliocene Model Intercomparison Project (PlioMIP). Results from the first phase (PlioMIP1) showed clear El Niño variability (albeit significantly reduced) and did not show the greatly reduced time-mean zonal SST gradient suggested by some of the proxies. In this work, we study El Niño–Southern Oscillation (ENSO) variability in the PlioMIP2 ensemble, which consists of additional global coupled climate models and updated boundary conditions compared to PlioMIP1. We quantify ENSO amplitude, period, spatial structure and “flavour”, as well as the tropical Pacific annual mean state in mid-Pliocene and pre-industrial simulations. Results show a reduced ENSO amplitude in the model-ensemble mean (−24 %) with respect to the pre-industrial, with 15 out of 17 individual models showing such a reduction. Furthermore, the spectral power of this variability considerably decreases in the 3–4-year band. The spatial structure of the dominant empirical orthogonal function shows no particular change in the patterns of tropical Pacific variability in the model-ensemble mean, compared to the pre-industrial. Although the time-mean zonal SST gradient in the equatorial Pacific decreases for 14 out of 17 models (0.2 ∘C reduction in the ensemble mean), there does not seem to be a correlation with the decrease in ENSO amplitude. The models showing the most “El Niño-like” mean state changes show a similar ENSO amplitude to that in the pre-industrial reference, while models showing more “La Niña-like” mean state changes generally show a large reduction in ENSO variability. The PlioMIP2 results show a reasonable agreement with both time-mean proxies indicating a reduced zonal SST gradient and reconstructions indicating a reduced, or similar, ENSO variability.

Description: The mid-Pliocene (∼3 Ma) is one of the most recent warm periods with high CO2 concentrations in the atmosphere and resulting high temperatures, and it is often cited as an analog for near-term future climate change. Here, we apply a moisture budget analysis to investigate the response of the large-scale hydrological cycle at low latitudes within a 13-model ensemble from the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2). The results show that increased atmospheric moisture content within the mid-Pliocene ensemble (due to the thermodynamic effect) results in wetter conditions over the deep tropics, i.e., the Pacific intertropical convergence zone (ITCZ) and the Maritime Continent, and drier conditions over the subtropics. Note that the dynamic effect plays a more important role than the thermodynamic effect in regional precipitation minus evaporation (PmE) changes (i.e., northward ITCZ shift and wetter northern Indian Ocean). The thermodynamic effect is offset to some extent by a dynamic effect involving a northward shift of the Hadley circulation that dries the deep tropics and moistens the subtropics in the Northern Hemisphere (i.e., the subtropical Pacific). From the perspective of Earth's energy budget, the enhanced southward cross-equatorial atmospheric transport (0.22 PW), induced by the hemispheric asymmetries of the atmospheric energy, favors an approximately 1∘ northward shift of the ITCZ. The shift of the ITCZ reorganizes atmospheric circulation, favoring a northward shift of the Hadley circulation. In addition, the Walker circulation consistently shifts westward within PlioMIP2 models, leading to wetter conditions over the northern Indian Ocean. The PlioMIP2 ensemble highlights that an imbalance of interhemispheric atmospheric energy during the mid-Pliocene could have led to changes in the dynamic effect, offsetting the thermodynamic effect and, hence, altering mid-Pliocene hydroclimate.

Description: Due to its dryness, the subtropical free troposphere plays a critical role in the radiative balance of the Earth's climate system. But the complex interactions of the dynamical and physical processes controlling the variability in the moisture budget of this sensitive region of the subtropical atmosphere are still not fully understood. Stable water isotopes can provide important information about several of the latter processes, namely subsidence drying, turbulent mixing, and dry and moist convective moistening. In this study, we use high-resolution simulations of the isotope-enabled version of the regional weather and climate prediction model of the Consortium for Small-Scale Modelling (COSMOiso) to investigate predominant moisture transport pathways in the Canary Islands region in the eastern subtropical North Atlantic. Comparison of the simulated isotope signals with multi-platform isotope observations (aircraft, ground- and space-based remote sensing) from a field campaign in summer 2013 shows that COSMOiso can reproduce the observed variability of stable water vapour isotopes on timescales of hours to days, thus allowing us to study the mechanisms that control the subtropical free-tropospheric humidity. Changes in isotopic signals along backward trajectories from the Canary Islands region reveal the physical processes behind the synoptic-scale isotope variability. We identify four predominant moisture transport pathways of mid-tropospheric air, each with distinct isotopic signatures: - air parcels originating from the convective boundary layer of the Saharan heat low (SHL) – these are characterised by a homogeneous isotopic composition with a particularly high δD (median mid-tropospheric δD=−122‰), which results from dry convective mixing of low-level moisture of diverse origin advected into the SHL; - air parcels originating from the free troposphere above the SHL – although experiencing the largest changes in humidity and δD during their subsidence over West Africa, these air parcels typically have lower δD values (median δD=−148‰) than air parcels originating from the boundary layer of the SHL; - air parcels originating from outside the SHL region, typically descending from tropical upper levels south of the SHL, which are often affected by moist convective injections from mesoscale convective systems in the Sahel – their isotopic composition is much less enriched in heavy isotopes (median δD=−175‰) than those from the SHL region; - air parcels subsiding from the upper-level extratropical North Atlantic – this pathway leads to the driest and most depleted conditions (median δD=−255‰) in the middle troposphere near the Canary Islands. The alternation of these transport pathways explains the observed high variability in humidity and δD on synoptic timescales to a large degree. We further show that the four different transport pathways are related to specific large-scale flow conditions. In particular, distinct differences in the location of the North African mid-level anticyclone and of extratropical Rossby wave patterns occur between the four transport pathways. Overall, this study demonstrates that the adopted Lagrangian isotope perspective enhances our understanding of air mass transport and mixing and offers a sound interpretation of the free-tropospheric variability of specific humidity and isotope composition on timescales of hours to days in contrasting atmospheric conditions over the eastern subtropical North Atlantic.

Description: Elemental carbon exists in different structural forms including graphite, diamond, fullerenes, and amorphous carbon. In nature, these materials are produced through abiotic chemical processes under high temperature and pressure but are considered generally inaccessible to biochemical synthesis or breakdown. Here, we identified and characterized elemental carbon isolated from consortia of anaerobic methanotrophic archaea (ANME) and sulfate-reducing bacteria (SRB), which together carry out the anaerobic oxidation of methane (AOM). Two different AOM consortia, ANME-1a/HotSeep-1 and ANME-2a/c/Seep-SRB, produce a black material with similar characteristics to disordered graphite and amorphous carbon. Stable isotope probing studies revealed that the carbon is microbially generated during AOM. In addition, we found that select methanogens also produce amorphous carbon with similar characteristics to the carbon from AOM consortia. Biogenic amorphous carbon may serve as a conductive element to facilitate electron transfer, or redox active functional groups associated with the carbon could act as electron donors and acceptors.

Description: Methanogens are considered as one of the earliest life forms on Earth, and together with anaerobic methane-oxidizing archaea, they have crucial effects on climate stability. However, the origin and evolution of anaerobic alkane metabolism in the domain Archaea remain controversial. Here, we present evidence that methylotrophic methanogenesis was the ancestral form of this metabolism. Carbon dioxide–reducing methanogenesis developed later through the evolution of tetrahydromethanopterin S-methyltransferase, which linked methanogenesis to the Wood-Ljungdahl pathway for energy conservation. Anaerobic multicarbon alkane metabolisms in Archaea also originated early, with genes coding for the activation of short-chain or even long-chain alkanes likely evolving from an ethane-metabolizing ancestor. These genes were likely horizontally transferred to multiple archaeal clades including Candidatus (Ca.) Bathyarchaeia, Ca. Lokiarchaeia, Ca. Hadarchaeia, and the methanogenic Ca. Methanoliparia.

Description: The Italian earthquake waveform data are collected here in a dataset suited for machine learning analysis (ML) applications. The dataset consists of nearly 1.2 million three-component (3C) waveform traces from about 50 000 earthquakes and more than 130 000 noise 3C waveform traces, for a total of about 43 000 h of data and an average of 21 3C traces provided per event. The earthquake list is based on the Italian Seismic Bulletin (http://terremoti.ingv.it/bsi, last access: 15 February 2020​​​​​​​) of the Istituto Nazionale di Geofisica e Vulcanologia between January 2005 and January 2020, and it includes events in the magnitude range between 0.0 and 6.5. The waveform data have been recorded primarily by the Italian National Seismic Network (network code IV) and include both weak- (HH, EH channels) and strong-motion (HN channels) recordings. All the waveform traces have a length of 120 s, are sampled at 100 Hz, and are provided both in counts and ground motion physical units after deconvolution of the instrument transfer functions. The waveform dataset is accompanied by metadata consisting of more than 100 parameters providing comprehensive information on the earthquake source, the recording stations, the trace features, and other derived quantities. This rich set of metadata allows the users to target the data selection for their own purposes. Much of these metadata can be used as labels in ML analysis or for other studies. The dataset, assembled in HDF5 format, is available at http://doi.org/10.13127/instance (Michelini et al., 2021).

Description: Published

Description: 5509–5544

Description: 4T. Sismicità dell'Italia

Description: JCR Journal

Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Gomaa, F., Utter, D. R., Powers, C., Beaudoin, D. J., Edgcomb, V. P., Filipsson, H. L., Hansel, C. M., Wankel, S. D., Zhang, Y., & Bernhard, J. M. Multiple integrated metabolic strategies allow foraminiferan protists to thrive in anoxic marine sediments. Science Advances, 7(22), (2021): eabf1586, https://doi.org/10.1126/sciadv.abf1586.

Description: Oceanic deoxygenation is increasingly affecting marine ecosystems; many taxa will be severely challenged, yet certain nominally aerobic foraminifera (rhizarian protists) thrive in oxygen-depleted to anoxic, sometimes sulfidic, sediments uninhabitable to most eukaryotes. Gene expression analyses of foraminifera common to severely hypoxic or anoxic sediments identified metabolic strategies used by this abundant taxon. In field-collected and laboratory-incubated samples, foraminifera expressed denitrification genes regardless of oxygen regime with a putative nitric oxide dismutase, a characteristic enzyme of oxygenic denitrification. A pyruvate:ferredoxin oxidoreductase was highly expressed, indicating the capability for anaerobic energy generation during exposure to hypoxia and anoxia. Near-complete expression of a diatom’s plastid genome in one foraminiferal species suggests kleptoplasty or sequestration of functional plastids, conferring a metabolic advantage despite the host living far below the euphotic zone. Through a unique integration of functions largely unrecognized among “typical” eukaryotes, benthic foraminifera represent winning microeukaryotes in the face of ongoing oceanic deoxygenation.

Description: his project was funded by the U.S. NSF IOS 1557430 and 1557566. H.L.F. acknowledges support from the Swedish Research Council VR (grant number 2017-04190).

Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Le Roux, V., Urann, B. M., Brunelli, D., Bonatti, E., Cipriani, A., Demouchy, S., & Monteleone, B. D. Postmelting hydrogen enrichment in the oceanic lithosphere. Science Advances, 7(24), (2021): eabf6071, https://doi.org/10.1126/sciadv.abf6071.

Description: The large range of H2O contents recorded in minerals from exhumed mantle rocks has been challenging to interpret, as it often records a combination of melting, metasomatism, and diffusional processes in spatially isolated samples. Here, we determine the temporal variations of H2O contents in pyroxenes from a 24-Ma time series of abyssal peridotites exposed along the Vema fracture zone (Atlantic Ocean). The H2O contents of pyroxenes correlate with both crustal ages and pyroxene chemistry and increase toward younger and more refractory peridotites. These variations are inconsistent with residual values after melting and opposite to trends often observed in mantle xenoliths. Postmelting hydrogen enrichment occurred by ionic diffusion during cryptic metasomatism of peridotite residues by low-degree, volatile-rich melts and was particularly effective in the most depleted peridotites. The presence of hydrous melts under ridges leads to widespread hydrogen incorporation in the oceanic lithosphere, likely lowering mantle viscosity compared to dry models.

Description: Funding for this study was supported by NSF EAR-P&G 1524311 and 1839128 to V.L.R. and the Andrew W. Mellon Foundation Award for Innovative Research to V.L.R. A.C. and D.B. were funded by the Italian Programma di Rilevante Interesse Nazionale PRIN 20178LPCPW and PRIN2017KY5ZX8, respectively. Revisions were performed within the duration of a “Visiting Scholar at SCIENCE 2020” award to V.L.R. (University of Copenhagen, Denmark), with support from the Department of Geosciences and Natural Resource Management, Section for Geology.

Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Clemens, S. C., Yamamoto, M., Thirumalai, K., Giosan, L., Richey, J. N., Nilsson-Kerr, K., Rosenthal, Y., Anand, P., & McGrath, S. M. Remote and local drivers of Pleistocene South Asian summer monsoon precipitation: a test for future predictions. Science Advances, 7(23), (2021): eabg3848, https://doi.org/10.1126/sciadv.abg3848.

Description: South Asian precipitation amount and extreme variability are predicted to increase due to thermodynamic effects of increased 21st-century greenhouse gases, accompanied by an increased supply of moisture from the southern hemisphere Indian Ocean. We reconstructed South Asian summer monsoon precipitation and runoff into the Bay of Bengal to assess the extent to which these factors also operated in the Pleistocene, a time of large-scale natural changes in carbon dioxide and ice volume. South Asian precipitation and runoff are strongly coherent with, and lag, atmospheric carbon dioxide changes at Earth’s orbital eccentricity, obliquity, and precession bands and are closely tied to cross-equatorial wind strength at the precession band. We find that the projected monsoon response to ongoing, rapid high-latitude ice melt and rising carbon dioxide levels is fully consistent with dynamics of the past 0.9 million years.

Description: S.C.C. and S.M.M. were supported by U.S. NSF OCE1634774. M.Y. was funded by JSPS grants JPMXS05R2900001 and 19H05595 and JAMSTEC Exp. 353 postcruise study. K.N.-K. and P.A. were supported by UK-IODP, Open University, and NERC (NE/L002493/1), K.T. was supported by the Technology and Research Initiative Fund, Arizona Board of Regents.

Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Seltzer, A. M., Bekaert, D. V., Barry, P. H., Durkin, K. E., Mace, E. K., Aalseth, C. E., Zappala, J. C., Mueller, P., Jurgens, B., & Kulongoski, J. T. Groundwater residence time estimates obscured by anthropogenic carbonate. Science Advances, 7(17), (2021): eabf3503, https://doi.org/10.1126/sciadv.abf3503.

Description: Groundwater is an important source of drinking and irrigation water. Dating groundwater informs its vulnerability to contamination and aids in calibrating flow models. Here, we report measurements of multiple age tracers (14C, 3H, 39Ar, and 85Kr) and parameters relevant to dissolved inorganic carbon (DIC) from 17 wells in California’s San Joaquin Valley (SJV), an agricultural region that is heavily reliant on groundwater. We find evidence for a major mid-20th century shift in groundwater DIC input from mostly closed- to mostly open-system carbonate dissolution, which we suggest is driven by input of anthropogenic carbonate soil amendments. Crucially, enhanced open-system dissolution, in which DIC equilibrates with soil CO2, fundamentally affects the initial 14C activity of recently recharged groundwater. Conventional 14C dating of deeper SJV groundwater, assuming an open system, substantially overestimates residence time and thereby underestimates susceptibility to modern contamination. Because carbonate soil amendments are ubiquitous, other groundwater-reliant agricultural regions may be similarly affected.

Description: his work was conducted as a part of the USGS National Water Quality Assessment Program (NAWQA) Enhanced Trends Project (https://water.usgs.gov/nawqa/studies/gwtrends/). Measurements at Argonne National Laboratory were supported by Department of Energy, Office of Science under contract DE-AC02-06CH11357. Measurements at Pacific Northwest National Laboratory were part of the Ultra-Sensitive Nuclear Measurements Initiative conducted under the Laboratory Directed Research and Development Program. PNNL is operated by Battelle for the U.S. Department of Energy under Contract DE-AC05-76RL01830. This work was also partially supported by NSF award OCE-1923915 (to A.M.S. and P.H.B. at WHOI).

Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Trembath-Reichert, E., Shah Walter, S. R., Ortiz, M. A. F., Carter, P. D., Girguis, P. R., & Huber, J. A. Multiple carbon incorporation strategies support microbial survival in cold subseafloor crustal fluids. Science Advances, 7(18), (2021): eabg0153, https://doi.org/10.1126/sciadv.abg0153.

Description: Biogeochemical processes occurring in fluids that permeate oceanic crust make measurable contributions to the marine carbon cycle, but quantitative assessments of microbial impacts on this vast, subsurface carbon pool are lacking. We provide bulk and single-cell estimates of microbial biomass production from carbon and nitrogen substrates in cool, oxic basement fluids from the western flank of the Mid-Atlantic Ridge. The wide range in carbon and nitrogen incorporation rates indicates a microbial community well poised for dynamic conditions, potentially anabolizing carbon and nitrogen at rates ranging from those observed in subsurface sediments to those found in on-axis hydrothermal vent environments. Bicarbonate incorporation rates were highest where fluids are most isolated from recharging bottom seawater, suggesting that anabolism of inorganic carbon may be a potential strategy for supplementing the ancient and recalcitrant dissolved organic carbon that is prevalent in the globally distributed subseafloor crustal environment.

Description: The Gordon and Betty Moore Foundation sponsored most of the observatory components at North Pond through grant GBMF1609. This work was supported by the National Science Foundation through grants NSF OCE-1745589, OCE-1635208, and OCE-1062006 to J.A.H. and NSF OCE-1635365 to P.R.G. and S.R.S.W.; NASA Postdoctoral Fellowship with the NASA Astrobiology Institute to E.T.-R.; L’Oréal USA For Women in Science Fellowship to E.T.-R.; and Woods Hole Partnership Education Program, sponsored by the Woods Hole Diversity Initiative to M.A.F.O. The Center for Dark Energy Biosphere Investigations (C-DEBI OCE-0939564) also supported the participation of J.A.H. and P.D.C. This is C-DEBI contribution number 564.

Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Johnson, A. C., Ostrander, C. M., Romaniello, S. J., Reinhard, C. T., Greaney, A. T., Lyons, T. W., & Anbar, A. D. Reconciling evidence of oxidative weathering and atmospheric anoxia on Archean Earth. Science Advances, 7(40), (2021): eabj0108, https://doi.org/10.1126/sciadv.abj0108.

Description: Evidence continues to emerge for the production and low-level accumulation of molecular oxygen (O2) at Earth’s surface before the Great Oxidation Event. Quantifying this early O2 has proven difficult. Here, we use the distribution and isotopic composition of molybdenum in the ancient sedimentary record to quantify Archean Mo cycling, which allows us to calculate lower limits for atmospheric O2 partial pressures (PO2) and O2 production fluxes during the Archean. We consider two end-member scenarios. First, if O2 was evenly distributed throughout the atmosphere, then PO2 〉 10–6.9 present atmospheric level was required for large periods of time during the Archean eon. Alternatively, if O2 accumulation was instead spatially restricted (e.g., occurring only near the sites of O2 production), then O2 production fluxes 〉0.01 Tmol O2/year were required. Archean O2 levels were vanishingly low according to our calculations but substantially above those predicted for an abiotic Earth system.

Description: We would like to thank our funding sources, including FESD “Dynamics of Earth System Oxygenation” (NSF EAR 1338810 to A.D.A.), NASA Earth and Space Science Fellowship awarded to A.C.J. (80NSSC17K0498), NSF EAR PF to A.C.J. (1952809), and WHOI Postdoctoral Fellowship to C.M.O. C.T.R. acknowledges support from the NASA Astrobiology Institute. We also acknowledge support from the Metal Utilization and Selection across Eons (MUSE) Interdisciplinary Consortium for Astrobiology Research, sponsored by the National Aeronautics and Space Administration Science Mission Directorate (19-ICAR19_2-0007).

Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Bekaert, D. V., Auro, M., Shollenberger, Q. R., Liu, M.-C., Marschall, H., Burton, K. W., Jacobsen, B., Brennecka, G. A., McPherson, G. J., von Mutius, R., Sarafian, A., & Nielsen, S. G. Fossil records of early solar irradiation and cosmolocation of the CAI factory: a reappraisal. Science Advances, 7(40), (2021): eabg8329, https://doi.org/10.1126/sciadv.abg8329.

Description: Calcium-aluminum–rich inclusions (CAIs) in meteorites carry crucial information about the environmental conditions of the nascent Solar System prior to planet formation. Based on models of 50V–10Be co-production by in-situ irradiation, CAIs are considered to have formed within ~0.1 AU from the proto-Sun. Here, we present vanadium (V) and strontium (Sr) isotopic co-variations in fine- and coarse-grained CAIs and demonstrate that kinetic isotope effects during partial condensation and evaporation best explain V isotope anomalies previously attributed to solar particle irradiation. We also report initial excesses of 10Be and argue that CV CAIs possess essentially a homogeneous level of 10Be, inherited during their formation. Based on numerical modeling of 50V–10Be co-production by irradiation, we show that CAI formation during protoplanetary disk build-up likely occurred at greater heliocentric distances than previously considered, up to planet-forming regions (~1AU), where solar particle fluxes were sufficiently low to avoid substantial in-situ irradiation of CAIs.

Description: This study was funded by NASA Emerging Worlds grant NNX16AD36G to S.G.N. and prepared by LLNL under contract DE-AC52-07NA27344 with release number LLNL-JRNL-819045. M.C.L acknowledges the support by the NASA grant 80NSSC20K0759. The UCLA ion microprobe facility is partially supported by a grant from the NSF Instrumentation and Facilities program.

Description: Geological archives record multiple reversals of Earth's magnetic poles, but the global impacts of these events, if any, remain unclear. Uncertain radiocarbon calibration has limited investigation of the potential effects of the last major magnetic inversion, known as the Laschamps Excursion 41 to 42 thousand years ago (ka). We use ancient New Zealand kauri trees (Agathis australis) to develop a detailed record of atmospheric radiocarbon levels across the Laschamps Excursion. We precisely characterize the geomagnetic reversal and perform global chemistry-climate modeling and detailed radiocarbon dating of paleoenvironmental records to investigate impacts. We find that geomagnetic field minima ~42 ka, in combination with Grand Solar Minima, caused substantial changes in atmospheric ozone concentration and circulation, driving synchronous global climate shifts that caused major environmental changes, extinction events, and transformations in the archaeological record.

Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Reusch, S., Biswas, A., Hirst, W. G., & Reber, S. Affinity purification of label-free tubulins from xenopus egg extracts. STAR Protocols, 1(3), (2020): 100151, doi:10.1016/j.xpro.2020.100151.

Description: Cytoplasmic extracts from unfertilized Xenopus eggs have made important contributions to our understanding of microtubule dynamics, spindle assembly, and scaling. Until recently, these in vitro studies relied on the use of heterologous tubulin. This protocol allows for the purification of physiologically relevant Xenopus tubulins in milligram yield, which are a complex mixture of isoforms with various post-translational modifications. The protocol is applicable to any cell or tissue of interest. For complete details on the use and execution of this protocol, please refer to Hirst et al. (2020).

Description: This article was prompted by our stay at the Marine Biological Laboratory (MBL), Woods Hole, MA, in the summer of 2016 funded by the Princeton-Humboldt Strategic Partnership Grant together with the lab of Sabine Petry (Princeton University). We are grateful to the National Xenopus Resource (NXR) for supplying frogs. For mass spectrometry, we would like to acknowledge the assistance of Benno Kuropka and Chris Weise from the Core Facility BioSupraMol supported by the Deutsche Forschungsgemeinschaft (DFG). We thank the Protein Expression Purification and Characterization (PEPC) facility at the MPI-CBG; in particular, we thank Aliona Bogdanova and Barbara Borgonovo. We thank all former and current members of the Reber lab for discussions and helpful advice, in particular Christoph Hentschel and Soma Zsoter for technical assistance. S.R. acknowledges funding from the IRI Life Sciences (Humboldt-Universität zu Berlin, Excellence Initiative/DFG). W.H. was supported by the Alliance Berlin Canberra co-funded by a grant from the Deutsche Forschungsgemeinschaft (DFG) for the International Research Training Group (IRTG) 2290 and the Australian National University.

Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in DiBenedetto, M., Qin, Z., & Suckale, J. Crystal aggregates record the pre-eruptive flow field in the volcanic conduit at Kilauea, Hawaii. Science Advances, 6(49), (2020): eabd4850, doi:10.1126/sciadv.abd4850.

Description: Developing reliable, quantitative conduit models that capture the physical processes governing eruptions is hindered by our inability to observe conduit flow directly. The closest we get to direct evidence is testimony imprinted on individual crystals or bubbles in the conduit and preserved by quenching during the eruption. For example, small crystal aggregates in products of the 1959 eruption of Kīlauea Iki, Hawaii contain overgrown olivines separated by large, hydrodynamically unfavorable angles. The common occurrence of these aggregates calls for a flow mechanism that creates this crystal misorientation. Here, we show that the observed aggregates are the result of exposure to a steady wave field in the conduit through a customized, process-based model at the scale of individual crystals. We use this model to infer quantitative attributes of the flow at the time of aggregate formation; notably, the formation of misoriented aggregates is only reproduced in bidirectional, not unidirectional, conduit flow.

Description: M.D. acknowledges support the Stanford Gerald J. Lieberman Fellowship and the Postdoctoral Scholarship from Woods Hole Oceanographic Institution.

Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Torres, J. P., Lin, Z., Watkins, M., Salcedo, P. F., Baskin, R. P., Elhabian, S., Safavi-Hemami, H., Taylor, D., Tun, J., Concepcion, G. P., Saguil, N., Yanagihara, A. A., Fang, Y., McArthur, J. R., Tae, H. S., Finol-Urdaneta, R. K., Özpolat, B. D., Olivera, B. M., & Schmidt, E. W. Small-molecule mimicry hunting strategy in the imperial cone snail, Conus imperialis. Science Advances, 7(11), (2021): eabf2704, https://doi.org/10.1126/sciadv.abf2704.

Description: Venomous animals hunt using bioactive peptides, but relatively little is known about venom small molecules and the resulting complex hunting behaviors. Here, we explored the specialized metabolites from the venom of the worm-hunting cone snail, Conus imperialis. Using the model polychaete worm Platynereis dumerilii, we demonstrate that C. imperialis venom contains small molecules that mimic natural polychaete mating pheromones, evoking the mating phenotype in worms. The specialized metabolites from different cone snails are species-specific and structurally diverse, suggesting that the cones may adopt many different prey-hunting strategies enabled by small molecules. Predators sometimes attract prey using the prey’s own pheromones, in a strategy known as aggressive mimicry. Instead, C. imperialis uses metabolically stable mimics of those pheromones, indicating that, in biological mimicry, even the molecules themselves may be disguised, providing a twist on fake news in chemical ecology.

Description: Research reported in this publication was supported by NIH R35GM12252, with contributions to biological work from NIH Fogarty International Center U19TW008163, NIH P01GM48677, and DOD CDMRP W81XWH-17-1-0413. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.

Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Guillermic, M., Cameron, L. P., De Corte, I., Misra, S., Bijma, J., de Beer, D., Reymond, C. E., Westphal, H., Ries, J. B., & Eagle, R. A. Thermal stress reduces pocilloporid coral resilience to ocean acidification by impairing control over calcifying fluid chemistry. Science Advances, 7(2), (2021): eaba9958, https://doi.org/10.1126/sciadv.aba9958.

Description: The combination of thermal stress and ocean acidification (OA) can more negatively affect coral calcification than an individual stressors, but the mechanism behind this interaction is unknown. We used two independent methods (microelectrode and boron geochemistry) to measure calcifying fluid pH (pHcf) and carbonate chemistry of the corals Pocillopora damicornis and Stylophora pistillata grown under various temperature and pCO2 conditions. Although these approaches demonstrate that they record pHcf over different time scales, they reveal that both species can cope with OA under optimal temperatures (28°C) by elevating pHcf and aragonite saturation state (Ωcf) in support of calcification. At 31°C, neither species elevated these parameters as they did at 28°C and, likewise, could not maintain substantially positive calcification rates under any pH treatment. These results reveal a previously uncharacterized influence of temperature on coral pHcf regulation—the apparent mechanism behind the negative interaction between thermal stress and OA on coral calcification.

Description: R.A.E. and J.B.R. acknowledge support from National Science Foundation grants OCE-1437166 and OCE-1437371. The work was also supported by the “Laboratoire d’Excellence” LabexMER (ANR-10-LABX-19), cofunded by a grant from the French government under the program “Investissements d’Avenir,” and an IAGC student grant 2017. R.A.E. acknowledges financial and logistical support from the Pritzker Endowment to UCLA IoES, and J.B.R. acknowledges support from the ZMT and the Hanse-Wissenschaftskolleg Fellowship Program and the NSF OCE award #1437371.

Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Skinner, C., Mill, A. C., Fox, M. D., Newman, S. P., Zhu, Y., Kuhl, A., & Polunin, N. V. C. Offshore pelagic subsidies dominate carbon inputs to coral reef predators. Science Advances, 7(8), (2021): eabf3792, https://doi.org/10.1126/sciadv.abf3792.

Description: Coral reefs were traditionally perceived as productive hot spots in oligotrophic waters. While modern evidence indicates that many coral reef food webs are heavily subsidized by planktonic production, the pathways through which this occurs remain unresolved. We used the analytical power of carbon isotope analysis of essential amino acids to distinguish between alternative carbon pathways supporting four key reef predators across an oceanic atoll. This technique separates benthic versus planktonic inputs, further identifying two distinct planktonic pathways (nearshore reef-associated plankton and offshore pelagic plankton), and revealing that these reef predators are overwhelmingly sustained by offshore pelagic sources rather than by reef sources (including reef-associated plankton). Notably, pelagic reliance did not vary between species or reef habitats, emphasizing that allochthonous energetic subsidies may have system-wide importance. These results help explain how coral reefs maintain exceptional productivity in apparently nutrient-poor tropical settings, but also emphasize their susceptibility to future ocean productivity fluctuations.

Description: Sample analysis funding was provided by NERC LSMSF grant BRIS/102/0717 and BRIS/125/1418. C.S. was supported by a Newcastle University SAgE DTA studentship and a cooperative agreement with Banyan Tree.

Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Hirst, W. G., Kiefer, C., Abdosamadi, M. K., Schäffer, E., & Reber, S. In Vitro reconstitution and imaging of microtubule dynamics by fluorescence and label-free microscopy. STAR Protocols, 1(3), (2020): 100177, doi:10.1016/j.xpro.2020.100177.

Description: Dynamic microtubules are essential for many processes in the lives of eukaryotic cells. To study and understand the mechanisms of microtubule dynamics and regulation, in vitro reconstitution with purified components has proven a vital approach. Imaging microtubule dynamics can be instructive for a given species, isoform composition, or biochemical modification. Here, we describe two methods that visualize microtubule dynamics at high speed and high contrast: (1) total internal reflection fluorescence microscopy and (2) label-free interference reflection microscopy.

Description: We thank the AMBIO imaging facility (Charité, Berlin) and Nikon at MBL for imaging support. We thank all former and current members of the Reber lab for discussion and helpful advice, in particular Christoph Hentschel and Soma Zsoter for technical assistance. S.R. acknowledges funding by the IRI Life Sciences (Humboldt-Universität zu Berlin, Excellence Initiative/DFG). W.H. was supported by the Alliance Berlin Canberra co-funded by a grant from the Deutsche Forschungsgemeinschaft (DFG) for the International Research Training Group (IRTG) 2290 and the Australian National University. C.K. thanks the Deutsche Forschungsgesellschaft (DFG, JA 2589/1-1). C.K. and M.A. thank Steve Simmert and Tobias Jachowski former and current members of the Schäffer lab.

Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Geisterfer, Z. M., Oakey, J., & Gatlin, J. C. . Microfluidic encapsulation of Xenopus laevis cell-free extracts using hydrogel photolithography. STAR Protocols, 1(3), (2020): 100221, doi:10.1016/j.xpro.2020.100221.

Description: Cell-free extract derived from the eggs of the African clawed frog Xenopus laevis is a well-established model system that has been used historically in bulk aliquots. Here, we describe a microfluidic approach for isolating discrete, biologically relevant volumes of cell-free extract, with more expansive and precise control of extract shape compared with extract-oil emulsions. This approach is useful for investigating the mechanics of intracellular processes affected by cell geometry or cytoplasmic volume, including organelle scaling and positioning mechanisms. For complete details on the use and execution of this protocol, please refer to Geisterfer et al. (2020).

Description: This work was made possible by an Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health under grant no. 2P20GM103432. It was also supported by additional funding provided by the NIGMS under grant no. R01GM113028, the NSF Faculty CAREER Program under award no. BBBE 1254608, Whitman Center fellowships at the Marine Biological Laboratory, and the Biomedical Scholars program of the Pew Charitable Trusts. We thank Drs. Aaron Groen and Tim Mitchison for their intellectual contributions and involvement in some of the pioneering experiments that set the foundation for this approach.

Description: Solar light/dark cycles and seasonal photoperiods underpin daily and annual rhythms of life on Earth. Yet, the Arctic is characterized by severalmonths of permanent illumination (‘‘midnight sun’’). To determine the persistence of 24h rhythms during the midnight sun, we investigated transcriptomic dynamics in the copepod Calanus finmarchicus during the summer solstice period in the Arctic, with the lowest diel oscillation and the highest altitude of the sun’s position. Here we reveal that in these extreme photic conditions, a widely rhythmic daily transcriptome exists, showing that very weak solar cues are sufficient to entrain organisms. Furthermore, at extremely high latitudes and under sea-ice, gene oscillations become re-organized to include 〈24h rhythms. Environmental synchronization may therefore be modulated to include non-photic signals (i.e. tidal cycles). The ability of zooplankton to be synchronized by extremely weak diel and potentially tidal cycles, may confer an adaptive temporal reorganization of biological processes at high latitudes.

Description: Methane emissions from boreal and arctic wetlands, lakes, and rivers are expected to increase in response to warming and associated permafrost thaw. However, the lack of appropriate land cover datasets for scaling field-measured methane emissions to circumpolar scales has contributed to a large uncertainty for our understanding of present-day and future methane emissions. Here we present the Boreal–Arctic Wetland and Lake Dataset (BAWLD), a land cover dataset based on an expert assessment, extrapolated using random forest modelling from available spatial datasets of climate, topography, soils, permafrost conditions, vegetation, wetlands, and surface water extents and dynamics. In BAWLD, we estimate the fractional coverage of five wetland, seven lake, and three river classes within 0.5 × 0.5∘ grid cells that cover the northern boreal and tundra biomes (17 % of the global land surface). Land cover classes were defined using criteria that ensured distinct methane emissions among classes, as indicated by a co-developed comprehensive dataset of methane flux observations. In BAWLD, wetlands occupied 3.2 × 106 km2 (14 % of domain) with a 95 % confidence interval between 2.8 and 3.8 × 106 km2. Bog, fen, and permafrost bog were the most abundant wetland classes, covering ∼ 28 % each of the total wetland area, while the highest-methane-emitting marsh and tundra wetland classes occupied 5 % and 12 %, respectively. Lakes, defined to include all lentic open-water ecosystems regardless of size, covered 1.4 × 106 km2 (6 % of domain). Low-methane-emitting large lakes (〉10 km2) and glacial lakes jointly represented 78 % of the total lake area, while high-emitting peatland and yedoma lakes covered 18 % and 4 %, respectively. Small (〈0.1 km2) glacial, peatland, and yedoma lakes combined covered 17 % of the total lake area but contributed disproportionally to the overall spatial uncertainty in lake area with a 95 % confidence interval between 0.15 and 0.38 × 106 km2. Rivers and streams were estimated to cover 0.12  × 106 km2 (0.5 % of domain), of which 8 % was associated with high-methane-emitting headwaters that drain organic-rich landscapes. Distinct combinations of spatially co-occurring wetland and lake classes were identified across the BAWLD domain, allowing for the mapping of “wetscapes” that have characteristic methane emission magnitudes and sensitivities to climate change at regional scales. With BAWLD, we provide a dataset which avoids double-accounting of wetland, lake, and river extents and which includes confidence intervals for each land cover class. As such, BAWLD will be suitable for many hydrological and biogeochemical modelling and upscaling efforts for the northern boreal and arctic region, in particular those aimed at improving assessments of current and future methane emissions. Data are freely available at https://doi.org/10.18739/A2C824F9X (Olefeldt et al., 2021).

Description: Lakes in permafrost regions are dynamiclandscape components and play an important role for climatechange feedbacks. Lake processes such as mineralizationand flocculation of dissolved organic carbon (DOC), oneof the main carbon fractions in lakes, contribute to thegreenhouse effect and are part of the global carbon cycle.These processes are in the focus of climate research, butstudies so far are limited to specific study regions. Inour synthesis, we analyzed 2167 water samples from 1833lakes across the Arctic in permafrost regions of Alaska,Canada, Greenland, and Siberia to provide first pan-Arcticinsights for linkages between DOC concentrations andthe environment. Using published data and unpublisheddatasets from the author team, we report regional DOCdifferences linked to latitude, permafrost zones, ecoregions,geology, near-surface soil organic carbon contents, andground ice classification of each lake region. The lakeDOC concentrations in our dataset range from 0 to1130 mg L−1(10.8 mg L−1median DOC concentration).Regarding the permafrost regions of our synthesis, wefound median lake DOC concentrations of 12.4 mg L−1(Siberia), 12.3 mg L−1(Alaska), 10.3 mg L−1(Greenland),and 4.5 mg L−1(Canada). Our synthesis shows a significantrelationship between lake DOC concentration and lakeecoregion. We found higher lake DOC concentrationsat boreal permafrost sites compared to tundra sites. Wefound significantly higher DOC concentrations in lakesin regions with ice-rich syngenetic permafrost deposits(yedoma) compared to non-yedoma lakes and a weak butsignificant relationship between soil organic carbon contentand lake DOC concentration as well as between ground icecontent and lake DOC. Our pan-Arctic dataset shows that theDOC concentration of a lake depends on its environmentalproperties, especially on permafrost extent and ecoregion, aswell as vegetation, which is the most important driver of lakeDOC in this study. This new dataset will be fundamental toquantify a pan-Arctic lake DOC pool for estimations of theimpact of lake DOC on the global carbon cycle and climatechange.

Description: 〈jats:p〉Abstract. The risk of carbon emissions from permafrost ground is linked to ground temperature and thus in particular to thermal insulation by vegetation and organic soil layers in summer and snow cover in winter. This ground insulation is strongly influenced by the presence of large herbivorous animals browsing for food. In this study, we examine the potential impact of large herbivore presence on the ground carbon storage in thermokarst landscapes of northeastern Siberia. Our aim is to understand how intensive animal grazing may affect permafrost thaw and hence organic matter decomposition, leading to different ground carbon storage, which is significant in the active layer. Therefore, we analysed sites with differing large herbivore grazing intensity in the Pleistocene Park near Chersky and measured maximum thaw depth, total organic carbon content and decomposition state by δ13C isotope analysis. In addition, we determined sediment grain size composition as well as ice and water content. We found the thaw depth to be shallower and carbon storage to be higher in intensively grazed areas compared to extensively and non-grazed sites in the same thermokarst basin. The intensive grazing presumably leads to a more stable thermal ground regime and thus to increased carbon storage in the thermokarst deposits and active layer. However, the high carbon content found within the upper 20 cm on intensively grazed sites could also indicate higher carbon input rather than reduced decomposition, which requires further studies. We connect our findings to more animal trampling in winter, which causes snow disturbance and cooler winter ground temperatures during the average annual 225 days below freezing. This winter cooling overcompensates ground warming due to the lower insulation associated with shorter heavily grazed vegetation during the average annual 140 thaw days. We conclude that intensive grazing influences the carbon storage capacities of permafrost areas and hence might be an actively manageable instrument to reduce net carbon emission from these sites. 〈/jats:p〉

Description: 〈jats:p〉Abstract. The combined effect of hot and dry extremes can have disastrous consequences for the society, economy, and the environment. While a significant number of studies have been conducted regarding the variability of the individual hot or dry extremes in Romania, the evaluation of the combined effect of these extremes (e.g. compound effect) is still lacking for this region. Thus, in this study we have assessed the spatio-temporal variability and trends of hot and dry summers in the eastern part of Europe, focusing on Romania, between 1950 and 2020 and we have analyzed the relationship between the frequency of hot summers and the prevailing large-scale atmospheric circulation. The length, spatial extent and frequency of HWs in Romania has increased significantly over the last 70 years, while for the drought conditions no significant changes have been observed. The rate of increase in the frequency and spatial extent of HWs has accelerated significantly after the 1990’s, while the smallest number of HWs was observed between 1970 and 1985. The hottest years, in terms of heatwave duration and frequency, were 2007, 2012, 2015, and 2019. One of the key drivers of hot summers, over our analyzed region, is the prevailing large-scale circulation, featuring an anticyclonic circulation over the central and eastern parts of Europe and enhanced atmospheric blocking activity associated with positive temperature anomalies underneath. We conclude that our study can help improve our understanding of the spatio-temporal variability of hot and dry summers, especially at the regional scale, as well as their driving mechanisms which might lead to a better predictability of these extreme events. 〈/jats:p〉

Description: We combine satellite data products to provide a first and general overview of the physical sea ice conditions along the drift of the international Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition and a comparison with previous years (2005–2006 to 2018–2019). We find that the MOSAiC drift was around 20 % faster than the climatological mean drift, as a consequence of large-scale low-pressure anomalies prevailing around the Barents–Kara–Laptev sea region between January and March. In winter (October–April), satellite observations show that the sea ice in the vicinity of the Central Observatory (CO; 50 km radius) was rather thin compared to the previous years along the same trajectory. Unlike ice thickness, satellite-derived sea ice concentration, lead frequency and snow thickness during winter months were close to the long-term mean with little variability. With the onset of spring and decreasing distance to the Fram Strait, variability in ice concentration and lead activity increased. In addition, the frequency and strength of deformation events (divergence, convergence and shear) were higher during summer than during winter. Overall, we find that sea ice conditions observed within 5 km distance of the CO are representative for the wider (50 and 100 km) surroundings. An exception is the ice thickness; here we find that sea ice within 50 km radius of the CO was thinner than sea ice within a 100 km radius by a small but consistent factor (4 %) for successive monthly averages. Moreover, satellite acquisitions indicate that the formation of large melt ponds began earlier on the MOSAiC floe than on neighbouring floes.

Description: The thermokarst lakes of permafrost regions play a major role in the global carbon cycle. These lakes are sources of methane to the atmosphere although the methane flux is restricted by an ice cover for most of the year. How methane concentrations and fluxes in these waters are affected by the presence of an ice cover is poorly understood. To relate water body morphology, ice formation and methane to each other, we studied the ice of three different water bodies in locations typical of the transition of permafrost from land to ocean in a continuous permafrost coastal region in Siberia. In total, 11 ice cores were analyzed as records of the freezing process and methane composition during the winter season. The three water bodies differed in terms of connectivity to the sea, which affected fall freezing. The first was a bay underlain by submarine permafrost (Tiksi Bay, BY), the second a shallow thermokarst lagoon cut off from the sea in winter (Polar Fox Lagoon, LG) and the third a land-locked freshwater thermokarst lake (Goltsovoye Lake, LK). Ice on all water bodies was mostly methane-supersaturated with respect to atmospheric equilibrium concentration, except for three cores from the isolated lake. In the isolated thermokarst lake, ebullition from actively thawing basin slopes resulted in the localized integration of methane into winter ice. Stable δ13C-CH4 isotope signatures indicated that methane in the lagoon ice was oxidized to concentrations close to or below the calculated atmospheric equilibrium concentration. Increasing salinity during winter freezing led to a micro-environment on the lower ice surface where methane oxidation occurred and the lagoon ice functioned as a methane sink. In contrast, the ice of the coastal marine environment was slightly supersaturated with methane, consistent with the brackish water below. Our interdisciplinary process study shows how water body morphology affects ice formation which mitigates methane fluxes to the atmosphere.

Description: In this study, the first fully continuous monitoring of water vapour isotopic composition at Neumayer Station III, Antarctica, during the 2-year period from February 2017 to January 2019 is presented. Seasonal and synoptic-scale variations in both stable water isotopes H182O and HDO are reported, and their links to variations in key meteorological variables are analysed. In addition, the diurnal cycle of isotope variations during the summer months (December and January 2017/18 and 2018/19) has been examined. Changes in local temperature and specific humidity are the main drivers for the variability in δ18O and δD in vapour at Neumayer Station III, on both seasonal and shorter timescales. In contrast to the measured δ18O and δD variations, no seasonal cycle in the Deuterium excess signal (d) in vapour is detected. However, a rather high uncertainty in measured d values especially in austral winter limits the confidence of this finding. Overall, the d signal shows a stronger inverse correlation with specific humidity than with temperature, and this inverse correlation between d and specific humidity is stronger for the cloudy-sky conditions than for clear-sky conditions during summertime. Back-trajectory simulations performed with the FLEXPART model show that seasonal and synoptic variations in δ18O and δD in vapour coincide with changes in the main sources of water vapour transported to Neumayer Station III. In general, moisture transport pathways from the east lead to higher temperatures and more enriched δ18O values in vapour, while weather situations with southerly winds lead to lower temperatures and more depleted δ18O values. However, on several occasions, δ18O variations linked to wind direction changes were observed, which were not accompanied by a corresponding temperature change. Comparing isotopic compositions of water vapour at Neumayer Station III and snow samples taken in the vicinity of the station reveals almost identical slopes, both for the δ18O–δD relation and for the temperature–δ18O relation.

Description: Hyrrokkin sarcophaga is a parasitic foraminifera that is commonly found in cold-water coral reefs where it infests the file clam Acesta excavata and the scleractinian coral Desmophyllum pertusum (formerly known as Lophelia pertusa). Here, we present measurements of the trace element and isotopic composition of these parasitic foraminifera, analyzed by inductively coupled optical emission spectrometry (ICP-OES), electron probe microanalysis (EPMA) and mass spectrometry (gas-source MS and inductively-coupled-plasma MS). Our results reveal that the geochemical signature of H. sarcophaga depends on the host organism it infests. Sr / Ca ratios are 1.1 mmol mol−1 higher in H. sarcophaga that infest D. pertusum, which could be an indication that dissolved host carbonate material is utilized in shell calcification, given that the aragonite of D. pertusum has a naturally higher Sr concentration compared to the calcite of A. excavata. Similarly, we measure 3.1 ‰ lower δ13C and 0.25 ‰ lower δ18O values in H. sarcophaga that lived on D. pertusum, which might be caused by the direct uptake of the host's carbonate material with a more negative isotopic composition or different pH regimes in these foraminifera (pH can exert a control on the extent of CO2 hydration/hydroxylation) due to the uptake of body fluids of the host. We also observe higher Mn / Ca ratios in foraminifera that lived on A. excavata but did not penetrate the host shell compared to specimen that penetrated the shell, which could be interpreted as a change in food source, changes in the calcification rate, Rayleigh fractionation or changing oxygen conditions. While our measurements provide an interesting insight into the calcification process of this unusual foraminifera, these data also indicate that the geochemistry of this parasitic foraminifera is unlikely to be a reliable indicator of paleoenvironmental conditions using Sr / Ca, Mn / Ca, δ18O or δ13C unless the host organism is known and its geochemical composition can be accounted for.