ALBERT

Description: We use a comprehensive suite of partially laminated high-resolution sediment cores from the Bering Sea, covering a depth transect from 1100 m to 2700 m to study deglacial surface ocean warming patterns, associated changes in biological productivity, oxygen minimum zone dynamics and continent-ocean links through Yukon river runoff. We apply a combination of planktic and benthic isotopes, x-ray fluorescence (XRF)-derived ele- mental ratios and a multi-proxy assessment of changes in upper ocean temperatures. Severe oxygen depletions occurred during the Bølling/Allerød (B/A) and early Holocene, which is in accordance with other locations in the North Pacific, especially the Alaska margin. Detailed analysis of the timing of lamination occurrence between the different sediment cores revealed that the onset of severe anoxia at the beginning of the B/A and early Holocene is a near-synchronous event, while the disappearance of laminations is a diachronic process. The deglacial Oxygen Minimum Zone(OMZ) strengthening is mainly driven by increased export production, visible in XRF-derived elemental ratios, and corresponding high accumulation rates of biogenic components. The export production in turn is a response to rising sea surface temperatures, decreased sea ice cover and increased thermal stratification, while a major nutrient source was the eastern continental shelf, which was flooded during the deglacial global sea level rise. It is discussed controversially whether oxygenation variations in the deglacial subarctic Pacific were coupled to changes in mid-depth water chemistry, or rather a response to physical processes like deep-intermediate ocean or mixed layer warming, or stratification changes. However, knowledge of the driving forcing mechanism for OMZ strengthening is of particular importance, as these are tightly coupled to the regional marine carbon budget, e.g. via the strength and efficiency of the biological pump. Here, our laminated sediments provided the opportunity to study ocean dynamics in exceptional detail, possible on decadal to annual timescales. Due to the correlation patterns of our records to the NGRIP oxygen isotope record through layer counts we presume that (i) the presence of laminations is tightly coupled to submillennial, short-term warm phases, especially during the Bølling-Allerød (B/A), (ii) that the laminations represent annual layered sediments (varves). The latter point in conjunction with our geochemical proxies strongly supports an atmospheric teleconnection between SE Asia, the North Atlantic and the North Pacific, with observed changes in mid-depth ocean dynamics occurring on fast, nearly decadal timescales. Thus, the Bering Sea OMZ is a highly sensitive system reacting almost instantaneously to small temperature changes and therefore has the potential to influence the global carbon budget on short timescales, in particular during episodes of rapidly warming climate.

Description: The aim of the presented study was to investigate the impact on the radiation budget of a biomass-burning plume, transported from Alaska to the High Arctic region of Ny-Ålesund, Svalbard, in early July 2015. Since the mean aerosol optical depth increased by the factor of 10 above the average summer background values, this large aerosol load event is considered particularly exceptional in the last 25 years. In situ data with hygroscopic growth equations, as well as remote sensing measurements as inputs to radiative transfer models, were used, in order to estimate biases associated with (i) hygroscopicity, (ii) variability of single-scattering albedo profiles, and (iii) plane-parallel closure of the modelled atmosphere. A chemical weather model with satellite-derived biomass-burning emissions was applied to interpret the transport and transformation pathways. The provided MODTRAN radiative transfer model (RTM) simulations for the smoke event (14:00 9 July–11:30 11 July) resulted in a mean aerosol direct radiative forcing at the levels of −78.9 and −47.0 W m ^-2 at the surface and at the top of the atmosphere, respectively, for the mean value of aerosol optical depth equal to 0.64 at 550 nm. This corresponded to the average clear-sky direct radiative forcing of −43.3 W/m ^2, estimated by radiometer and model simulations at the surface. Ultimately, uncertainty associated with the plane-parallel atmosphere approximation altered results by about 2 W m^−2. Furthermore, model-derived aerosol direct radiative forcing efficiency reached on average −126 W m^−2/τ550 and −71 W^m−2/τ550 at the surface and at the top of the atmosphere, respectively. The heating rate, estimated at up to 1.8 K day^−1 inside the biomass-burning plume, implied vertical mixing with turbulent kinetic energy of 0.3 m^2s^−2

Description: A new 21.3m firn core was drilled in 2015 at a coastal Antarctic high-accumulation site in Adélie Land (66.78◦ S; 139.56◦ E, 602 m a.s.l.), named Terre Adélie 192A (TA192A). The mean isotopic values (−19.3 ‰ ± 3.1 ‰ for δ18O and 5.4 ‰±2.2 ‰ for deuterium excess) are consistent with other coastal Antarctic values. No significant isotope–temperature relationship can be evidenced at any timescale. This rules out a simple interpretation in terms of local temperature. An observed asymmetry in the δ18O seasonal cycle may be explained by the precipitation of air masses coming from the eastern and western sectors in autumn and winter, recorded in the d-excess signal showing outstanding values in austral spring versus autumn. Significant positive trends are observed in the annual d-excess record and local sea ice extent (135–145◦ E) over the period 1998–2014. However, process studies focusing on resulting isotopic compositions and particularly the deuterium excess–δ18O relationship, evidenced as a potential fingerprint of moisture origins, as well as the collection of more isotopic measurements in Adélie Land are needed for an accurate interpretation of our signals.

Description: The timing and intensity of snowmelt processes on sea ice are key drivers determining the seasonal sea-ice energy and mass budgets. In the Arctic, satellite passive microwave and radar observations have revealed a trend towards an earlier snowmelt onset during the last decades, which is an important aspect of Arctic amplification and sea ice decline. Around Antarctica, snowmelt on perennial ice is weak and very different than in the Arctic, with most snow surviving the summer. Here we compile time series of snowmelt-onset dates on seasonal and perennial Antarctic sea ice from 1992 to 2014/15 using active microwave observations from European Remote Sensing Satellite (ERS-1/2), Quick Scatterometer (QSCAT) and Advanced Scatterometer (ASCAT) radar scatterometers. We define two snowmelt transition stages: A weak backscatter rise indicating the initial warming and destructive metamorphism of the snowpack (pre-melt), followed by a rapid backscatter rise indicating the onset of thaw-freeze cycles (snowmelt). Results show large interannual variability with an average pre-melt onset date of 29 November and melt onset of 10 December, respectively, on perennial ice, without any significant trends over the study period, consistent with the small trends of Antarctic sea ice extent. There was a latitudinal gradient from early snowmelt onsets in mid-November in the northern Weddell Sea to late (end-December) or even absent snowmelt conditions in the southern Weddell Sea. We show that QSCAT Ku-band (13.4 GHz signal frequency) derived pre-melt and snowmelt onset dates are earlier by 20 and 18 days, respectively, than ERS and ASCAT C-band (5.6 GHz) derived dates. This offset has been considered when constructing the time series. Snowmelt onset dates from passive microwave observations (37 GHz) are later by 14 and 6 days than those from the scatterometers, respectively. Based on these characteristic differences between melt onset dates observed by different microwave wavelengths, we developed a conceptual model which illustrates how the seasonal evolution of snow temperature profiles may affect different microwave bands with different penetration depths. These suggest that future multi-frequency active/passive microwave satellite missions could be used to resolve melt processes throughout the vertical snow column of thick snow on perennial Antarctic sea ice.

Description: Recent observations of near-surface soil temperatures over the circumpolar Arctic show accelerated warming of permafrost-affected soils. The availability of a comprehensive near-surface permafrost and active layer dataset is critical to better understanding climate impacts and to constraining permafrost thermal conditions and its spatial distribution in land system models. We compiled a soil temperature dataset from 72 monitoring stations in Alaska using data collected by the US Geological Survey, the National Park Service, and the University of Alaska Fairbanks permafrost monitoring networks. The array of monitoring stations spans a large range of latitudes from 60.9 to 71.3 N and elevations from near sea level to~ 1300 m, comprising tundra and boreal forest regions. This dataset consists of monthly ground temperatures at depths up to 1 m, volumetric soil water content, snow depth, and air temperature during 1997–2016. These data have been quality controlled in collection and processing. Meanwhile, we implemented data harmonization evaluation for the processed dataset. The final product (PF-AK, v0. 1) is available at the Arctic Data Center (https://doi. org/10.18739/A2KG55).

Description: Although quantitative isotope data from speleothems has been used to evaluate isotope-enabled model simulations, currently no consensus exists regarding the most appropriate methodology through which to achieve this. A number of modelling groups will be running isotope-enabled palaeoclimate simulations in the framework of the Coupled Model Intercomparison Project Phase 6, so it is timely to evaluate different approaches to using the speleothem data for data–model comparisons. Here, we illustrate this using 456 globally distributed speleothem δ18O records from an updated version of the Speleothem Isotopes Synthesis and Analysis (SISAL) database and palaeoclimate simulations generated using the ECHAM5-wiso isotope-enabled atmospheric circulation model. We show that the SISAL records reproduce the first-order spatial patterns of isotopic variability in the modern day, strongly supporting the application of this dataset for evaluating model-derived isotope variability into the past. However, the discontinuous nature of many speleothem records complicates the process of procuring large numbers of records if data–model comparisons are made using the traditional approach of comparing anomalies between a control period and a given palaeoclimate experiment. To circumvent this issue, we illustrate techniques through which the absolute isotope values during any time period could be used for model evaluation. Specifically, we show that speleothem isotope records allow an assessment of a model’s ability to simulate spatial isotopic trends. Our analyses provide a protocol for using speleothem isotope data for model evaluation, including screening the observations to take into account the impact of speleothem mineralogy on δ18O values, the optimum period for the modern observational baseline and the selection of an appropriate time window for creating means of the isotope data for palaeo-time-slices.

Description: We present here the first results, for the preindustrial and mid-Holocene climatological periods, of the newly developed isotope-enhanced version of the fully coupled Earth system model MPI-ESM, called hereafter MPI-ESM-wiso. The water stable isotopes H16O, H18O and HDO have been implemented into all components of the coupled model setup. The mid-Holocene provides the opportunity to evaluate the model response to changes in the seasonal and latitudinal distribution of insolation induced by different orbital forcing conditions. The results of our equilibrium simulations allow us to evaluate the performance of the isotopic model in simulating the spatial and temporal variations of water isotopes in the different compartments of the hydrological system for warm climates. For the preindustrial climate, MPI-ESM-wiso reproduces very well the observed spatial distribution of the isotopic content in precipitation linked to the spatial variations in temperature and precipitation rate. We also find a good model–data agreement with the observed distribution of isotopic composition in surface seawater but a bias with the presence of surface seawater that is too 18O-depleted in the Arctic Ocean. All these results are improved compared to the previous model version ECHAM5/MPIOM. The spatial relationships of water isotopic composition with temperature, precipitation rate and salinity are consistent with observational data. For the preindustrial climate, the interannual relationships of water isotopes with temperature and salinity are globally lower than the spatial ones, consistent with previous studies. Simulated results under mid-Holocene conditions are in fair agreement with the isotopic measurements from ice cores and continental speleothems. MPI-ESM-wiso simulates a decrease in the isotopic composition of precipitation from North Africa to the Tibetan Plateau via India due to the enhanced monsoons during the mid-Holocene. Over Greenland, our simulation indicates a higher isotopic composition of precipitation linked to higher summer temperature and a reduction in sea ice, shown by positive isotope–temperature gradient. For the Antarctic continent, the model simulates lower isotopic values over the East Antarctic plateau, linked to the lower temperatures during the mid-Holocene period, while similar or higher isotopic values are modeled over the rest of the continent. While variations of isotopic contents in precipitation over West Antarctica between mid-Holocene and preindustrial periods are partly controlled by changes in temperature, the transport of relatively 18O-rich water vapor near the coast to the western ice core sites could play a role in the final isotopic composition. So, more caution has to be taken about the reconstruction of past temperature variations during warm periods over this area. The coupling of such a model with an ice sheet model or the use of a zoomed grid centered on this region could help to better describe the role of the water vapor transport and sea ice around West Antarctica. The reconstruction of past salinity through isotopic content in sea surface waters can be complicated for regions with strong ocean dynamics, variations in sea ice regimes or significant changes in freshwater budget, giving an extremely variable relationship between the isotopic content and salinity of ocean surface waters over small spatial scales. These complicating factors demonstrate the complexity of interpreting water isotopes as past climate signals of warm periods like the mid-Holocene. A systematic isotope model intercomparison study for further insights on the model dependency of these results would be beneficial.

Description: The denudation history of active orogens is often interpreted in the context of modern climate gradients. Here we address the validity of this approach and ask what are the spatial and temporal variations in palaeoclimate for a latitudinally diverse range of active orogens? We do this using high-resolution (T159, ca. 80 × 80 km at the Equator) palaeoclimate simulations from the ECHAM5 global atmospheric general circulation model and a statistical cluster analysis of climate over different orogens (Andes, Himalayas, SE Alaska, Pacific NW USA). Time periods and boundary conditions considered include the Pliocene (PLIO, ∼3Ma), the Last Glacial Maximum (LGM, ∼21ka), mid-Holocene (MH, ∼6ka), and pre-industrial (PI, reference year 1850). The regional simulated climates of each orogen are described by means of cluster analyses based on the variability in precipitation, 2 m air temperature, the intra-annual amplitude of these values, and monsoonal wind speeds where appropriate. Results indicate the largest differences in the PI climate existed for the LGM and PLIO climates in the form of widespread cooling and reduced precipitation in the LGM and warming and enhanced precipitation during the PLIO. The LGM climate shows the largest deviation in annual precipitation from the PI climate and shows enhanced precipitation in the temperate Andes and coastal regions for both SE Alaska and the US Pacific Northwest. Furthermore, LGM precipitation is reduced in the western Himalayas and enhanced in the eastern Himalayas, resulting in a shift of the wettest regional climates eastward along the orogen. The cluster-analysis results also suggest more climatic variability across latitudes east of the Andes in the PLIO climate than in other time slice experiments conducted here. Taken together, these results highlight significant changes in late Cenozoic regional climatology over the last ∼3Myr. Comparison of simulated climate with proxy-based reconstructions for the MH and LGM reveal satisfactory to good performance of the model in reproducing precipitation changes, although in some cases discrepancies between neighbouring proxy observations highlight contradictions between proxy observations themselves. Finally, we document regions where the largest magnitudes of late Cenozoic changes in precipitation and temperature occur and offer the highest potential for future observational studies that quantify the impact of climate change on denudation and weathering rates.

Description: In austral spring 2016 the Antarctic region experienced anomalous sea ice retreat in all sectors, with sea ice extent in October and November 2016 being the lowest in the Southern Hemisphere over the observational period (1979–present). The extreme sea ice retreat was accompanied by widespread warming along the coastal areas as well as in the interior of the Antarctic continent. This exceptional event occurred along with a strong negative phase of the Southern Annular Mode (SAM) and the moistest and warmest spring on record, over large areas covering the Indian Ocean, the Ross Sea and the Weddell Sea. In October 2016, the positive anomalies of the totally integrated water vapor (IWV) and 2 m air temperature (T2m) over the Indian Ocean, western Pacific, Bellingshausen Sea and southern part of Ross Sea were unprecedented in the last 39 years. In October and November 2016, when the largest magnitude of negative daily sea ice concentration anomalies was observed, repeated episodes of poleward advection of warm and moist air took place. These results suggest the importance of moist and warm air intrusions into the Antarctic region as one of the main contributors to this exceptional sea ice retreat event.

Description: To resolve the mechanisms behind the major climate reorganisation which occurred between 0.9 and 1.2Ma, the recovery of a suitable 1.5 million-year-old ice core is fundamental. The quest for such an Oldest Ice core requires a number of key boundary conditions, of which the poorly known basal geothermal heat flux (GHF) is lacking. We use a transient thermodynamical 1D vertical model that solves for the rate of change of temperature in the vertical, with surface temperature and modelled GHF as boundary conditions. For each point on the ice sheet, the model is forced with variations in atmospheric conditions over the last 2Ma, and modelled ice-thickness variations. The process is repeated for a range of GHF values to determine the value of GHF that marks the limit between frozen and melting conditions over the whole ice sheet, taking into account 2Ma of climate history. These threshold values of GHF are statistically compared to existing GHF data sets. The new probabilistic GHF fields obtained for the ice sheet thus provide the missing boundary conditions in the search for Oldest Ice. High spatial resolution radar data are examined locally in the Dome Fuji and Dome C regions, as these represent the ice core community's primary drilling sites. GHF, bedrock variability, ice thickness and other essential criteria combined highlight a dozen major potential Oldest Ice sites in the vicinity of Dome Fuji and Dome C, where GHF allows for Oldest Ice.

Description: Polar ice core water isotope records are commonly used to infer past changes in Antarctic temperature, motivating an improved understanding and quantification of the temporal relationship between δ18O and temperature. This can be achieved using simulations performed by atmospheric general circulation models equipped with water stable isotopes. Here, we evaluate the skills of the high-resolution water-isotope-enabled atmospheric general circulation model ECHAM5-wiso (the European Centre Hamburg Model) nudged to European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis using simulations covering the period 1960–2013 over the Antarctic continent. We compare model outputs with field data, first with a focus on regional climate variables and second on water stable isotopes, using our updated dataset of water stable isotope measurements from precipitation, snow, and firn–ice core samples. ECHAM5-wiso simulates a large increase in temperature from 1978 to 1979, possibly caused by a discontinuity in the European Reanalyses (ERA) linked to the assimilation of remote sensing data starting in 1979. Although some model–data mismatches are observed, the (precipitation minus evaporation) outputs are found to be realistic products for surface mass balance. A warm model bias over central East Antarctica and a cold model bias over coastal regions explain first-order δ18O model biases by too strong isotopic depletion on coastal areas and underestimated depletion inland. At the second order, despite these biases, ECHAM5-wiso correctly captures the observed spatial patterns of deuterium excess. The results of model–data comparisons for the inter-annual δ18O standard deviation difer when using precipitation or ice core data. Further studies should explore the importance of deposition and post-deposition processes affecting ice core signals and not resolved in the model. These results build trust in the use of ECHAM5-wiso outputs to investigate the spatial, seasonal, and inter-annual δ18O–temperature relationships. We thus make the first Antarctica-wide synthesis of prior results. First, we show that local spatial or seasonal slopes are not a correct surrogate for inter-annual temporal slopes, leading to the conclusion that the same isotope–temperature slope cannot be applied for the climatic interpretation of Antarctic ice core for all timescales. Finally, we explore the phasing between the seasonal cycles of deuterium excess and δ18O as a source of information on changes in moisture sources affecting the δ18O–temperature relationship. The few available records and ECHAM5-wiso show different phase relationships in coastal, intermediate, and central regions. This work evaluates the use of the ECHAM5-wiso model as a tool for the investigation of water stable isotopes in Antarctic precipitation and calls for extended studies to improve our understanding of such proxies.

Description: The effect of external forcings on atmospheric circulation is debated. Due to the short observational period, the analysis of the role of external forcings is hampered, making it difficult to assess the sensitivity of atmospheric circulation to external forcings, as well as persistence of the effects. In observations, the average response to tropical volcanic eruptions is a positive North Atlantic Oscillation (NAO) during the following winter. However, past major tropical eruptions exceeding the magnitude of eruptions during the instrumental era could have had more lasting effects. Decadal NAO variability has been suggested to follow the 11-year solar cycle, and linkages have been made between grand solar minima and negative NAO. However, the solar link to NAO found by modeling studies is not unequivocally supported by reconstructions, and is not consistently present in observations for the 20th century. Here we present a reconstruction of atmospheric winter circulation for the North Atlantic region covering the period 1241–1970 CE. Based on seasonally resolved Greenland ice core records and a 1200-year-long simulation with an isotope-enabled climate model, we reconstruct sea level pressure and temperature by matching the spatiotemporal variability in the modeled isotopic composition to that of the ice cores. This method allows us to capture the primary (NAO) and secondary mode (Eastern Atlantic Pattern) of atmospheric circulation in the North Atlantic region, while, contrary to previous reconstructions, preserving the amplitude of observed year-to-year atmospheric variability. Our results show five winters of positive NAO on average following major tropical volcanic eruptions, which is more persistent than previously suggested. In response to decadal minima of solar activity we find a high-pressure anomaly over northern Europe, while a reinforced opposite response in pressure emerges with a 5-year time lag. On centennial timescales we observe a similar response of circulation as for the 5-year time-lagged response, with a high-pressure anomaly across North America and south of Greenland. This response to solar forcing is correlated to the second mode of atmospheric circulation, the Eastern Atlantic Pattern. The response could be due to an increase in blocking frequency, possibly linked to a weakening of the subpolar gyre. The long-term anomalies of temperature during solar minima shows cooling across Greenland, Iceland and western Europe, resembling the cooling pattern during the Little Ice Age (1450–1850 CE). While our results show significant correlation between solar forcing and the secondary circulation pattern on decadal (r = 0.29, p 〈 0.01) and centennial timescales (r = 0.6, p 〈 0.01), we find no consistent relationship between solar forcing and NAO. We conclude that solar and volcanic forcing impacts different modes of our reconstructed atmospheric circulation, which can aid in separating the regional effects of forcings and understanding the underlying mechanisms.

Description: North Pacific Intermediate water (NPIW) is a dominant water mass controlling ∼400-1200m depth North Pacific Ocean, meanwhile there is a cessation of North Pacific deep water (NPDW) formation in in modern observations. In contrast, paleoceanographic evidences have recorded NPDW formations during last glacial periods. This sug- gests either a rapid or gradual shutting down process of NPDW formation during the last deglaciation. Here, we use an Earth System Model to diagnose the physical and corresponding biogeochemical evolutions in the North Pacific Ocean before and after the last deglaciation, as well as potential changes during rapid climate shifts of the last deglaciation. Linked to different background climate conditions and varying Atlantic Meridional Over- turning Circulation states, we characterize the modelled NPIW and NPDW changes and builds up linkages to marine records. Our results further develop our understanding about the deglacial switch from NPDW to modern NPIW-only formation process.

Description: Abstract. When combined, the three-dimensional imaging of different physical properties of architectural monumen- tal structures acquired through different methodologies can highlight with efficiency the characteristics of the stone building materials. In this work, we compound high res- olution Digital Color Images (DCI) and Terrestrial Laser Scanner (TLS) data for a dense 3-D reconstruction of an ancient pillar in a nineteenth century building in the town of Cagliari, Italy. The TLS technique was supported by a digital photogrammetry survey in order to obtain a natural color texturized 3-D model of the studied pillar. Geometri- cal anomaly maps showing interesting analogies were com- puted both from the 3-D model derived from the TLS ap- plication and from the high resolution 3-D model detected with the photogrammetry. Starting from the 3-D reconstruc- tion from previous techniques, an acoustic tomography in a sector of prior interest of the investigated architectural ele- ment was planned and carried out. The ultrasonic tomogra- phy proved to be an effective tool for detecting internal decay or defects, locating the position of the anomalies and estimat- ing their sizes, shapes, and characteristics in terms of elastic- mechanical properties. Finally, the combination of geophysi- cal and petrographical data sets represents a powerful method for understanding the quality of the building stone materials in the shallow and inner parts of the investigated architectural structures.

Description: Regione Autonoma della Sardegna (RAS) (Sardinian Autonomous Region), Regional Law 7th August 2007, no. 7, Promotion of scientific research and technological innovation in Sardinia (Italy).

Description: Published

Description: 57-62

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

Description: JCR Journal

Description: The Istituto Nazionale di Geofisica e Vulcanologia runs the Italian National Seismic Network (about 400 stations, seismometers, accelerometers and GPS antennas) and other networks at national scale for monitoring earthquakes and tsunami as a part of the National Civil Protection System coordinated by the Italian Department of Civil Protection. This work summarises the acquisition and the distribution of the data and the analysis that are carried out for seismic surveillance and tsunami alert.

Description: INGV and DPC

Description: Published

Description: 31-38

Description: 1IT. Reti di monitoraggio

Description: N/A or not JCR

Description: This paper describes ESM-SnowMIP, an international coordinated modelling effort to evaluate current snow schemes, including snow schemes that are included in Earth system models, in a wide variety of settings against local and global observations. The project aims to identify crucial processes and characteristics that need to be improved in snow models in the context of local- and global-scale modelling. A further objective of ESM-SnowMIP is to better quantify snow-related feedbacks in the Earth system. Although it is not part of the sixth phase of the Coupled Model Intercomparison Project (CMIP6), ESM-SnowMIP is tightly linked to the CMIP6-endorsed Land Surface, Snow and Soil Moisture Model Intercomparison (LS3MIP).

Description: In this study, we present results obtained from modelling the mid-Pliocene warm period using the Community Earth System Models (COSMOS, version: COSMOS-landveg r2413, 2009) with the two different sets of boundary conditions prescribed for the two phases of the Pliocene Model Intercomparison Project (PlioMIP). Boundary conditions, model forcing, and modelling methodology of the two phases of PlioMIP, tagged PlioMIP1 and PlioMIP2,differ considerably in palaeogeography, in particular with regards to the state of ocean gateways, ice-masks, vegetation and topography. Further differences between model setups as suggested for PlioMIP1 and PlioMIP2 consider updates to the concentration of atmospheric carbon dioxide (CO2), that is specified as 405 and 400 parts per million by volume (ppmv) for PlioMIP1 and PlioMIP2, respectively, as well as minor differences in the concentrations of methane (CH4) and nitrous oxide (N2O) due to changes in the protocol of the Paleoclimate Model Intercomparison Project (PMIP) from phase 3 to phase 4. With this manuscript, we bridge the gap between our contributions to PlioMIP1 (Stepanek and Lohmann, 2012) and PlioMIP2 (Stepanek et al., 2019). We highlight some of the effects that differences in the chosen Mid-Pliocene model setup (PlioMIP2 vs. PlioMIP1) have on the climate state as derived with the COSMOS, as this information will be valuable in the framework of the model-model and model-data-comparison within PlioMIP2. We evaluate the model sensitivity to improved mid-Pliocene boundary conditions using PlioMIP’s core mid-Pliocene experiments for PlioMIP1 and PlioMIP2, and present further simulations where we test model sensitivity to variations in palaeogeography, orbit and concentration of CO2. Firstly,we highlight major changes in boundary conditions from PlioMIP1 to PlioMIP2 and also the limitations recorded from the initial effort. The results derived from of our simulations show that COSMOS simulates a mid-Pliocene climate state that is 0.08 K colder in PlioMIP2, if compared to PlioMIP1. On one hand, high-latitude warming,which is supported by proxy evidence of the mid-Pliocene, is underestimated in simulations of both PlioMIP1 andPlioMIP2. On the other hand, spatial variations in surface air temperature (SAT), sea surface temperature (SST) as well as the distribution of sea ice suggest improvement of simulated SAT and SST in PlioMIP2 if employing the updated palaeogeography. The PlioMIP2 Mid-Pliocene simulation produces warmer SSTs in the Arctic and North Atlantic Ocean than derived from the respective PlioMIP1 climate state. The difference in prescribed CO2accountsfor 1.1 K of warming in the Arctic, leading to an ice-free summer in the PlioMIP1 simulation, and a quasi-ice-free summer in PlioMIP2. Furthermore, employing different orbital forcings in simulating the Mid-Pliocene lead to pronounced annual and seasonal variations, which is not accounted for by marine and terrestrial reconstruction of the time-slice.

Description: The Antarctic temperature changes over the past millennia remain more uncertain than in many other continental regions. This has several origins: (1) the number of high-resolution ice cores is small, in particular on the East Antarctic plateau and in some coastal areas in East Antarctica; (2) the short and spatially sparse instrumental records limit the calibration period for reconstructions and the assessment of the methodologies; (3) the link between isotope records from ice cores and local climate is usually complex and dependent on the spatial scales and timescales investigated. Here, we use climate model results, pseudo-proxy experiments and data assimilation experiments to assess the potential for reconstructing the Antarctic temperature over the last 2 millennia based on a new database of stable oxygen isotopes in ice cores compiled in the frame- work of Antarctica2k (Stenni et al., 2017). The well-known covariance between δ18O and temperature is reproduced in the two isotope-enabled models used (ECHAM5/MPI-OM and ECHAM5-wiso), but is generally weak over the different Antarctic regions, limiting the skill of the reconstructions. Furthermore, the strength of the link displays large variations over the past millennium, further affecting the potential skill of temperature reconstructions based on statistical methods which rely on the assumption that the last decades are a good estimate for longer temperature reconstructions. Using a data assimilation technique allows, in theory, for changes in the δ18O–temperature link through time and space to be taken into account. Pseudoproxy experiments confirm the benefits of using data assimilation methods instead of statistical methods that provide reconstructions with unrealistic variances in some Antarctic subregions. They also confirm that the relatively weak link between both variables leads to a limited potential for reconstructing temperature based on δ18O. However, the reconstruction skill is higher and more uniform among reconstruction methods when the reconstruction target is the Antarctic as a whole rather than smaller Antarctic subregions. This consistency between the methods at the large scale is also observed when reconstructing temperature based on the real δ18O regional composites of Stenni et al. (2017). In this case, temperature reconstructions based on data assimilation confirm the long-term cooling over Antarctica during the last millennium, and the later onset of anthropogenic warming compared with the simulations without data assimilation, which is especially visible in West Antarctica. Data assimilation also allows for models and direct observations to be reconciled by reproducing the east–west contrast in the recent temperature trends. This recent warming pattern is likely mostly driven by internal variability given the large spread of individual Paleoclimate Modelling Intercomparison Project (PMIP)/Coupled Model Intercomparison Project (CMIP) model realizations in simulating it. As in the pseudoproxy framework, the reconstruction methods perform differently at the subregional scale, especially in terms of the variance of the time series produced. While the potential benefits of using a data assimilation method instead of a statistical method have been highlighted in a pseudoproxy framework, the instrumental series are too short to confirm this in a realistic setup.

Description: Ice-wedge polygons are common features of lowland tundra in the continuous permafrost zone and prone to rapid degradation through melting of ground ice. There are many interrelated processes involved in ice-wedge thermokarst and it is a major challenge to quantify their influence on the stability of the permafrost underlying the landscape. In this study we used a numerical modelling approach to investigate the degradation of ice wedges with a focus on the influence of hydrological conditions. Our study area was Samoylov Island in the Lena River delta of northern Siberia, for which we had in situ measurements to evaluate the model. The tailored version of the CryoGrid 3 land surface model was capable of simulating the changing microtopography of polygonal tundra and also regarded lateral fluxes of heat, water, and snow. We demonstrated that the approach is capable of simulating ice-wedge degradation and the associated transition from a low-centred to a high-centred polygonal microtopography. The model simulations showed ice-wedge degradation under recent climatic conditions of the study area, irrespective of hydrological conditions. However, we found that wetter conditions lead to an earlier onset of degradation and cause more rapid ground subsidence. We set our findings in correspondence to observed types of ice-wedge polygons in the study area and hypothesized on remaining discrepancies between modelled and observed ice-wedge thermokarst activity. Our quantitative approach provides a valuable complement to previous, more qualitative and conceptual, descriptions of the possible pathways of ice-wedge polygon evolution. We concluded that our study is a blueprint for investigating thermokarst landforms and marks a step forward in understanding the complex interrelationships between various processes shaping ice-rich permafrost landscapes.

Description: Warming of the Arctic led to an increase in permafrost temperatures by about 0.3 �C during the last decade. Permafrost warming is associated with increasing sediment water content, permeability, and diffusivity and could in the long term alter microbial community composition and abundance even before permafrost thaws. We studied the long-term effect (up to 2500 years) of submarine permafrost warming on microbial communities along an onshore–offshore transect on the Siberian Arctic Shelf displaying a natural temperature gradient of more than 10 �C. We analysed the in situ development of bacterial abundance and community composition through total cell counts (TCCs), quantitative PCR of bacterial gene abundance, and amplicon sequencing and correlated the microbial community data with temperature, pore water chemistry, and sediment physicochemical parameters. On timescales of centuries, permafrost warming coincided with an overall decreasing microbial abundance, whereas millennia after warming microbial abundance was similar to cold onshore permafrost. In addition, the dissolved organic carbon content of all cores was lowest in submarine permafrost after millennial-scale warming. Based on correlation analysis, TCC, unlike bacterial gene abundance, showed a significant rank-based negative correlation with increasing temperature, while bacterial gene copy numbers showed a strong negative correlation with salinity. Bacterial community composition correlated only weakly with temperature but strongly with the pore water stable isotopes �18O and �D, as well as with depth. The bacterial community showed substantial spatial variation and an overall dominance of Actinobacteria, Chloroflexi, Firmicutes, Gemmatimonadetes, and Proteobacteria, which are amongst the microbial taxa that were also found to be active in other frozen permafrost environments. We suggest that, millennia after permafrost warming by over 10 �C, microbial community composition and abundance show some indications for proliferation but mainly reflect the sedimentation history and paleoenvironment and not a direct effect through warming.

Description: The Global Ocean Data Analysis Project (GLODAP) is a synthesis effort providing regular compilations of surface to bottom ocean biogeochemical data, with an emphasis on seawater inorganic carbon chemistry and related variables determined through chemical analysis of water samples. This update of GLODAPv2, v2.2019, adds data from 116 cruises to the previous version, extending its coverage in time from 2013 to 2017, while also adding some data from prior years. GLODAPv2.2019 includes measurements from more than 1.1 million water samples from the global oceans collected on 840 cruises. The data for the 12 GLODAP core variables (salinity, oxygen, nitrate, silicate, phosphate, dissolved inorganic carbon, total alkalinity, pH, CFC-11, CFC-12, CFC-113, and CCl4) have undergone extensive quality control, especially systematic evaluation of bias. The data are available in two formats: (i) as submitted by the data originator but updated to WOCE exchange format and (ii) as a merged data product with adjustments applied to minimize bias. These adjustments were derived by comparing the data from the 116 new cruises with the data from the 724 quality-controlled cruises of the GLODAPv2 data product. They correct for errors related to measurement, calibration, and data handling practices, taking into account any known or likely time trends or variations. 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, and 5 % in the halogenated transient tracers. The compilation also includes data for several other variables, such as isotopic tracers. These were not subjected to bias comparison or adjustments. The original data, their documentation and DOI codes are available in the Ocean Carbon Data System of NOAA NCEI (https://www.nodc.noaa.gov/ocads/oceans/GLODAPv2_2019/, last access: 17 September 2019). This site also provides access to the merged data product, which is provided as a single global file and as four regional ones – the Arctic, Atlantic, Indian, and Pacific oceans – under https://doi.org/10.25921/xnme-wr20 (Olsen et al., 2019). The product files also include significant ancillary and approximated data. These were obtained by interpolation of, or calculation from, measured data. This paper documents the GLODAPv2.2019 methods and provides a broad overview of the secondary quality control procedures and results.

Description: We present a Lagrangian convective transport scheme developed for global chemistry and transport models, which considers the variable residence time that an air parcel spends in convection. This is particularly important for accurately simulating the tropospheric chemistry of short-lived species, e.g., for determining the time available for heterogeneous chemical processes on the surface of cloud droplets. In current Lagrangian convective transport schemes air parcels are stochastically redistributed within a fixed time step according to estimated probabilities for convective entrainment as well as the altitude of detrainment. We introduce a new scheme that extends this approach by modeling the variable time that an air parcel spends in convection by estimating vertical updraft velocities. Vertical updraft velocities are obtained by combining convective mass fluxes from meteorological analysis data with a parameterization of convective area fraction profiles. We implement two different parameterizations: a parameterization using an observed constant convective area fraction profile and a parameterization that uses randomly drawn profiles to allow for variability. Our scheme is driven by convective mass fluxes and detrainment rates that originate from an external convective parameterization, which can be obtained from meteorological analysis data or from general circulation models. We study the effect of allowing for a variable time that an air parcel spends in convection by performing simulations in which our scheme is implemented into the trajectory module of the ATLAS chemistry and transport model and is driven by the ECMWF ERA-Interim reanalysis data. In particular, we show that the redistribution of air parcels in our scheme conserves the vertical mass distribution and that the scheme is able to reproduce the convective mass fluxes and detrainment rates of ERA-Interim. We further show that the estimated vertical updraft velocities of our scheme are able to reproduce wind profiler measurements performed in Darwin, Australia, for velocities larger than 0.6 m s−1. SO2 is used as an example to show that there is a significant effect on species mixing ratios when modeling the time spent in convective updrafts compared to a redistribution of air parcels in a fixed time step. Furthermore, we perform long-time global trajectory simulations of radon-222 and compare with aircraft measurements of radon activity.

Description: Holocene permafrost from ice wedge polygons in the vicinity of large seabird breeding colonies in the Thule District, NW Greenland, was drilled to explore the relation between permafrost aggradation and seabird presence. The latter is reliant on the presence of the North Water Polynya (NOW) in the northern Baffin Bay. The onset of peat accumulation associated with the arrival of little auks (Alle alle) in a breeding colony at Annikitisoq, north of Cape York, is radiocarbon-dated to 4400 cal BP. A thick-billed murre (Uria lomvia) colony on Appat (Saunders Island) in the mouth of the Wolstenholme Fjord started 5650 cal BP. Both species provide marine-derived nutrients (MDNs) that fertilize vegetation and promote peat growth. The geochemical signature of organic matter left by the birds is traceable in the frozen Holocene peat. The peat accumulation rates at both sites are highest after the onset, decrease over time, and were about 2-times faster at the little auk site than at the thick-billed murre site. High accumulation rates induce shorter periods of organic matter (OM) decomposition before it enters the perennially frozen state. This is seen in comparably high C=N ratios and less depleted 13C, pointing to a lower degree of OM decomposition at the little auk site, while the opposite pattern can be discerned at the thick-billed murre site. Peat accumulation rates correspond to 15N trends, where decreasing accumulation led to increasing depletion in 15N as seen in the little-auk-related data. In contrast, the more decomposed OM of the thick-billed murre site shows almost stable 15N. Late Holocene wedge ice fed by cold season precipitation was studied at the little auk site and provides the first stable-water isotopic record from Greenland with mean 18O of 8:00:8, mean D of 36:25:7, mean d excess of 7:70:7, and a 18O-D slope of 7.27, which is close to those of the modern Thule meteoric water line. The syngenetic ice wedge polygon development is mirrored in testacean records of the little auk site and delineates polygon low-center, dry-out, and polygon-high-center stages. The syngenetic permafrost formation directly depending on peat growth (controlled by bird activity) falls within the period of neoglacial cooling and the establishment of the NOW, thus indirectly following the Holocene climate trends.

Description: Investigating the biogeochemistry of dissolved organic matter (DOM) requires the synthesis of data from several complementary analytical techniques. The traditional approach to data synthesis is to search for correlations between measurements made on the same sample using different instruments. In contrast, data fusion simultaneously decomposes data from multiple instruments into the underlying shared and unshared components. Here, Advanced Coupled Matrix and Tensor Factorization (ACMTF) was used to identify the molecular fingerprint of DOM fluorescence fractions in Arctic fjords. ACMTF explained 99.84% of the variability with six fully shared components. Individual molecular formulas were linked to multiple fluorescence components and vice versa. Molecular fingerprints differed in diversity and oceanographic patterns, suggesting a link to the biogeochemical sources and diagenetic state of DOM. The fingerprints obtained through ACMTF were more specific compared to traditional correlation analysis and yielded greater compositional insight. Multivariate data fusion aligns extremely complex, heterogeneous DOM data sets and thus facilitates a more holistic understanding of DOM biogeochemistry.

Description: Recent studies pointed to a high ice nucleating activity (INA) in the Arctic sea surface microlayer (SML). However, related chemical information is still sparse. In the present study, INA and free glucose concentrations were quantified in Arctic SML and bulk water samples from the marginal ice zone, the ice-free ocean, melt ponds, and open waters within the ice pack. T50 (defining INA) ranged from −17.4 to −26.8 °C. Glucose concentrations varied from 0.6 to 51 μg/L with highest values in the SML from the marginal ice zone and melt ponds (median 16.3 and 13.5 μg/L) and lower values in the SML from the ice pack and the ice-free ocean (median 3.9 and 4.0 μg/L). Enrichment factors between the SML and the bulk ranged from 0.4 to 17. A positive correlation was observed between free glucose concentration and INA in Arctic water samples (T50(°C) = (−25.6 ± 0.6) + (0.15 ± 0.04)·Glucose(μg/L), RP = 0.66, n = 74). Clustering water samples based on phytoplankton pigment composition resulted in robust but different correlations within the four clusters (RP between 0.67 and 0.96), indicating a strong link to phytoplankton-related processes. Since glucose did not show significant INA itself, free glucose may serve as a potential tracer for INA in Arctic water samples.

Description: 〈b〉Stochastic downscaling of precipitation in complex orography: a simple method to reproduce a realistic fine-scale climatology〈/b〉〈br〉 Silvia Terzago, Elisa Palazzi, and Jost von Hardenberg〈br〉 Nat. Hazards Earth Syst. Sci., 18, 2825-2840, https://doi.org/10.5194/nhess-18-2825-2018, 2018〈br〉 This study proposes a modification to a stochastic downscaling method for precipitation, RainFARM, to improve the representation of the statistics of the daily precipitation at fine scales (1 km) in mountain areas. This method has been demonstrated in the Alps and it has been found to reconstruct small-scale precipitation distribution. It can be employed in a number of applications, including the analysis of extreme events and their statistics and hydrometeorological hazards.

Description: 〈b〉Soil lacquer peel DIY: simply capturing beauty〈/b〉〈br〉 Cathelijne R. Stoof, Jasper H. J. Candel, Laszlo van der Wal, and Gert Peek〈br〉 SOIL Discuss., https//doi.org/10.5194/soil-2018-27,2018〈br〉 〈b〉Manuscript under review for SOIL〈/b〉 (discussion: final response, 2 comments)〈br〉 Teaching and outreach of soils is often done with real life snapshots of soils and sediments in lacquer or glue peels. While it may seem hard, anyone can make such a peel. Illustrated with handmade drawings and instructional video, we explain how to capture soils in peels using readily available materials. A new twist to old methods makes this more safe, simple and successful, and thus a true DIY (do it yourself) activity, highlighting the value and beauty of the ground below our feet.

Description: 〈b〉Description of the Baseline Surface Radiation Network (BSRN) station at the Izaña Observatory (2009–2017): measurements and quality control/assurance procedures〈/b〉〈br〉 Rosa Delia García, Emilio Cuevas, Ramón Ramos, Victoria Eugenia Cachorro, Alberto Redondas, and José A. Moreno-Ruiz〈br〉 Geosci. Instrum. Method. Data Syst. Discuss., https//doi.org/10.5194/gi-2018-41,2018〈br〉 〈b〉Revised manuscript accepted for GI〈/b〉 (discussion: closed, 3 comments)〈br〉 IZA is a high-mountain station located in Tenerife (Canary Islands, Spain; at 28.3° N, 16.5° W, 2373 m a.s.l.) and is a representative site of the subtropical North Atlantic free troposphere. It contributes with basic-BSRN radiation measurements, such as, global shortwave radiation, direct radiation, diffuse radiation and longwave downward radiation and extended-BSRN measurements, including ultraviolet ranges, shortwave upward radiation and longwave.

Description: 〈b〉High-spatial resolution probability maps of drought duration and magnitude across Spain〈/b〉〈br〉 Fernando Domínguez-Castro, Sergio M. Vicente-Serrano, Miquel Tomás-Burguera, Marina Peña-Gallardo, Santiago Beguería, Ahmed El Kenawy, Yolanda Luna, and Ana Morata〈br〉 Nat. Hazards Earth Syst. Sci. Discuss., https//doi.org/10.5194/nhess-2018-289,2018〈br〉 〈b〉Manuscript under review for NHESS〈/b〉 (discussion: open, 0 comments)〈br〉 We mapped – for the first time – the probability of occurrence of drought over Spain, with the overriding aim of improving current drought assessment, management and mitigation measures and strategies across the region. Spatially, our estimations suggest a higher probability of extreme drought events in southern and central areas of Spain, compared to northern and eastern regions. Nevertheless, there are strong differences between drought indices, as well as among drought timescales.

Description: 〈b〉Effect of deforestation and subsequent land use management on soil carbon stocks in the South American Chaco〈/b〉〈br〉 Natalia Andrea Osinaga, Carina Rosa Álvarez, and Miguel Angel Taboada〈br〉 SOIL, 4, 251-257, https://doi.org/10.5194/soil-4-251-2018, 2018〈br〉 The sub-humid Argentine Chaco, originally covered by forest, has been subjected to clearing since the end of the 1970s and replacement of the forest by no-till farming. The organic carbon stock content up to 1 m depth varied as follows: forest 〉 pasture 〉 continuous cropping, with no impact of the number of years under cropping. The incorporation of pastures of warm-season grasses was able to mitigate the decrease of C stocks caused by cropping and so could be considered sustainable management.

Description: 〈b〉Description of the Baseline Surface Radiation Network (BSRN) station at the Izaña Observatory (2009–2017): measurements and quality control/assurance procedures〈/b〉〈br〉 Rosa Delia García, Emilio Cuevas, Ramón Ramos, Victoria Eugenia Cachorro, Alberto Redondas, and José A. Moreno-Ruiz〈br〉 Geosci. Instrum. Method. Data Syst. Discuss., https//doi.org/10.5194/gi-2018-41,2018〈br〉 〈b〉Revised manuscript accepted for GI〈/b〉 (discussion: closed, 3 comments)〈br〉 IZA is a high-mountain station located in Tenerife (Canary Islands, Spain; at 28.3° N, 16.5° W, 2373 m a.s.l.) and is a representative site of the subtropical North Atlantic free troposphere. It contributes with basic-BSRN radiation measurements, such as, global shortwave radiation, direct radiation, diffuse radiation and longwave downward radiation and extended-BSRN measurements, including ultraviolet ranges, shortwave upward radiation and longwave.

Description: 〈b〉Bayesian earthquake dating and seismic hazard assessment using chlorine-36 measurements (BED v1)〈/b〉〈br〉 Joakim Beck, Sören Wolfers, and Gerald P. Roberts〈br〉 Geosci. Model Dev., 11, 4383-4397, https://doi.org/10.5194/gmd-11-4383-2018, 2018〈br〉 Seismic hazard assessment requires records of earthquake recurrence with many slip events. Current data from paleoseismology on individual faults are sparse and do not provide stable estimates of earthquake recurrence. We propose a statistical model-based method to study timings of earthquakes over the past few millennia. The results agree with historical earthquakes for faults in the Italian Apennines, and can aid future studies of fault interactions over multiple earthquake cycles.

Description: 〈b〉Challenges to implementing bottom-up flood risk decision analysis frameworks: how strong are social networks of flooding professionals?〈/b〉〈br〉 James O. Knighton, Osamu Tsuda, Rebecca Elliott, and M. Todd Walter〈br〉 Hydrol. Earth Syst. Sci., 22, 5657-5673, https://doi.org/10.5194/hess-22-5657-2018, 2018〈br〉 Decision-making for flood risk management is often the collective effort of professionals within government, NGOs, private practice, and advocacy groups. Our research investigates differences among flood experts within Tompkins County, New York (USA). We explore how they differ in their perceptions of flooding risk, desired project outcomes, and knowledge. We observe substantial differences among experts, and recommend formally acknowledging these perceptions when engaging in flood management.

Description: 〈b〉High variability of particulate organic carbon export along the North Atlantic GEOTRACES section GA01 as deduced from 〈sup〉234〈/sup〉Th fluxes〈/b〉〈br〉 Nolwenn Lemaitre, Frédéric Planchon, Hélène Planquette, Frank Dehairs, Debany Fonseca-Batista, Arnout Roukaerts, Florian Deman, Yi Tang, Clarisse Mariez, and Géraldine Sarthou〈br〉 Biogeosciences, 15, 6417-6437, https://doi.org/10.5194/bg-15-6417-2018, 2018〈br〉 We investigated the surface particulate organic carbon export fluxes in the North Atlantic with the objective of better understanding the biological carbon pump. Our results highlighted that exports depended on the intensity and stage of the bloom, the phytoplankton size and community structures. After comparing with primary production, we concluded that, during our study, the North Atlantic behaves like most of the highly productive areas in the world's ocean, with a low export efficiency.

Description: 〈b〉Influence of radiative forcing factors on ground–air temperature coupling during the last millennium: implications for borehole climatology〈/b〉〈br〉 Camilo Melo-Aguilar, J. Fidel González-Rouco, Elena García-Bustamante, Jorge Navarro-Montesinos, and Norman Steinert〈br〉 Clim. Past, 14, 1583-1606, https://doi.org/10.5194/cp-14-1583-2018, 2018〈br〉 Air–ground temperature coupling is the central assumption of borehole temperature reconstructions. Here, this premise is assessed from a pseudo-reality perspective by considering last millennium ensembles of simulations from the Community Earth System Model. The results show that long-term variations in the energy fluxes at the surface during industrial times, due to the influence of external forcings, impact the long-term air–ground temperature coupling.

Description: 〈b〉A General Analytical Model for Head Response to Oscillatory Pumping in Unconfined Aquifers: Consider the Effects of Delayed Gravity Drainage and Initial Condition〈/b〉〈br〉 Ching-Sheng Huang, Ya-Hsin Tsai, Hund-Der Yeh, and Tao Yang〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-482,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 2 comments)〈br〉 This study develops a new model describing head fluctuation induced by oscillatory pumping test (OPT) in unconfined aquifer with the effects of delayed gravity drainage (DGD) and initial condition regarding the hydraulic head prior to OPT. The DGD reduces to instantaneous gravity drainage when a dimensionless parameter exceeds 500. A pseudo-steady state model excluding initial condition causes a time shift from the actual transient model in predicting simple harmonic motion of head fluctuation.

Description: 〈b〉Direct or indirect recharge on groundwater in the middle-latitude desert of Otindag, China?〈/b〉〈br〉 Bing-Qi Zhu, Xiao-Zong Ren, and Patrick Rioual〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-395,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 Although rainfall is scarce in global deserts, the Otindag Desert is abundant of water resources (mainly groundwater). To understand the water origin in this desert, stable and radioactive isotopes and hydrochemistry of natural waters were investigated. The groundwaters in the desert were young but not of meteoric origin, i.e., out of control by the modern and palaeo- direct recharge. The tectonic control, but not the climate control, is essentially responsible for the water origin there.

Description: 〈b〉Effect of high dust amount on surface temperature during the Last Glacial Maximum: a modelling study using MIROC-ESM〈/b〉〈br〉 Rumi Ohgaito, Ayako Abe-Ouchi, Ryouta O'ishi, Toshihiko Takemura, Akinori Ito, Tomohiro Hajima, Shingo Watanabe, and Michio Kawamiya〈br〉 Clim. Past, 14, 1565-1581, https://doi.org/10.5194/cp-14-1565-2018, 2018〈br〉 The behaviour of dust in terms of climate can be investigated using past climate. The Last Glacial Maximum (LGM; 21000 years before present) is known to be dustier. We investigated the impact of plausible dust distribution on the climate of the LGM using an Earth system model and found that the higher dust load results in less cooling over the polar regions. The main finding is that radiative perturbation by the high dust loading does not necessarily cool the surface surrounding Antarctica.

Description: 〈b〉A simple predictive model for the eddy propagation trajectory in the South China Sea〈/b〉〈br〉 Jiaxun Li, Guihua Wang, Huijie Xue, and Huizan Wang〈br〉 Ocean Sci. Discuss., https//doi.org/10.5194/os-2018-116,2018〈br〉 〈b〉Manuscript under review for OS〈/b〉 (discussion: open, 0 comments)〈br〉 A novel predictive model is built for eddy propagation trajectory using the multiple linear regression method. This simple model has related various oceanic parameters to eddy propagation position changes in the South China Sea (SCS). The performance of the proposed model is examined in the SCS based on twenty years of satellite altimeter data, and demonstrates its significant forecast skills over a 4-week forecast window comparing to the traditional persistence method.

Description: 〈b〉Influence of radiative forcing factors on ground–air temperature coupling during the last millennium: implications for borehole climatology〈/b〉〈br〉 Camilo Melo-Aguilar, J. Fidel González-Rouco, Elena García-Bustamante, Jorge Navarro-Montesinos, and Norman Steinert〈br〉 Clim. Past, 14, 1583-1606, https://doi.org/10.5194/cp-14-1583-2018, 2018〈br〉 Air–ground temperature coupling is the central assumption of borehole temperature reconstructions. Here, this premise is assessed from a pseudo-reality perspective by considering last millennium ensembles of simulations from the Community Earth System Model. The results show that long-term variations in the energy fluxes at the surface during industrial times, due to the influence of external forcings, impact the long-term air–ground temperature coupling.

Description: 〈b〉Effect of high dust amount on surface temperature during the Last Glacial Maximum: a modelling study using MIROC-ESM〈/b〉〈br〉 Rumi Ohgaito, Ayako Abe-Ouchi, Ryouta O'ishi, Toshihiko Takemura, Akinori Ito, Tomohiro Hajima, Shingo Watanabe, and Michio Kawamiya〈br〉 Clim. Past, 14, 1565-1581, https://doi.org/10.5194/cp-14-1565-2018, 2018〈br〉 The behaviour of dust in terms of climate can be investigated using past climate. The Last Glacial Maximum (LGM; 21000 years before present) is known to be dustier. We investigated the impact of plausible dust distribution on the climate of the LGM using an Earth system model and found that the higher dust load results in less cooling over the polar regions. The main finding is that radiative perturbation by the high dust loading does not necessarily cool the surface surrounding Antarctica.

Description: 〈b〉Direct or indirect recharge on groundwater in the middle-latitude desert of Otindag, China?〈/b〉〈br〉 Bing-Qi Zhu, Xiao-Zong Ren, and Patrick Rioual〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-395,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 Although rainfall is scarce in global deserts, the Otindag Desert is abundant of water resources (mainly groundwater). To understand the water origin in this desert, stable and radioactive isotopes and hydrochemistry of natural waters were investigated. The groundwaters in the desert were young but not of meteoric origin, i.e., out of control by the modern and palaeo- direct recharge. The tectonic control, but not the climate control, is essentially responsible for the water origin there.

Description: 〈b〉Inter-comparison of Atmospheric Trace Gas Dispersion Models: Barnett Shale Case Study〈/b〉〈br〉 Anna Karion, Thomas Lauvaux, Israel Lopez Coto, Colm Sweeney, Kimberly Mueller, Sharon Gourdji, Wayne Angevine, Zachary Barkley, Aijun Deng, Arlyn Andrews, Ariel Stein, and James Whetstone〈br〉 Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-736,2018〈br〉 〈b〉Manuscript under review for ACP〈/b〉 (discussion: open, 0 comments)〈br〉 In this study, we use atmospheric methane concentration observations collected during an airborne campaign to compare different model-based emissions estimates from the Barnett Shale oil and natural gas production basin in Texas, U.S.A. We find that the tracer dispersion model has a significant impact on the results, because the models differ in their simulation of vertical dispersion. Additional work is needed to evaluate and improve vertical mixing in the tracer dispersion models.

Description: 〈b〉Insights into the morphology of multicomponent organic/inorganic aerosols from molecular dynamics simulations〈/b〉〈br〉 Katerina S. Karadima, Vlasis G. Mavrantzas, and Spyros N. Pandis〈br〉 Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-1098,2018〈br〉 〈b〉Manuscript under review for ACP〈/b〉 (discussion: open, 0 comments)〈br〉 We explore the morphologies of multicomponent nanoparticles through atomistic molecular dynamics simulations under atmospherically relevant conditions. Phase separation is predicted for almost all simulated nanoparticles either between organics and inorganics or between hydrophobic and hydrophilic constituents. Three main particle types were identified: organic islands at the surface, inorganic core-organic shell morphologies, and complex structures with hydrophobic and hydrophilic domains.

Description: 〈b〉Nitric oxide (NO) in the Bohai and Yellow Seas〈/b〉〈br〉 Ye Tian, Chao Xue, Chun-Ying Liu, Gui-Peng Yang, Pei-Feng Li, Wei-Hua Feng, and Hermann W. Bange〈br〉 Biogeosciences Discuss., doi:10.5194/bg-2018-446,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 1 comment)〈br〉 Nitric oxide (NO) seems to be widespread with different functions in marine ecosystem but know little about it. Concentrations of NO were in the range of from below the detection limit to 616 pmol L〈sup〉−1〈/sup〉 in the surface and to 482 pmol L〈sup〉−1〈/sup〉 in the bottom of the Bohai and Yellow Seas. The study region was a source of the atmospheric NO. NO sea-to-air fluxes were much lower than NO photoproduction rates, implying that the NO produced in the mixed layer was rapidly consumed before enter the atmosphere.

Description: 〈b〉CORDEX-WRF v1.3: Development of a module for theWeather Research and Forecasting (WRF) model to support the CORDEX community〈/b〉〈br〉 Lluís Fita, Jan Polcher, Theodore M. Giannaros, Torge Lorenz, Josipa Milovac, Giannis Sofiadis, Eleni Katragkou, and Sophie Bastin〈br〉 Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2018-241,2018〈br〉 〈b〉Manuscript under review for GMD〈/b〉 (discussion: open, 0 comments)〈br〉 Regional climate experiments coordinated throughout CORDEX aim to study and provide high quality climate data over a given region. This data is used by climate change mitigation and adaptation policies studies and stake holders. CORDEX requires a list of variables, which most of them are not provided by atmospheric models. Aiming to help the community and to maximize use of CORDEX exercises, we create a new module for the WRF model to directly produce them adding 〈q〉generic〈/q〉 and 〈q〉additional〈/q〉 ones.

Description: 〈b〉Retrieval of liquid water cloud properties from POLDER-3 measurements using a neural network ensemble approach〈/b〉〈br〉 Antonio Di Noia, Otto P. Hasekamp, Bastiaan van Diedenhoven, and Zhibo Zhang〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-345,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉This paper describes a neural network algorithm for the estimation of liquid water cloud optical properties from the Polarization and Directionality of Earth's Reflectances-3 (POLDER-3) instrument, on board the Polarization & Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar (PARASOL) satellite. The algorithm has been trained on synthetic multi-angle, multi-wavelength measurements of reflectance and polarization, and has been applied to the processing of one year of POLDER-3 data. Comparisons of the retrieved cloud properties with Moderate resolution Imaging Spectroradiometer (MODIS) products show negative biases around −2 in retrieved cloud optical thicknesses (COTs) and between −1 and −2 μm in retrieved cloud effective radii. Comparisons with existing POLDER-3 datasets suggest that the proposed scheme may have enhanced capabilities for cloud effective radius retrieval at least over land. An additional feature of the presented algorithm is that it provides COT and effective radius retrievals at the native POLDER-3 Level 1B pixel level.〈/p〉

Description: 〈b〉Carbon–nitrogen coupling under three schemes of model representation: a traceability analysis〈/b〉〈br〉 Zhenggang Du, Ensheng Weng, Lifen Jiang, Yiqi Luo, Jianyang Xia, and Xuhui Zhou〈br〉 Geosci. Model Dev., 11, 4399-4416, https://doi.org/10.5194/gmd-11-4399-2018, 2018〈br〉 In this study, based on a traceability analysis technique, we evaluated alternative representations of C–N interactions and their impacts on the C cycle using the TECO model framework. Our results showed that different representations of C–N coupling processes lead to divergent effects on plant production, C residence time, and thus the ecosystem C storage capacity. Identifying those effects can help us to improve the N limitation assumptions employed in terrestrial ecosystem models.

Description: 〈b〉Model evaluation by a cloud classification based on multi-sensor observations〈/b〉〈br〉 Akio Hansen, Felix Ament, Verena Grützun, and Andrea Lammert〈br〉 Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2018-259,2018〈br〉 〈b〉Manuscript under review for GMD〈/b〉 (discussion: open, 0 comments)〈br〉 Clouds are responsible for large uncertainties in atmospheric models, whereby the evaluation is very challenging due to their complexity. The Cloudnet project uses multi-sensor observations to create a comprehensive Target Classification showing the cloud structure and phase, but there is no comparable model output available. The presented cloud classification algorithm generates a consistent product, which provides a comprehensive view on clouds and is used for further in-depth evaluation.

Description: 〈b〉Model evaluation by a cloud classification based on multi-sensor observations〈/b〉〈br〉 Akio Hansen, Felix Ament, Verena Grützun, and Andrea Lammert〈br〉 Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2018-259,2018〈br〉 〈b〉Manuscript under review for GMD〈/b〉 (discussion: open, 0 comments)〈br〉 Clouds are responsible for large uncertainties in atmospheric models, whereby the evaluation is very challenging due to their complexity. The Cloudnet project uses multi-sensor observations to create a comprehensive Target Classification showing the cloud structure and phase, but there is no comparable model output available. The presented cloud classification algorithm generates a consistent product, which provides a comprehensive view on clouds and is used for further in-depth evaluation.

Description: 〈b〉Monitoring Groundwater Storage Depletion Using Gravity Recovery and Climate Experiment (GRACE) Data in the Semi-Arid Catchments〈/b〉〈br〉 Nizar Abou Zaki, Ali Torabi Haghighi, Pekka M. Rossi, Mohammad J. Tourian, and Bjørn Klove〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-471,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 Groundwater is considered a main source of fresh water in semi-arid climatic zones, especially for agricultural usage. This study compares in-situ groundwater volume variation measurements with GRACE derived water mass data. The study concludes the possibility of using GRACE data to monitor groundwater depletion in catchments that lack measured data. GRACE data can here help in drawing general conclusions for integrated water resources management, and sustainable usage of this resources.

Description: 〈b〉Heat, salt, and volume transports in the eastern Eurasian Basin of the Arctic Ocean from 2 years of mooring observations〈/b〉〈br〉 Andrey V. Pnyushkov, Igor V. Polyakov, Robert Rember, Vladimir V. Ivanov, Matthew B. Alkire, Igor M. Ashik, Till M. Baumann, Genrikh V. Alekseev, and Arild Sundfjord〈br〉 Ocean Sci., 14, 1349-1371, https://doi.org/10.5194/os-14-1349-2018, 2018〈br〉 This study describes along-slope volume, heat, and salt transports derived from observations collected between 2013 and 2015 in the eastern Eurasian Basin of the Arctic Ocean using a cross-slope array of six moorings. Inferred transport estimates may have wide implications and should be considered when assessing high-latitude ocean dynamics.

Description: 〈b〉Arctic Mediterranean Exchanges: A consistent volume budget and trends in transports from two decades of observations〈/b〉〈br〉 Svein Østerhus, Rebecca Woodgate, Héðinn Valdimarsson, Bill Turrell, Laura de Steur, Detlef Quadfasel, Steffen M. Olsen, Martin Moritz, Craig M. Lee, Karin Margretha H. Larsen, Steingrímur Jónsson, Clare Johnson, Kerstin Jochumsen, Bogi Hansen, Beth Curry, Stuart Cunningham, and Barbara Berx〈br〉 Ocean Sci. Discuss., https//doi.org/10.5194/os-2018-114,2018〈br〉 〈b〉Manuscript under review for OS〈/b〉 (discussion: open, 1 comment)〈br〉 Two decades of observations of the Arctic Mediterranean (AM) exchanges shows that the exchanges have been stable in terms of volume transport during a period when many other components of the global climate system have changed. The total AM-import is found to be 9.1 Sv and has a seasonal variation of amplitude close to 17 Sv and maximum import in October. Roughly one third of the imported water leaves the AM as surface outflow with the remain two thirds leaving.

Description: 〈b〉Stochastic hydrogeology's biggest hurdles analyzed and its big blind spot〈/b〉〈br〉 Yoram Rubin, Ching-Fu Chang, Jiancong Chen, Karina Cucchi, Bradley Harken, Falk Heße, and Heather Savoy〈br〉 Hydrol. Earth Syst. Sci., 22, 5675-5695, https://doi.org/10.5194/hess-22-5675-2018, 2018〈br〉 This paper addresses questions related to the adoption of stochastic methods in hydrogeology, looking at factors such as environmental regulations, financial incentives, higher education, and the collective feedback loop involving these factors. We show that stochastic hydrogeology's blind spot is in focusing on risk while ignoring uncertainty, to the detriment of its potential clients. The imbalance between the treatments of risk and uncertainty is shown to be common to multiple disciplines.

Description: 〈b〉Simulating secondary organic aerosol from anthropogenic and biogenic precursors: comparison to outdoor chamber experiments, effect of oligomerization on SOA formation and reactive uptake of aldehydes〈/b〉〈br〉 Florian Couvidat, Marta G. Vivanco, and Bertrand Bessagnet〈br〉 Atmos. Chem. Phys., 18, 15743-15766, https://doi.org/10.5194/acp-18-15743-2018, 2018〈br〉 Several new parameterizations and mechanisms for SOA formation are developed based on available experimental results. To evaluate the parameterizations, a box model was developed to simulate SOA formation from monoterpenes and aromatics in the environmental chamber EUPHORE. This box model takes oligomerization, nonideality of the aerosol, multiphase partitioning, aging, vapor wall losses and particle-phase diffusion into account. All these phenomena are rarely taken into account together.

Description: 〈b〉Heat, salt, and volume transports in the eastern Eurasian Basin of the Arctic Ocean from 2 years of mooring observations〈/b〉〈br〉 Andrey V. Pnyushkov, Igor V. Polyakov, Robert Rember, Vladimir V. Ivanov, Matthew B. Alkire, Igor M. Ashik, Till M. Baumann, Genrikh V. Alekseev, and Arild Sundfjord〈br〉 Ocean Sci., 14, 1349-1371, https://doi.org/10.5194/os-14-1349-2018, 2018〈br〉 This study describes along-slope volume, heat, and salt transports derived from observations collected between 2013 and 2015 in the eastern Eurasian Basin of the Arctic Ocean using a cross-slope array of six moorings. Inferred transport estimates may have wide implications and should be considered when assessing high-latitude ocean dynamics.

Description: 〈b〉Ideas and perspectives: Tree–atmosphere interaction responds to water-related stem variations〈/b〉〈br〉 Tim van Emmerik, Susan Steele-Dunne, Pierre Gentine, Rafael S. Oliveira, Paulo Bittencourt, Fernanda Barros, and Nick van de Giesen〈br〉 Biogeosciences, 15, 6439-6449, https://doi.org10.5194/bg-15-6439-2018, 2018〈br〉 Trees are very important for the water and carbon cycles. Climate and weather models often assume constant vegetation parameters because good measurements are missing. We used affordable accelerometers to measure tree sway of 19 trees in the Amazon rainforest. We show that trees respond very differently to the same weather conditions, which means that vegetation parameters are dynamic. With our measurements trees can be accounted for more realistically, improving climate and weather models.

Description: 〈b〉Do sun spots influence the onset of ENSO and PDO events in the Pacific Ocean?〈/b〉〈br〉 Franklin Isaac Ormaza-González and María Esther Espinoza-Celi〈br〉 Ocean Sci. Discuss., https//doi.org/10.5194/os-2018-125,2018〈br〉 〈b〉Manuscript under review for OS〈/b〉 (discussion: open, 0 comments)〈br〉 Sea surface temperature is affected by sun energy which in turn varies in time due to astronomical factors and sun activity. The activity can be estimated by sun spots (SS). Some oceanographic events like inter-annual El/La Niño/Niña as well as decadal processes should be affected by SS. It was found correlation between SS and various oceanographic indexes in time series from 1954 to 2017. This fact should be considered when dealing and modelling forecasts of such indexes.

Description: 〈b〉Monitoring Groundwater Storage Depletion Using Gravity Recovery and Climate Experiment (GRACE) Data in the Semi-Arid Catchments〈/b〉〈br〉 Nizar Abou Zaki, Ali Torabi Haghighi, Pekka M. Rossi, Mohammad J. Tourian, and Bjørn Klove〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-471,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 Groundwater is considered a main source of fresh water in semi-arid climatic zones, especially for agricultural usage. This study compares in-situ groundwater volume variation measurements with GRACE derived water mass data. The study concludes the possibility of using GRACE data to monitor groundwater depletion in catchments that lack measured data. GRACE data can here help in drawing general conclusions for integrated water resources management, and sustainable usage of this resources.

Description: 〈b〉Do sun spots influence the onset of ENSO and PDO events in the Pacific Ocean?〈/b〉〈br〉 Franklin Isaac Ormaza-González and María Esther Espinoza-Celi〈br〉 Ocean Sci. Discuss., https//doi.org/10.5194/os-2018-125,2018〈br〉 〈b〉Manuscript under review for OS〈/b〉 (discussion: open, 0 comments)〈br〉 Sea surface temperature is affected by sun energy which in turn varies in time due to astronomical factors and sun activity. The activity can be estimated by sun spots (SS). Some oceanographic events like inter-annual El/La Niño/Niña as well as decadal processes should be affected by SS. It was found correlation between SS and various oceanographic indexes in time series from 1954 to 2017. This fact should be considered when dealing and modelling forecasts of such indexes.

Description: 〈b〉Arctic Mediterranean Exchanges: A consistent volume budget and trends in transports from two decades of observations〈/b〉〈br〉 Svein Østerhus, Rebecca Woodgate, Héðinn Valdimarsson, Bill Turrell, Laura de Steur, Detlef Quadfasel, Steffen M. Olsen, Martin Moritz, Craig M. Lee, Karin Margretha H. Larsen, Steingrímur Jónsson, Clare Johnson, Kerstin Jochumsen, Bogi Hansen, Beth Curry, Stuart Cunningham, and Barbara Berx〈br〉 Ocean Sci. Discuss., https//doi.org/10.5194/os-2018-114,2018〈br〉 〈b〉Manuscript under review for OS〈/b〉 (discussion: open, 1 comment)〈br〉 Two decades of observations of the Arctic Mediterranean (AM) exchanges shows that the exchanges have been stable in terms of volume transport during a period when many other components of the global climate system have changed. The total AM-import is found to be 9.1 Sv and has a seasonal variation of amplitude close to 17 Sv and maximum import in October. Roughly one third of the imported water leaves the AM as surface outflow with the remain two thirds leaving.

Description: 〈b〉Forcing mechanisms of the terdiurnal tide〈/b〉〈br〉 Friederike Lilienthal, Christoph Jacobi, and Christoph Geißler〈br〉 Atmos. Chem. Phys., 18, 15725-15742, https://doi.org/10.5194/acp-18-15725-2018, 2018〈br〉 The terdiurnal solar tide is an atmospheric wave, owing to the daily variation of solar heating with a period of 8 h. Here, we present model simulations of this tide and investigate the relative importance of possible forcing mechanisms because they are still under debate. These are, besides direct solar heating, nonlinear interactions between other tides and gravity wave–tide interactions. As a result, solar heating is most important and nonlinear effects partly counteract this forcing.

Description: 〈b〉Statistics on clouds and their relation to thermodynamic conditions at Ny-Ålesund using ground-based sensor synergy〈/b〉〈br〉 Tatiana Nomokonova, Kerstin Ebell, Ulrich Löhnert, Marion Maturilli, Christoph Ritter, and Ewan O'Connor〈br〉 Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-1144,2018〈br〉 〈b〉Manuscript under review for ACP〈/b〉 (discussion: open, 0 comments)〈br〉 In this study, properties of clouds at the French–German Arctic Research station in Ny-Ålesund are related to in-cloud thermodynamic conditions. The used dataset was collected within the Arctic Amplification project with a set of active and passive remote instruments. The results are compared with a model output. A significant divergence in observations and modelling of single layer ice and mixed-phase clouds was found.

Description: 〈b〉Measurements of spectral irradiance during the solar eclipse of 21 August 2017: reassessment of the effect of solar limb darkening and of changes in total ozone〈/b〉〈br〉 Germar Bernhard and Boyan Petkov〈br〉 Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-1048,2018〈br〉 〈b〉Manuscript under review for ACP〈/b〉 (discussion: open, 0 comments)〈br〉 Solar radiation at ultraviolet, visible, and infrared wavelengths was measured during the total solar eclipse of 21 August 2017. Data were used to study the wavelength-dependent changes of solar radiation at Earth's surface and to validate parameterizations of solar limb darkening (LD), which describes the change of the Sun's brightness between its center and its edge. The study highlights the importance of the LD effect when calculating total ozone and aerosol optical depth during an eclipse.

Description: 〈b〉Constraints on Enhanced Weathering and related carbon sequestration – a cropland mesocosm approach〈/b〉〈br〉 Thorben Amann, Jens Hartmann, Eric Struyf, Wagner de Oliveira Garcia, Elke K. Fischer, Ivan Janssens, Patrick Meire, and Jonas Schoelynck〈br〉 Biogeosciences Discuss., doi:10.5194/bg-2018-398,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 1 comment)〈br〉 Weathering is a major control on atmospheric CO〈sub〉2〈/sub〉 at geologic time scales. Enhancement of this process can be used to actively remove CO〈sub〉2〈/sub〉 from the atmosphere. Field results are still scarce and with this experiment we try to add some near natural insights into dissolution processes. Results show CO〈sub〉2〈/sub〉 sequestration potentials but also highlight the strong variability of outcomes that can be expected in natural environments. Such experiments are of utmost importance to identify key processes.

Description: 〈b〉Evaluation of atmospheric nitrogen inputs into marine ecosystems of the North Sea and Baltic Sea – part B: contribution by shipping and agricultural emissions〈/b〉〈br〉 Daniel Neumann, Hagen Radtke, Matthias Karl, and Thomas Neumann〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-365,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 0 comments)〈br〉 The contribution of atmospheric nitrogen deposition to the marine dissolved inorganic nitrogen (DIN) pool of the North and Baltic Sea was assessed for the year 2012. Atmospheric deposition accounted for approximately 10 % to 15 % of the DIN but its residence time differed between both water bodies. The nitrogen contributions of atmospheric shipping and agricultural imissions also were assessed. Particularly the latter source had a large impact in coastal regions.

Description: 〈b〉Trends in air pollutants and health impacts in three Swedish cities over the past three decades〈/b〉〈br〉 Henrik Olstrup, Bertil Forsberg, Hans Orru, Mårten Spanne, Hung Nguyen, Peter Molnár, and Christer Johansson〈br〉 Atmos. Chem. Phys., 18, 15705-15723, https://doi.org/10.5194/acp-18-15705-2018, 2018〈br〉 This article analyzes the health effects caused by changes in air pollution concentrations during the period of 1990–2015 in Stockholm, Gothenburg, and Malmö: the three largest cities in Sweden. The air pollutants that have been measured and analyzed are NO〈sub〉〈i〉x〈/i〉〈/sub〉, NO〈sub〉2〈/sub〉, O〈sub〉3〈/sub〉, and PM〈sub〉10〈/sub〉. NO〈sub〉〈i〉x〈/i〉〈/sub〉 and NO〈sub〉2〈/sub〉 exhibit decreasing trends during this period, with beneficial effects on public health. An overall conclusion is that public health can largely benefit from reduced air pollution levels.

Description: 〈b〉Recovery of the three-dimensional wind and sonic temperature data from a physically deformed sonic anemometer〈/b〉〈br〉 Xinhua Zhou, Qinghua Yang, Xiaojie Zhen, Yubin Li, Guanghua Hao, Hui Shen, Tian Gao, Yirong Sun, and Ning Zheng〈br〉 Atmos. Meas. Tech., 11, 5981-6002, https://doi.org/10.5194/amt-11-5981-2018, 2018〈br〉 The three-dimensional wind and sonic temperature data from a physically deformed sonic anemometer was successfully recovered by developing equations, algorithms, and related software. Using two sets of geometry data from production calibration and return re-calibration, this algorithm can recover wind with/without transducer shadow correction and sonic temperature with crosswind correction, and then obtain fluxes at quality as expected. This study is applicable as a reference for related topics.

Description: 〈b〉Doppler W-band polarization diversity space-borne radar simulator for wind studies〈/b〉〈br〉 Alessandro Battaglia, Ranvir Dhillon, and Anthony Illingworth〈br〉 Atmos. Meas. Tech., 11, 5965-5979, https://doi.org/10.5194/amt-11-5965-2018, 2018〈br〉 A new technique is proposed to simulated winds in clouds as they could be observed by a space-borne Doppler 3 mm wavelength radar. Results show that, in the presence of cloud inhomogeneity and of vertical wind shear, measured winds can be corrected and produce unbiased estimates of line-of-sight winds that can then be assimilated in numerical models to improve weather forecasts.

Description: 〈b〉Wave run-up prediction and observation in a micro-tidal beach〈/b〉〈br〉 Diana Di Luccio, Guido Benassai, Giorgio Budillon, Luigi Mucerino, Raffaele Montella, and Eugenio Pugliese Carratelli〈br〉 Nat. Hazards Earth Syst. Sci., 18, 2841-2857, https://doi.org/10.5194/nhess-18-2841-2018, 2018〈br〉 Forecasting and hindcasting the action of sea storms on piers, coastal structures and beaches is important to mitigate their effects. To this end, with particular regard to low coasts and beaches, we have configured a computational model chain based partly on open-access models and partly on an ad-hoc-developed numerical calculator to evaluate beach wave run-up levels. The results were validated by a set of specially conceived video-camera-based experiments on a micro-tidal beach.

Description: 〈b〉Evaluation of the seasonal formation of subsurface negative preformed nitrate anomalies in the subtropical North Pacific and North Atlantic〈/b〉〈br〉 Robert T. Letscher and Tracy A. Villareal〈br〉 Biogeosciences, 15, 6461-6480, https://doi.org10.5194/bg-15-6461-2018, 2018〈br〉 The formation rates of oxygen to nitrogen anomalies in the subtropical North Pacific and North Atlantic were estimated from time series data. We find that vertically migrating phytoplankton, which traverse ~ 100–150 m in the upper ocean over days to acquire nutrients from waters at depth and return to the surface for photosynthesis, likely explain the observed anomalies and help sustain surface ocean productivity and the biological pump throughout the annual cycle in the subtropical ocean.

Description: 〈b〉Evaluation of soil moisture from CCAM-CABLE simulation, satellite based models estimates and satellite observations: Skukuza and Malopeni flux towers regional case study〈/b〉〈br〉 Floyd Vukosi Khosa, Mohau Jacob Mateyisi, Martina Reynita van Der Merwe, Gregor Timothy Feig, Francois Alwyn Engelbrecht, and Michael John Savage〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-546,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 The paper evaluates soil moisture outputs from three structurally distinct models against in situ data. Our goal is to find how site and region representative the model outputs are. This is a question of interest as some of the models have a specific regional focus on their inceptions. Much focus is placed on how the models capture the soil moisture signal. We find that there is agreement on seasonal patterns between the models and observations with a tolerable level of model uncertainty.

Description: 〈b〉Wave run-up prediction and observation in a micro-tidal beach〈/b〉〈br〉 Diana Di Luccio, Guido Benassai, Giorgio Budillon, Luigi Mucerino, Raffaele Montella, and Eugenio Pugliese Carratelli〈br〉 Nat. Hazards Earth Syst. Sci., 18, 2841-2857, https://doi.org/10.5194/nhess-18-2841-2018, 2018〈br〉 Forecasting and hindcasting the action of sea storms on piers, coastal structures and beaches is important to mitigate their effects. To this end, with particular regard to low coasts and beaches, we have configured a computational model chain based partly on open-access models and partly on an ad-hoc-developed numerical calculator to evaluate beach wave run-up levels. The results were validated by a set of specially conceived video-camera-based experiments on a micro-tidal beach.

Description: 〈b〉Measurements of spectral irradiance during the solar eclipse of 21 August 2017: reassessment of the effect of solar limb darkening and of changes in total ozone〈/b〉〈br〉 Germar Bernhard and Boyan Petkov〈br〉 Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-1048,2018〈br〉 〈b〉Manuscript under review for ACP〈/b〉 (discussion: open, 0 comments)〈br〉 Solar radiation at ultraviolet, visible, and infrared wavelengths was measured during the total solar eclipse of 21 August 2017. Data were used to study the wavelength-dependent changes of solar radiation at Earth's surface and to validate parameterizations of solar limb darkening (LD), which describes the change of the Sun's brightness between its center and its edge. The study highlights the importance of the LD effect when calculating total ozone and aerosol optical depth during an eclipse.

Description: 〈b〉Global sounding of 〈i〉F〈/i〉 region irregularities by COSMIC during a geomagnetic storm〈/b〉〈br〉 Klemens Hocke, Huixin Liu, Nicholas Pedatella, and Guanyi Ma〈br〉 Ann. Geophys. Discuss., https//doi.org/10.5194/angeo-2018-117,2018〈br〉 〈b〉Manuscript under review for ANGEO〈/b〉 (discussion: open, 0 comments)〈br〉 The GPS radio occultation data of the COSMIC-FORMOSAT-3 mission are used to visualize the global distribution of ionospheric irregularities in the F2 region during a geomagnetic storm, at solar minimum, and at solar maximum.

Description: 〈b〉Ice cliff contribution to the tongue-wide ablation of Changri Nup Glacier, Nepal, central Himalaya〈/b〉〈br〉 Fanny Brun, Patrick Wagnon, Etienne Berthier, Joseph M. Shea, Walter W. Immerzeel, Philip D. A. Kraaijenbrink, Christian Vincent, Camille Reverchon, Dibas Shrestha, and Yves Arnaud〈br〉 The Cryosphere, 12, 3439-3457, https://doi.org/10.5194/tc-12-3439-2018, 2018〈br〉 On debris-covered glaciers, steep ice cliffs experience dramatically enhanced melt compared with the surrounding debris-covered ice. Using field measurements, UAV data and submetre satellite imagery, we estimate the cliff contribution to 2 years of ablation on a debris-covered tongue in Nepal, carefully taking into account ice dynamics. While they occupy only 7 to 8 % of the tongue surface, ice cliffs contributed to 23 to 24 % of the total tongue ablation.

Description: 〈b〉Particle number size distribution and new particle formation under the influence of biomass burning at a high altitude background site at Mt. Yulong (3410 m), China〈/b〉〈br〉 Dongjie Shang, Min Hu, Jing Zheng, Yanhong Qin, Zhuofei Du, Mengren Li, Jingyao Fang, Jianfei Peng, Yusheng Wu, Sihua Lu, and Song Guo〈br〉 Atmos. Chem. Phys., 18, 15687-15703, https://doi.org/10.5194/acp-18-15687-2018, 2018〈br〉 Biomass burning (BB) activities have a great impact on the particle number size distribution in the upper troposphere of the Tibetan Plateau (TP), which could affect regional and global climate. We found that the cloud condensation nuclei concentration was 2–8 times higher during BB influenced periods than during clean periods on the TP. An unexpectedly low new particle formation frequency was found in clean atmosphere on the TP, due to low concentrations of anthropogenic precursors, i.e., SO〈sub〉2〈/sub〉.

Description: 〈b〉Ice-nucleating ability of aerosol particles and possible sources at three coastal marine sites〈/b〉〈br〉 Meng Si, Victoria E. Irish, Ryan H. Mason, Jesús Vergara-Temprado, Sarah J. Hanna, Luis A. Ladino, Jacqueline D. Yakobi-Hancock, Corinne L. Schiller, Jeremy J. B. Wentzell, Jonathan P. D. Abbatt, Ken S. Carslaw, Benjamin J. Murray, and Allan K. Bertram〈br〉 Atmos. Chem. Phys., 18, 15669-15685, https://doi.org/10.5194/acp-18-15669-2018, 2018〈br〉 Using the concentrations of ice-nucleating particles (INPs) and total aerosol particles measured at three coastal marine sites, the ice-nucleating ability of aerosol particles on a per number basis and a per surface-area basis were determined as a function of size. The ice-nucleating ability was strongly dependent on size, with larger particles being more efficient. This type of information can help determine the sources of INPs and constrain the future modelling of INPs and mixed-phase clouds.

Description: 〈b〉Particle number size distribution and new particle formation under the influence of biomass burning at a high altitude background site at Mt. Yulong (3410 m), China〈/b〉〈br〉 Dongjie Shang, Min Hu, Jing Zheng, Yanhong Qin, Zhuofei Du, Mengren Li, Jingyao Fang, Jianfei Peng, Yusheng Wu, Sihua Lu, and Song Guo〈br〉 Atmos. Chem. Phys., 18, 15687-15703, https://doi.org/10.5194/acp-18-15687-2018, 2018〈br〉 Biomass burning (BB) activities have a great impact on the particle number size distribution in the upper troposphere of the Tibetan Plateau (TP), which could affect regional and global climate. We found that the cloud condensation nuclei concentration was 2–8 times higher during BB influenced periods than during clean periods on the TP. An unexpectedly low new particle formation frequency was found in clean atmosphere on the TP, due to low concentrations of anthropogenic precursors, i.e., SO〈sub〉2〈/sub〉.

Description: 〈b〉HESS Opinions: Incubating deep-learning-powered hydrologic science advances as a community〈/b〉〈br〉 Chaopeng Shen, Eric Laloy, Amin Elshorbagy, Adrian Albert, Jerad Bales, Fi-John Chang, Sangram Ganguly, Kuo-Lin Hsu, Daniel Kifer, Zheng Fang, Kuai Fang, Dongfeng Li, Xiaodong Li, and Wen-Ping Tsai〈br〉 Hydrol. Earth Syst. Sci., 22, 5639-5656, https://doi.org/10.5194/hess-22-5639-2018, 2018〈br〉 Recently, deep learning (DL) has emerged as a revolutionary tool for transforming industries and scientific disciplines. We argue that DL can offer a complementary avenue toward advancing hydrology. New methods are being developed to interpret the knowledge learned by deep networks. We argue that open competitions, integrating DL and process-based models, more data sharing, data collection from citizen scientists, and improved education will be needed to incubate advances in hydrology.

Description: 〈b〉HESS Opinions: Incubating deep-learning-powered hydrologic science advances as a community〈/b〉〈br〉 Chaopeng Shen, Eric Laloy, Amin Elshorbagy, Adrian Albert, Jerad Bales, Fi-John Chang, Sangram Ganguly, Kuo-Lin Hsu, Daniel Kifer, Zheng Fang, Kuai Fang, Dongfeng Li, Xiaodong Li, and Wen-Ping Tsai〈br〉 Hydrol. Earth Syst. Sci., 22, 5639-5656, https://doi.org/10.5194/hess-22-5639-2018, 2018〈br〉 Recently, deep learning (DL) has emerged as a revolutionary tool for transforming industries and scientific disciplines. We argue that DL can offer a complementary avenue toward advancing hydrology. New methods are being developed to interpret the knowledge learned by deep networks. We argue that open competitions, integrating DL and process-based models, more data sharing, data collection from citizen scientists, and improved education will be needed to incubate advances in hydrology.

Description: 〈b〉A simple predictive model for the eddy propagation trajectory in the South China Sea〈/b〉〈br〉 Jiaxun Li, Guihua Wang, Huijie Xue, and Huizan Wang〈br〉 Ocean Sci. Discuss., https//doi.org/10.5194/os-2018-116,2018〈br〉 〈b〉Manuscript under review for OS〈/b〉 (discussion: open, 0 comments)〈br〉 A novel predictive model is built for eddy propagation trajectory using the multiple linear regression method. This simple model has related various oceanic parameters to eddy propagation position changes in the South China Sea (SCS). The performance of the proposed model is examined in the SCS based on twenty years of satellite altimeter data, and demonstrates its significant forecast skills over a 4-week forecast window comparing to the traditional persistence method.

Description: 〈b〉Challenges to implementing bottom-up flood risk decision analysis frameworks: how strong are social networks of flooding professionals?〈/b〉〈br〉 James O. Knighton, Osamu Tsuda, Rebecca Elliott, and M. Todd Walter〈br〉 Hydrol. Earth Syst. Sci., 22, 5657-5673, https://doi.org/10.5194/hess-22-5657-2018, 2018〈br〉 Decision-making for flood risk management is often the collective effort of professionals within government, NGOs, private practice, and advocacy groups. Our research investigates differences among flood experts within Tompkins County, New York (USA). We explore how they differ in their perceptions of flooding risk, desired project outcomes, and knowledge. We observe substantial differences among experts, and recommend formally acknowledging these perceptions when engaging in flood management.

Description: 〈b〉Nitric oxide (NO) in the Bohai and Yellow Seas〈/b〉〈br〉 Ye Tian, Chao Xue, Chun-Ying Liu, Gui-Peng Yang, Pei-Feng Li, Wei-Hua Feng, and Hermann W. Bange〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-446,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 1 comment)〈br〉 Nitric oxide (NO) seems to be widespread with different functions in marine ecosystem but know little about it. Concentrations of NO were in the range of from below the detection limit to 616 pmol L〈sup〉−1〈/sup〉 in the surface and to 482 pmol L〈sup〉−1〈/sup〉 in the bottom of the Bohai and Yellow Seas. The study region was a source of the atmospheric NO. NO sea-to-air fluxes were much lower than NO photoproduction rates, implying that the NO produced in the mixed layer was rapidly consumed before enter the atmosphere.

Description: 〈b〉Hess Opinions: Socio-economic and ecological trade-offs of flood management – benefits of a transdisciplinary approach〈/b〉〈br〉 Karl Auerswald, Peter Moyle, Simon Paul Seibert, and Juergen Geist〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-544,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 The demand for flood protection often results in the construction of more and bigger levees along rivers. We highlight that such technical solutions often result in undesired socioeconomic and ecological consequences such as increased downstream flooding risk, changes of groundwater levels and a loss of aquatic and terrestrial biodiversity. We propose a transdisciplinary approach of integrated flood management and green infrastructure instead of reliance on technical protection measures.

Description: 〈b〉Towards a more complete quantification of the global carbon cycle〈/b〉〈br〉 Miko U. F. Kirschbaum, Guang Zeng, Fabiano Ximenes, Donna L. Giltrap, and John R. Zeldis〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-436,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 0 comments)〈br〉 Globally, we add carbon to the atmosphere from fossil fuels and deforestation, balanced by ocean uptake and atmospheric increase. The difference is a residual sink equated to plant uptake. But this omits cement carbonation and pools of plastic, bitumen, wood, landfills and lakes, and transport by wind erosion, volatile C compounds and river transport. This reduces the residual sink from 3.6 to 2.1 GtC yr〈sup〉−1〈/sup〉 with important implications for natural feedbacks to amplify or negate human C emissions.

Description: 〈b〉Insights into the morphology of multicomponent organic/inorganic aerosols from molecular dynamics simulations〈/b〉〈br〉 Katerina S. Karadima, Vlasis G. Mavrantzas, and Spyros N. Pandis〈br〉 Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-1098,2018〈br〉 〈b〉Manuscript under review for ACP〈/b〉 (discussion: open, 0 comments)〈br〉 We explore the morphologies of multicomponent nanoparticles through atomistic molecular dynamics simulations under atmospherically relevant conditions. Phase separation is predicted for almost all simulated nanoparticles either between organics and inorganics or between hydrophobic and hydrophilic constituents. Three main particle types were identified: organic islands at the surface, inorganic core-organic shell morphologies, and complex structures with hydrophobic and hydrophilic domains.

Description: 〈b〉Hess Opinions: Socio-economic and ecological trade-offs of flood management – benefits of a transdisciplinary approach〈/b〉〈br〉 Karl Auerswald, Peter Moyle, Simon Paul Seibert, and Juergen Geist〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-544,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 The demand for flood protection often results in the construction of more and bigger levees along rivers. We highlight that such technical solutions often result in undesired socioeconomic and ecological consequences such as increased downstream flooding risk, changes of groundwater levels and a loss of aquatic and terrestrial biodiversity. We propose a transdisciplinary approach of integrated flood management and green infrastructure instead of reliance on technical protection measures.

Description: 〈b〉Retrieval of liquid water cloud properties from POLDER-3 measurements using a neural network ensemble approach〈/b〉〈br〉 Antonio Di Noia, Otto P. Hasekamp, Bastiaan van Diedenhoven, and Zhibo Zhang〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-345,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉This paper describes a neural network algorithm for the estimation of liquid water cloud optical properties from the Polarization and Directionality of Earth's Reflectances-3 (POLDER-3) instrument, on board the Polarization & Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar (PARASOL) satellite. The algorithm has been trained on synthetic multi-angle, multi-wavelength measurements of reflectance and polarization, and has been applied to the processing of one year of POLDER-3 data. Comparisons of the retrieved cloud properties with Moderate resolution Imaging Spectroradiometer (MODIS) products show negative biases around −2 in retrieved cloud optical thicknesses (COTs) and between −1 and −2 μm in retrieved cloud effective radii. Comparisons with existing POLDER-3 datasets suggest that the proposed scheme may have enhanced capabilities for cloud effective radius retrieval at least over land. An additional feature of the presented algorithm is that it provides COT and effective radius retrievals at the native POLDER-3 Level 1B pixel level.〈/p〉

Description: 〈b〉Carbon–nitrogen coupling under three schemes of model representation: a traceability analysis〈/b〉〈br〉 Zhenggang Du, Ensheng Weng, Lifen Jiang, Yiqi Luo, Jianyang Xia, and Xuhui Zhou〈br〉 Geosci. Model Dev., 11, 4399-4416, https://doi.org/10.5194/gmd-11-4399-2018, 2018〈br〉 In this study, based on a traceability analysis technique, we evaluated alternative representations of C–N interactions and their impacts on the C cycle using the TECO model framework. Our results showed that different representations of C–N coupling processes lead to divergent effects on plant production, C residence time, and thus the ecosystem C storage capacity. Identifying those effects can help us to improve the N limitation assumptions employed in terrestrial ecosystem models.

Description: 〈b〉Estimation of soil erosion considering soil loss tolerance in karst area〈/b〉〈br〉 Yue Cao, Shijie Wang, Xiaoyong Bai, Huiwen Li, Cheng Zeng, Yichao Tian, Fei Chen, Luhua Wu, and Mingming Wang〈br〉 Nat. Hazards Earth Syst. Sci. Discuss., https//doi.org/10.5194/nhess-2018-310,2018〈br〉 〈b〉Manuscript under review for NHESS〈/b〉 (discussion: open, 0 comments)〈br〉 Due to the soil holding capacity is very limited in karst area, it is necessary to consider the allowable loss of soil. Here we took thermodynamic dissolution model of carbonate rocks and the lithological characteristics to estimate soil loss tolerance, then corrected and quantitatively evaluated the soil erosion. We identified the spatial pattern of soil loss tolerance in karst area, found RUSLE overestimated soil erosion in karst area and proposed an idea for evaluating soil erosion in karst.

Description: 〈b〉Potential of INSAT-3D sounder-derived total precipitable water product for weather forecast〈/b〉〈br〉 Shailesh Parihar, Ashim Kumar Mitra, Mrutyunjay Mohapatra, and Rajjev Bhatla〈br〉 Atmos. Meas. Tech., 11, 6003-6012, https://doi.org/10.5194/amt-11-6003-2018, 2018〈br〉 This paper is based on operational work carried out at IMD, New Delhi using the INSAT-3D satellite-derived sounder product TPW for weather events such as rainfall and thunderstorms. The INSAT-3D TPW has been used by forecasters as well as many other users over the last 2 years. This work mainly brings out an in-depth validation with in situ ground measurement data as well as a GNSS system for its suitability in weather prediction. This paper can be utilized operationally for weather purposes.

Description: 〈b〉Evaluation of the seasonal formation of subsurface negative preformed nitrate anomalies in the subtropical North Pacific and North Atlantic〈/b〉〈br〉 Robert T. Letscher and Tracy A. Villareal〈br〉 Biogeosciences, 15, 6461-6480, https://doi.org/10.5194/bg-15-6461-2018, 2018〈br〉 The formation rates of oxygen to nitrogen anomalies in the subtropical North Pacific and North Atlantic were estimated from time series data. We find that vertically migrating phytoplankton, which traverse ~ 100–150 m in the upper ocean over days to acquire nutrients from waters at depth and return to the surface for photosynthesis, likely explain the observed anomalies and help sustain surface ocean productivity and the biological pump throughout the annual cycle in the subtropical ocean.

Description: 〈b〉Strength and limits of transient mid to late Holocene simulations with dynamical vegetation〈/b〉〈br〉 Pascale Braconnot, Dan Zhu, Olivier Marti, and Jérôme Servonnat〈br〉 Clim. Past Discuss., https//doi.org/10.5194/cp-2018-140,2018〈br〉 〈b〉Manuscript under review for CP〈/b〉 (discussion: open, 0 comments)〈br〉 This study discusses a simulation of the last 6000 years realized with a climate model in which vegetation and carbon cycle are fully interactive. The long term southward shift in northern hemisphere tree line and Afro-Asian monsoon rain are reproduced. The results show substantial change in tree composition with time over Eurasia and the role of traces gazes in the recent past. They highlight the limitations due to model set up and multiple pre-industrial vegetation states.