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Glacier and ice sheet surfaces host diverse communities of microorganisms whose activity (or inactivity) influences biogeochemical cycles and ice melting. Supraglacial microbes endure various environmental extremes including resource scarcity, frequent temperature fluctuations above and below the freezing point of water, and high UV irradiance during summer followed by months of total darkness during winter. One strategy that enables microbial life to persist through environmental extremes is dormancy, which despite being prevalent among microbial communities in natural settings, has not been directly measured and quantified in glacier surface ecosystems. Here, we use a combination of metabarcoding and metatranscriptomic analyses, as well as cell‐specific activity (BONCAT) incubations to assess the diversity and activity of microbial communities from glacial surfaces in Iceland and Greenland. We also present a new ecological model for glacier microorganisms and simulate physiological state‐changes in the glacial microbial community under idealized (i) freezing, (ii) thawing, and (iii) freeze–thaw conditions. We show that a high proportion (>50%) of bacterial cells are translationally active in‐situ on snow and ice surfaces, with Actinomycetota, Pseudomonadota, and Planctomycetota dominating the total and active community compositions, and that glacier microorganisms, even when frozen, could resume translational activity within 24 h after thawing. Our data suggest that glacial microorganisms respond rapidly to dynamic and changing conditions typical of their natural environment. We deduce that the biology and biogeochemistry of glacier surfaces are shaped by processes occurring over short (i.e., daily) timescales, and thus are susceptible to change following the expected alterations to the melt‐regime of glaciers driven by climate change. A better understanding of the activity of microorganisms on glacier surfaces is critical in addressing the growing concern of climate change in Polar regions, as well as for their use as analogues to life in potentially habitable icy worlds. [ABSTRACT FROM AUTHOR]

The physical interactions between ice sheets and their surroundings are major factors in determining the state of the climate system, yet many current Earth system models omit them entirely or approximate them in a heavily parameterised manner. In this work we have improved the snow and ice sheet surface physics in the FAMOUS climate model, with the aim of improving the representation of polar climate and implementing a bidirectional coupling to the Glimmer dynamic ice sheet model using the water and energy fluxes calculated by FAMOUS. FAMOUS and Glimmer are both low-resolution, computationally affordable models used for multi-millennial simulations. Glaciated surfaces in the new FAMOUS-ice are modelled using a multi-layer snow scheme capable of simulating compaction of firn and the percolation and refreezing of surface melt. The low horizontal resolution of FAMOUS compared to Glimmer is mitigated by implementing this snow model on sub-grid-scale tiles that represent different elevations on the ice sheet within each FAMOUS grid box. We show that with this approach FAMOUS-ice can simulate relevant physical processes on the surface of the modern Greenland ice sheet well compared to higher-resolution climate models and that the ice sheet state in the coupled FAMOUS-ice–Glimmer system does not drift unacceptably. FAMOUS-ice coupled to Glimmer is thus a useful tool for modelling the physics and co-evolution of climate and grounded ice sheets on centennial and millennial timescales, with applications to scientific questions relevant to both paleoclimate and future sea level rise. [ABSTRACT FROM AUTHOR]

Greenland ice sheet rainfall is expected to increase under a warming climate. Yet, there have been no active long‐term in‐situ rainfall records on the ice sheet due to observational difficulties. Here, we utilize the state‐of‐the‐art 5 km polar non‐hydrostatic regional climate model NHM‐SMAP to evaluate the ice sheet's rainfall over 40 years (1980–2019). The largest trends include a fourfold increase in annual rainfall for the northwestern ice sheet; 3.1 Gt year−1 or 12 mm m−2 year−1. September ice‐sheet‐wide rainfall amount and intensity increase by 7.5 Gt month−1 and 20.8 mm h−1 year−1. In the last two decades, the increasing September maximum hourly rainfall rate exceeded 50 mm h−1 six times. The increased surface water delivery has numerous implications, including for snow metamorphism and ice flow dynamics. Plain Language Summary: We find that rainfall has increased over the Greenland ice sheet from 1980 to 2019. Among the eight major ice‐sheet drainage areas, the northwestern sector stands out as an increasing rainfall hotspot where the annual rainfall has increased fourfold. For the entire ice sheet, September's total rainfall and its intensity increased by 224% and 54% above the 1981–2010 baseline over the last 40 years. An increase in late melt season rainfall is expected to contribute to an increase in late summer snow and ice melt. Our results provide the first detailed quantification of the state of ice sheet rainfall climatology. Key Points: A 5 km horizontal resolution non‐hydrostatic regional climate model is used to evaluate Greenland ice sheet rainfall from 1980 to 2019The northwestern sector stands out as a hotspot of increasing rainfallBoth the amount and intensity of September ice‐sheet‐wide rainfall have significantly increased in the 40 years from 1980 to 2019 [ABSTRACT FROM AUTHOR]

Radiative transfer in snow and ice is often not modeled explicitly in regional climate models. In this study, we evaluate a new englacial radiative transfer scheme and assess the surface mass and energy budget for the Greenland ice sheet in the latest version of the regional climate model RACMO2, version 2.3p3. We also evaluate the modeled (sub)surface temperature and melt, as radiation penetration now enables internal heating. The results are compared to the previous model version and are evaluated against stake measurements and automatic weather station data of the K-transect and PROMICE projects. In addition, subsurface snow temperature profiles are compared at the K-transect, Summit, and southeast Greenland. The surface mass balance is in good agreement with observations, with a mean bias of - 31 mm w.e. yr -1 (- 2.67 %), and only changes considerably with respect to the previous RACMO2 version around the ice margins and near the percolation zone. Melt and refreezing, on the other hand, are changed more substantially in various regions due to the changed albedo representation, subsurface energy absorption, and meltwater percolation. Internal heating leads to higher snow temperatures in summer, in agreement with observations, and introduces a shallow layer of subsurface melt. Hence, this study shows the consequences and necessity of radiative transfer in snow and ice for regional climate modeling of the Greenland ice sheet. [ABSTRACT FROM AUTHOR]

The future surface mass balance (SMB) will influence the ice dynamics and the contribution of the Antarctic ice sheet (AIS) to the sea level rise. Most of recent Antarctic SMB projections were based on the fifth phase of the Coupled Model Intercomparison Project (CMIP5). However, new CMIP6 results have revealed a +1.3 ∘C higher mean Antarctic near-surface temperature than in CMIP5 at the end of the 21st century, enabling estimations of future SMB in warmer climates. Here, we investigate the AIS sensitivity to different warmings with an ensemble of four simulations performed with the polar regional climate model Modèle Atmosphérique Régional (MAR) forced by two CMIP5 and two CMIP6 models over 1981–2100. Statistical extrapolation enables us to expand our results to the whole CMIP5 and CMIP6 ensembles. Our results highlight a contrasting effect on the future grounded ice sheet and the ice shelves. The SMB over grounded ice is projected to increase as a response to stronger snowfall, only partly offset by enhanced meltwater run-off. This leads to a cumulated sea-level-rise mitigation (i.e. an increase in surface mass) of the grounded Antarctic surface by 5.1 ± 1.9 cm sea level equivalent (SLE) in CMIP5-RCP8.5 (Relative Concentration Pathway 8.5) and 6.3 ± 2.0 cm SLE in CMIP6-ssp585 (Shared Socioeconomic Pathways 585). Additionally, the CMIP6 low-emission ssp126 and intermediate-emission ssp245 scenarios project a stabilized surface mass gain, resulting in a lower mitigation to sea level rise than in ssp585. Over the ice shelves, the strong run-off increase associated with higher temperature is projected to decrease the SMB (more strongly in CMIP6-ssp585 compared to CMIP5-RCP8.5). Ice shelves are however predicted to have a close-to-present-equilibrium stable SMB under CMIP6 ssp126 and ssp245 scenarios. Future uncertainties are mainly due to the sensitivity to anthropogenic forcing and the timing of the projected warming. While ice shelves should remain at a close-to-equilibrium stable SMB under the Paris Agreement, MAR projects strong SMB decrease for an Antarctic near-surface warming above +2.5 ∘C compared to 1981–2010 mean temperature, limiting the warming range before potential irreversible damages on the ice shelves. Finally, our results reveal the existence of a potential threshold (+7.5 ∘C) that leads to a lower grounded-SMB increase. This however has to be confirmed in following studies using more extreme or longer future scenarios. [ABSTRACT FROM AUTHOR]

Observations and models agree that the Greenland Ice Sheet (GrIS) surface mass balance (SMB) has decreased since the end of the 1990s due to an increase in meltwater runoff and that this trend will accelerate in the future. However, large uncertainties remain, partly due to different approaches for modelling the GrIS SMB, which have to weigh physical complexity or low computing time, different spatial and temporal resolutions, different forcing fields, and different ice sheet topographies and extents, which collectively make an inter-comparison difficult. Our GrIS SMB model intercomparison project (GrSMBMIP) aims to refine these uncertainties by intercomparing 13 models of four types which were forced with the same ERA-Interim reanalysis forcing fields, except for two global models. We interpolate all modelled SMB fields onto a common ice sheet mask at 1 km horizontal resolution for the period 1980–2012 and score the outputs against (1) SMB estimates from a combination of gravimetric remote sensing data from GRACE and measured ice discharge; (2) ice cores, snow pits and in situ SMB observations; and (3) remotely sensed bare ice extent from MODerate-resolution Imaging Spectroradiometer (MODIS). Spatially, the largest spread among models can be found around the margins of the ice sheet, highlighting model deficiencies in an accurate representation of the GrIS ablation zone extent and processes related to surface melt and runoff. Overall, polar regional climate models (RCMs) perform the best compared to observations, in particular for simulating precipitation patterns. However, other simpler and faster models have biases of the same order as RCMs compared with observations and therefore remain useful tools for long-term simulations or coupling with ice sheet models. Finally, it is interesting to note that the ensemble mean of the 13 models produces the best estimate of the present-day SMB relative to observations, suggesting that biases are not systematic among models and that this ensemble estimate can be used as a reference for current climate when carrying out future model developments. However, a higher density of in situ SMB observations is required, especially in the south-east accumulation zone, where the model spread can reach 2 m w.e. yr -1 due to large discrepancies in modelled snowfall accumulation. [ABSTRACT FROM AUTHOR]

The physical interactions between ice sheets and their surroundings are major factors in determining the state of the climate system, yet many current Earth System models omit them entirely or approximate them in a heavily parameterised manner. In this work we have improved the snow and ice sheet surface physics in the FAMOUS climate model, with the aim of improving the representation of polar climate and implementing a bidirectional coupling to the Glimmer dynamic ice sheet model using the water and energy fluxes calculated by FAMOUS. FAMOUS and Glimmer are both low resolution, computationally affordable models used for multi-millennial simulations. Glaciated surfaces in the new FAMOUS-ice are modelled using a multi-layer snow scheme capable of simulating compaction of firn and the percolation and refreezing of surface melt. The low horizontal resolution of FAMOUS compared to Glimmer is mitigated by implementing this snow model on sub-gridscale tiles that represent different elevations on the ice sheet within each FAMOUS grid-box. We show that with this approach FAMOUS-ice can simulate relevant physical processes on the surface of the modern Greenland ice sheet well compared to higher resolution climate models, and that the ice sheet state in the coupled FAMOUS-ice-Glimmer system does not drift unacceptably. FAMOUS-ice coupled to Glimmer is thus a useful tool for modelling the physics and co-evolution of climate and grounded ice sheets on centennial and millennial timescales, with applications to scientific questions relevant to both paleoclimate and future sea level rise. [ABSTRACT FROM AUTHOR]

The ERA5 reanalysis, recently made available by the European Centre for Medium-Range Weather Forecasts (ECMWF), is a new reanalysis product at a high resolution replacing ERA-Interim and is considered to provide the best climate reanalysis over Greenland to date. However, so far little is known about the performance of ERA5 over the Greenland Ice Sheet (GrIS). In this study, we compare the near-surface climate from the new ERA5 reanalysis to ERA-Interim, the Arctic System Reanalysis (ASR) as well as to a state-of-the-art polar regional climate model (MAR). The results show (1) that ERA5 does not outperform ERA-Interim significantly when compared with near-surface climate observations over GrIS, but ASR better models the near-surface temperature than both ERA reanalyses. (2) Polar regional climate models (e.g., MAR) are still a useful tool to downscale the GrIS climate compared to ERA5, as in particular the near-surface temperature in summer has a key role for representing snow and ice processes such as the surface melt. However, assimilating satellite data and using a more recent radiative scheme enable both ERA and ASR reanalyses to represent more satisfactorily than MAR the downward solar and infrared fluxes. (3) MAR near-surface climate is not affected when forced at its lateral boundaries by either ERA5 or ERA-Interim. Therefore, forcing polar regional climate models with ERA5 starting from 1950 will enable long and homogeneous surface mass balance reconstructions. [ABSTRACT FROM AUTHOR]

Knowledge of how the Antarctic Ice Sheet (AIS) responded in the geologic past to warming climates will provide powerful insight into its poorly understood role in future global sea level change. Study of past natural climate changes allows us to determine the sensitivity of the AIS to higher-than-present atmospheric carbon dioxide (CO2) concentrations and global temperatures, thereby providing the opportunity to improve the skill and performance of ice sheet models used for Intergovernmental Panel on Climate Change (IPCC) future projections. Antarctic and Southern Ocean (south of 60°S latitude) marine sediment records obtained over the last 50 years by seven scientific ocean drilling expeditions have revolutionized our understanding of Earth's climate system and the evolution and dynamics of the Antarctic ice sheets through the Cenozoic (0-65 million years ago). These records document an ice-free subtropical Antarctica between ~52 and 40 million years ago when CO2 was ~1,000 ppm; the initiation of continental-scale Antarctic ice sheets ~34 million years ago as CO2 dropped below 800 ppm; evidence for a dynamic, largely terrestrial, ice sheet driving global sea level changes of up to 40 m amplitude between 34 and 15 million years ago; and colder periods of highly dynamic, marine-based ice sheets contributing up to 20 m of global sea level rise when CO2 levels were in the range of 500-300 ppm between ~14 and 3 million years ago. Notwithstanding these discoveries, paleoenvironmental records obtained around Antarctica are still limited in their geographical coverage and do not provide a basis for comprehensive understanding of how different sectors of Antarctica respond to climate perturbations. Transects of drill cores spanning ice-proximal to ice-distal environments across the continental margin and at sensitive locations that have been identified by models and recent observations are needed to fully understand temporal and spatial ice volume changes that result from complex ice sheet-ocean-atmosphere interactions. These records are also critical for reconstructing equator-to-pole temperature gradients through time to better understand global climate change, interhemispheric long-distance transmission of changes through the atmosphere and ocean (teleconnections), and the amplification of climate signals in the polar regions. Future Antarctic scientific ocean drilling will remain key to obtaining records of past Antarctic Ice Sheet dynamics that can be integrated into coupled ice sheet-climate models for improved projections of sea level change. Thus, keeping an eye on ice sheet stability is critical for improving the accuracy and precision of predictions of future changes in global and regional temperatures and sea level rise. [ABSTRACT FROM AUTHOR]

Abstract The polar climate of Antarctica results in the lowest erosion rates on Earth. The low long-term erosion history of high elevation mountain tops that are exposed above the ice preserve a record of climate change that can be accessed using cosmogenic nuclides. However, unravelling the complexity of the long-term denudation histories of Antarctic summits is frequently hampered by intermittent ice cover. The aim of this work is to identify denudation rate changes in a surface that has been continuously exposed since the middle Miocene. We have measured stable (3He) and radioactive (10Be) cosmogenic nuclides in olivine from lherzolite xenoliths from the summit of the Mount Hampton shield volcano within the West Antarctic Ice Sheet. The peak (3200 m) has never been covered by the current ice sheet and local ice caps, consequently the data record the subaerial erosion history of a mountain top within the Antarctic interior. The 10Be concentrations in the olivines yield minimum exposure ages (33 to 501 ka) that are significantly younger than those derived from the cosmogenic 3He (90 to 1101 ka). The data reveal a complex exposure history that provide an integrated long-term erosion rate of between 0.2 and 0.7 m/My that is most likely caused by mechanical weathering. Inverse modelling shows that the data are readily explained by episodic erosion, consisting of one to five erosion pulses that may record major regional climatic changes. Highlights • Cosmogenic 3He 10Be data revealed episodic erosion on the summit of Mount Hampton within the West Antarctic Ice Sheet. • Data require 1–5 erosional pulses that may record past changes in climate. • Long-term average erosion rate of the summit is ~0.4 m/My. [ABSTRACT FROM AUTHOR]

The article offers several forecasts regarding science in 2019. Topics include research projects related to the impact of global warming on polar ice, the role of meteorologist Kelvin Droegemeier in advising U.S. President Donald Trump on science policy, and the possible impact of African swine fever on pig populations in places including China.

Mass changes of the Antarctic ice sheet impact sea-level rise as climate changes, but recent rates have been uncertain. Ice, Cloud and land Elevation Satellite (ICESat) data (2003-08) show mass gains from snow accumulation exceeded discharge losses by 82±25 Gt a-1, reducing global sea-level rise by 0.23mma-1. European Remote-sensing Satellite (ERS) data (1992-2001) give a similar gain of 112±61 Gt a-1. Gains of 136 Gt a-1 in East Antarctica (EA) and 72 Gt a-1 in four drainage systems (WA2) in West Antarctic (WA) exceed losses of 97 Gt a-1 from three coastal drainage systems (WA1) and 29 Gt a-1 from the Antarctic Peninsula (AP). EA dynamic thickening of 147 Gt a-1 is a continuing response to increased accumulation (>50%) since the early Holocene. Recent accumulation loss of 11 Gt a-1 in EA indicates thickening is not from contemporaneous snowfall increases. Similarly, the WA2 gain is mainly (60 Gt a-1) dynamic thickening. In WA1 and the AP, increased losses of 66±16 Gt a-1 from increased dynamic thinning from accelerating glaciers are 50% offset by greater WA snowfall. The decadal increase in dynamic thinning in WA1 and the AP is approximately one-third of the long-term dynamic thickening in EA and WA2, which should buffer additional dynamic thinning for decades. [ABSTRACT FROM AUTHOR]

The north and south poles of the earth (hereinafter referred to as the polar regions) are important components of the earth system. Changes in the material balance and movement of the polar ice shelf reflect the influence of the polar regions on global climate change and are also a response to global climate change. Through a comprehensive investigation of ice-shelf kinematics, with sufficient accuracy, it is possible to obtain ice-shelf elevation, movement-state data, ice-shelf material balance state, and the ice-shelf movement dynamics mechanism. Due to the extremely harsh environment in polar regions, remote sensing is currently widely used. Manual and equipment monitoring methods show insufficient accuracy or discontinuous time series. There is an urgent need to obtain continuous real-time ice-shelf kinematics-related parameters on the ground to verify the reliability of the parameters obtained by satellite remote sensing. These parameters should be combined with remote sensing monitoring to provide data support. In this paper, a monitoring system for the movement of polar ice and shelf ice cover is developed, and it is proposed that various data can be acquired by integrating high-precision GPS (global positioning system) and other sensors. Solutions to the problem of low-temperature power supply in the polar regions, data acquisition and storage strategies, and remote communication methods are proposed. Testing and remote sensing validation verified that the developed acquisition system can fulfill the requirements for monitoring the movement of the polar unmanned ice shelves and ice sheets. [ABSTRACT FROM AUTHOR]

The climate of the polar regions has dramatically changed over the last decades. This may have resulted from external forcing (e.g. from greenhouse gas emissions), but also from natural interactions between the components of the climate system (notably the atmosphere, the marine and continental cryosphere, and the ocean). Quantifying the specific contribution of each component is critical to understand decadal variability in the polar regions. Based on the complementary scientific expertise of its project partners, the PARAMOUR project aims at revealing the fundamental drivers of climate variability and assessing the predictability in the polar regions by developing and running a coupled atmosphere-ocean-ice sheet regional climate model over both hemispheres. Also, a smaller scale model setup will be developed for the Totten glacier region in Antarctica, as the Totten glacier is a highly dynamic glacier that, in recent years, has been strongly influenced by the sub-shelf intrusion of warm ocean currents. The models / components used will be the atmospheric model COSMO-CLM, the land surface model Community Land Mode, the ocean-ice model NEMO and the ice sheet models BISICLES and f.ETISh.The purpose of this poster presentation is to present the PARAMOUR project to the geo-science community. Our focus in the PARAMOUR project is on atmospheric feedback processes such as those between clouds and radiation and those between surface albedo and atmospheric processes (for example the darkening of the surface due to scouring by wind). During the course of the project we plan to i) develop a coupled atmosphere-ocean-sea ice-ice sheet model configuration for the northern hemisphere, southern hemisphere and Totten glacier region, ii) analyze the interactions between the atmosphere, ocean, sea ice and ice shelves at scales between a few hundreds of meters and a few kilometers and iii) investigate how these interactions influence the variability and predictability of the system, both in the past and in the future. [ABSTRACT FROM AUTHOR]

The Antarctic is an important region for the Earth's energy balance and climate. Here, we investigate the spatial patterns of Antarctic temperature change across a range of timescales. We use multiple ice-core water isotope records and an improved method for inverting water-isotope ratios to moisture-source and precipitation-site temperatures. We find that between the Last Glacial Maximum and the Holocene, East Antarctic warming was less than previously thought, and less than concurrent warming in West Antarctica; the latter point is confirmed by independent temperature estimates. More broadly, we identify a pattern of temperature variability in which lower, warmer sites show more temperature change than higher, colder sites. This spatial pattern of change is robust across a range timescales, including glacial-interglacial, AIM events and millennial variability, is consistent with observed changes in the last century, and holds for both warming and cooling trends. Because this pattern persists across climate changes driven by diverse forcing over a range of timescales, it may reflect a fundamental aspect of Earth's energy balance. We investigate potential sources for this pattern using a hierarchy of model complexities. We identify a likely cause, temperature-dependent radiative feedbacks, that is timescale independent. These results have implications for quantifying changes in ice sheet surface elevation through the deglaciation and for polar climate dynamics more generally. [ABSTRACT FROM AUTHOR]

The climate of polar regions is characterized by large fluctuations and has recently experienced dramatic changes. In the Antarctic, some regions have warmed less than the global average with some sea ice advance, in particular in the Ross Sea, while other regions have warmed significantly and displayed sea ice loss. While the ability to predict decadal climate variations has been confirmed in various parts of the world, polar regions have been given little attention so far, mostly because in these areas, observational data is sparse and global climate models suffer from systematic biases. Moreover, the Antarctic climate has been shown to strongly depend on complex feedback mechanisms between several distinct components (atmosphere, ocean circulation, sea ice, ice sheets...). Finally, global climate models involved in current decadal prediction experiments run at a rather coarse (~1°) resolution and are therefore likely missing a whole variety of processes holding predictability. Therefore, advancing decadal predictions in the polar regions is only possible if the coupling of the climate components is properly taken into account, and if cutting-edge models are used on local configurations, allowing higher resolution (~1/4°), while making full use of the ever-increasing observational data base at the disposal of the community. This poster presents a new coupled Southern Ocean model configuration that aims at fulfilling the conditions described above, along with first results. Our configuration uses NEMO-LIM for the ocean (including sea ice), COSMO-CLM for the atmosphere and f.ETISh for the marine ice sheets. [ABSTRACT FROM AUTHOR]

Due to their ability to produce climate projections, General circulation models (GCM) are often used to provide estimates of the surface mass balance (SMB) of the Antarctic ice sheet that can be used to constrain ice sheet models. However, GCM still benefit from a poor representation of polar climate specificities such as stable boundary layers, polar clouds or interactions between snow-covered surfaces and the atmosphere. In this study, we highlight the importance of downscaling GCM outputs from the Fifth Climate Model Intercomparison Project (CMIP5) with a regional climate model to provide accurate estimates of the Antarctic SMB. For that purpose, the regional climate model MAR is forced by 6-hourly outputs from ACCESS1.3 that is currently considered as one of the best GCM from CMIP5 over the Antarctic ice sheet. Estimates of the SMB computed by MAR and ACCESS1.3 are evaluated against SMB observations. Even if the temporal variability of the SMB is forced by the driving GCM, the comparison shows that MAR improves the spatial variability of the Antarctic SMB, emphasizing the added value of using a polar RCM for downscaling GCM outputs at high latitudes. [ABSTRACT FROM AUTHOR]