Cenozoic climate has evolved through stepwise quasi-equilibrium states in response to declining CO2 concentration. As a result, terrestrial polar ice sheets developed in Antarctica ~35 million years ago describing relatively large glacial-interglacial changes, prior to an increasing marine-based ice sheet component by ~15 Ma with lower glacial-interglacial variability, before returning to large glacial-interglacial amplitudes in response to the intensification of Northern Hemisphere Ice Sheets (~2.7 Ma). While mean surface temperature scales linearly with the total concentration of carbon in the atmosphere, this is not the case for past variations in global mean sea-level whose amplitudes are climate-state (CO2)-dependent. By examining past climate drivers (atmospheric CO2) and the response of ice volume (sea level), polar ice sheets are seen to demonstrate vastly different sensitivities under changing climate states highlighted by the ‘100-kyr’ problem of non-linear ice sheet change.
In this study, a new independent global ice volume (sea-level) record (X-PlioSeaNZ: 3.3 – 1.7 Ma) is used to evaluate the deep-sea oxygen isotope proxy record (δ18Obenthic). An empirical, power-law relationship emerges between δ18Obenthic and sea-level in contrast to long-standing linear δ18Obenthic calibrations. This relationship suggests relatively higher deep-ocean temperature contribution to δ18Obenthic signal and correspondingly lower global ice volume estimates under warmer past climates. It also demonstrates the need for variable ice volume-δ18Obenthic calibrations in response to the evolving bipolar ice sheet geographies over the last ~3 million years (Myr). Consequently, as the Earth system adjusts to 2-3°C of global warming over the coming decades and centuries, a lower paleo-ice sheet sensitivity (compared to the Last Glacial Maximum) is expected for ice sheet configurations where marine based ice sheets act as a buffer to terrestrial based ice sheets and brings geologic reconstructions into agreement with current projections for future sea-level rise.
How to cite: Grant, G.: Climate state dependence of ice sheet variability, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13026, https://doi.org/10.5194/egusphere-egu25-13026, 2025.
The Greenland Ice Sheet is a key contributor to contemporary global sea-level rise, but its long-term history remains highly uncertain. The landscape covered by the ice sheet comprises ∼79% of Greenland and is one of the most sparsely mapped regions on Earth. However, sub-ice geomorphology offers a unique record of environmental conditions prior to and during glaciation, and of the ice sheet’s response to changing climate.
Here we use ice-surface morphology and radio-echo sounding data to identify, and quantify the morphology of, valley networks beneath the Greenland Ice Sheet. Our mapping reveals intricate subglacial valley networks beneath the ice-sheet interior that appear to have a fluvial origin. By contrast, in the southern and eastern coastal highlands, valleys have been substantially modified by glacial erosion. We use geomorphometric analysis and simple ice-sheet model experiments to infer that these valleys were incised beneath erosive mountain valley glaciers during one or more phases of Greenland’s glacial history when ice was restricted to the southern and eastern highlands.
These inferred early mountain ice masses contained ~0.5 metres of sea-level equivalent (compared to 7.4 metres in the modern Greenland Ice Sheet). We believe the most plausible time for the formation of this landscape was prior to the growth of a continental-scale ice sheet in the late Pliocene, with the possibility of further incision having occurred during particularly warm and/or long-lived Pleistocene interglacials. Our findings therefore provide new data-based constraints on early Greenland Ice Sheet extent and dynamics that can serve as valuable boundary conditions in models of regional and global palaeoclimate during past warm periods that are important analogues for climate change in the 21st century and beyond.
How to cite: Paxman, G., Jamieson, S., Tinto, K., Austermann, J., Dolan, A., and Bentley, M.: Constraining the extent of the Greenland Ice Sheet during warmer climates of the Pliocene and Pleistocene: insights from subglacial geomorphology, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3494, https://doi.org/10.5194/egusphere-egu25-3494, 2025.
The Marine Isotope Stage (MIS) 12-MIS 11 glacial cycle (490-396 Ka) has been recognized as anomalous by researchers due to the longevity of the interglacial interval. MIS 12 sea level low stand is inferred to be similar to Last Glacial Maximum (LGM), however, due to limited geomorphological data, major uncertainties remain with respect to where the ice was distributed and the relative size of the ice sheets. With the lowest increase in insolation from glacial to interglacial of the past 800 kyrs, MIS 11 was almost twice as long as the other interglacials of the past 500 kyrs. A prevailing hypothesis for the duration of MIS 11 proposes that the large MIS 12 ice sheets, when exposed to a weak insolation increase, gradually released meltwater and deglaciated throughout the interglacial period, contributing to its extended duration. This freshwater influx triggered a positive feedback, promoting the release of oceanic CO2 into the atmosphere, which amplified insolation-driven warming and further prolonged the interglacial period.
Given the lack of terrestrial paleoclimate data, ice and climate modelling may offer a way to improve the understanding of this curious interval. Previous modeling work of this interval has been with either highly parameterized, low-resolution coupled ice-climate models, climate models with forced ice sheets, snapshot climate models with pre-industrial ice sheets, or ice sheet models with forced climate. Few models span the entire duration of the glacial cycle. For the first time, we transiently simulate the entire interval with the fully coupled ice sheet-climate LCIce model that resolves both atmospheric and ocean circulation. Parametric uncertainties are addressed by ensemble simulation. This presentation focuses on ensemble analysis of the ice sheets and climate of the glacial cycle as well as sensitivity testing of the two hypothesized drivers for length of MIS 11: meltwater flux during deglaciation and atmospheric CO2 concentration.
How to cite: Parnell, A. and Tarasov, L.: Ensemble simulation of the MIS 12-MIS 11 glacial cycle using a fully coupled climate-ice sheet model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-577, https://doi.org/10.5194/egusphere-egu25-577, 2025.
A mechanistic understanding of the main drivers of Quaternary climate variability, especially during the mid-Pleistocene transition (MPT; around 1.2–0.8 million years ago) remains a significant challenge in paleoclimate research. Climate changes during that time include a pronounced shift from 41-kyr to 100-kyr periodicity of glacial cycles as imprinted on sea level reconstructions, and the emergence of much larger ice sheets. While several modeling studies have focused on the interplay between the climate system and northern hemispheric ice sheets during the MPT, the role of Antarctica in driving and responding to climate change at that time remains largely unknown.
Here, we use the Parallel Ice Sheet Model (PISM) to simulate the transient evolution of the Antarctic Ice Sheet throughout the last 3 million years. PISM is forced by a climate index approach that is based on snapshots of climatic conditions in the past. Climate snapshots are derived from the Community Earth System Models (COSMOS), a general circulation model that simulates atmosphere, ocean, sea ice and land vegetation in dependence of reconstructions of paleogeography, orbital configuration, and greenhouse gas concentrations. Interpolation in times between snapshots is linear and based on a convolution of the EPICA Dome C record and the Lisiecki-Raymo benthic isotope stack.
Our simulations indicate that between 1.9 Ma and 800 ka BP, several Antarctic drainage basins crossed critical thresholds at different times, for example leading to the formation of a stable marine-based West Antarctic Ice Sheet. We further examine the characteristics of these thresholds and their associated state transitions. Additionally, our findings suggest that these thresholds, and their interplay, amplified eccentricity-driven climate variability both before and during the MPT, providing new insights into the complex interactions between Antarctic ice sheet dynamics and climate during this period.
How to cite: Wirths, C., Hermant, A., Stepanek, C., Stocker, T., and Sutter, J.: Unravelling abrupt transitions of Antarctic Ice Sheet dynamics during the mid-Pleistocene transition, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8670, https://doi.org/10.5194/egusphere-egu25-8670, 2025.
This study examines the interactions between the Northern Hemisphere ice sheets and the ocean during the last glacial period. Using the iLOVECLIM climate model of intermediate complexity coupled with the GRISLI ice sheet model, we explore the consequences of an amplification of the melt rates beneath ice shelves on ice sheet dynamics and the associated feedbacks. First, the amplification of oceanic basal melt rates leads to significant freshwater release from both increased calving and basal melt fluxes. Grounding line retreat and dynamic thinning occur over the Eurasian and Iceland ice sheets, while the oceanic perturbation fails to trigger a grounding line migration over the coasts of Greenland and the eastern part of the Laurentide ice sheet. Second, similarly to hosing experiments with no coupling between the climate and the ice sheets, the influx of fresh water temporarily increases sea-ice extent, reduces convection in the Labrador Sea, weakens the Atlantic meridional overturning circulation, lowers surface temperatures in the Northern Hemisphere, and increases the subsurface temperatures in the Nordic Seas. Third, the freshwater release and latent heat effect on ocean temperatures lead to a decrease in ice sheet discharge (negative feedback) for the Greenland and Eurasian ice sheets. In the experiments, the Laurentide ice sheet does not feature significant volume variations. Nonetheless, we show that we are able to trigger a grounding line retreat and a North American ice sheet volume decrease, by imposing ad-hoc constant oceanic melt rates in a second set of perturbation experiments. However, the Hudson Strait ice stream also does not exhibit the past dynamical instability indicated by the presence of Laurentide origin ice rafted debris in the North Atlantic sediment records. This suggests that the fully coupled model is too stable, specifically in the Hudson Bay region. To help address this issue, different modelling choices regarding the basal ice sheet dynamics are considered. This emphasizes the need for further research using fully coupled models to explore the triggering mechanisms of massive iceberg discharges and to clarify the role of the ocean in these events.
How to cite: Abot, L., Quiquet, A., and Waelbroeck, C.: Ice sheet-ocean interactions at 40 kyr BP : Insights from a coupled ice sheet-climate model of intermediate complexity., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4341, https://doi.org/10.5194/egusphere-egu25-4341, 2025.
During the Holocene, the Greenland Ice Sheet (GrIS) experienced substantial thinning, with some regions losing up to 600 meters of ice.
Ice sheet reconstructions, paleoclimatic records, and geological evidence indicate that during the Last Glacial Maximum, the GrIS extended far beyond its current boundaries and was connected with the Innuitian Ice Sheet (IIS) in the northwest. We investigate these long-term geometry changes and explore several possible factors driving those changes by using the Parallel Ice Sheet Model (PISM) to simulate the GrIS thinning throughout the Holocene period, from 11.7 ka ago to the present. We perform an ensemble study of 841 model simulations in which key model parameters are systematically varied to determine the parameter values that, with quantified uncertainties, best reproduce the 11.7 ka of surface elevation records derived from ice cores, providing confidence in the modeled GrIS historical evolution. We find that since the Holocene onset, 11.7 ka ago, the GrIS mass loss has contributed 5.3±0.3 m to the mean global sea level rise, which is consistent with the ice-core-derived thinning curves spanning the time when the GrIS and the Innuitian Ice Sheet were bridged. Our results suggest that the ice bridge collapsed 4.9±0.5 ka ago and that the GrIS is still responding to these past changes today. Our results have implications for future mass-loss projections, which should account for the long-term, transient trend.
How to cite: Lauritzen, M. L., Solgaard, A. M., Rathmann, N. M., Vinther, B. M., Grindsted, A., Noël, B., Aðalgeirsdóttir, G., and Hvidberg, C. S.: Modeled Greenland Ice Sheet evolution constrained by ice-core-derived Holocene elevation histories, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1396, https://doi.org/10.5194/egusphere-egu25-1396, 2025.
So far, melting of the Greenland Ice Sheet (GrIS) has been the biggest contributor from the Earth’s cryosphere to global sea-level rise. Major uncertainties remain about how oceanic heat is transported across the shelf and through the fjords to the faces of marine-terminating glaciers, and how this affects rates of ice melt and calving. In turn, the increasing supply of meltwater and nutrients to the ocean around Greenland is impacting marine ecosystems as primary productivity rises, subsequently increasing the potential for carbon to be buried as “blue carbon” in Greenland’s fjords as warming continues. In July-August 2024, the UK-funded KANG-GLAC project completed a 40-day multidisciplinary research cruise to SE Greenland where the 40-strong scientific party made a suite of integrated geological, ocean and biological observations. The main aims of the project are two-fold. First, it aims to better understand how marine-terminating glaciers respond to oceanic heat on longer timescales (decades to centuries) by reconstructing glacier and ice-sheet behaviour during the Holocene and in particular during the climatic warm period of the Holocene Thermal Maximum. Second, the project will quantify nutrient cycling in the water column and uppermost seafloor sediments in order to improve our knowledge of marine ecosystem response to meltwater supply from the GrIS. The cruise on the UK’s premier polar research vessel, the RRS Sir David Attenborough, is the start of a 3.5 year project. Here, we will present an overview of our field observations in this past-to-future project and outline the plans for future data-driven modelling of the Greenland Ice Sheet.
How to cite: Hogan, K., Colm, O. C., Abrahamsen, P., Howe, J., Inall, M., Lloyd, J., Manno, C., März, C., Roberts, D., Tarling, G., Sime, L., Voss, J., Tarasov, L., and Andresen, C. and the SD041 Shipboard Scientific Party: Early Results from KANG-GLAC: A Project to Understand Holocene Ice Sheet-Ocean Interaction and Marine Productivity in SE Greenland, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19646, https://doi.org/10.5194/egusphere-egu25-19646, 2025.
The Greenland Ice Sheet (GrIS), a major driver of global sea-level rise, holds approximately 7 meters of sea-level equivalent. Despite its critical role, significant uncertainties remain about its mass balance and response to climate forcing over the past few centuries, particularly before the satellite era. This study aims to address these gaps by reconstructing a high-resolution (1x1 km) monthly surface mass balance (SMB) dataset spanning AD 1421–2024 and quantifying its contributions to historical and contemporary sea-level changes using the Positive Degree Day (PDD) modelling approach.
The novel SMB dataset integrates long-term climate reanalysis inputs (ERA5 and ModE-RA). They are then validated and corrected against available ice-core records and weather station observations using a Bayesian approach to formally constrain the uncertainties. Preliminary analysis indicates signidficant SMB-driven mass loss due to climatic forcing during recent past, potentially offering new insights into the relative contributions of SMB and ice dynamics to GrIS total mass changes during latter half of the last millennium.
These results represent a significant advancement in understanding the GrIS’s historical behaviour and links with climate change and can form a valuable baseline for improving the accuracy of future SMB and sea-level rise projections. By addressing critical knowledge gaps, this work enhances our ability to predict the long-term impacts of climate change on the GrIS and global sea levels.
How to cite: Javed, A., Hanna, E., Wake, L., Wilkinson, R., Morlighem, M., and Mcconnell, J.: Greenland Ice Sheet under climate change: Perspective from a high-resolution modelling simulation from 1421-2024 , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4663, https://doi.org/10.5194/egusphere-egu25-4663, 2025.
Despite ice cores providing high-resolution climate records, few ice cores extracted from the West Antarctic Ice Sheet (WAIS) cover the Holocene, nor extend into the last glacial period. Marine ice-sheet basins, such as those underlying the WAIS, have been shown to be particularly vulnerable to retreat and possible collapse during past warm periods, and thus have significant potential to contribute to global sea-level rise. Dynamic thinning and retreat of ice are underway in the Amundsen Sea and Bellingshausen Sea sectors of the WAIS, yet this Pacific-facing region remains relatively data-poor for informing estimates of past and future retreat rates and sea-level contributions.
In 2010/11, a 136 m ice core was drilled at the three-way ice divide between Ferrigno Ice Stream, Pine Island Glacier, and Evans Ice Stream catchments. To further investigate this region, we analyse the internal structure across this region imaged through three intersecting radar surveys: (1) a 2004/05 UK/BAS survey, conducted with the Polarimetric Airborne Survey INstrument (PASIN), (2) a 2009/10 ground-based survey of Ferrigno Ice Stream, carried out with 3 MHz radar; and (3) NASA Operation Ice Bridge airborne surveys acquired in 2016 and 2018, which utilised the Multichannel Coherent Radar Depth Sounder 2 (MCoRDS2). We provide dating control to the traced englacial stratigraphy from tying it to the age-depth profile provided by the WAIS Divide Ice Core in central West Antarctica.
We then utilise a 1-D numerical ice-flow model, optimised by shallow ice-core data and these dated internal reflection horizons at the three-way ice divide, to infer palaeo-accumulation rates throughout the Holocene, and place age constraints on the age of the oldest ice at a proposed deep ice-core drill site at Ferrigno Ice Stream. We show that the method is robust and effectively synthesises the shallow ice-core data and the dated internal reflection horizons to reconstruct past climate records. The modelled maximum age at the three-way ice divide is around 24.77 ka +/- 6.88 ka, with a resolution of around 0.6 ka m-1at the depth of the oldest ice, making this an ideal site for a new deep ice core in West Antarctica. In addition, the ice core would be located in a coastal area and may provide key insights glacial extent during deglaciation.
How to cite: Davis, H., Bingham, R., Hein, A., Hogg, A., Martín, C., and Thomas, E.: A combined radiostratigraphy- and ice-core- derived age scale for ice at the divide between the Amundsen, Bellingshausen and Weddell seas, West Antarctica, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6677, https://doi.org/10.5194/egusphere-egu25-6677, 2025.
The relative contributions of anthropogenic climate change and internal variability in sea level rise from the Antarctic Ice Sheet are yet to be determined. This is primarily because of uncertainty arising from poorly constrained model parameters and chaotic forcing as well as a relatively short observation period. Using an established uncertainty quantification framework (known as calibrate-emulate-sample), we have quantified, for the first time, the role of anthropogenic climate change on retreat of a major Antarctic glacier. We find that anthropogenic trends in forcing, beginning in the 1960s, are only responsible for approximately 15% of the retreat of this glacier since its retreat began in the 1940s. Most of the retreat is attributable to the inertia associated with a slow retreat over the Holocene. We also find, however, that trends in forcing dominate retreat beyond the 21st century, with ice sheet retreat stabilized if anthropogenic trends plateau.
How to cite: Bradley, A., Bett, D., Holland, P., Arthern, R., and Williams, R.: To what extent is climate change responsible for retreat of the Pine Island Glacier over the 20th century?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-118, https://doi.org/10.5194/egusphere-egu25-118, 2025.
The Nioghalvfjerdsfjorden glacier (NG) and Zachariae Isstrøm (ZI) are major contributors to the mass balance of northeast Greenland, which drain 12% of the Greenland Ice Sheet. Accurate measurements of these two glaciers are crucial to the estimation of the mass balance in northeast Greenland. They also serve as an important parameter for reflecting climate change and predicting future sea level rise. In the past, early ice velocity data were scarce, primarily due to challenges in difficulties in image orthorectification caused by large distortions and low quality in historical remote sensing imagery. We proposed a systematic process for orthorectification of CORONA KH-4A imagery, which has proven to be both efficient and accurate in velocity mapping at a precision of 25m. By employing a hierarchical network densification approach based on ARGON KH-5 and CORONA KH-4A imagery, we have successfully reconstructed the ice flow velocity fields for NG and ZI from 1963 to 1967. Combining with other ice velocity products, we have obtained the ice velocity of NG and ZI spanning a period nearly 60 years. The results indicate that the average ice flow velocity near the grounding line has increased by 12.4% for NG and a substantial 81.4% for ZI from 1963 to 2020. While ZI is experiencing accelerated mass loss, the NG is still in a relatively stable state under the similar climate condition. The slight fluctuations in ice velocity for NG may be due to the unique topography and the hindering effect of ice rises, suggesting the climate change may have a comparatively less impact on it.
How to cite: An, L., Dai, L., Liu, X., and Li, R.: Study on the Instability of Two Large Glaciers in Northeast Greenland in Recent 60 Years, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15269, https://doi.org/10.5194/egusphere-egu25-15269, 2025.
Atmospheric rivers are transient channels of intense water vapor that account for up to 90% of the poleward moisture transport from mid-latitudes. Though short-lived, these events can deliver extreme amounts of heat and rainfall that have been widely reported to accelerate ablation and ice mass loss across the Arctic. However, the impact of atmospheric river fueled snowfall has received less attention, partly due to the limited availability of empirical evidence and direct observations. Here, we explore the potential of atmospheric rivers to deliver intense snowfall to the Greenland ice sheet and thereby replenish its health through enhanced mass accumulation. Specifically, we use new firn-core isotopic analyses and glacio-meteorological datasets from Southeast Greenland to examine the origin and impact of atmospheric rivers on regional mass balance. To this end, we sampled firn core stratigraphy from the upper accumulation area of Southeast Greenland and related it to meteorological observations, to demonstrate that an intense atmospheric river in mid-March 2022 delivered up to 11.6 gigatons per day of extreme snowfall to this region of the ice sheet.
We show that this immense snowfall not only recharged the snowpack and offset Greenland ice sheet net mass loss by 8% in 2022, but also raised local albedo thereby delaying the onset of summer bare-ice melt by 11 days, despite warmer than average spring temperatures. Since 2010, synoptic analysis of ERA5 data reveals that snow accumulation across Southeast Greenland increased by 20 mm water equivalent per year, driven by enhanced Atlantic cyclonicity. Depending on their seasonal timing, our study demonstrates that the impact of atmospheric rivers on the mass balance of the Greenland ice sheet is not exclusively negative. Moreover, their capacity to contribute consequential ice mass recharge may become increasingly significant under ongoing Arctic amplification and predicted poleward intrusion of mid-latitude moisture.
How to cite: Bailey, H. and Hubbard, A.: Mass Recharge of the Greenland Ice Sheet driven by an IntenseAtmospheric River, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21018, https://doi.org/10.5194/egusphere-egu25-21018, 2025.
The Greenland Ice Sheet (GrIS) has become the single largest contributor to present day sea-level rise, with mass loss driven by changes in Surface Mass Balance (SMB). As the largest component of SMB, snow accumulation is critical to monitor as Arctic warming continues at an accelerated rate. Snowfall patterns across GrIS are influenced by a complex interaction of many interdependent climate variables, leading to high inter-annual spatial variability. As a result, regional climate models (RCMs) often fail to adequately capture this variability and carry substantial uncertainties, leading to biased estimations of ice mass loss. Here, we present a novel method to bias-adjust RCM precipitation output with in-situ SMB records from the SUMup dataset (2024 release), including over two million data points from radar, ice-core, snow pit and stake measurements. RCM output data is first decomposed into Empirical Orthogonal Functions (EOFs), reflecting different modes of spatial variability, and Principal Components (PCs), capturing temporal fluctuations correlating to various climate indices. The SUMup in-situ measurements are used to derive a set of coefficients to scale the model mean climatology and each EOF and PC through least-squares optimisation. We provide monthly bias-adjusted accumulation maps for HIRHAM5-ERA5 output between 1960-2023 and CARRA between 1991-2023, highlighting regional biases in the models through time.
Preliminary mean bias maps for HIRHAM5 show that the model underestimates accumulation in the south and interiors of the ice sheet by 20-80% or 30-90 mm/year, while the west and east margins of the accumulation zone are overestimated by 20-60% or 30-150 mm/year. In the winter and spring, the model tends to underestimate accumulation overall by 50-100 mm/year, while the reverse is true for the summer and autumn, when accumulation is mostly overestimated, reaching up to 200 mm/year in the north west.
How to cite: Lindsey-Clark, J., Grinsted, A., and Hvidberg, C.: New monthly maps of accumulation over the Greenland Ice Sheet, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11420, https://doi.org/10.5194/egusphere-egu25-11420, 2025.
It is highly challenging to include both the Antarctic and Greenland ice sheets in a state-of-the-art earth system model. Our presentation demonstrates our system's design, the essential steps before coupling the entire system, the challenges faced in the coupling process, and the initial findings from our series of simulations for warming scenarios spanning the next few centuries until 2500.
We will highlight the existing limitations in the computed climate conditions that affect the behavior of ice sheets. These motivate our system's design. For instance, ocean temperature biases in the marginal seas around Antarctica inhibit its direct use to determine basal melting of floating ice shelves fringing Antarctica despite extensive tuning efforts. As a result, we have developed a flexible framework deemed necessary to adequately represent the currently observed ice sheet state. The still delicate integration of ice sheets into climate models directs the spin-up procedure of ice sheet models. The procedure's results and its consequences are presented and discussed. In particular, the available iceberg calving mechanism has been demanding in our simulations because we allow for freely waxing or waning ice shelf edges around Antarctica, unprecedented in coupled climate-ice sheet model systems.
Finally, the first results of our fully coupled simulations complete the presentation. These focus on the interaction between the climate system and Antarctica or Greenland and its influence on primary climatic conditions. In our model system, interacting ice sheets shape the climate state, creating feedback loops that affect the ice sheet state itself. This interaction may ultimately counteract the disintegration of ice sheets. Supposed it is a robust result, it implies that standalone ice sheet simulations may overestimate future sea level contributions.
How to cite: Rodehacke, C., Ackermann, L., Gierz, P., Masoum, A., and Lohmann, G.: Greenland and Antarctica as Interacting Constitutes in AWI-ESM, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16025, https://doi.org/10.5194/egusphere-egu25-16025, 2025.
Mass loss from the Antarctic Ice Sheet is the main source of uncertainty in projections of future sea-level rise. These uncertainties essentially stem from the fact that some regions, such as Thwaites Glacier, may reach a tipping point, defined as irreversible mass loss on human time scales, with a warming climate. The exact timing of when these tipping points may occur remains difficult to determine, allowing for a large divergence in timing of onset and mass loss in model projections. Previous studies have emphasized the difficulties assessing the most suitable observable and the record length necessary to predict such an abrupt collapse within the Early Warning Indicators (EWI) framework. In particular, Rosier et al. (2021) showed that EWI robustly detect the onset of the marine ice sheet instability in realistic geometries such as Pine Island Glacier. The goal of this work is to determine the physical processes that influence the rate of grounding-line retreat of Thwaites Glacier and to test the capability of EWI to predict the onset of such a collapse. Ultimately, this study aims at mapping potential safety bands of grounding-line positions where the glacier may still recover or alternatively reach a ‘stable’ state.
How to cite: Moreno-Parada, D., Coulon, V., and Pattyn, F.: Safety Bands of Thwaites Glacier, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10219, https://doi.org/10.5194/egusphere-egu25-10219, 2025.
The future evolution of the Antarctic Ice Sheet with progressing warming constitutes one of the, if not the main uncertainty in projections of future sea-level change. As the largest potential source of sea-level rise and one of the key tipping elements in the climate system, robust projections are needed to inform coastal adaptation planning worldwide.
Using historically-calibrated perturbed-parameter ensembles of projections with two ice-sheet models, we assess the response of the Antarctic Ice Sheet and associated uncertainties to a wide range of climate futures extending to the year 2300 and beyond.
We show that the near-term projections of the Antarctic Ice Sheet are strongly influenced by ice-sheet model sensitivities, especially under limited warming, until strong changes in Antarctic climate beyond the end of the century, as projected under unmitigated emissions, clearly dominate the ice-sheet evolution. Irrespective of the wide range of uncertainties explored in our ensembles, large-scale ice loss is triggered in both West and East Antarctica under higher warming scenarios, but can be avoided by reaching net-zero emissions well before 2100. This leads to a multi-meter difference in the committed Antarctic sea-level contribution projected under low and very high emission pathways by the end of the millennium. Our results suggest that the next years and decades are decisive for the multi-centennial fate of the Antarctic Ice Sheet.
How to cite: Klose, A. K., Coulon, V., Edwards, T., Turner, F., Pattyn, F., and Winkelmann, R.: From short-term uncertainties to long-term certainties in the future evolution of the Antarctic Ice Sheet, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16952, https://doi.org/10.5194/egusphere-egu25-16952, 2025.
As the second largest ice body on Earth, comprising an ice volume of 7.4 m sea level equivalent, the Greenland ice sheet is one of the main contributors to global sea level rise. Though observational and modelling efforts have increased substantially in recent years, major uncertainties remain regarding the ice sheet – climate interactions and feedback mechanisms that drive the ice sheet’s long-term mass loss. To improve sea level projections and the representation of such interactions in model simulations, efforts are currently emerging to couple ice sheet and regional climate models. However, so far, only a few coupled ice sheet – regional climate model simulations have been performed, and these do not extend beyond the centennial timescale. They therefore provide limited insights into the evolution and critical thresholds of the ice sheet – climate system over longer timescales.
As such, to obtain a better understanding of the ice sheet – climate interactions and potential feedback mechanisms over Greenland, we coupled our Greenland Ice Sheet Model (GISM) with a high-resolution regional climate model, the Modèle Atmosphérique Régional (MAR), and performed millennial-length simulations. The global climate model forcing for MAR during these simulations consisted of the IPSL-CM6A-LR model output under the SSP5-8.5 scenario, which was available until 2300. After this date, the climate was held constant, and we prolonged our coupled simulations until the year 3000.
Specifically, we performed three coupled simulations for the period 1990-3000 with differing coupling complexity: full two-way coupling, one-way coupling and zero-way coupling. In the two-way coupled set-up, the ice sheet topography and surface mass balance were communicated yearly between both models, such that ice sheet – climate interactions were fully captured. In the one-way coupled set-up only the surface mass balance – elevation feedback was considered, through interpolation of the yearly SMB onto the changing ice sheet topography. And lastly, in the zero-way coupled set-up the ice sheet – climate interactions were entirely omitted.
The results show that the ice sheet evolution is determined by positive as well as negative feedback mechanisms, that act over different timescales. The main observed negative feedback in our simulations is related to changing wind speeds at the ice sheet margin, due to which the integrated ice mass loss remains fairly similar for all simulations up to 2300, regardless of the differently evolving ice sheet geometries. Beyond this time however, positive feedback mechanisms related to decreasing surface elevation and changing precipitation patterns dominate the ice sheet – climate system and strongly accelerate the integrated ice mass loss. Hence, over longer timescales and for a realistic representation of the evolving ice sheet geometry, it is indispensable to account for ice sheet – climate interactions as was done in our two-way coupled ice sheet – regional climate model set-up.
How to cite: Paice, C., Fettweis, X., and Huybrechts, P.: The role of Greenland ice sheet – climate interactions from 1000-year coupled simulations with MAR-GISM, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20846, https://doi.org/10.5194/egusphere-egu25-20846, 2025.
The Antarctic Ice Sheet (AIS) is expected to be one of the dominant contributors to sea level rise in the near future. However, its future sea-level contribution is subject to substantial uncertainties related to modeling of physical processes. One key process is sub-shelf melting, which is particularly important in ice-shelf cavities, where warmer water intrusions could destabilize the corresponding ice shelves. This is of particular interest in the West Antarctic Ice Sheet, where many regions are marine based. Another fundamental process is Glacial Isostatic Adjustment, which is associated with the lithospheric rebound in response to changes in the ice load. Here, we use a 3D ice-sheet-shelf model coupled with a novel isostasy model to analyze the role of interactions between the ice, the ocean and the lithosphere in AIS projections during the next millennium. We combine experiments testing the sensitivity of several parameters concerning basal melting laws and different isostatic adjustment methods, under mean climatic conditions with high and low emissions scenarios.
How to cite: Juarez-Martinez, A., Swierczek-Jereczek, J., Blasco, J., Alvarez-Solas, J., Robinson, A., and Montoya, M.: Simulated ice-ocean-bedrock interactions in Antarctica until year 3000, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9731, https://doi.org/10.5194/egusphere-egu25-9731, 2025.
Anthropogenic climate change poses a challenge to the stability of current ice sheets. Rising atmospheric temperatures accelerate surface melting in Greenland. Increased ocean temperatures can lead to ice loss at the margins of Antarctica, with positive feedbacks facilitating further ice loss. Both processes impact the Earth System by leading to rising sea level, increasing temperatures through albedo feedbacks, and altering global oceanic circulation. Past records indicate that there is a bipolar interaction between the ice sheets of the Northern and Southern Hemispheres modulated by the Atlantic Meridional Overturning Circulation (AMOC) that could ultimately affect their individual stability. Could the future response of the Greenland and Antarctic ice sheets perturb the AMOC in a manner that changes their own stability landscape? Here we will present the first results of the future evolution of the Greenland and Antarctic ice sheets as simulated with the ice-sheet model Yelmo coupled to a box model representing the oceanic circulation. We will show the coupled effects of the shrinking mass of the ice sheets on the AMOC stability and its feedback on the evolution of the ice sheets themselves.
How to cite: Pérez Montero, S., Alvarez-Solas, J., Robinson, A., and Montoya, M.: Stability of the Greenland and Antarctic ice sheets coupled by the Atlantic ocean circulation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9305, https://doi.org/10.5194/egusphere-egu25-9305, 2025.
Anthropogenic greenhouse gas emissions and resulting global warming raise uncertainties in the future of currently existing ice sheets. The Antarctic ice sheet, which contains the equivalent of 58 meters of potential sea level rise, is expected to have a relatively small role on sea level rise in this century, but is expected to continue to lose mass afterwards and could become a major driver of sea level rise on longer timescales (Van Breedam et al., 2020; Winkelmann et al., 2015).
The Antarctic ice sheet interacts with the solid Earth, the ocean and the atmosphere, resulting in various positive and negative feedbacks, enhancing or limiting ice sheet growth (Fyke et al., 2018). Positive feedback mechanisms, such as the albedo-melt and elevation-temperature feedbacks, enhance the ice sheet's response to an initial change in forcing, potentially resulting in nonlinear changes, and it is thus crucial to model these feedbacks on long timescales, when significant changes of the ice sheet’s topography can occur. Nonlinear changes can lead to a hysteresis behaviour, with widely different equilibrium states for a given CO2 level or temperature anomaly, depending on the initial condition (Pollard and de Conto, 2005; Garbe et al., 2020; Van Breedam et al., 2023).
In this study, we explore the hysteresis of the Antarctic ice sheet from the present-day configuration, using an intermediate complexity climate model, iLOVECLIM, representing the atmosphere, ocean and vegetation, coupled to an ice sheet model, GRISLI. Simulations start from either a pre-industrial ice sheet or an ice-free, isostatically rebounded geometry, and different CO2 levels are applied.
Crucially, the albedo-melt feedback is accounted for in our coupled setting, which strengthens nonlinear behaviour and leads to critical CO2 thresholds for the ice sheet melt or growth. This enhances the ice sheet hysteresis, with widely different equilibrium ice volumes at a given CO2 level, depending on the initial ice sheet geometry. The CO2 thresholds either trigger the complete Antarctic ice sheet loss or near-complete regrowth. The orbital configuration influences these CO2 thresholds : a higher (lower) summer insolation in the Southern Hemisphere decreases (increases) the CO2 threshold for Antarctic deglaciation (glaciation).
These findings highlight the importance of ice sheet-atmosphere interactions, notably the albedo-melt feedback, in projecting future long-term ice sheet behavior. Neglecting these feedbacks could lead to an overestimation of CO2 thresholds for the Antarctic ice sheet destabilization, with implications for future long-term sea level rise under high emission scenarios.
This study has recently been accepted in Geophysical Research Letters.
How to cite: Leloup, G., Quiquet, A., Roche, D., Dumas, C., and Paillard, D.: Hysteresis of the Antarctic ice sheet with a coupled climate-ice-sheet model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12628, https://doi.org/10.5194/egusphere-egu25-12628, 2025.
Posters on site: Tue, 29 Apr, 14:00–15:45 | Hall X4
The Miocene epoch was a warm period characterised by elevated atmospheric CO₂ levels compared to the present day. These CO₂ concentrations are similar to those predicted for future climate scenarios, making the Miocene an important period to deepen our understanding of warmer climates. While Greenland ice cores have provided highly valuable data for the late Quaternary, terrestrial palaeoclimate archives extending deeper in time in the Arctic remain sparse, leaving a significant gap in our knowledge of Greenland's climate history.
Speleothems are an excellent archive for obtaining high-resolution terrestrial climate data. During speleothem formation, dripwater can be trapped as fluid inclusions, preserving the isotopic signature of ancient meteoric water. This study focuses on four speleothems from a cave in eastern North Greenland. U-Pb dating indicates that the speleothems were deposited during the middle and late Miocene. We analysed the stable H isotopic composition of primary fluid inclusions to reconstruct the isotopic composition of palaeo-dripwater. Carbon and oxygen isotopes of the speleothem calcite were also measured in order to estimate quantitative temperatures for eastern North Greenland during middle and late Miocene. Our initial results show that during such an elevated CO2 world, mean annual air temperatures were substantially elevated above modern values.
Macroscopically, all speleothems are comprised of translucent and light brown calcite. Microscopically, the dominant fabric is coarsely crystalline columnar calcite. Fluid inclusion petrography shows the presence of both fluid inclusion-rich and inclusion-poor areas in the late Miocene speleothems, while primary fluid inclusions are abundant in the two middle Miocene speleothems. The mean water content obtained from crushing varies from 0.2 µL to 1.0 µL between the speleothems.
How to cite: Friedrich, L., Koltai, G., Moseley, G. E., Czuppon, G., Demény, A., Wang, J., Cheng, H., Donner, A., Dublyansky, Y., and Spötl, C.: Preliminary insights into Miocene palaeoprecipitation and palaeotemperature using speleothem fluid inclusion isotopes from eastern North Greenland, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15980, https://doi.org/10.5194/egusphere-egu25-15980, 2025.
A major obstacle in both paleo and future simulations of the Antarctic Ice Sheet is that most studies do not include interactive ice sheets. Although this is a current area of development, most studies use stand alone climate models to force separate ice sheet models to study the potential impacts of climate changes on ice sheets; however this method ignores consequent impacts of the ice sheets on the ocean-atmosphere system, leading to simulations that may under or over estimate retreat in a warmer climate. The few model simulations that do include ice sheet-climate feedbacks disagree on the overall sign of the these feedbacks.
Here we are developing a new coupling between an established ice sheet (PSU-ISM) and climate model (HadCM3) that has been used extensively for paleoclimate applications. These models are suitable for performing multiple simulations over thousands of years. The ice sheet model output will be used to update the ice sheet in the climate model. The climate model orography and land sea mask will be modified to match that in the ice sheet model and ice sheet discharge will be added as a freshwater flux, modelled via change in salinity around the Southern Ocean. The models have been coupled offline and we are next automating this process so that simulations can be repeated over shorter timescales. This will allow the model to develop feedbacks more quickly rather than being limited to the length of the run. The model has been developed using pre-industrial idealised simulations. The main focus of the work is on reproducing the AIS response and sea level rise during the middle Miocene warm interval that matches proxy records more closely without having to add unrealistic CO2 forcing.
How to cite: Byrne, L.: Development of a new coupled ice sheet-climate model for simulations of the Antarctic Ice Sheet under a warm climate, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21116, https://doi.org/10.5194/egusphere-egu25-21116, 2025.
The Greenland ice sheet (GrIS) formed more than 1 Ma ago and has evolved over many glacial-interglacial cycles. As it still adjusts to past changes, correctly capturing its present-day state is essential to accurately predict its future evolution and contribution to sea level rise. Furthermore, the past offers numerous examples of the GrIS‘ response to warmer climates, possibly analogous to its future fate.
Here, the Parallel Ice Sheet Model (PISM) is utilized to investigate the evolution of the GrIS over past glacial-interglacial cycles. For simulations over such long timescales, the computationally inexpensive PDD scheme is commonly used to calculate surface melt. However, PDD schemes do not capture spatial and temporal differences in surface mass balance sensitivity to temperature and cannot drive glacial-interglacial ice volume changes as they neglect the positive feedback between melt and albedo. To address this, we instead use the Diurnal Energy Balance Model (dEBM-simple) module. It takes into account seasonally and latitudinally varying melt contributions from solar shortwave radiation and changes in albedo in addition to temperature-driven melt to achieve a better representation of orbital timescales.
We calibrate PISM-dEBM-simple with present-day melt rates from the regional climate model RACMO. The calibrated model is then used to investigate the different patterns of growth and retreat of the GrIS over the past glacial-interglacial cycles emerging from using the PDD or the dEBM module in PISM. The enhanced sensitivity of the dEBM to insolation results in an earlier and greater mass loss at the onset of the Holocene, primarily from low-elevation regions and ice shelves.
How to cite: Schwermer, I., Munck Solgaard, A., Langgaard Lauritzen, M., Noël, B., Nuterman, R., and Schøtt Hvidberg, C.: Modelling the evolution of the Greenland ice sheet over glacial-interglacial cycles, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17469, https://doi.org/10.5194/egusphere-egu25-17469, 2025.
Ice sheet models are essential tools for studying ice sheet dynamics in response to the climate evolution during the Quaternary glacial-interglacial cycles. Here, we develop a new version of the Northern Hemisphere ice sheet model (NHISM, Zweck and Huybrechts, 2005) by adding a user-friendly ice shelf module and other new characteristics, such as the configurable horizontal resolution and coupled sea level change. This new ice sheet-ice shelf coupled model is named NHISM1.1. The ice shelf module is based on the shallow shelf approximation, allowing simulation of ice stream advance into the ocean and the transformation between floating and grounded ice. NHISM1.1 is first used to conduct offline equilibrium ice-sheet simulations driven by observed present-day climate. It simulates a reasonable spatial distribution of the Northern Hemisphere ice sheets with a bias of less than 10% in the Greenland Ice Sheet volume compared to observation. We then use NHISM1.1 to perform offline transient ice sheet simulations for two distinct periods in the past, the Last Deglaciation and the entire MIS-11 period. In both cases, NHISM1.1 is driven by climate outputs of transient simulations performed with the LOVECLIM1.3 model. The performance of NHISM1.1 and the influence of various model configurations are evaluated by comparison with proxy reconstructions and other model simulations as well as sensitivity experiments. Our ice sheet simulations show that the NH ice sheets are largely consistent with geological evidence and that the incorporation of an ice shelf module is critical in properly reproducing glacial inception. By combining the analysis of climate simulations from LOVECLIM1.3 and offline ice sheet simulations from NHISM1.1, we propose that insolation plays a dominant role in driving the initial cooling of the Northern Hemisphere and the regrowth of its ice sheets during the MIS-11 glacial inception.
How to cite: Liu, W., Yin, Q., Huybrechts, P., and Goelzer, H.: Modelling the Northern Hemisphere ice sheet evolution during the last deglaciation and MIS-11 with an ice sheet-ice shelf coupled model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10037, https://doi.org/10.5194/egusphere-egu25-10037, 2025.
Understanding the dynamic response of the Greenland Ice Sheet (GrIS) during past climate warmings is essential for predicting its behaviour as global warming accelerates. However, detailed reconstructions of GrIS growth and retreat are limited due to lack of long high-resolution sedimentary records in proximity to its major glacial outlets. Here, new osmium isotope data are presented, from IODP Expedition 400 Hole U1604B, obtained from the lower slope of the Melville Bugt Trough Mouth Fan on the northwest Greenland margin. The osmium isotope analyses are integrated with shipboard sedimentary proxies to trace sediment sources and reconstruct glacial meltwater flux. Preliminary results from the studied interval show sediment proxy variations suggesting significant changes in sediment sources and depositional conditions. Between ~29 and 24 m CSF-A 187Os/188Os are radiogenic (~2.3 – 2.5). In contrast, immediately above this section between ~24 and 22 m CSF-A depth 187Os/188Os are distinctly less radiogenic (~1.3). The latter depth interval is also characterized by a peak in Ca/K ratios, decreased magnetic susceptibility and natural gamma radiation. The current preliminary age-model for Hole 1604B suggests that the studied core interval could represent the end of the Saalian Glacial. As such, we hypothesize the change in the sediment proxies is interpreted to record enhanced glacial meltwater and sediment delivery, potentially following ice sheet break-up at the end of the Saalian glacial and transition into the Eemian interglacial. Our multi-proxy findings provide new insight into the relationship between GrIS, Innuitian/Laurentide Ice Sheets, and regional sedimentation patterns during a significant glacial to interglacial transition, with important implications for understanding of GrIS response to abrupt climate warming.
How to cite: Huang, S., Selby, D., Lloyd, J., and Knutz, P.: Investigating Osmium Isotopes and Sedimentological Records for the end of the Saalian Glacial from Northwest Baffin Bay, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19795, https://doi.org/10.5194/egusphere-egu25-19795, 2025.
Cruise SD041 of the UK research vessel the RRS Sir David Attenborough to the continental shelf offshore of SE Greenland took place in July-August 2024. The cruise was part of the UK NERC-funded ‘Kang-Glac’ project, a large multi-disciplinary, international, research project jointly led by British Antarctic Survey and Durham University, UK. The cruise collected a range of geological, geophysical, oceanographic and biological data from the continental shelf offshore of Kangerlussuaq Fjord, SE Greenland, and in several adjoining fjords. The aim of the Kang-Glac project is to investigate the response of the Greenland Ice Sheet to ocean warming during the last 11,700 years of the Holocene. During the cruise marine geophysical data in the form of multibeam swath bathymetric imagery of seafloor landforms and sub-bottom profiler data of shallow acoustic stratigraphy were collected, in addition to a suite of sediment cores. Data collection targeted a large cross-shelf bathymetric trough (‘Kang-Trough’) which extended from the mouth of Kangerlussuaq Fiord to the edge of the continental shelf, as well as a series of smaller fjords to the northeast. These marine geophysical data and sediment cores provide a clear record of an extensive Greenland Ice Sheet (GrIS) which expanded and retreated across the shelf via Kang-Trough. Landforms comprise well developed streamlined subglacial bedforms which show convergent GrIS flow into the trough, as well as occasional transverse moraines recording episodic retreat. Sediment cores recovered subglacial tills recording a grounded ice sheet in the cross-shelf trough overlain by a range of deglacial glacimarine facies recording retreat by melting and iceberg calving. Cores from the adjacent trough mouth fan on the continental slope targeted glacigenic debris flows which likely were deposited when the GrIS was grounded at the shelf edge and delivered glacigenic debris onto the slope. Collectively the data provide new insights into past GrIS extent, dynamics, and the nature of associated glacigenic sediment delivery from the LGM through the Holocene in the SE sector of the Greenland continental margin.
How to cite: O Cofaigh, C., Hogan, K., Lloyd, J., Hunt, M., Snowman Andresen, C., Larter, R., and Roberts, D.: Geomorphological and sedimentological evidence of past Greenland Ice Sheet advance and retreat on the continental shelf offshore of SE Greenland as revealed by ‘Kang-Glac’ cruise SD041 , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13742, https://doi.org/10.5194/egusphere-egu25-13742, 2025.
The timing of the Greenland Ice Sheet's retreat from its extent during the Last Glacial Maximum is a key element in constraining the sensitivity of the ice sheet to climate forcing. Although different deglaciation models have been published in previous years (Bennike, 2002; Funder et al., 2011; Sinclair et al., 2016; Leger et al., 2024), these models are limited by the number of samples used or their geographical extent. Therefore, the models have not been able to adequately resolve the deglaciation chronology of the Greenland Ice Sheet.
In this project, we aim to develop a Greenland-wide deglaciation model based on a new compilation of 14C dates, cosmogenic nuclide dates, OSL dates, and geomorphological evidence. The new compilation of 14C samples will be provided as an open-access database: GreenDated.
Within GreenDated, we aim to include all published 14C data from Greenland and the surrounding ocean shelf. All sample entries will as a minimum include information on location, and a categorization of the depositional environment and the sampled material. These steps will ensure accessibility for future users and enable easy extraction of data from the database. We will also recalibrate all the 14C data using the newest calibration curves (Heaton et al., 2020; Reimer et al., 2020) and adjust for differences in old normalization techniques, enabling easy recalibration of data for future users. Lastly, we will conduct a quality assessment based on the protocol used in the Dated (Hughes et al., 2016) and SvalHola (Farnsworth et al., 2020) databases, with the addition of an automated scoring system, seeking to limit bias from the authors.
Ultimately, the deglaciation model and the accompanying GreenDated database will provide a complete and thorough constraint on the Greenland Ice Sheet’s retreat from the Last Glacial Maximum position.
References:
Bennike, O. (2002) ‘Late Quaternary history of Washington Land, North Greenland’, Boreas, 31(3), pp. 260–272. https://doi.org/10.1111/j.1502-3885.2002.tb01072.x.
Farnsworth, W.R. et al. (2020) ‘Holocene glacial history of Svalbard: Status, perspectives and challenges’, Earth-Science Reviews, 208, p. 103249. https://doi.org/10.1016/j.earscirev.2020.103249.
Funder, S. et al. (2011) ‘The Greenland Ice Sheet During the Past 300,000 Years: A Review’, Developments in Quaternary Science, 15, pp. 699–713. https://doi.org/10.1016/B978-0-444-53447-7.00050-7.
Heaton, T.J. et al. (2020) ‘Marine20—The Marine Radiocarbon Age Calibration Curve (0–55,000 cal BP)’, Radiocarbon, 62(4), pp. 779–820. https://doi.org/10.1017/rdc.2020.68.
Hughes, A.L.C. et al. (2016) ‘The last Eurasian ice sheets – a chronological database and time-slice reconstruction, DATED-1’, Boreas, 45(1), pp. 1–45. https://doi.org/10.1111/bor.12142.
Leger, T.P.M. et al. (2024) ‘A Greenland-wide empirical reconstruction of paleo ice sheet retreat informed by ice extent markers: PaleoGrIS version 1.0’, Climate of the Past, 20(3), pp. 701–755. https://doi.org/10.5194/cp-20-701-2024.
Reimer, P.J. et al. (2020) ‘The IntCal20 Northern Hemisphere Radiocarbon Age Calibration Curve (0–55 cal kBP)’, Radiocarbon, 62(4), pp. 725–757. https://doi.org/10.1017/rdc.2020.41.
inclair, G. et al. (2016) ‘Diachronous retreat of the Greenland ice sheet during the last deglaciation’, Quaternary Science Reviews, 145, pp. 243–258. https://doi.org/10.1016/j.quascirev.2016.05.040.
How to cite: Rosenberg, A., Luetzenburg, G., Bennike, O., Kjellerup Kjeldsen, K., and Krog Larsen, N.: A Greenland-wide Holocene deglaciation model and building an accompanying 14C database, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11339, https://doi.org/10.5194/egusphere-egu25-11339, 2025.
In the coming century, the Greenland Ice Sheet (GrIS) is expected to be one of the main contributors to global sea-level rise. In addition, it is thought to be a tipping element due to the existence of positive feedbacks governing its mass balance. Previous studies have explored its stability across a range of temperatures, from present-day conditions to a global warming of 4°C, showing a threshold behavior in its response. However, it is known this threshold has already been exceeded in the past. During the Holocene Thermal Maximum, when Greenland temperatures were 2–4°C warmer than today, the ice sheet retreated beyond its present-day margin but did not fully disappear. Ice losses depend on the level of warming, but also on the rate of forcing and how long the forcing remains above the threshold. Therefore, we propose studying the stability of the ice sheet over a broader temperature range: from the Last Glacial Maximum to a warming of +4°C, and examining its current state within the bifurcation diagram. For this purpose, we use the ice-sheet model Yelmo coupled with the regional moisture-energy balance model REMBO and a linear parameterization of the oceanic basal melting.
How to cite: Gutiérrez-González, L., Álvarez-Solas, J., Montoya, M., and Robinson, A.: Mapping the stability of the Greenland Ice Sheet, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19292, https://doi.org/10.5194/egusphere-egu25-19292, 2025.
The reconstruction of Antarctic surface mass balance (SMB) is essential for understanding ice sheet dynamics and sea level rise, yet existing datasets are limited to the satellite era (1979-present) because little is known about the sea surface conditions (SSCs) before 1979. Using a new SSCs product derived from a particle filtering reconstruction of the southern climate before 1979 to constrain the regional atmospheric model MAR, we expand the known SMB time series up to 1958. The dataset has been evaluated against AWS and SMB measurement campaigns to ensure a good agreement throughout the simulation period, substantially better than when MAR is forced by ERA5 SSCs (HadISST2). We also investigate the influence of the sea ice extent drop on SMB observed between the 70s and the 80s, analogous to the one observed in 2016. This extended dataset offers improved insight into past ice sheet mass changes and highlights the importance of long-term SMB reconstructions for further understanding the role of the Antarctic ice sheet in Earth's climate system.
How to cite: Maure, D., Kittel, C., Lambin, C., Dalaiden, Q., Goosse, H., and Fettweis, X.: Extending our knowledge of Antarctic SMB further back in time, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11215, https://doi.org/10.5194/egusphere-egu25-11215, 2025.
The Greenland Ice Sheet (GIS) has been experiencing significant mass loss since the 1990s, driven by the intensifying effects of global warming. However, this global trend is modulated by distinct annual and interannual variations, highlighting the complex interplay between the ice sheet, atmospheric systems, and the ocean. In this study, we analyzed GIS mass changes from early 2002 to late 2023 using data from the GRACE and GRACE-FO missions, focusing on the dominant temporal cycles and their relationships with climatic indices and parameters.
Using Empirical Orthogonal Functions (EOF) applied to mass variation data from the COST-G solution, we identified five leading modes of variability, accounting for 67.5% of the total variance. The primary mode capture both the annual cycle and longer-term periodicities, while subsequent modes highlight interannual oscillations, with cycles ranging from 4 to 11 years.
We examined the interactions between GIS mass changes and six key climatic drivers: the North Atlantic Oscillation (NAO), Greenland Blocking Index (GBI), Atlantic Multidecadal Oscillation (AMO), temperature duration and intensity, precipitation, and surface albedo. Cumulative indices and parameters enabled direct comparisons with the accumulated mass changes since 2002. Through Wavelet Analysis and cross-correlations, we uncovered significant links with varying time lags. They lead to a complete annual cycle and some interannual relationship between them. For instance, a positive NAO phase enhances precipitation, while the AMO displays a surprising 3.5-year delayed response to mass variations.
Additionally, our findings reveal a connection between 11-year cycles in NAO, GBI, and temperature to solar activity, while 4 to 7-year cycles align with potential atmospheric oscillations and Earth’s internal geodynamics.
This study highlights the GIS as a dynamic system modulated by interrelated processes operating on annual to decadal timescales. We have only investigated Greenland in its globality, but we know that the response to external forcing at a scale of a basin or a glacier differs. It will be important to examine this point as the integrations of multi-scale climatic drivers is important to understand past variations and project future changes under a warming climate. Such understanding is vital for assessing global sea-level rise and formulating mitigation strategies.
How to cite: Cambier, F., Darrozes, J., Llubes, M., Seoane, L., and Ramillien, G.: Links between GRACE/GRACE-FO derived temporal mass variations in Greenland and climatic indices, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-332, https://doi.org/10.5194/egusphere-egu25-332, 2025.
In this study, surface mass balance (SMB) is estimated from snow accumulation data collected in the nearby area of Concordia Station. Results from the Italian and French stake farms are jointly analyzed. The Italian stake farm is located ~800 m southwest of the Concordia Station and consists of 13 stakes; observations started at the end of 2010 with almost monthly sampling. Some measurements are also available for the 2006-2010 period from a previous stake farm which was located ~300 m east of the current site. The French stake farm is located ~2 km south of the base and consists of 50 stakes; observations started in 2004 with yearly sampling conducted during austral summer. Snow build-up measurements at individual stakes show a strong variability caused by the interaction of wind-driven snow with surface micro-relief. Over the period of common observations, the present Italian stake farm generally underestimates the snow accumulation with respect to the French one, except for three years in which an overestimation is observed. Over the 2011-2023 period, the mean yearly accumulation recorded by the Italian and French stake farms is 7.3±0.2 cm and 8.4±0.1 cm, respectively. Bootstrap simulation has been performed to: (i) assess the significance of the differences between the two datasets; (ii) evaluate the effect of the different size of the stake farms and their distance to the Station on the measurements. Comparison of the observations with reanalysis datasets (ERA5 and MERRA2) and regional models (RACMO, MAR) has been also performed, with the first ones providing the best agreement with the observations. The potential shadowing effect of the station has also been investigated by analyzing the wind direction during the snowfall events, suggesting that buildings may influence accumulation when they are upwind with respect to the stake farms. Additionally, two more stake farms, located 25 km north and south of Concordia Station, are also analyzed to study the accumulation gradient across Dome C, confirming previous results of a continentality effect. On average, yearly accumulation increases by 0.7±0.2 cm over the 50 km span between the southern and northern stake farms. Results should be valuable for validating SMB estimates obtained from reanalysis, regional climate models and remote-sensing data.
How to cite: Stefanini, C., Stenni, B., Masiol, M., Dreossi, G., Frezzotti, M., Favier, V., Becherini, F., Scarchilli, C., Ciardini, V., and Carugati, G.: Snow accumulation rates at Concordia Station from stake farm observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5578, https://doi.org/10.5194/egusphere-egu25-5578, 2025.
Bridging the knowledge gap between the recent decades and the preceding centuries of Greenland Ice Sheet (GrIS) history is essential for improving projections of its contribution to future sea-level rise. Evidence from relative sea-level reconstructions from salt marshes in southern Greenland suggests that GrIS mass loss began around 1850, well before significant anthropogenic warming—a pattern not yet captured in existing simulations of late Holocene GrIS evolution. Extending reconstructions of GrIS surface mass balance (SMB) as far back as possible, by leveraging newly available climate datasets from ~AD 1400 is critical to understanding its sensitivity to climate forcings during key periods such as the Little Ice Age.
By addressing the underrepresentation of dynamic components and calculation of pre-20th century mass changes, this project aims to provide critical insights into GrIS-climate interactions and refine predictions of GrIS contributions to global sea-level rise. To achieve this aim, we will first develop a 1x1-km resolution monthly SMB dataset using ModE-RA, a new palaeoclimate reanalysis product spanning 1421-2024. This new SMB dataset will be used as input to ice sheet model simulations to assess the spatial and temporal interplay between climate, SMB and ice dynamics.
Here we will present initial results of (1) GrIS temperature, precipitation and SMB fields for 1421 to 2024 AD and (2) historical simulations using the ice sheet model Úa to reconstruct ice thickness and margin changes outside of the observational period.
How to cite: Wake, L., Javed, A., Hill, E., Hanna, E., and Gudmundsson, H.: Bridging the gap between the modern and historical: Extending the mass balance reconstruction of the Greenland Ice Sheet from 1421 to 2024 AD, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11803, https://doi.org/10.5194/egusphere-egu25-11803, 2025.
Modern West Antarctic ice loss is generally driven by warm circumpolar deep water (CDW) reaching ice shelf grounding zones. Understanding what controls CDW delivery remains a challenge, in part because of the multiple scales involved. Most global models are too coarse to capture critical regional processes, while simulations with high-resolution regional models depend on imposed boundary conditions, precluding the possibility of capturing coupled processes across scales. Here, we analyze a novel multi-member ensemble of global high-resolution (0.1° ocean, 0.25° atmosphere) Community Earth System Model (CESM) simulations over the historical period (1850-2005). We compare the high-resolution runs to equivalent simulations at ~1 to 2° resolution, as well as to observational products (e.g. ECCO, WOA). We show that biases in key ocean properties in the Southern Ocean are significantly improved in the high-resolution simulations. This includes better representation of CDW in the high-resolution runs. We use these comparisons to explore new insights on the atmosphere and ice conditions that promote CDW delivery toward the ice shelves.
How to cite: Berdahl, M., Leguy, G., Steig, E. J., Lipscomb, W. H., and Otto-Bliesner, B. L.: Global High-Resolution Modeling: A New Lens on the Southern Ocean, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7500, https://doi.org/10.5194/egusphere-egu25-7500, 2025.
The accelerated melting of the Greenland ice sheet, driven by recent global warming, has attracted significant attention regarding the long-term variations in its mass balance. While several analyses have utilized snow melting indicators derived from microwave brightness temperatures observed through satellites, there is a lack of studies examining the diurnal behavior of these temperatures during the melting season. The Advanced Microwave Satellite Radiometer 2 (AMSR2) aboard the Global Change Observation Mission – Water (GCOM-W) satellite provides multiple daily observations on the Greenland ice sheet, enabling the investigation of diurnal changes in brightness temperature. This study aims to clarify the short-term relationship between snow melting and spaceborne microwave brightness temperatures during the summer of 2012, a period marked by extensive melting of the Greenland ice sheet. To examine the timing of snowmelt, snow surface temperature data collected by the Automated Weather Station (AWS) at a site on the ice sheet in north-west Greenland were utilized. The time series of snow surface temperatures from July to August 2012 were analyzed, revealing distinct patterns across three periods: Period A (early-July: snow temperature of 0°C only during the day), Period B (mid-July: snow temperature of 0°C throughout the day), and Period C (mid-August: snow temperature below 0°C all day). In the north-west regions, Snow Index (Tb18H − Tb36H: Difference in brightness temperature between 18 GHz-H and 36 GHz-H) values, indicative of snow cover, showed significantly different short-term variations between the periods. During Period A, Snow Index values were positive throughout the day and decreased towards the afternoon. In contrast, during Period B, Snow Index values were negative throughout the day, with no significant diurnal changes observed. During Period C, Snow Index values returned to positive again and, as in the previous period, no significant changes were observed during the day. These results suggest the possibility of monitoring diurnal melting with high temporal resolution through short-term variations in spaceborne microwave brightness temperature. These variations across the Greenland ice sheet, including other frequency channels, will be further discussed during the conference day.
How to cite: Suzuki, T., Shimada, R., Kachi, M., and Tanikawa, T.: Short-term variations of spaceborne microwave brightness temperature on the Greenland ice sheet during the 2012 melting season., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7794, https://doi.org/10.5194/egusphere-egu25-7794, 2025.
The mass loss from the Greenland ice sheet has increased over the last two decades, and is now a major contributor to the global mean sea level rise. While the interior of the Greenland ice sheet has remained relatively stable, the mass loss from the ice sheet margins have spread to the north and since 2007 propagated into interior Greenland. We present here an assessment of the interior stability in North Greenland over the last three decades using GPS data, remote sensing data, and climate model output. We compile GPS survey data from interior ice core sites in North Greenland at GRIP (1992-1996), NorthGRIP (1996-2001), NEEM (2007-2015), and EastGRIP (2015-2022), and compare with surface mass balance estimates, and remote sensing observations to assess changes over the last decades. While the surface elevation has remained relatively stable at the northern ice divide sites, an inferred northward migration of the ice divide in Northwest Greenland observed in 2007-2015 coincided with the onset of thinning along the ice margin in the Baffin Bay area. The surface elevation near the summit of the Greenland ice sheet lowered slightly over the last 30 years, during a period of widespread thinning along the western margin. The observations are discussed in relation to regional changes in surface mass balance and the dynamical response to mass loss at the ice margin.
How to cite: Hvidberg, C. S., Grinsted, A., Keller, K., Kjær, H. A., Rathmann, N., Lauritzen, M. L., Dahl-Jensen, D., Mottram, R., Hansen, N., Olesen, M., Simonsen, S., Sørensen, L. S., Solgaard, A. M., and Karlsson, N. B.: Stability of interior North Greenland – an assessment from GPS and satellite data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17048, https://doi.org/10.5194/egusphere-egu25-17048, 2025.
The importance of employing a two-way coupled climate-ice sheet model for future sea level projection has been revealed by LOVECLIP simulation. However, it still has several limitations. LOVECLIM, the climate model used in LOVECLIP, is unsuitable for short-term simulation. Additionally, LOVECLIM with a low-resolution T21 cannot solve regional-scale changes over the Antarctic region. Therefore, we newly coupled CESM1.2 to the Penn State Ice Sheet Model (PSUIM). CESM1.2 consists of the Community Atmosphere Model (CAM) with a f09 resolution for the atmosphere and Parallel Ocean Program version 2 (POP2) with a gx1v6 resolution for the ocean. Using coupled CESM1.2-PSUIM, we projected the responses of Greenland and Antarctic ice sheets, as well as future climate and sea level rise under the Representative Concentration Pathway scenarios.
How to cite: Park, J.: Coupled CESM1.2 to Penn State University Ice Sheet Model and future sea level projection, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6338, https://doi.org/10.5194/egusphere-egu25-6338, 2025.
The Antarctic Ice Sheet (AIS) could become the largest single contributor to future sea level rise (SLR). However, its response to rising global mean temperature remains highly uncertain, and potential Solar Radiation Modification (SRM) interventions during the 21st century further complicate the projections. Among these interventions, Stratospheric Aerosol Injections (SAI) have been proposed to limit atmospheric warming and potentially moderate or prevent AIS’ impact on SLR. This study examines the dynamic response of Antarctica to such SAI interventions, in the short-term (until the year 2100) and on centennial time scales. We use the Parallel Ice Sheet Model (PISM) forced by the Community Earth System Model 2 (CESM2) to compare the evolution of AIS under SAI scenarios with that under the Shared Socioeconomic Pathway 2-4.5 (SSP2-4.5). Our findings indicate that, on centennial timescales, SAI may be counterproductive in mitigating sea level rise due to the reduced Antarctic surface mass balance compared to the SSP2-4.5 scenario. Ice shelf thinning and grounding line dynamics emerge as dominant factors driving mid- and long-term AIS behavior, where ice dynamics dominate over the effects of constant climate forcing. Variations in the sliding law parameterization further influence simulated outcomes. Unsurprisingly, the results are highly dependent on the individual earth system model employed. To address this, we compare our findings with a suite of the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6) scenarios, as well as additional SRM simulations performed using the Hadley Centre Global Environment Model version 2 (HadGEM2-ES).
How to cite: Corrà, M., Hermant, A., Visioni, D., Goddard, P. B., Jones, A., Spezia, E., and Sutter, J.: Modeling Antarctic Ice Sheet Dynamics in Response to Solar Radiation Management, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9630, https://doi.org/10.5194/egusphere-egu25-9630, 2025.
Current projections of Antarctic Ice Sheet dynamics during the next centuries are subject to large uncertainties both reflecting the ice sheet model setup as well as the climate pathways taken into consideration. Assessing both, we present ice sheet model projections of the Antarctic Ice Sheet’s evolution during the next centuries using PISM. We employ PISM at continental scale forced by Earth system model data tailored to specific global temperature scenarios via an adaptive greenhouse gas emissions approach. The scenarios reflect a range of transient temperature overshoot (during the 21st and 22nd century) and stabilization trajectories until the year 2500 resulting either in 1.5 °C or 3°C warming. We account for various ice sheet sensitivities and initialize PISM with a present-day state obtained by a paleo thermal spin-up and further tuned on present-day conditions. For each climate scenario, a wide range of physical parameterizations is explored, to consider different ice sheet responses. Comparing the results with a historical baseline control simulation, a relative loss of ice volume proportional to temperature rise is observed across all parameters in the various scenarios. Additionally, tipping points can be identified for certain parameterisations, beyond which no significant differences are observed between stabilization and overshoot scenarios indicating an already destabilised West Antarctic Ice Sheet at present. We compare these results with model projections based on a selection of the CMIP6 scenarios to illustrate the range of Antarctic Ice Sheet responses under uncertain future climate trajectories.
How to cite: Spezia, E., Corrà, M., Bodart, J., Višnjević, V., Lacroix, F. K. M., Frölicher, T., and Sutter, J.: Assessing Antarctic Ice Sheet dynamics under temporary overshoot and long-term temperature stabilization scenarios , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10066, https://doi.org/10.5194/egusphere-egu25-10066, 2025.
Projections of Antarctica's future sea-level contribution are still subject to great uncertainties, especially with respect to changes in surface mass balance and sub-shelf melting. While the climatic forcing used as boundary condition for ice sheet models cover the average trend in mass balance with global warming, extreme events, such as heatwaves, are typically not yet considered. However, a number of record-breaking extreme events have been observed in recent years in Antarctica already and may become more frequent or extreme with ongoing climate change. Here we investigate the effects of heatwaves on ice-sheet dynamics: using a storyline approach for conducting a suite of numerical ice-sheet simulations, we explore the additional Antarctic contribution to future sea-level rise when atmospheric extreme events are considered in projections. We set this into perspective with anomalous freshwater fluxes from ocean-driven melting (and calving) and investigate the potential for abrupt shifts and tipping dynamics, which extreme events may cause or pre-condition.
How to cite: Nicola, L., Beckmann, J., McCormack, F., and Winkelmann, R.: Towards understanding the effects of extreme events on Antarctic ice-sheet dynamics , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11651, https://doi.org/10.5194/egusphere-egu25-11651, 2025.
Extensive surface melting has been observed during the austral summer, particularly in the Antarctic Peninsula and peripheral regions. A warming climate change is expected to further increase both precipitation and surface melting due to rising air temperatures. The precipitation, including both liquid and solid phases, contributes to maintaining ice mass, whereas surface melting reduces ice thickness and promotes hydrofracturing of ice shelves, resulting in acceleration of ice mass loss. The Surface Energy and Mass balance model of Intermediate Complexity (SEMIC) is a cost-effective and simplified model which emulates surface energy and mass balance processes. However, its application to Antarctica has not yet been fully explored. In this study, we assess the performance of SEMIC, forced with daily and monthly ERA5 reanalysis data, in reproducing current surface mass balance (SMB) and surface melting. Furthermore, we evaluate future projections of SMB and surface melting under the sustainable (SSP1-2.6) and high-warming (SSP5-8.5) climate scenarios from CMIP6, extending to the end of the 21st century. Our results reveal that SEMIC effectively represents current SMB and surface melting when driven by both daily and monthly forcing, although it underestimates the extent of surface melting in internal ice sheet. Projections indicate that total surface melting volume under SSP1-2.6 and SSP5-8.5 scenarios is projected to gradually increase to 170.1 ± 65.1 Gt yr-1 and 892.4 ± 505.2 Gt yr-1, respectively, during 2090-2100. Under the warming scenario, the area experiencing surface melting exceeding collapse threshold (> 725 mm yr-1) increases significantly by the mid-21st century. While total precipitation is projected to increase, this is offset by an increase in surface melting, resulting in minimal net changes in SMB by the end of the 21st century.
How to cite: Park, I.-W., Jin, E. K., Lee, W. S., and Lee, K.-K.: Revisiting Antarctic surface melting under climate change by the end of the 21st century using a simple surface energy balance approach, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14498, https://doi.org/10.5194/egusphere-egu25-14498, 2025.
Version 3 of the Community Ice Sheet Model (CISM) is scheduled for release later this year along with version 3 of the Community Earth System Model (CESM). CISM is a parallel, open-source ice flow code, written in Fortran and Python, which can be run as a standalone ice sheet or glacier model or as a coupled component of CESM and NorESM. The model supports several Stokes-flow approximations and has participated in many community intercomparison projects, including ISMIP6, CalvingMIP, and GlacierMIP3.
CISM3 will include new physics options for basal sliding, basal hydrology, iceberg calving, and extrapolating sub-ice-shelf temperature and salinity. A new initialization procedure allows the rate of ice mass change to match observations at the beginning of a projection simulation. Coupled CISM–CESM simulations can include two-way climate coupling with multiple ice sheets, including Antarctica. CISM3 also has an exciting new capability to initialize and simulate mountain glaciers.
To improve user experience, CISM3 will include new Python tools for setting up glacier and ice sheet simulations and analyzing ice-sheet-relevant fields from other CESM components. CISM is now more integrated with CESM than ever before, by leveraging the Common Infrastructure for Modeling the Earth (CIME) case control and testing system for verification and validation.
This presentation showcases examples and results using CISM3’s new tools and capabilities.
How to cite: Leguy, G., Lipscomb, W., Thayer-Calder, K., Minallah, S., Petrini, M., Goeltzer, H., van den Akker, T., Sacks, B., Vertenstein, M., and Berdahl, M.: Version 3 of the Community Ice Sheet Model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15073, https://doi.org/10.5194/egusphere-egu25-15073, 2025.
We present the first results of future Antarctic climate simulations with the polar-adapted Regional Atmospheric Climate Model (RACMO2.4p1). As part of the PolarRES project, two climate storylines are explored, examining the response of the Antarctic surface mass balance (SMB) to two plausible future climates with varying degree of Antarctic sea ice loss and changes to upper atmospheric circulation. For this RACMO2.4p1 is run on a 11 km horizontal grid forced with high emission scenario SSP3-7.0 simulations from CESM2 and MPI-ESM for the period 2015-2100. To evaluate the model performance using climate model data, we compare historical simulations (1985-2015) forced by CESM2 and MPI-ESM to those forced by ERA5. We examine shifts in Antarctic precipitation and SMB between the current and future climate, and relate those changes to changes in atmopsheric circulation, atmospheric moisture budget and presence of sea ice.
How to cite: Hofsteenge, M. G., van de Berg, W. J., van Dalum, C. T., Verro, K., van Tiggelen, M., and van den Broeke, M.: Modelling future Antarctic climate and surface mass balance with RACMO2.4p1 (2015-2100), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15319, https://doi.org/10.5194/egusphere-egu25-15319, 2025.
Understanding how key regional circulation features respond to future global warming is essential for projections of Antarctic Ice Sheet dynamics, and future global sea level rise. The Southern Annular Mode (SAM) influences the strength and location of the mid-latitude tropospheric westerly jet, which controls the transport of warm air and moisture towards the AIS. The Amundsen Sea Low (ASL), a permanent low-pressure system off the coast Antarctica affects regional wind patterns, precipitation and ocean circulation. These features can also impact the exchange of heat and carbon dioxide between the ocean and atmosphere, impacting sea ice extent and the stability of ice shelves. Under global warming scenarios, changes in these atmospheric features may significantly alter surface mass balance, surface melt, temperature and precipitation patterns over the AIS.
This study uses UK Earth System Model (UKESM) overshoot experiments that explore future emission increase, stabilization, and reduction simulations to investigate the interactions between atmospheric circulation features and the Antarctic cryosphere. These idealised simulations are forced only by CO2 concentrations and currently extend up to 650 years duration, allowing exploration of the response of the AIS to a range of global warming scenarios, and asses potential reversibility under future CO2 reduction.
This research utilises these simulations to identify trends in the SAM, ASL and westerly jets. Initial results show a deepening of the absolute pressure of the ASL, a poleward shift and strengthening of the westerly jet, with trends increasing and reversibility diminishing with higher global warming scenarios. These simulations are then used to identify any relationship between these features and trends in temperature, precipitation and surface melt over regions of the AIS and ice shelves, providing insights into the long-term stability of the AIS under varying climate scenarios.
How to cite: Taylor, S., Orr, A., Cornford, S., Bracegirdle, T., and Smith, R.: Exploring Antarctic Circulation-Ice Sheet Interactions in UKESM Climate Projections Through 2500 and Beyond, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16564, https://doi.org/10.5194/egusphere-egu25-16564, 2025.
The Antarctic Ice Sheet has contributed 0 to 7.7m to the global mean sea level during the Last Interglacial, according to recent publications (Barnett et al., 2023; Dyer et al., 2021; Dumitru et al., 2023; Shackleton et al., 2020). This large uncertainty suggests that the Antarctic ice sheet could have been similar to present-day geometry, but it could also have had a major retreat such as the collapse of the West Antarctic Ice Sheet and more. For example, Clark et al. 2020 simulate the West Antarctic Ice Sheet collapse in their modeling work. They suggest that a longer period of reduced Atlantic Meridional Overturning Circulation (AMOC) during the penultimate deglaciation compared to the last deglaciation could have led to greater subsurface warming and subsequent larger Antarctic Ice Sheet retreat.
Here we study the response of the Antarctic ice sheet during the penultimate deglaciation (∼ 138–128 ka) to different evolutions of the AMOC. We use the ice sheet model GRISLI (Quiquet et al. 2018), including the recently implemented sub-shelf melt module PICO (Reese et al. 2018). The climate forcings, including Northern Hemisphere ice sheets evolution, are obtained from fully coupled Earth System Model simulations using the intermediate complexity model iLOVECLIM (Roche et al. 2014). We run 2 sets of ice sheet simulations. In the first set the Northern Hemisphere ice sheets are fully coupled and therefore provide freshwater fluxes directly to the oceans according to ice sheets melt (Quiquet and Roche 2024). In the second set the freshwater fluxes given in the North Atlantic Ocean are idealized. With the second set, we also test the impact of the timing and duration of the freshwater flux on the ice sheet retreat. We hypothesize that both the duration and timing of reduced AMOC can significantly affect the sensitivity of the Antarctic Ice Sheet. A larger subsurface warming in the Southern Ocean can be triggered by longer AMOC reduction, and the resilience of the ice sheet to this warming depends on its geometry during the deglaciation.
How to cite: Menthon, M., Bakker, P., Quiquet, A., and Roche, D.: Does the AMOC strength matter for the Antarctic ice sheet retreat during the penultimate deglaciation? , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17480, https://doi.org/10.5194/egusphere-egu25-17480, 2025.
The polar ice sheets are melting faster due to climate change, with the contribution of the Greenland and Antarctic ice sheets being the largest uncertainty in projecting future sea level rise. Understanding this is crucial for assessing impacts on the environment and ecosystems. Most of the existing modelling studies focus on ice sheet response to atmospheric and oceanic forcing. However, the ice sheets closely interact with and influence the Earth’s climate. With the goal of better representing ice sheet and climate processes and feedbacks, we aim to integrate Greenland and Antarctic dynamic ice sheet components into the Norwegian Earth System Model (NorESM). NorESM is a global, CMIP-type coupled model for the physical climate system and biogeochemical processes over land, ocean, sea ice and atmosphere. In its latest release, NorESM features interactive coupling with a dynamic Greenland Ice Sheet (GrIS) component, although this coupling does not explicitly include ocean forcing at the marine-terminating margins of the ice sheet. In this presentation, we will show preliminary results of NorESM simulations featuring (1) a new interactive coupling with the Community Ice Sheet Model (CISM) over both the Antarctic and Greenland domains, and (2) a new ocean and ice sheet coupling allowing us to force the ice sheets with horizontally and vertically resolved NorESM ocean properties. We will discuss work in progress, highlighting recent advances and most pressing challenges of our coupling approach.
How to cite: Petrini, M., Vertenstein, M., Goelzer, H., Lipscomb, W. H., Leguy, G. R., Sacks, W. J., Thayer-Calder, K., Chandler, D. M., and Langebroek, P. M.: Coupling the polar ice sheets to the Norwegian Earth System Model: advances and challenges, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20400, https://doi.org/10.5194/egusphere-egu25-20400, 2025.
