Anthropogenic climate change will drive extensive mass loss across both the Antarctic (AIS) and Greenland Ice Sheets (GrIS), with the potential for feedbacks on the global climate system, especially in polar regions. Historically, the high latitude North Atlantic and Southern Ocean have been the most critical regions for global anthropogenic heat and carbon uptake, but our understanding of how this uptake will be altered by future freshwater discharge is incomplete. Here, we assess each ice sheet’s impact on the global ocean storage of anthropogenic heat and carbon for a high-emission scenario over the 21$^{\textrm{st}}$ century using a coupled Earth system model. Notably, combined AIS and GrIS freshwater engenders distinct anthropogenic heat and carbon storage anomalies as the two diagnostics respond disparately in the high latitude Southern Ocean and North Atlantic. We explore the impact of contemporaneous mass loss from both ice sheets on anthropogenic heat and carbon storage and quantify the linear and nonlinear contributions of each ice sheet. We find that GrIS mass loss exerts a primary control on the 21$^{st}$-century evolution of both global oceanic heat and carbon storage, with AIS impacts appearing after the 2080s. Non-linear impacts of simultaneous ice sheets’ discharge have a non-negligible contribution to the evolution of both heat and carbon storage. Further, anthropogenic heat changes are realized more quickly in response to ice sheet discharge than anthropogenic carbon. Our results highlight the need to incorporate both ice sheets actively in climate models in order to accurately project future global climate.

The simulation of ice sheet-climate interaction such as surface mass balance fluxes are sensitive to model grid resolution. Here we simulate the multicentury evolution of the Greenland Ice Sheet (GrIS) and its interaction with the climate using the Community Earth System Model version 2.2 (CESM2.2) including an interactive GrIS component (the Community Ice Sheet Model v2.1 [CISM2.1]) under an idealized warming scenario (atmospheric CO2 increases by 1% yr−1 until quadrupling the pre-industrial level and then is held fixed). A variable-resolution (VR) grid with 1/4◦ regional refinement over broader Arctic and 1◦ resolution elsewhere is applied to the atmosphere and land components, and the results are compared to conventional 1◦ lat-lon grid simulations to investigate the impact of grid refinement. An acceleration of GrIS mass loss is found at around year 110, caused by rapidly increasing surface melt as the ablation area expands with associated albedo feedback and increased turbulent fluxes. Compared to the 1◦ runs, the VR run features slower melt increase, especially over Western and Northern Greenland, which slope gently towards the peripheries. This difference pattern originates primarily from the weaker albedo feedback in the VR run, complemented by its smaller cloud longwave radiation. The steeper VR Greenland surface topography favors slower ablation zone expansion, thus leading to its weaker albedo feedback. The sea level rise contribution from the GrIS in the VR run is 53 mm by year 150 and 831 mm by year 350, approximately 40% and 20% smaller than the 1◦ runs, respectively.

Multidecadal satellite observations indicate that the Antarctic Ice Sheet (AIS) is losing mass at an accelerating rate, potentially impacting many aspects of the coupled climate system. While previous studies have demonstrated the importance of AIS freshwater discharge for regional and global climate processes using climate model experiments, many have applied unrealistic freshwater forcing. Here, we explore the potential Southern Ocean impacts of realistic AIS mass loss over the 21$^{st}$ century in the Community Earth System Model version 2 (CESM2) by applying observation-based historical and ice sheet model-based future AIS freshwater forcing. The added freshwater reduces wintertime deep convective area by 72\% while retaining 83\% more sea ice. Congruent with other studies, we find the increased freshwater discharge extensively impacts local and remote Southern Ocean surface and subsurface temperature and stratification. These results demonstrate the necessity of accounting for AIS mass loss in global climate models for projecting future climate.

Sub-grid-scale processes occurring at or near the surface of an ice sheet have a potentially large impact on local and integrated net accumulation of snow via redistribution and sublimation. Given observational complexity, they are either ignored or parameterized over large-length scales. Here, we train random forest models to predict 1-km variability in net accumulation over the Antarctic Ice Sheet using atmospheric variables and topographic characteristics as predictors. Observations of net snow accumulation from both in situ and airborne radar data provide the input observable targets needed to train the random forest models. We find that kilometer-scale processes modify local net accumulation by as much as 172% of the atmospheric model mean. The correlation in space between the predicted net accumulation variability and satellite-derived surface-height change indicates that kilometer-scale processes operate differently through time, driven largely by the seasonal anomalies in snow accumulation.

Atmospheric rivers (ARs) are efficient mechanisms for transporting atmospheric moisture from low latitudes to the Antarctic Ice Sheet (AIS). While AR events occur infrequently, they can lead to extreme precipitation and surface melt events on the AIS. Here we estimate the contribution of ARs to total Antarctic precipitation, by combining precipitation from atmospheric reanalyses and an polar-specific AR detection algorithm. We show that ARs contribute substantially to Antarctic precipitation, especially on East Antarctica at elevations below 3000 meters. ARs play a vital role in explaining the substantial year-to-year variability in Antarctic precipitation. Our results highlight that ARs are an important component for understanding present and future Antarctic mass balance trends and variability.

The Greenland Ice Sheet (GrIS) mass balance is examined with an Earth system/ice sheet model that interactively couples the GrIS to the land and atmosphere. The simulation runs from 1850 to 2100, with historical and SSP5-8.5 forcing. By mid-21st century, the cumulative contribution to global mean sea level rise (SLR) is 23 mm. Over the second half of the 21st century, the surface mass balance becomes negative in all drainage basins, and an additional 86 mm of SLR is contributed. The annual mean GrIS mass loss in the last two decades is 2.7 mm sea level equivalent (SLE) yr-1. Strong decrease in SMB (3.1 mm SLE yr-1) is counteracted by a reduction in ice discharge from thinning and retreat of outlet glaciers. The southern GrIS drainage basins contribute 73% of the mass loss by mid-century. This decreases to 55% by 2100, as surface runoff in the northern basins strongly increases.