The simulation of ice sheet-climate interactions, such as surface mass balance fluxes, is sensitive to model grid resolution. Here we simulate the multi-century 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 (Formula presented.) increases by 1% (Formula presented.) until quadrupling the pre-industrial level and then is held fixed). A variable-resolution (VR) grid with 1/ (Formula presented.) regional refinement over the broader Arctic and (Formula presented.) resolution elsewhere is applied to the atmosphere and land components, and the results are compared with conventional (Formula presented.) lat-lon grid simulations to investigate the impact of grid refinement. Compared with the (Formula presented.) runs, the VR run features a slower rate of surface melt, especially over the western and northern GrIS, where the ice surface slopes gently toward the periphery. This difference pattern originates primarily from higher snow albedo and, thus, weaker albedo feedback in the VR run. The VR grid better captures the CISM ice sheet topography by reducing elevation discrepancies between CAM and CISM and is, therefore, less reliant on the downscaling algorithm, which is known to underestimate albedo gradients. 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% less than that of the (Formula presented.) runs, respectively.

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Antarctic atmospheric rivers (ARs) are a form of extreme weather that transport heat and moisture from the Southern Hemisphere subtropics and/or mid-latitudes to the Antarctic continent. Present-day AR events generally have a positive influence on the Antarctic ice-sheet mass balance by producing heavy snowfall, yet they also cause melt of sea ice and coastal ice sheet areas, as well as ice shelf destabilization. In this Review, we explore the atmospheric dynamics and impacts of Antarctic ARs over their life cycle to better understand their net contributions to ice-sheet mass balance. ARs occur in high-amplitude pressure couplets, and those strong enough to reach the Antarctic are often formed within Rossby waves initiated by tropical convection. Antarctic ARs are rare events (~3 days per year per location) but have been responsible for 50–70% of extreme snowfall events in East Antarctica since the 1980s. However, they can also trigger extensive surface melting events, such as the final ice shelf collapse of Larsen A in 1995 and Larsen B in 2002. Climate change will likely cause stronger ARs as anthropogenic warming increases atmospheric water vapour. Future research must determine how these climate change impacts will alter the relationship among Antarctic ARs, net ice-sheet mass balance and future sea-level rise.@en