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1. Late Holocene ice-mass changes recorded in a relative sea-level record from Joinville Island, Antarctica

   https://doi.org/10.1130/G46649.1  

   Zurbuchen, Julie; Simms, Alexander R. (September 2019, Geology)

   Abstract Recent ice-mass loss driven by warming along the Antarctic Peninsula has resulted in rapid changes in uplift rates across the region. Are such events only a function of recent warming? If not, does the Earth response to such events last long enough to be preserved in Holocene records of relative sea level (RSL), and thus have a bearing on global-scale glacial isostatic adjustment (GIA) models (e.g. ICE-6G)? Answering such questions in Antarctica is hindered by the scarcity of RSL reconstructions within the region. Here, a new RSL reconstruction for Antarctica is presented based on beach ridges from Joinville Island on the Antarctic Peninsula. We find that RSL has fallen 4.9 ± 0.58 m over the past 3100 yr, and that the island experienced a significant increase in the rate of RSL fall from 1540 ± 125 cal. (calibrated) yr B.P. to 1320 ± 125 cal. yr B.P. This increase in the rate of RSL fall is likely due to the viscoelastic response of the solid Earth to terrestrial ice-mass loss from the Antarctic Peninsula, similar to the Earth response experienced after ice-mass loss following acceleration of glaciers behind the collapsed Larsen B ice shelf in 2002 C.E. Additionally, slower rates of beach-ridge progradation from 695 ± 190 cal. yr B.P. to 235 ± 175 cal. yr B.P. potentially reflect erosion of beach ridges from a RSL rise induced by a local glacial advance. The rapid response of the Earth to minor ice-mass changes recorded in the RSL record further supports recent assertions of a more responsive Earth to glacial unloading and at time scales relevant for GIA of Holocene and Pleistocene sea levels. Thus, current continental and global GIA models may not accurately capture the ice-mass changes of the Antarctic ice sheets at decadal and centennial time scales. 

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2. Ocean variability beneath Thwaites Eastern Ice Shelf driven by the Pine Island Bay Gyre strength

   https://doi.org/10.1038/s41467-022-35499-5  

   Dotto, Tiago S.; Heywood, Karen J.; Hall, Rob A.; Scambos, Ted A.; Zheng, Yixi; Nakayama, Yoshihiro; Hyogo, Shuntaro; Snow, Tasha; Wåhlin, Anna K.; Wild, Christian; et al (December 2022, Nature Communications)

   Abstract West Antarctic ice-shelf thinning is primarily caused by ocean-driven basal melting. Here we assess ocean variability below Thwaites Eastern Ice Shelf (TEIS) and reveal the importance of local ocean circulation and sea-ice. Measurements obtained from two sub-ice-shelf moorings, spanning January 2020 to March 2021, show warming of the ice-shelf cavity and an increase in meltwater fraction of the upper sub-ice layer. Combined with ocean modelling results, our observations suggest that meltwater from Pine Island Ice Shelf feeds into the TEIS cavity, adding to horizontal heat transport there. We propose that a weakening of the Pine Island Bay gyre caused by prolonged sea-ice cover from April 2020 to March 2021 allowed meltwater-enriched waters to enter the TEIS cavity, which increased the temperature of the upper layer. Our study highlights the sensitivity of ocean circulation beneath ice shelves to local atmosphere-sea-ice-ocean forcing in neighbouring open oceans. 

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3. The Sensitivity of the Spatial Pattern of Sea Level Changes to the Depth of Antarctic Meltwater Fluxes

   https://doi.org/10.1029/2024GL110633  

   Eisenman, Ian; Basinski‐Ferris, Aurora; Beer, Emma; Zanna, Laure (October 2024, Geophysical Research Letters)

   Abstract Regional patterns of sea level rise are affected by a range of factors including glacial melting, which has occurred in recent decades and is projected to increase in the future, perhaps dramatically. Previous modeling studies have typically included fluxes from melting glacial ice only as a surface forcing of the ocean or as an offline addition to the sea surface height fields produced by climate models. However, observational estimates suggest that the majority of the meltwater from the Antarctic Ice Sheet actually enters the ocean at depth through ice shelf basal melt. Here we use simulations with an ocean general circulation model in an idealized configuration. The results show that the simulated global sea level change pattern is sensitive to the depth at which Antarctic meltwater enters the ocean. Further analysis suggests that the response is dictated primarily by the steric response to the depth of the meltwater flux. 

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4. Antarctic Ice‐Sheet Meltwater Reduces Transient Warming and Climate Sensitivity Through the Sea‐Surface Temperature Pattern Effect

   https://doi.org/10.1029/2022GL101249  

   Dong, Yue; Pauling, Andrew G.; Sadai, Shaina; Armour, Kyle C. (December 2022, Geophysical Research Letters)

   Abstract Coupled global climate models (GCMs) generally fail to reproduce the observed sea‐surface temperature (SST) trend pattern since the 1980s. The model‐observation discrepancies may arise in part from the lack of realistic Antarctic ice‐sheet meltwater input in GCMs. Here we employ two sets of CESM1‐CAM5 simulations forced by anomalous Antarctic meltwater fluxes over 1980–2013 and through the 21st century. Both show a reduced global warming rate and an SST trend pattern that better resembles observations. The meltwater drives surface cooling in the Southern Ocean and the tropical southeast Pacific, in turn increasing low‐cloud cover and driving radiative feedbacks to become more stabilizing (corresponding to a lower effective climate sensitivity). These feedback changes can contribute as substantially as ocean heat uptake efficiency changes in reducing the global warming rate. Accurately projecting historical and future warming thus requires improved representation of Antarctic meltwater and its impacts. 

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5. Winds and Meltwater Together Lead to Southern Ocean Surface Cooling and Sea Ice Expansion

   https://doi.org/10.1029/2023GL105948  

   Roach, Lettie_A; Mankoff, Kenneth_D; Romanou, Anastasia; Blanchard‐Wrigglesworth, Edward; Haine, Thomas_W_N; Schmidt, Gavin_A (December 2023, Geophysical Research Letters)

   Abstract Southern Ocean surface cooling and Antarctic sea ice expansion from 1979 through 2015 have been linked both to changing atmospheric circulation and melting of Antarctica's grounded ice and ice shelves. However, climate models have largely been unable to reproduce this behavior. Here we examine the contribution of observed wind variability and Antarctic meltwater to Southern Ocean sea surface temperature (SST) and Antarctic sea ice. The free‐running, CMIP6‐class GISS‐E2.1‐G climate model can simulate regional cooling and neutral sea ice trends due to internal variability, but they are unlikely. Constraining the model to observed winds and meltwater fluxes from 1990 through 2021 gives SST variability and trends consistent with observations. Meltwater and winds contribute a similar amount to the SST trend, and winds contribute more to the sea ice trend than meltwater. However, while the constrained model captures much of the observed sea ice variability, it only partially captures the post‐2015 sea ice reduction. 

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