Influence of fast ice on future ice shelf melting in the Totten Glacier area, East Antarctica

Abstract

Abstract. The Totten Glacier in East Antarctica is of major climatic interest because of the large fluctuations in its grounding line and potential vulnerability to climate change. Here, we use a series of high-resolution, regional NEMO-LIM-based (Nucleus for European Modelling of the Ocean coupled with the Louvain-la-Neuve sea ice model) experiments, which include an explicit treatment of ocean–ice shelf interactions, as well as a representation of grounded icebergs and fast ice, to investigate the changes in ocean–ice interactions in the Totten Glacier area between the recent past (1995–2014) and the end of the 21st century (2081–2100) under SSP4–4.5 climate change conditions. By the end of the 21st century, the wide areas of multiyear fast ice simulated in the recent past are replaced by small patches of first year fast ice along the coast, which decreases the total summer sea ice extent. The Antarctic Slope Current is accelerated by about 116 %, which decreases the heat exchange across the shelf and tends to reduce the ice shelf basal melt rate, but this effect is counterbalanced by the effect of the oceanic warming. As a consequence, despite the accelerated Antarctic Slope Current, the Totten ice shelf melt rate is increased by 91 % due to the intrusion of warmer water into its cavity. The representation of fast ice dampens the ice shelf melt rate increase throughout the 21st century, as the Totten ice shelf melt rate increase reaches 136 % when fast ice is not taken into account. The Moscow University ice shelf melt rate increase is even more impacted by the representation of fast ice, with a 36 % melt rate increase with fast ice, compared to a 75 % increase without a fast ice representation. This influence of the representation of fast ice in our simulations on the basal melting rate trend over the 21st century is explained by the large impact of the fast ice for present-day conditions (∼25 % difference in m yr−1), while the impact decreases significantly at the end of the 21st century (∼4 % difference in m yr−1). As a consequence, the reduction in the fast ice extent in the future induces a decrease in the fast ice effect on the ice shelf melt rate that partly compensates for the increase due to warming of the ocean. This highlights the importance of including a representation of fast ice to simulate realistic ice shelf melt rate increase in East Antarctica under warming conditions.

Eddy and tidal driven basal melting of the Totten and Moscow University ice shelves

“…Other model estimates of ice shelf melt rates for 2014 are limited (Mohajerani et al, 2018;Li et al, 2016), as are direct estimates of mass loss from the Totten and Moscow University glaciers. Recent model work on the Totten Glacier area showed the mean areaaveraged basal melt rate from 1995 to 2014 for the TIS is 9.1 ± 4.6 m yr -1 , and for the MUIS is 5.9 ± 5.4 m yr -1 (Van Achter et al, 2022), which compares well to our results 6.7 m yr -1 and 9.7 m yr -1 for TIS and MUIS. Mohajerani et al (2018) showed the mass balance estimates from two surface mass balance (SMB) models of Totten and Moscow University glaciers for the year 2014 around 100 Gt, which is close to our result (94 Gt).…”

Subglacial Freshwater Drainage Increases Simulated Basal Melt of the Totten Ice Shelf

“…Previous modeling (e.g., Gwyther et al, 2014;Van Achter et al, 2022;Xia et al, 2023) indicated that inflow into the cavity (Figures 1a and 1b) is on the eastern side and can carry relatively warm water (see Figure S1 in Supporting Information S1). Ice shelf meltwater flows out of the cavity adjacent to the western grounding line as a topographically constrained boundary current, before exiting the cavity.…”

Antarctic Landfast Sea Ice: A Review of Its Physics, Biogeochemistry and Ecology

“…Van Achter, Fichefet, Goosse, Pelletier, et al. (2022) and Van Achter, Fichefet, Goosse, and Moreno‐Chamarro (2022) studied the effects of realistic fast ice on the basal melt of the adjacent Totten and Moscow University ice shelves (∼112°E–122°E, 67°S) in present‐day and future warming conditions. Both analyses greatly benefited from more realistic on‐shelf ice‐ocean interaction made possible with prognostic fast ice.…”

“…By definition, fast ice is stationary sea ice which forms and remains attached to the coastline or among grounded icebergs. Given that prognostic simulation of fast ice in three dimensions has been achieved only very recently in the Antarctic (Huot et al., 2021; Van Achter, Fichefet, Goosse, Pelletier, et al., 2022; Van Achter, Fichefet, Goosse, & Moreno‐Chamarro, 2022, expanded upon in Section 5 here), a one‐dimensional (vertical) approach has more commonly been adopted to model fast‐ice thickness.…”

“…Recent work (Huot et al, 2021;Van Achter, Fichefet, Goosse, & Moreno-Chamarro, 2022;Van Achter, Fichefet, Goosse, Pelletier, et al, 2022) has demonstrated the significant achievement of realistic prognostic Antarctic fast-ice simulation in regional high-resolution sea ice-ocean models with a spatial resolution of approximately 2 km for the first time, by combining the modified tensile strength parameterization of König Beatty and Holland (2010) and Lemieux et al (2016) together with a relatively simple "fastening" mechanism whereby grounded icebergs are prescribed as single grid cell "islands" (but without dynamic or thermodynamic interactions with the ocean in the case of Huot et al, 2021). The latter study used their realistic fast-ice simulation to study in detail the effects of increasing the resolution of the atmospheric forcing component of the model, finding that their model was able to accurately reproduce the location and strength of sea-ice production.…”