Annual mass budget of Antarctic ice shelves from 1997 to 2021

Abstract

Antarctic ice shelves moderate the contribution of the Antarctic Ice Sheet to global sea level rise; however, ice shelf health remains poorly constrained. Here, we present the annual mass budget of all Antarctic ice shelves from 1997 to 2021. Out of 162 ice shelves, 71 lost mass, 29 gained mass, and 62 did not change mass significantly. Of the shelves that lost mass, 68 had statistically significant negative mass trends, 48 lost more than 30% of their initial mass, and basal melting was the dominant contributor to that mass loss at a majority (68%). At many ice shelves, mass losses due to basal melting or iceberg calving were significantly positively correlated with grounding line discharge anomalies; however, the strength and form of this relationship varied substantially between ice shelves. Our results illustrate the utility of partitioning high-resolution ice shelf mass balance observations into its components to quantify the contributors to ice shelf mass change and the response of grounded ice.

Fig. 1.. Pan-Antarctic ice shelf freshwater flux.

(A) Cumulative ice shelf freshwater flux from 1997 to 2021 overlain on the 2010–2021 average ice shelf basal melt rates and a 750-m Moderate Resolution Imaging Spectroradiometer (MODIS) image mosaic (102). Only ice shelves with a freshwater flux greater than 50 Gt are plotted. (B to F) Regional ice shelf cumulative freshwater flux time series. LA, Larsen A; LB, Larsen B; LC, Larsen C; LD, Larsen D; LE, Larsen E; HCC, Hayes Coats Coast; WRD, Wilma Robert Downer; Tracy T., Tracy Tremenchus; C. Charcot, Commandant Charcot; PIG, Pine Island Glacier; GVI, George VI.

Fig. 2.. Pan-Antarctic ice shelf mass change.

(A) Cumulative ice shelf mass change from 1997 to 2021 overlain on the 2010–2021 average ice shelf basal melt rates and a 750-m MODIS image mosaic (102). Circle area is capped at 500 Gt and only ice shelves with significant mass change are plotted. (B) Ice shelf mass change time series for each labeled region and for Antarctica (black). (C to G) Relative ice shelf mass change time series for individual ice shelves colored as in (A). LA, Larsen A; LB, Larsen B; LC, Larsen C; LD, Larsen D; LE, Larsen E; HCC, Hayes Coats Coast; WRD, Wilma Robert Downer; Tracy T., Tracy Tremenchus; C. Charcot, Commandant Charcot; PIG, Pine Island Glacier; GVI, George VI; Vin. Bay, Vincennes Bay; H. Piedmont, Hamilton Piedmont; H. Bay, Harmon Bay; Walgreen C2, Walgreen Coast 2; E. Bay, Eltanin Bay; R. Pen2, Rydberg Peninsula 2.

Fig. 3.. Partitioned ice shelf mass change time series.

Stacked time series of cumulative ice shelf (A) total mass change, (C) mass change due to calving, (D) mass change due to basal melting, (E) grounding line discharge anomalies relative to 1997 values, and (F) SMB anomalies relative to the 1979–2008 climatological mean, with some of the dominant ice shelves for each component labeled. All ice shelves are shown, ordered by contribution to the total for each variable. Negative values (shown in red colors) indicate the overall mass loss or a contribution to mass loss, and the black line shows the pan-Antarctic total. (B) Pan-Antarctic time series for each of the budget components.

Fig. 4.. Ice shelf mass changes due to area and thickness changes.

The contribution of time-integrated area change and basal melt–induced thickness change to the mass change of each ice shelf. Each point represents an ice shelf that has gained mass (background blue shading) or lost mass (background red shading) overall from 1997 to 2021. The symbol color indicates the ice shelf centroid longitude. Ice shelves with significant mass change are indicated by solid fill symbols and error bars (gray whiskers). Note that the percentage contributions do not sum to 100 because discharge, SMB anomalies, and grounding line migration also contribute to the overall mass change.

Fig. 5.. Relationships between cumulative retreat, thinning, and discharge change.

(A) The relationship between time-dependent cumulative ice shelf retreat and cumulative grounding line discharge change from 1997 to 2021. (B) The equivalent of (A) but for basal melt–induced thinning. Each point represents the cumulative mass change up to each year in the time series (note that the points are not necessarily ordered chronologically). Only shelves with net discharge increases are plotted and shelves with significant (P < 0.05) positive (R > 0.25) relationships between cumulative retreat or thinning and discharge change are plotted with filled markers.