Annual mass budget of Antarctic ice shelves from 1997-2021

Antarctic ice shelves moderate the contribution of the Antarctic Ice Sheet to global sea level rise by resisting the flow of ice into the ocean. However, the mass budget of Antarctic ice shelves and the impact of ice shelf mass change on grounded ice remain poorly constrained. Here, we present an annually partitioned ice shelf mass budget from 1997 to 2021 for all Antarctic ice shelves. Antarctic ice shelf mass decreased overall by 4,949 ± 1,499 Gt due to terminus retreat (4,818 ± 695 Gt), thinning (2,201 ± 1,401 Gt) and surface mass loss (24 ± 82 Gt), which were partially offset by increases in grounding line discharge (2094 ± 761 Gt). Thinning was the dominant mass loss term for the majority (65-86 %) of ice shelves that lost mass, but both thinning and retreat were equally related to increases in grounding line discharge. These observations provide a 24-year record of the state of Antarctic ice shelves, their freshwater inputs to the Southern Ocean and the impact of recent ice shelf mass change on grounding line discharge.