Antarctic calving loss rivals ice-shelf thinning

• Published in: Nature (London) Vol. 609; no. 7929; pp. 948 - 953
• Main Authors: Greene, Chad A., Gardner, Alex S., Schlegel, Nicole-Jeanne, Fraser, Alexander D.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 29.09.2022; Nature Publishing Group
• Subjects: 704/106/125; 704/106/829/2737; Altimetry; Buttresses; Coastal evolution; Coasts; Glaciers; Humanities and Social Sciences; Ice; Ice sheets; Ice shelves; Land ice; multidisciplinary; Net losses; Radar; Radar data; Radar satellites; Satellites; Science; Science (multidisciplinary); Sea level; Sea level rise; Structural integrity; Thinning; Trends; Antarctica
• ISSN: 0028-0836; 1476-4687; 1476-4687
• DOI: 10.1038/s41586-022-05037-w

Antarctica’s ice shelves help to control the flow of glacial ice as it drains into the ocean, meaning that the rate of global sea-level rise is subject to the structural integrity of these fragile, floating extensions of the ice sheet 1 – 3 . Until now, data limitations have made it difficult to monitor the growth and retreat cycles of ice shelves on a large scale, and the full impact of recent calving-front changes on ice-shelf buttressing has not been understood. Here, by combining data from multiple optical and radar satellite sensors, we generate pan-Antarctic, spatially continuous coastlines at roughly annual resolution since 1997. We show that from 1997 to 2021, Antarctica experienced a net loss of 36,701 ± 1,465 square kilometres (1.9 per cent) of ice-shelf area that cannot be fully regained before the next series of major calving events, which are likely to occur in the next decade. Mass loss associated with ice-front retreat (5,874 ± 396 gigatonnes) has been approximately equal to mass change owing to ice-shelf thinning over the past quarter of a century (6,113 ± 452 gigatonnes), meaning that the total mass loss is nearly double that which could be measured by altimetry-based surveys alone. We model the impacts of Antarctica’s recent coastline evolution in the absence of additional feedbacks, and find that calving and thinning have produced equivalent reductions in ice-shelf buttressing since 2007, and that further retreat could produce increasingly significant sea-level rise in the future. Data from multiple satellite sensors show that Antarctica lost almost 37,000 km 2 of ice-shelf area from 1997 to 2021, and that calving losses are as important as ice-shelf thinning.