Abrupt Holocene ice loss due to thinning and ungrounding in the Weddell Sea Embayment

• Published in: Nature geoscience 2024-03, Vol.17 (3), p.227-232
• Main Authors: Grieman, Mackenzie M., Nehrbass-Ahles, Christoph, Hoffmann, Helene M., Bauska, Thomas K., King, Amy C. F., Mulvaney, Robert, Rhodes, Rachael H., Rowell, Isobel F., Thomas, Elizabeth R., Wolff, Eric W.
• Format: Article
• Language: English
• Subjects: 704/106/125; 704/106/413; Ablation; Air Content; Antarctic ice sheet; Buttresses; Continental shelves; Earth and Environmental Science; Earth Sciences; Earth System Sciences; Geochemistry; Geology; Geophysics/Geodesy; Glaciation; Glaciers; Holocene; Holocene ice; Ice; Ice calving; Ice cores; Ice front; Ice fronts; Ice sheet models; Ice sheets; Ice shelves; Ice streams; Land ice; Last Glacial Maximum; Outflow; Shelf edge; Sodium; Thinning
• ISSN: 1752-0894; 1752-0908
• DOI: 10.1038/s41561-024-01375-8

The extent of grounded ice and buttressing by the Ronne Ice Shelf, which provides resistance to the outflow of ice streams, moderate West Antarctic Ice Sheet stability. During the Last Glacial Maximum, the ice sheet advanced and was grounded near the Weddell Sea continental shelf break. The timing of subsequent ice sheet retreat and the relative roles of ice shelf buttressing and grounding line changes remain unresolved. Here we use an ice core record from grounded ice at Skytrain Ice Rise to constrain the timing and speed of early Holocene ice sheet retreat. Measured δ 18 O and total air content suggest that the surface elevation of Skytrain Ice Rise decreased by about 450 m between 8.2 and 8.0 kyr before 1950 ce (±0.13 kyr). We attribute this elevation change to dynamic thinning due to flow changes induced by the ungrounding of ice in the area. Ice core sodium concentrations suggest that the ice front of this ungrounded ice shelf then retreated about 270 km (±30 km) from 7.7 to 7.3 kyr before 1950 ce . These centennial-scale changes demonstrate how quickly ice mass can be lost from the West Antarctic Ice Sheet due to changes in grounded ice without extensive ice shelf calving. Our findings both support and temporally constrain ice sheet models that exhibit rapid ice loss in the Weddell Sea sector in the early Holocene. The Ronne Ice Shelf of the West Antarctic Ice Sheet retreated rapidly in the early Holocene due to ice sheet dynamic thinning and subsequent ungrounding, according to an ice core record from Skytrain Ice Rise.