Simulated Twentieth‐Century Ocean Warming in the Amundsen Sea, West Antarctica. Issue 5 (7th March 2022)

• Record Type: Journal Article
• Authors: Naughten, Kaitlin A.; Holland, Paul R.; Dutrieux, Pierre; Kimura, Satoshi; Bett, David T.; Jenkins, Adrian
• Is Part Of: Geophysical research letters. Volume 49:Issue 5(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-03-07
• Subjects: Antarctica -- Amundsen Sea -- ocean modeling -- ice shelves -- sea level rise; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL094566
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Rapid ice loss is occurring in the Amundsen Sea sector of the West Antarctic Ice Sheet. This ice loss is assumed to be a long‐term response to oceanographic forcing, but ocean conditions in the Amundsen Sea are unknown prior to 1994. Here we present a modeling study of Amundsen Sea conditions from 1920 to 2013, using an ensemble of ice‐ocean simulations forced by climate model experiments. We find that during the early twentieth century, the Amundsen Sea likely experienced more sustained cool periods than at present. Warm periods become more dominant over the simulations (mean trend 0.33°C/century) causing an increase in ice shelf melting. The warming is likely driven by an eastward wind trend over the continental shelf break that is partly anthropogenically forced. Our simulations suggest that the Amundsen Sea responded to historical greenhouse gas forcing, and that future changes in emissions are also likely to affect the region. Plain Language Summary: Ice loss from the West Antarctic Ice Sheet is one of the fastest growing contributions to sea level rise. The pattern of melting suggests that the ocean has been warming in the Amundsen Sea, but we don't know what the ocean was like in this region before observations started in 1994. In this study, we model the ocean conditions over the last century, using a set of 20 ice‐ocean simulations fed with the output of larger climate models. Our simulations suggest that the Amundsen Sea used to be cooler than it is today. Over the last century, ocean temperatures have increased, but this is hard to detect in observations because the trend is obscured by frequent swings between cold and warm conditions. The main cause of the warming in our simulations is changes in the winds near the edge of the Amundsen Sea that pump more warm water from the deep ocean onto the shallower continental shelf. These wind trends are partly caused by greenhouse gas emissions from the burning of fossil fuels. Whether the Amundsen Sea continues to warm, or whether temperatures stabilize, will likely hinge on the success of future climate policies to reduce emissions. Key Points: An ensemble of ice‐ocean simulations is used to study conditions in the Amundsen Sea over the twentieth century The simulations show a long‐term ocean warming trend on the continental shelf, which is not yet clear in the shorter observational record The trends are partly driven by anthropogenic forcing, suggesting the ocean and ice shelves may also be sensitive to future climate policy