Ice‐Shelf Melt Response to Changing Winds and Glacier Dynamics in the Amundsen Sea Sector, Antarctica

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Donat‐magnin, Marion, Jourdain, Nicolas, Spence, Paul, Le Sommer, Julien, Gallée, Hubert, Durand, Gaël
• Other Authors: Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes 2016-2019 (UGA 2016-2019 ), University of New South Wales Sydney (UNSW)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2017
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Amundsen Sea; Antarctic; Southern Ocean; Antarc*; Antarctica; Ice Sheet; Ice Shelf; Pine Island
• Online Access: https://hal.science/hal-03001289; https://hal.science/hal-03001289/document; https://hal.science/hal-03001289/file/2017JC013059.pdf; https://doi.org/10.1002/2017JC013059

International audience It has been suggested that the coastal Southern Ocean subsurface may warm over the 21st century in response to strengthening and poleward shifting winds, with potential adverse effects on West Antarctic glaciers. However, using a 1/128 ocean regional model that includes ice-shelf cavities, we find a more complex response to changing winds in the Amundsen Sea. Simulated offshore subsurface waters get colder under strengthened and poleward shifted winds representative of the SAM projected trend. The buoyancy-driven circulation induced by ice-shelf melt transports this cold offshore anomaly onto the continental shelf, leading to cooling and decreased melt below 450 m. In the vicinity of ice-shelf fronts, Ekman pumping contributes to raise the isotherms in response to changing winds. This effect overwhelms the horizontal transport of colder offshore waters at intermediate depths (between 200 and 450 m), and therefore increases melt rates in the upper part of the ice-shelf cavities, which reinforces the buoyancydriven circulation and further contributes to raise the isotherms. Then, prescribing an extreme grounding line retreat projected for 2100, the total melt rates simulated underneath Thwaites and Pine Island are multiplied by 2.5. Such increase is explained by a larger ocean/ice interface exposed to CDW, which is then amplified by a stronger melt-induced circulation along the ice draft. Our main conclusions are that (1) outputs from ocean models that do not represent ice shelf cavities (e.g., CMIP5 models) should not be directly used to predict the thermal forcing of future ice shelf cavities; (2) coupled ocean/ice sheet models with a velocity-dependent melt formulation are needed for future projections of glaciers experiencing a significant grounding line retreat.