An Amundsen Sea source of decadal temperature changes on the Antarctic continental shelf

Abstract

Mass loss from the Antarctic Ice Sheet is dominated by basal melting–induced warm ocean water. Ice-sheet mass loss and thinning of buttressing ice shelves occur primarily in the Amundsen and Bellingshausen Seas. Here, we show that in a global ocean simulation using the 0.25° Nucleus for European Modeling of Ocean (NEMO) model driven by the JRA55 reanalysis from 1982 to 2017, the Amundsen sector of the Antarctic continental shelf acts as a gateway, regulating the on-shelf access of warm Circumpolar Deep Water (CDW) from the deep ocean and its westward transfer to other sectors up to ca. 90° E, particularly the Ross Sea. As a result, anomalies in Antarctic-shelf-averaged temperature mainly originate in the Amundsen sector. These changes are primarily governed by shifts in the Amundsen Sea Low associated with tropical climate variability, modulating the on-shelf transport of CDW via wind-driven perturbations to ocean currents. The ensuing temperature anomalies progress westward from the Amundsen Sea via three distinct routes: a slow, convoluted westward pathway on the shelf via the Antarctic Coastal Current; a faster westward pathway along the shelf break via the Antarctic Slope Current and then onto the shelf along topographic troughs; and a third, eastward route toward the Bellingshausen sector, whereby temperature anomalies are transported into a region of local wind-generated changes farther north. These results emphasize the importance of the Amundsen sector for climate variability over the Antarctic shelves.