Intermittent Reduction in Ocean Heat Transport Into the Getz Ice Shelf Cavity During Strong Wind Events.

The flow of warm water toward the western Getz Ice Shelf along the Siple Trough, West Antarctica, is intermittently disrupted during short events of Winter Water deepening. Here we show, using mooring records, that these 5–10 days‐long events reduced the heat transport toward the ice shelf cavity by 25% in the winter of 2016. The events coincide with strong easterly winds and polynya opening in the region, but the Winter Water deepening is controlled by non‐local coastal Ekman downwelling rather than polynya‐related surface fluxes. The thermocline depth anomalies are forced by Ekman downwelling at the northern coast of Siple Island and propagate to the ice front as a coastal trapped wave. During the events, the flow at depth does no longer continue along isobaths into the ice shelf cavity but aligns with the ice front. Plain Language Summary: Ocean‐driven melting of the floating ice shelves that fringe the West Antarctica Ice Sheet has increased during the last decades. The transport of ocean heat toward the base of the ice shelves displays a large variability on daily to decadal timescales; still, the processes behind this variability are not well known. The western Getz Ice Shelf in West Antarctica experienced a persistent inflow of warm ocean water during 2016–2017, but the inflow was disrupted by intermittent events of reduced heat transport. The causes for these events are studied here, and it appears that atmospheric processes in the form of surface winds and locally reduced sea ice cover are important. Strong easterly winds push the sea ice off‐coast and depress the cold surface waters toward the ocean floor. This deepening of the cold layer happens about 100 km away from the mooring site, but influences the heat transport under the ice shelf remotely through waves traveling along the coast. Simultaneously, the ocean currents are deflected at the ice front, which causes a substantial decrease of the heat transport toward the base of the ice shelves during these events. Key Points: Observations at the western Getz Ice Shelf show eight intermittent events of Winter Water deepening below 350 m depth during winter 2016The events are associated with strong easterly winds and caused by non‐local Ekman downwellingThe ocean heat transport into the Getz Ice Shelf cavity is reduced by 25% in the winter of 2016 due to the events [ABSTRACT FROM AUTHOR]