How iceberg calving and grounding change the circulation and hydrography in the Filchner Ice Shelf‐Ocean System

Abstract

The formation of bottom water in the southern Weddell Sea is strongly influenced by the flow of Ice Shelf Water (ISW) out of the Filchner‐Ronne Ice Shelf cavity. The breakout of three giant icebergs in 1986 and their grounding on the shallow Berkner Bank modified the circulation and water mass formation in the Filchner Trough and the adjacent sea areas. Hydrographic measurements along the Filchner Ice Shelf front, carried out with RV Polarstern in 1995, show significant changes in the water mass characteristics and flow patterns in the Filchner Trough in comparison to measurements from the early 1980s. Changes in the trough will affect the flow over the sill to the deep Weddell Abyssal Plain. We combine a three‐dimensional ocean circulation model with conductivity‐temperature‐depth and stable isotope measurements to investigate the details of the circulation in front of and beneath the Filchner Ice Shelf. We assess the impact of stranded icebergs and a more southerly ice shelf front position caused by a 1986 iceberg calving event on the circulation and observed water mass properties. Results indicate variations of the flow pattern in the Filchner Trough and on Berkner Bank, where High‐Salinity Shelf Water, the feedstock for ISW, is produced. The calving and grounding impacts illustrate the sensitivity of the ice shelf‐ocean system to perturbations in local bathymetric settings.