The ice front as a topographic barrier for ocean heat transport

• Published in: Nature
• Main Author: Steiger, Nadine
• Other Authors: orcid:0000-0002-7533-6583
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: The University of Bergen 2021
• Subjects: Antarctic; Getz; Getz Ice Shelf; Southern Ocean; The Antarctic; West Antarctica; Antarc*; Antarctica; Ice Sheet; Ice Shelf; Ice Shelves; Iceberg*
• Online Access: https://hdl.handle.net/11250/2760582

Antarctic ice shelves are the link between the Southern Ocean and the Antarctic Ice Sheet. The floating ice shelves restrain the seaward flow of the grounded ice, which is balanced by iceberg calving and ocean-induced basal melting. An increase in oceanic heat flux towards the West Antarctic ice shelves during the last decades has caused the ice shelves to thin. Nevertheless, the observed melt rates are lower than expected from the oceanic heat available on the continental shelf, suggesting that not all the heat is used to melt the ice shelves. Ice shelves extend several hundred meters into the ocean and terminate with a vertical wall, the ice front, that poses a topographic barrier to the ocean heat transport towards the sub-ice shelf cavities. Little is known about the influence of the discontinuity in water column thickness on the southward currents that transport warm and dense Circumpolar Deep Water from north of the continental shelf towards the ice shelf cavities. This thesis improves our understanding of the ocean dynamics and the drivers of heat transport variability in the vicinity of the ice front, based on mooring observations in front of the Getz Ice Shelf in West Antarctica, laboratory experiments, and idealized numerical modelling. From the mooring observations, we infer in Paper I that only a small fraction of the southward heat transport eventually reaches the Getz Ice Shelf cavity, due to the different response of the barotropic (depth-constant) and the baroclinic (depth-varying) components of the current to the ice front. The barotropic component is blocked and deflected at the ice front; only the baroclinic, bottom-intensified component enters the ice shelf cavity. Results from laboratory experiments on a rotating platform support these observations. The experiments show that the barotropic current follows lines of constant water column thickness and turns at the ice front, while the baroclinic, dense current follows lines of constant bed topography and enters the cavity without being ...