Current structure at the Amundsen Sea shelf break

Abstract

The West Antarctic Ice Sheet has been losing mass at an increasing rate over the past decades. Ocean heat transport to the ice-ocean interface has been identified as an important contributor to this mass loss and the role it plays in ice sheet stability makes it crucial to understand its drivers in order to make accurate future projections of global sea level. While processes closer to the iceocean interface modulate this heat transport, its ultimate source is located in the deep basin off the continental shelf as a core of relatively warm, salty water underlying a colder, fresher shallow surface layer. To reach the marine terminating glaciers and the base of floating ice shelves, this warm, salty water mass must cross the bathymetric obstacle of the shelf break. Troughs in the shelf break have been identified to facilitate this transport and to act as conduits for the warm and salty Circumpolar Deep Water (CDW) towards the ice sheet. The formation of an eastward undercurrent underlying the westward wind-driven shelf break current that turns onto the shelf in the central trough has been shown to be the responsible feature for the on-shelftransport of warm water from hydrographic and mooring observations and numerical model results. We use data from hydrographic moorings to ascertain the temporal persistence of this pattern in the central shelf break trough. Using observations from two moorings and hydrographic and ADCP sections, we aim to identify whether the same pattern exists in a less clearly defined shelf break depression further west that acts as the main pathway for CDW to Dotson and eastern Getz Ice shelves. We finally examine if the shelf break mooring observations can be used to investigate the variability of CDW transport across the shelf break into the Getz-Dotson Trough and the coherence of current variability along the shelf break.