Classifying Oceanographic Structures in the Amundsen Sea, Antarctica. Issue 5 (8th March 2021) - Boehme, Lars
Abstract: The remote and often ice‐covered Amundsen Sea Embayment in Antarctica is important for transporting relatively warm modified Circumpolar Deep Water (mCDW) to the Western Antarctic Ice Sheet, potentially accelerating its thinning and contribution to sea level rise. To investigate potential pathways and variability of mCDW, 3809 CTD profiles (instrumented seal and ship‐based data) are classified using a machine learning approach (Profile Classification Model). Five vertical regimes are identified, and areas of larger variability highlighted. Three spatial regimes are captured: Off‐Shelf, Eastern and Central Troughs. The on‐shelf profiles further show a separation between cold and warm modes. The variability is higher north of Burke Island and at the southern end of the Eastern Trough, which reflects the convergence of different mCDW pathways between the Eastern and the Central Trough. Finally, a clear but variable clockwise circulation is identified in Pine Island Bay. Plain Language Summary: The glaciers of West Antarctica are melting and could change sea level by about 30 cm or more by 2100. Pine Island and Thwaites Glaciers, both flowing into the Amundsen Sea, are currently retreating partly driven by warm water melting the glaciers from below. This water sits only a few degrees above freezing, but can still accelerate the melt and sea level rise. This warm water comes from the deeper Southern Ocean further north and travels through deep channels onto the shallower Amundsen Sea shelf following deeper troughs until reaching the glaciers further south. Understanding the pathways and the variability of this warm water on its way south is of high importance. Here, we use a machine learning method to identify different pathways from a large number of observations. Key Points: A machine learning Profile Classification Model is used to identify water column structures in the Amundsen Sea Embayment Two different regimes with warm and cold modes are identified in the Central and Eastern Troughs Areas with higher variability are highlighted, associated with convergence of pathways of warm waters