The importance of the western Weddell Sea to Weddell Sea Deep Water formation

• Main Author: Rücker van Caspel, Mathias
• Other Authors: Kanzow, Torsten, Hellmer, Hartmut, Schröder, Michael, Timmermann, Ralph, Rhein, Monika
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universität Bremen 2016
• Subjects: Weddell Sea; Larsen Ice Shelf; dense water formation; Antarctic Bottom Water; 500; 500 Science; ddc:500; Antarctic; Weddell; South Scotia Ridge; Antarc*; Ice Shelf; Ice Shelves; Sea ice
• Online Access: https://media.suub.uni-bremen.de/handle/elib/1077; https://nbn-resolving.org/urn:nbn:de:gbv:46-00105356-16

The dense water flowing out from the Weddell Sea (WS), the Weddell Sea Deep Water (WSDW), significantly contributes to Antarctic Bottom Water (AABW) and plays an important role in the Meridional Overturning Circulation. However, the relative importance of the western Weddell Sea as a major source region remains unclear. Several studies hypothesized that the continental shelf off Larsen Ice Shelf (LIS) is important for deep and bottom water production, but the role of the Larsen Ice Shelf remains speculative. In this work the importance of the western WS including the LIS to the production of WSDW is investigated using in situ observations and results from numerical simulations. Measurements made during the Polarstern cruise ANT XXIX-3 (2013) in the northwestern WS add evidence to the importance of the western WS as a dense water source. An Optimum Multiparameter Analysis shows that the dense water found near the shelf break in front of the former Larsen A and B ice shelves, together with a very dense water observed off Larsen C Ice Shelf, increases the thickness and changes the _/S characteristics of WSDW that leaves the WS through gaps in the South Scotia Ridge to form AABW. A numerical experiment performed with the Finite Element Sea-ice Ocean Model (FESOM) was used to verify the hypothesis that the continental shelf of the western WS is important for dense water formation. The model results show the changes in the thermohaline properties of the WSDW flowing along the continental slope of the western WS, as well as an increase in the transport downstream. The variability along the continental slope can be explained by fluctuations of the large-scale circulation, namely theWeddell Gyre. In addition, there is no indication that dense waters are formed in the continental shelf of the western WS, and the exchanges between continental shelf and continental slope are small. These results suggest that the area is not important for WSDW formation as previously inferred from the sparse observations mainly along the ...