Eddy/tidal Water Mass Transformation and Transport in the Weddell Sea

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

The Weddell Sea supports a range of processes that are critical to the Antarctic and global-scale ocean circulation and to climate. Warm Deep Water (WDW), found offshore at mid-depth, makes incursions up onto the continental shelf that have the potential to drive rapid retreat of the Filchner-Ronne ice shelf. A modified form of WDW mixes with High Salinity Shelf Water produced in coastal polynyas, and with Ice Shelf water produced by basal melting of marine-terminating glaciers produces Antarctic Bottom Water (AABW). The net export of AABW ventilates around 50% of the subsurface ocean, and globally stores around 30 times as much carbon as the atmosphere. Thus the significant observed warming and freshening of AABW over the past few decades may indicate a rearrangement of the Antarctic circulation, with implications for long-term changes in deep-ocean oxygen concentration, atmospheric carbon dioxide concentration, and rises in sea level that are yet to be quantified. This project is using high performance numerical simulation (high-res MIT Global Circulation Model) to evaluate the relative roles of tides and eddies in the series of water mass transformation that leads to ABW production. Turbulent features such as mesoscale and sub-mesoscale features (sometimes called ?ocean weather?) are small, making their spatial and temporal representation in models computationally intensive. Key questions being asked are the role of mesoscale eddies in transporting circumpolar Warm Deep Water up onto the continental shelves where they give up their heat, and in export of AABW into the deep central Weddell Gyre. Mesoscale, submesoscale and tidal eddies are known to be critical to understanding AABW water mass transformation, and to the broader Southern Ocean circulation. Changes or rearrangements in Antarctic oceanic circulation features in turn may have implications for the uptake of excess CO2 and heat into the oceans, stability of the Antarctic ice shelves, and sea level-rise. The project will provide a post-doctoral research position and help commence the career of an early career faculty member. Regional model velocity and property fields will be made available to the wider scientific community for the purpose of planning observational campaigns, and in order to foster future collaborations to investigate biogeochemical tracer transport and atmosphere-ocean exchange around the Antarctic continental margins