Variability and dynamics of along-shelf exchange in the west Antarctic Peninsula (wAP)

Xin Wang1, Carlos F Moffat1, Borja Aguiar-González1, Michael S Dinniman2, John Michael Klinck II3 and David Sutherland4, (1)University of Delaware, Newark, DE, United States, (2)Old Dominion University, Center for Coastal Physical Oceanography, Norfolk, VA, United States, (3)Old Dominion University, Center for Coastal Physical Oceanography, Norfolk, United States, (4)University of Oregon, Department of Earth Sciences, Eugene, OR, United States
Abstract:
The strong along-shelf temperature gradient in the west Antarctic Peninsula (wAP) shelf, between Bransfield Strait (BS) and the Central wAP (CwAP), is thought to be a key control on the spatial pattern of glacier retreat along the coast. However, the variability and dynamics of exchange that sustain this thermal gradient are poorly understood. Here, we investigate the exchange along the wAP shelf using both a state-of-the-art numerical model and available hydrographic data. The ROMS setup includes a 1.5 km horizontal resolution grid and coupled with a dynamic sea ice model, including the sea ice dynamics and thermodynamics.

The analysis of a 2-year run (2009-2010) reveals a pronounced seasonal cycle of along-shelf exchange in the BS-CwAP system, modulated by the interplay between cold Weddell-sourced water inflow around BS and modified Circumpolar Deep Water (mCDW)from CwAP. In winter/spring, there is a net flux of cold BS water towards the CwAP. This largely reverses in summer/fall, with a net flow of warm water towards BS from the CwAP. The exchange occurs in the form of narrow, bottom-trapped buoyant currents forced in several gaps between islands separating BS and the CwAP. The seasonal variation of the along-shelf exchange seems to be driven by the wind forcing modulating the inflow of Weddell water into BS. The model results are consistent with several key observed features in the hydrographic structure.

Our results suggest a fairly dynamic thermal gradient along the wAP, with the cold/warm boundary moving about 300 km along the coast throughout the year, and narrow cold/warm intrusions extending far from one basin to the other. The implications for our understanding of glacier retreat along the wAP shelf are discussed.