Wind-driven export of Weddell Sea slope water

• Main Authors: Meijers AJS, Meredith MP, Abrahamsen EP, Morales Maqueda MA, Jones DC, Naveira Garabato AC
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Wiley-Blackwell
• Subjects: Antarctic; Antarctic Peninsula; South Scotia Ridge; The Antarctic; Weddell; Weddell Sea; Antarc*
• Online Access: https://eprint.ncl.ac.uk/fulltext.aspx?url=228600/9A07D0DB-8F40-410B-BDEE-4E895BE839AF.pdf&pub_id=228600

The export of waters from the Weddell Gyre to lower latitudes is an integral component of the southern subpolar contribution to the three-dimensional oceanic circulation. Here, we use more than 20 years of repeat hydrographic data on the continental slope on the northern tip of the Antarctic Peninsula and five years of bottom lander data on the slope at 1000 m to show the intermittent presence of a relatively cold, fresh westward-flowing current. This is often bottom intensified between 600-2000 dbar with velocities of over 20 cms −1 , transporting an average of 1.5±1.5 Sv. By comparison with hydrography on the continental slope within the Weddell Sea and modelled tracer release experiments we show that this slope current is an extension of the Antarctic Slope Current that has crossed the South Scotia Ridge west of Orkney Plateau. On monthly to interannual timescales the density of the slope current is negatively correlated ( r >0.6 with a significance of over 95%) with eastward wind stress over the northern Weddell Sea, but lagging it by 6-13 months. This relationship holds in both the high temporal resolution bottom lander time series and the 20+ year annual hydrographic occupations and agrees with Weddell Sea export variability observed further east. We compare several alternative hypotheses for this wind-stress/export relationship and find that it is most consistent with wind-driven acceleration of the gyre boundary current, possibly modulated by eddy dynamics, and represents a mechanism by which climatic perturbations can be rapidly transmitted as fluctuations in the supply of intermediate-level waters to lower latitudes.