MONITORING STRATIFICATION AND CURRENTS AT THE CONTINENTAL SLOPE OF THE SCOTIA SEA, ANTARCTICA

• Other Authors: Chapman, Piers, Orsi, Alejandro H
• Format: Thesis
• Language: unknown
• Published: 2013
• Subjects: Antarctic Circumpolar Current; Antarctic Slope Current; Southern Ocean; Scotia Sea; South Scotia Ridge; Antarctic; The Antarctic; Weddell Sea; Weddell; Antarc*; Antarctica; International Polar Year
• Online Access: http://hdl.handle.net/1969.1/ETD-TAMU-2011-05-9699; http://hdl.handle.net/1969.1/148803

The most notable mixing that takes place in the Southern Ocean exists when the Antarctic Circumpolar Current (ACC) encounters abrupt changes in the ocean floor topography. Therefore, the spatial and vertical distribution of mixing in the southern Scotia Sea is fundamental to fully understanding the rapid ventilation of the Circumpolar Deep Water (CDW) in an area where the ACC readily interacts with the Antarctic Slope Current (ASC). The objective of this study is to describe the dramatic freshening and cooling of CDW at the northern flank of the South Scotia Ridge (SSR) near 53?W, a study area during the ACROSS program of the International Polar Year. It is aimed at understanding how the deep ocean is more directly ventilated along intermediate density layers, which can rapidly transmit climate-related changes observed in the colder Antarctic slope waters to the rest of the world deep ocean. Two ACROSS moorings (M1 and M2) were deployed in February 2009 at the slope of the SSR near 53?W to directly measure velocity and physical properties at the ASC. M1 was located at 600 m water depths, and M2 at 1800 m, with a total of nine current meters and fourteen Temperature-Conductivity-Pressure recorders set approximately 100-200 m apart from each other on the line. All instruments were recovered in January 2010. The major water masses found within the study area are: Antarctic Surface Water, modified CDW, and deep and bottom waters. The record-length mean velocity field is dominated by a strong (> 20 cm s-1) southwestward current at the upper slope, the ASC. Intrusions of the ACC are evident throughout the record. When the ACC impinges on the SSR, slope-modified CDW is formed by the local mixing between ventilated slope water from the Weddell Sea and Bransfield Straits and CDW from the Scotia Sea. Outflow of MCDW to the abyssal Scotia Sea is facilitated by energetic frontal interactions with the SSR. The associated intermediate-depth export of slope waters by this active mechanism is relevant to the Meridional Overturning Circulation, thus it contributes to the large-scale redistribution of ocean heat that couples Antarctic convention to global climate.