On the circulation and water masses over the Antarctic continental slope and rise between 80 and 150°E

Abstract

The circulation and water masses in the region between 80 and 150°E and from the Antarctic continental shelf to the Southern Boundary of the Antarctic Circumpolar Current (ACC) (∼62°S) are described from hydrographic and surface drifter data taken as part of the multi-disciplinary experiment, Baseline Research Oceanography Krill and the Environment (BROKE). Two types of bottom water are identified, Adelie Land Bottom Water, formed locally between 140 and 150°E, and Ross Sea Bottom Water. Ross Sea Bottom Water is found only at 150°E, whereas Adelie Land Bottom Water is found throughout the survey region. The bottom water mass properties become progressively warmer and saltier to the west, suggesting a westward flow. All of the eight meridional CTD sections show an Antarctic Slope Front of varying strength and position with respect to the shelf break. In the water formation areas (between 140 and 150°E) and 104°E, the Antarctic Slope Front is more “V” shaped, while elsewhere it is one-sided. The shape of the slope front, and the presence or absence of water formation there, are consistent with other meridional sections in the Weddel Sea and simple theories of bottom-water formation (Gill, 1973. Deep-Sea Research 20, 111–140; Whitworth et al., 1998. In: Jacobs and Weiss (Eds.), Ocean, Ice and Atmosphere: Interactions at the Antartic Continental Margin, Antarctic Research Series. American Geophysical Union, Washington, pp. (1−27). ADCP surface velocities and buoy drift tracks show a strong westward flow over the shelf and slope regions. In the region 90–100°E there is a strong eastward flow of the waters just south of the Southern Boundary of the ACC, suggesting a recirculation of the westward slope current and the presence of a weak cyclonic gyre. Using the ADCP velocities as a reference for the CTD data, the average westward transport in this region is 29.4±14.7 Sv.