The transport of the Weddell Gyre across the Prime Meridian

Current-meter observations from instruments moored from 1996 to 2001 are used to determine the structure and the volume transport of the Weddell Gyre on the Greenwich Meridian. The record length mean volume transport is 45 Sv to the east within the northern and 56 Sv to the west within the southern limb of the Weddell Gyre. Thus I I Sv must leave the gyre circulation west of the Greenwich Meridian and enter it east of it. The deficit occurs with 8 Sv mainly in the Circumpolar Deep Water (CDW)/Warm Deep Water (WDW) layer. Surface waters and Weddell Sea Deep Water (WSDW) contribute 2 and 3 Sv, respectively. In contrast to this, 3 Sv more of Weddell Sea Bottom Water (WSBW) flow in the northern limb to the east, than in the southern limb to the west, which suggests a WSBW formation rate of about 3 Sv in the western Weddell Sea. In the Southern Boundary of the Antarctic Circumpolar Current (ACC) a volume transport of 35 +/- 16 Sv was found using geostrophic calculations adjusted with two measurements of the absolute velocity. The large heat content of the northern limb points to an extensive heat exchange between the Weddell Sea and the world ocean west of the Prime Meridian. Hence, the heat transport as well as the volume transport suggest that the water masses of the Weddell Gyre are not exclusively replaced in its eastern part, but that there is a significant exchange of water masses to the west of the Prime Meridian. (c) 2005 Elsevier Ltd. All rights reserved.