Southern ACC Front to the northeast of South Georgia: Pathways, characteristics, and fluxes

Abstract

In December 2000 we conducted high‐resolution hydrographic and towed undulator transects across the South Georgia shelf and into the deep waters of the Georgia Basin. The Southern Antarctic Circumpolar Current Front (SACCF) was observed flowing northwestward close to the base of the slope at 53.7°S, with a second manifestation around 53.4°S having flow in the reverse direction. Both crossings had a significant barotropic component aligned with the flow. The region of the SACCF was characterized by large‐scale undulations of properties on horizontal scales of 5–10 km, similar to the local internal Rossby radius. We observe a distinct surface temperature gradient associated with the SACCF in the vicinity of South Georgia and demonstrate the usefulness of this by tracing the course of the front around the island with advanced very high resolution radiometer data. A distinct northward deflection of the front to the north of South Georgia is probably due to topographic steering by the North Georgia Rise. The signature of the SACCF is pronounced in the Circumpolar Deep Water, with strong isopycnal interleaving indicative of cross‐frontal mixing. The salinity of the Weddell Sea Deep Water is marginally higher between the two manifestations of the SACCF, reflecting the different pathways from its source regions in the Weddell Sea. Remarkably strong vertical gradients of potential temperature and salinity exist in the bottom 100 m of the water column (at depths of around 3500 m) because of the vertical juxtaposition of waters that have taken different routes around the Northeast Georgia Rise.

Transport of Antarctic krill (Euphausia superba) across the Scotia Sea. Part I: Circulation and particle tracking simulations

“…Fig. 1), that seems to be an important mechanism in steering the SACCF to the north of South Georgia before it turns eastward (Meredith et al, 2003). However, the general early eastward turn of the SACCF agrees with more recent studies that have not observed the SACCF in the previously reported location from Orsi et al (1993).…”

“…Trathan et al (2000) did not find evidence of the SACCF, but found the Polar Front in this region and concluded the potential for great variability in this region. Observations and modeling studies in this area have shown the importance of eddyshedding off the SACCF (Thorpe et al, 2002;Meredith et al, 2003) and the high variability of the front itself.…”

Control of sedimentation by active tectonics, glaciation and contourite-depositing currents in Endurance Basin, South Georgia

“…Situated between the Polar Front (PF) and the Southern Antarctic Circumpolar Current Front (SACCF) (Meredith et al, 2003), the proximal basins south of South Georgia represent an ideal and under-utilised location to investigate the palaeoflow of the ACC (Figure 1.B). This current transports >100 Sv eastwards and the deep water components exported from the Southern Ocean ventilate the majority of the world's oceans; it is, therefore, a key component of the global thermohaline system (Orsi et al, 1995;Orsi et al, 1999;Gebbie and Huybers, 2011).…”

Physical and behavioural influences on larval fish retention: contrasting patterns in two Antarctic fishes

“…The island is separated from the surrounding deep ocean by a shelf of about 50 to 150 km width, with an average depth of about 200 m. To the west of South Georgia, and separated by a deep channel of about 1500 m depth, is Shag Rocks, a further shallow plateau with several rocky outcrops. South Georgia and Shag Rocks lie in the path of the Antarctic Circumpolar Current (ACC), with the Polar Front (PF) lying to the north, and the Southern ACC Front (SACCF) looping anticyclonically around South Georgia from the south before retroflecting to the east (Orsi et al 1995, Thorpe et al 2002, Meredith et al 2003b. Despite its location within the ACC, the shelf waters adjacent to South Georgia often show properties that are markedly different from the open ocean waters beyond, indicating that cross-shelf-break transport can be restricted (Brandon et al 1999, Meredith et al 2005.…”