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Abyssal connections of Antarctic Bottom Water in a Southern Ocean State Estimate

Erik van Sebille, Paul Spence, Matthew Mazloff, Matthew England, Stephen Rintoul and Oleg Saenko
In Geophysical Research Letters, 2013, volume 40, pages 2177-2182 doi:10.1002/grl.50483.

Abstract

Antarctic Bottom Water (AABW) is formed in a few locations around the Antarctic continent, each source with distinct temperature and salinity. After formation, the different AABW varieties cross the Southern Ocean and flow into the subtropical abyssal basins. It is shown here, using the analysis of Lagrangian trajectories within the Southern Ocean State Estimate (SOSE) model, that the pathways of the different sources of AABW have to a large extent amalgamated into one pathway by the time it reaches 31S in the deep subtropical basins. The Antarctic Circumpolar Current appears to play an important role in the amalgamation, as 70% of the AABW completes at least one circumpolar loop before reaching the subtropical basins. This amalgamation of AABW pathways suggests that on decadal to centennial time scales, changes to properties and formation rates in any of the AABW source regions will be conveyed to all three subtropical abyssal basins.

Movie



Movie showing the pathways of the particles in SOSE that form AABW, colour coded for depth (see colorer). The time after formation is shown in the title

Key figure

AABW connectivity

Figure 3: a) The connectivity between the four formation regions and the three subtropical ocean basins as diagnosed from the Lagrangian particles on top of the bathymetry of the SOSE model in blue shading. The legends on the bottom show the percentage of particles that forms (right legend) and ends (left legend) on each of the sections, color-coded on the map. The pie charts (the surface of which is scaled to the proportion of particles in that region) show for each of the four formation regions in which subtropical basins (green) the particles end; and for each of the three end sections in which of the four formation regions (red) the particles form. This analysis suggests that the outflow distributions on the different formation and end sections are relatively similar, indicating a merging of bottom water types within the Southern Ocean. (b) The time it takes the particles to reach the abyssal ocean at 31°S from their formation region, color-coded for the source regions. Most particles reach 31S within 100 years. (c) The number of circumpolar loops made by the particles before they reach 31S, also color-coded for the source regions. Most particles perform at least one circumpolar loop.