On the export of dense water from the Weddell and Ross Seas

Abstract

We describe the seasonal and interannual variability of volume transports in Weddell and Ross Seas using the 1/12◦20-yr simulation of the OCCAM global ocean general circulation model. The average simulated full-depth cumulative volume transports were 28.5±2.9 Sv (1 Sv ≡ 106 m3s−15) and 13.4±5.2 Sv, across the main export regions of the Weddell and Ross Seas, respectively. The values of mean outflow of Antarctic Bottom Water (AABW) (defined by neutral density γ n≥ 28.27 kg m−3) from the Weddell and Ross Seas of 10.6±3.1 Sv and 0.5±0.7 Sv, respectively, agree with the range reported in historical observational studies. Variability in AABW export is predominantly at periods of ∼ 1 yr and 2–4 yr. The transit time taken by AABW sourced in the Southern Weddell Sea to reach the main Weddell export zone is ∼ 2 yr. Lagged correlation between the thermohaline properties of AABW source waters and AABW export indicates that recent shelf waters freshening trends are likely related to changes in the AABW outflow rates.