P06 The Southern Ocean: where Ocean, Ice and Atmosphere Meet

IAPSO (Physical Oceanography)

30-Jun-2015, 08:30 - 10:00

Abstract content:

Zonal variability of the Southern Ocean heat budget

The three-dimensional structure of the upper cell of the Southern Ocean overturning circulation depends on the effects of topography and the spatial variability of surface forcing, both wind and air-sea heat and freshwater fluxes. Air-sea heat flux products and adjusted air-sea heat flux from the data assimilating state estimate show a strong zonal dipole of ocean heat gain in the Indian and Atlantic sectors and ocean cooling in the Pacific sector of the Southern Ocean. The spatial variability of the upper ocean heat budget in the Antarctic Circumpolar Current is investigated using a high resolution Southern Ocean state estimate for the years 2005-2010. The time-mean heat budget solution in the Atlantic/Indian is primarily a balance between ocean heat gain is and cooling by divergence of Ekman transport driven by westerly winds. In the Pacific sector where air-sea heat fluxes are mostly negative and Ekman transport is also cooling, this is balanced by warming from divergence of geostrophic advection which is more similar to the heat balance found in western boundary current regions. Vertical advection of heat is important locally and vertical eddy advection is particularly important for warming the upper ocean in regions downstream of major topographic features. The results support that topographic steering and zonal asymmetry in surface forcing lead to substantial zonal asymmetries in upper ocean dynamics. This spatial variability in the heat budget is important for explaining spatial patterns in observed multi-decadal upper ocean heat content trends, which are likely caused by changes in ocean circulation due to anthropogenic heat uptake.

V. Tamsitt1, L. Talley1, M. Mazloff1.
1University of California San Diego, Scripps Institution of Oceanography, La Jolla, USA.


Southern Ocean     Heat Budget     Air-sea fluxes     Antarctic Circumpolar Current     Eddies     Heat uptake     state estimation     spatial variability