Antarctic climate: ocean fluxes and variability

Abstract

The Southern Ocean plays a major role in the global overturning circulation, providing
an important route for the return flow of deep water subducted in the North Atlantic.
The World Ocean Circulation Experiment (WOCE) provided an unprecedented picture
of the state of the world’s oceans and set new standards for high quality in-situ
hydrographic data. This study combines the existing WOCE data set with new
hydrographic sections, and output from global and regional ocean models to examine
the mean state of the Southern Ocean circulation and the balance of fluxes around the
Antarctic Circumpolar current.

A historical data set in the region of Drake Passage is examined to study the large-scale
water mass variability between 1926-2005. The water mass properties of the Lower
Circumpolar Deep Water is constant within error bounds throughout the data set. A
warming and freshening signal in the surface waters from 1997-2005 to the north of the
Sub-Antarctic Front along SR01b is also presented.

The major part of this work is based around an inverse study of the Southern Ocean that
combines the WOCE data-set with contemporary sections, and other forcing fields to
examine the balance of fluxes throughout the Southern Ocean. The study examines the
effect of different parameterisations of the dianeutral mixing in the Southern Ocean, in
light of the differing views of localised deep turbulent mixing from observations, and an
adiabatic ocean interior from residual mean studies, The freshwater balance in the
model is presented and its implications on the water mass formation and transformation
of the upper and lower cells of the overturning circulation is discussed in detail.

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Identifiers

ORCID for Eelco Rohling: orcid.org/0000-0001-5349-2158

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