The Ekman Streamfunction: a wind-derived metric to quantify the Southern
Ocean overturning circulation
Abstract
We introduce a novel wind-derived metric to quantify variability in the
Southern Ocean overturning circulation. This metric, which we call the
Ekman streamfunction, integrates the Ekman pumping vertical velocity
zonally and northwards from the Antarctic coastline to a given latitude.
To evaluate the relationship between the Ekman streamfunction and
Southern Ocean overturning circulation, we use a global 0.1
ocean–sea-ice model driven with interannual forcing (1958-2018).
Throughout much of the Southern Ocean, strong correlations
(r>0.9) exist between the Ekman streamfunction and the
Southern Ocean overturning circulation on monthly and annual timescales.
A regression analysis identifies regions where Ekman streamfunction
variability coincides with >4Sv changes in the overturning;
one such location is where the wind stress curl changes sign and the
Ekman pumping velocity is highly variable. This study offers a new
approach to infer recent changes in the Southern Ocean overturning
circulation from existing datasets of wind stress.