Frontal movements and property fluxes: Contributions to heat and freshwater trends in the Southern Ocean

• Published in: Journal of Geophysical Research
• Main Authors: Meijers, AJS, Bindoff, NL, Rintoul, SR
• Format: Article in Journal/Newspaper
• Language: English
• Published: Amer Geophysical Union 2011
• Subjects: Earth Sciences; Oceanography; Physical Oceanography; Antarctic; Southern Ocean; The Antarctic; Antarc*
• Online Access: https://doi.org/10.1029/2010JC006832; http://ecite.utas.edu.au/76877

We examine the synoptic variability of temperature and salinity in the Southern Oceanusing a static gravest empirical mode (GEM) mapping based on historical hydrographyand a time]evolving projection of the GEM created using satellite altimetry (satGEM).The GEM and satGEM projections allow the separation of observed trends into acomponent due to a shift of the circumpolar fronts (adiabatic) using the satGEM and acomponent due to changes in water masses (diabatic) expressed as a temporal trend inresidual between historical hydrography and the static GEM. The mean southwardmovement of the Antarctic Circumpolar Current (ACC) fronts drives an adiabatic warmingof 1.196 } 0.090 W m−2 distributed over most of the ACC and at all depths. This isstrongest where the meridional temperature gradient is largest, such as in the upper1000 dbar of the Subantarctic Front (SAF). There is a weak adiabatic freshening of 6.57 }0.18 mm yr−1 m−2, concentrated mainly below the Antarctic Intermediate Water and southof the SAF. Residuals between historical hydrography and the static GEM field, drivenby diabatic changes in the water mass structure, have temporal trends in temperatureand salinity. When these trends are integrated over the whole ACC there is a net cooling of−0.628 } 0.129 W m−2 and strong freshening of 30.27 } 0.70 mm yr−1 m−2. By combiningthe diabatic and adiabatic components and integrating over the ACC the net increase in heatand freshwater in the region is 0.570 } 0.099 W m−2 and 36.91 } 0.72 mm yr−1 m−2,respectively. The sum of the adiabatic and diabatic changes are consistent with previoustrends inferred from observations.