The Southern Ocean plays a key role in the global-scale distribution and redistribution of heat, and in the planet's hydrological cycle1,2. Observations suggest that changes in the global water cycle may already be apparent (e.g.,3). The stratification of the Southern Ocean is delicately poised and particularly sensitive to changes in the freshwater balance4. Substantial uncertainty remains with regard to the high-latitude contributions to the global heat and water cycles, their sensitivities to climate change and variability, and their impacts.
For more detailed information on the science rationale behind Theme 1 please download the SOOS Initial Science and Implementation Strategy.
Freshwater fluxes from melting sea ice, sub-ice shelf melting and precipitation are of the same order of magnitude in the Southern Ocean, and all three components need to be measured. Concurrently, sustained measurements of the exchange of heat across the ocean-atmosphere boundary are required, including in ice-influenced regions, and the redistribution of this heat by ocean circulation. Variables that need to be measured include atmospheric circulation (winds, storms, evaporation, precipitation, moisture flux); temperature and heat fluxes; the horizontal and vertical circulation of the ocean, including beneath the sea ice, through the annual cycle; sea-ice extent, thickness and distribution; and the contribution of glacial ice(ice shelf melt and iceberg production). New satellites promise synoptic observations of aspects of the heat and freshwater balances, including snow and ice thickness, that cannot be measured at high spatial or temporal resolution using conventional means, but these new sensors are in critical need of data sets for validation.
CTD in the Southern Ocean. Photo: Paul Holland BAS