Publication Date:
2023-06-15
Description:
The hydrological cycle is expected to intensify in a warming climate. However, observational evidence of such changes in the Southern Ocean is difficult to obtain due to sparse measurements and a complex superposition of changes in precipitation, sea ice, and glacial meltwater. To unravel these signals, we leverage a unique dataset of salinity and seawater oxygen isotope (δ〈sup〉18〈/sup〉O) observations collected in the Indian sector of the Southern Ocean. Much of the surface south (north) of 46°S experienced a freshening (salinification) associated with decreases (increases) in δ〈sup〉18〈/sup〉O between 1993 and 2021. Many processes have been proposed to explain surface salinity changes, including intensified freshwater fluxes from the atmosphere or increased glacial meltwater or from intensification of sea ice freshwater transport. However, the contribution of each mechanism that led to observed changes of the Southern Ocean surface waters, remains unclear. Here, we argue that the atmospheric water cycle has intensified in Indian sector of the Southern Ocean between 1993 and 2021, increasing the salinity in subtropical surface waters by 0.06 g kg〈sup〉-1〈/sup〉 per decade, and decreasing it in subpolar surface waters by -0.02 g kg〈sup〉-1〈/sup〉 per decade. In the subpolar region, this salinity decrease is countered by a salinity increase of 0.008 g kg〈sup〉-1〈/sup〉 per decade from reduced sea ice melt, and enhanced by a salinity decrease of -0.005 g kg〈sup〉-1〈/sup〉 per decade from increased glacial melt. These changes extend the growing evidence for an acceleration of the atmospheric water cycle and a melting cryosphere that is expected from global warming.
Language:
English
Type:
info:eu-repo/semantics/conferenceObject
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