The upwelling of warm Circumpolar Deep Water is a key process in the global climate system, transporting heat, nutrients, and carbon poleward towards Antarctic ice shelves.
Dr Ali Mashayek and colleagues from the Scripps Institution of Oceanography and UC San Diego have recently co-authored a paper published in Communications Earth & Environment, in which physical and chemical seawater properties from repeat ship-based observations are used to classify Southern Ocean water masses and show changes in warm water abundance south of the Antarctic Circumpolar Current over the past two decades. A random forest model ensemble is then trained to extend this classification to a monthly gridded Argo climatology beginning in 2004, enabling further decomposition of the spatial and temporal variability of the signal.
Both analyses reveal an increase in upper-2000 m warm water thickness near the continent, consistent with a circumpolar-mean poleward redistribution of the upper Circumpolar Deep Water core of 1.26 km yr−1 (95% CI: 0.53–1.98). Together, these shifts suggest enhanced heat flux towards the Antarctic shelf, with implications for basal ice shelf melting and sea-level rise.