SIE and SST variability in the Southern Ocean

collaborators: Stephen Riser

Figure showing Southern Ocean sea surface temperature (SST) and sea ice extent (SIE) variability over the past four decades. (a) Time series of monthly SST anomalies in the Southern Ocean (south of 50S) for the 1982--2018 period. (b) Time series of monthly Antarctic SIE anomalies between 1980--2018. SST data were sourced from the NOAA Optimum Interpolation Sea Surface Temperature V2 dataset. Sea ice data were sourced from monthly mean sea ice concentration estimates from version 3 of the CDR (NASA Team Algorithm). Monthly anomalies were computed relative to a 1980--2015 climatology. Both time series were smoothed with a three-month running mean filter.

In stark contrast to the Arctic region, the Southern Ocean has experienced sea ice expansion and surface cooling over much of the past four decades. These decadal trends have been near-circumpolar in extent, with particularly intense cooling and ice growth occurring between 2000–2015. Following a four year period that featured record-breaking sea ice expansion, these trends came to an abrupt halt in late 2016 when Antarctic sea ice extent (SIE) plummeted to record low levels. The dramatic loss in sea ice cover was accompanied by an equally stunning increase in sea surface temperature (SST), which peaked in early 2017 and led to one of the warmest Southern Ocean summers on record. While SSTs across the Southern Ocean returned to normal within a few months, Antarctic SIE has yet to recover from the losses it incurred in 2016.

For the final chapter of my PhD thesis, I diagnosed the drivers that led to these abrupt changes in SIE and SST.

Publications: in prep

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Earle Wilson
Postdoctoral Scholar