On the role of the Antarctic Slope Front on the occurrence of the Weddell Sea polynya under climate change
听
Student Seminar Series
Department of Atmospheric & Oceanic Sciences
presents
a talk by
Joe Lockwood
MSc student
On the role of the Antarctic Slope Front on the occurrence of the Weddell Sea polynya under climate change
Polynyas, which are large holes in sea ice, are believed to have a significant impact on the climate through feedback with the atmosphere and modification of the global ocean circulation. A study by de Lavergne et al. (2014) found that CMIP5 models predict a slow down or even cessation of these events into the future due to ocean freshening. Here we revisit the conclusion of a cessation of the Weddell Sea Polynya (WSP) under climate change. We hypothesis that, because of their relatively coarse resolutions in the ocean, CMIP5 models are unable to capture important processes involved in the formation of the polynyas and in their response to climate change. To investigate that hypothesis, we use pre-industrial control and 1%CO2 rise/year simulations of the high resolution GFDL CM2.6 and of the CMIP5 models that form polynyas in the Weddell Sea to investigate the response of the polynya to climate change. We find that, under climate change, CM2.6 forms WSP at the same time and with the same duration as under preindustrial forcing. In contrast, the CMIP5 models show either a cessation or slowdown of these events under climate change due to open ocean surface freshening. Furthermore, we find that CMIP5 models cannot accurately capture the shelf Antarctic Slope Current and Antarctic Slope Front, which when resolved in CM2.6, constrains freshening driven by sea ice melt and enhanced runoff to remain on the shelf region. Open ocean stratification is then enhanced by freshening in CMIP5 models, resulting in a slowdown of these WSP events. These results point to the need to improve simulations of shelf ocean circulation used in climate change projections.