Reconstructing the Amundsen Sea Low from Remotely-Sensed Records of Annual West Antarctic Snow Accumulation

Observations over recent decades reveal rapid changes in ice shelves and fast-flowing grounded ice in West Antarctica. The rate of ice loss is modulated by upwelling of circumpolar deep water, which in turn is related to the regional wind pattern. The Amundsen Sea Low (ASL) is a primary non-zonal component of the circumpolar circulation and influences many aspects of West Antarctic climate including precipitation, temperature, and sea-ice extent. Here we show that using remotely-sensed histories of snow accumulation in West Antarctica allows significant reconstruction of the position and depth of the Amundsen Sea Low.

We use high-frequency airborne radar data (NASA Operation IceBridge) to infer annual accumulation rates from 2004 to 2014 at two sites in West Antarctica – the Ford Ranges (67S,140W) and Ellsworth Land (74S, 70W). In order to reconstruct the depth and position of the ASL, we use reanalysis (ERA-Interim) predictions of snowfall at these sites to develop a linear relationship with the sector and central pressure, latitude and longitude of the ASL index for the period 1979 to 2003, thus keeping the observations and statistical relationships independent. Using these linear relationships, the two remotely-sensed accumulation histories reconstructed 65% of the variance of the ASL sector pressure, 64% of the central pressure, 36% of the longitude, and 44% of the latitude.

These results indicate that histories of snow accumulation derived from ice-cores will allow useful reconstructions of the ASL beyond the satellite era. These records will provide important context for recent atmospheric, oceanic and ice-sheet changes. We are working to develop more and longer accumulation histories from the high-frequency airborne radar as well as more comprehensive techniques for reconstruction of atmospheric circulation including the ASL.