Antarctic Station Based Pressure Variations during the 20th Century

A key component in understanding climate variations across Antarctica, whether from the Southern Annular Mode (SAM) or from tropical teleconnections, is understanding changes in the atmospheric circulation. Normally depicted as changes in advection patterns, these circulation changes are routinely inferred from variations (anomalies) in the surface and/or mean sea level pressure patterns. In this vein, recent studies demonstrate that (a) changes in the atmospheric circulation due to tropical forcing are an important player in temperature variations in West Antarctica and the Antarctic Peninsula and (b) temperature trends across the Antarctic Peninsula are reversing despite no significant changes in the sign/magnitude of the SAM. Together these conclusions suggest that climate variations across Antarctica are quite complicated and many forcing mechanisms need to be considered, especially to detect and attribute trends and decadal scale variability. Yet, as with much of Antarctic data, researchers are left with neither long-term point (station) measurements of pressure variations across Antarctica, nor gridded pressure data from reanalyses or models that can be deemed reliable, given very little in situ data to constrain the solution across the high southern latitudes. This talk presents station-based reconstructions of 17 Antarctic manned stations by seasons. We employ principal component regression using midlatitude pressure observations as predictors individually for each Antarctic station. We are able to reconstruct the austral summer and winter pressure back until 1905 with fairly high skill, and modest skill in austral spring and autumn. The reconstruction skill along the Antarctic Peninsula is considerably higher in all seasons. A few reconstructions are used to place the recent atmospheric circulation changes in a longer historical context, thereby highlighting the uniqueness of these recent changes. Future work includes conducting a spatial Antarctic-wide pressure reconstruction back until 1905.