Seasonal and Interannual variability in Surface Temperature and Salinity across the ACC in the Drake Passage from 2002 to 2014

The Southern Ocean is particularly sensitive to climate change, responding to winds that have increased and shifted over the past several decades and significant warming in the core of the Antarctic Circumpolar Current (ACC). Predicting the response of the Southern Ocean to climate change requires a better understanding of changes in the ACC fronts and water masses. Seasonal and interannual variability in temperature, salinity and winds across the ACC in the Drake Passage are investigated using repeat underway transects of thermosalinograph data taken from the U.S. polar supply vessel, the ASRV L.M. Gould between 2002 and 2014. Temperature and salinity have strong seasonal cycles characterized by a distinct warming/freshening in the austral summer (DJFM). A comparatively weak summer/winter cycle is found in wind magnitude and direction. The location of the Polar Front is identified in each individual transect using a strongest gradient method in both temperature and salinity. The Polar Front location is relatively constant in latitude throughout the year. Interannual anomalies in salinity, temperature and wind across the Drake Passage are tested for temporally lagged correlations with two major climatemodes, the Southern Annular Mode and the El Nino/Southern Oscillation. The strongest significant correlations were less than 0.5, and occurred at varying temporal lags. Finally, the long term temporal trends in salinity and temperature are explored for individual latitude bands across the Drake Passage. The southernmost latitudes demonstrate a freshening and a warming, while the northernmost latitudes are characterized by an increase in salinity and a cooling.