Decadal warming of the coldest Antarctic Bottom Water flow through the Vema Channel

Abstract

A decadal warming trend of Antarctic Bottom Water flowing through the Vema Channel is reanalyzed. Our data base consists of 94 high precision, full depth stations from 19 visits to the Vema Sill plus twelve stopovers at two additional key locations. Originally a long-term temperature increase in the near-bottom jet was noted from 1992 onward, after a period of rather constant abyssal temperatures since 1972. From today's perspective the apparent stagnant temperature level until 1991 can be interpreted as a period of feeble rising in comparison with a perspicuous warming trend of 2.8 mK yr-1 in the following 15 years. However, the clearly manifested temperature rise is superimposed with fluctuations. For the first time the available time series appears long enough to indicate an associated slight freshening of the bottom water. An attempt is made to trace the observed variability back to its source region in the Weddell Sea. Copyright 2007 by the American Geophysical Union.