Long-term hydrographic changes at 52 and 66¡W in the North Atlantic Subtropical Gyre & Caribbean

In July—September 1997 two hydrographic lines were done in the western N. Atlantic along longitudes of 52 and 66¡W as part of the WOCE one-time hydrographic survey of the oceans. Each of these two lines approximately repeated earlier ones done during the International Geophysical Year(s) (IGY) and the mid-1980s. Because of this repeated sampling, long-term hydrographic changes in the water masses can be examined. In this report, we focus on temperature and salinity changes within the subtropical gyre mainly between latitudes of 20 and 35¡N and compare our results to those presented by Bryden et al. (1996), who examined changes along a zonal line at 24¡N, most recently occupied in 1992. Since this most recent 24¡N section in 1992, substantial changes have occurred in the western part of the subtropical gyre at the depths of the Labrador Sea Water (LSW). In particular, we see clear evidence for colder, fresher Labrador Sea Water throughout the gyre on our two recent sections that was not yet present in 1992 at similar longitudes along 24¡N. At shallower depths inhabited by waters that are an admixture of Mediterranean (MW) and Antarctic Intermediate Waters (AAIW), our recent survey shows an increase in salinity, which can only be attributed to changes in wate