Decadal Changes In Deep Water Properties In The Northwest North Atlantic

No abstracts are to be cited without prior reference to the author.

Denmark Strait Overflow Water (DSOW), the densest component of the deep waters of the North Atlantic, originates in the Greenland Sea and is exported to the North Atlantic through Denmark Strait. DSOW is transported along the deep western boundary and fills the bottommost layers of the Labrador Sea and Newfoundland Basin. Long-term changes in air-sea interaction cause changes in the North Atlantic thermohaline circulation and are accompanied by changes in the formation and export of DSOW. These changes influence the circulation and water properties of the deep waters throughout the western North Atlantic. This paper summarises the spatial and temporal patterns of changes in DSOW properties in the Labrador Sea based on historical and recent observations covering the past four decades. For the period studied, the salinity and temperature of the DSOW layer in the deep Labrador Sea achieved their maximum values in the rnid-1960's. A subsequent freshening and cooling by approximately 0.02 psu and 0.2° C led to relative minimum values in the early and mid-1980's. A recovery to more saline and warmer values was noted in the late l 980's. The l 990's witnessed a second period of freshening and cooling that produced record low temperatures in 1996. Annual transects of the Labrador Sea carried out since 1990 allow a closer study of the changes during the past decade. This part of the record reveals noticeable year-to-year variations in addition to the noted trends.