LONG-TERM TRENDS OF TEMPERATURE, SALINITY, DENSITY, AND TRANSIENT TRACERS IN THE CENTRAL GREENLAND SEA

We present long-term observations of temperature, salinity, tritium/He -3, chlorofluorocarbon-11 (CFC11), and chlorofluorocarbon-12 (CFC 12) for the central Greenland Gyre. The time series span the periods betwe en 1952 and 1994 (temperature), 1981 and 1994 (salinity), 1972 and 199 4 (tritium/He-3), and 1982 and 1994 (CFCs). The correlation between hy drographic and transient tracer data indicates that low temperatures i n the deep water in the early 1950s and between 1960 and 1980 reflect periods of higher deep water formation rates whereas periods of increa sing temperatures in the late 1950s and between 1980 and 1994 are rela ted to low deep water formation rates. However, the transient tracer o bservations obtained in the 1980s and early 1990s indicate that even d uring periods of low deep water formation, some water from the upper w ater column contributed to deep water formation between 1980 and 1994. In 1994, the deep water reached temperatures and salinities of -1.149 degrees C and 34.899, respectively, and no longer fits most of the cl assical definitions of Greenland Sea Deep Water (-1.29 degrees C < The ta < -1.0 degrees C, 34.58 < S < 34.90). The temperature increase in t he water column between 200 and 2000m depth between 1980 and 1994 corr esponds to an average heating rate of about 5 W m(-2) over this period , resulting in a decrease in density. The 13-year warming could be bal anced by intensive cooling in two winters. The surface salinity steadi ly increased from 34.50 in 1991 to 34.85 in 1994.