Two standard sections across the deep water channel separating the Faroese
Plateau from the Scottish continental shelf have been surveyed regularly si
nce the start of the 20th century. There have been significant changes in t
he characteristics of surface, intermediate and deep water masses during th
is period. At intermediate depths; the presence of Norwegian Sea Arctic Int
ermediate Water (NSAIW) was evident as a salinity minimum during the first
decade of the century. During the decades 1960-1980 this salinity minimum d
isappeared, and only four water types were identified in the Channel. Since
1980 the salinity of the intermediate water has again decreased, due to ch
anges in the atmospheric forcing over the Nordic Seas, and it is again evid
ent on a theta S curve as a distinct minimum. The salinity of the bottom wa
ter in the Channel has also decreased (0.01/decade) linearly since the mid-
1970s, although at a slower rate than the intermediate water (0.02/decade).
The decline in salinity of the bottom water cannot be accounted for by cha
nges in the salinity of upper Norwegian Sea Deep Water (NSDW), which Faroe
Shetland Channel Bottom Water (FSCBW) has traditionally been assumed to be
composed of. There is evidence that the upper level of NSDW has become deep
er outside the Channel owing to a reduced supply from the Greenland Sea. Th
is has resulted in a change in the composition of FSCBW, from being approxi
mately 60% NSDW during the period 1970-1985 to 40% NSDW since 1990. Thus, t
he thermohaline circulation of the Nordic Seas has lost its deep water conn
ection. The associated freshening of FSCBW has propagated out through the C
hannel into the North Atlantic and has resulted in a reduction of the salin
ity (0.02/decade) and transport (1-7%/decade) of Iceland Scotland Overflow
Water (ISOW) into the North Atlantic. (C) 1999 Elsevier Science Ltd. All ri
ghts reserved.