Fróðskaparrit - 01.01.1998, Page 158

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CHANGES IN ATLANTIC WATER INFLOW INTO THE NORDIC SEAS
the three flow branches (NIIC, FC and SC
on Figure 1) have different origins, differ-
ent properties (e.g. temperature) and to
some extent they also deliver these proper-
ties to different areas northeast of the ridge.
The westernmost branches (NIIC and FC)
derive from the open Atlantic Ocean and
are colder and less saline than the eastern-
most branch (SC) which has a more conti-
nental component. After crossing the ridge,
the westernmost branches affect the south-
eastern parts of the Nordic Seas most di-
rectly while the Shetland Current (SC)
probably has a larger effect on the North
Sea and the Barents Sea.
Much effort has gone into establishing
quantitative estimates of the Atlantic water
flux across the ridge, but only with the de-
velopment of modern current measuring in-
strumentation has this been possible and a
quantitative flux budget may now be pre-
sented (Fig. 2) although it is still prelimi-
nary. It appears that the total exchange bud-
get is fairly consistent with Worthingtons
(Deep-Sea Res., Vol.17, 1970) suggestion,
even though the pathways and details are
quite different from his scheme and the
most important inflow path seems to be the
Iceland-Faroe branch.
For climatic and biological problems, the
most important question is how much the
inflow varies in strength on seasonal to
decadal and longer timescales. Hydro-
graphical investigations have indicated the
existence of such variations. Thus, the Ice-
land-Faroe inflow branch seems to vary in
extent seasonally and also seems to have
decreased from the mid-eighties to the ear-
ly nineties. Quantitative estimates of the
flux variations are not available, however,
and we do not know whether the three in-
flow branches vary in phase to give a sig-
nificant variation in the total flux or switch
the inflow between them, leaving the total
flux more or less unchanged. For reliable
answers to this question we will have to
await the results of ongoing, long-term cur-
rent measurement programmes.
Fig. 2. Preliminary flux estimates for the inflow of
Atlantic water through the Iceland-Scotland Gap in Sv
(Sverdrup = 106 m3/s) based on resultsfrom the
Nordic WOCE project. An additional inflow of
approximately 1 Sv occurs west oflceland.
Mynd 2. Fyribils meting av mongdini av Atlants-
sjógvi, sum rekur inn millum ísland og Skotland,
grundað á úrslit frá Nordic WOCE kanningunum.