The Mean Sea Level Pressure (MSLP) Gradient across the Denmark Strait as Index for the Oceanographic Conditions in North Icelandic Waters

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The oceanographic conditions in Icelandic waters are closely related to atmospheric forcing. In the present paper winter means of the atmospheric sea level pressure gradient across the Denmark Strait are correlated to a time series of temperature at station S3 off North Iceland. These data show that variations in North Icelandic shelf waters are closely related to the gradient. The correlation between 3-years moving averages of the gradient and the temperature at S3, one year delayed, was 0.73. This climatic relation clearly reflected the abrupt change from Atlantic to Arctic conditions on the North Icelandic shelf in the 1960s and the variability since then. Further, the effects of the variations on water mass properties in the southern Norwegian Sea are discussed. Biological effects have been observed on all levels in the food web. Various authors describe related biological variations, from the primary production level to cod and herring. The cod responded to the climatic variability and the associated narrowing habitat with a decline in abundance. The stock of herring that earlier was grazing north of Iceland, changed its migration pattern, and has not yet returned.