Long-term temperature ternds in Norwegian coastal waters

Abstract

Time series of sea surface temperature at four meteorological stations on the coast of Norway are compared with observations from three fixed oceanographic stations in Norwegian coastal waters. The longest time series at the meteorological stations cover the period after 1867 Five-year-running means for the January-March and July-September quarters are presented. The fixed oceanographic stations have been operated since 1935, though with gaps in the observations. Fluctuations of duration varying betweeen about 5 and 20 years are observed in all time series, and there is fair agreement between the observations at all stations in summer and winter. The observations suggest that these fluctuations may be of advective nature. A more long-term trend towards warming is observed at the meteorological stations. This warming was more conspicuous in summer than in winter. In summer the trend vvas clearly observed for nearly 50 years after the turn of the century. In winter there are indications of a weak temperature increase from the beginning of the observational period. It is suggested that this trend is due to direct heat transfer in the region.