Long-term hydrographic variability patterns off the Norwegian coast and in the Skagerrak

The Norwegian Coastal Oceanographic Observing System consists of observations of temperature and salinity in the surface layer, carried out at fixed positions from coastal liners, and measurements in the whole water column, carried out by local observers. The observations date back to 1935. Additionally, long-term data from the Institute of Marine Research station in Flødevigen on the Skagerrak coast and some selected data from the Torungen-Hirtshals hydrographic section are included. These data have been used to elucidate the long-term hydrographic variability along the Norwegian coast. Four relatively warm winter periods could be identified in the surface layer, culminating around 1950, 1960, 1975, and in 1990-1992. The long-term temperature and salinity trend 1950-1989 is negative along the whole coast. The 1990s, however, are characterized by having the highest mean decadal temperature for the hole period of observations alon g the southern coast. The importance of the 1990s in the surface layer is gradually reduced northwards. Along the northernmost coast, other decades, such as the 1950s or the 1960s, show higher decadal mean tem ­perature. Also for the salinity the 1990s show high values along the southern coast, while other high salinity decades dominate further north. The high temperatures and salinities along the southern coast in the 1990s are caused by an increase in the Atlantic inflow in the late 1980s and early 1990s combined with the atmospheric conditions associated with periods of a high level of the North Atlantic Oscillations.

Article from Marine Science Symposia Vol. 219 - "Hydrobiological variability in the ICES Area, 1990-1999", symposium held in Edinburgh, 8-10 August 2001. To access  the remaining articles please click on the keyword "MSS Vol. 219".