Christine Gommenginger
National Oceanography Centre, Southampton

Executive Summary

Observational evidence for salinity changes and trends in the North Atlantic and UK waters is summarised annually in the International Council for the Exploration of the Sea (ICES) Report on Ocean Climate (IROC) (ICES, 2006). The Inter-Agency Committee on Marine Science and Technology (IACMST) published a comprehensive report in 2004 reviewing the status of various ocean parameters, including salinity, in UK Marine Waters (IACMST, 2004). The main points are:

• There are only few long-term time series of salinity measurements in UK waters and these do not indicate any overall long-term trend.
• Records from the Atlantic around the UK which are most influenced by in-flowing Atlantic waters reveal a general pattern of low salinity in the mid-late 1970s, followed by three decades of quite large inter-annual variability, probably closely associated with changes in the atmospheric circulation (North Atlantic Oscillation). Salinity records from the Faroe-Shetland Channel and the Ellett Line indicate a trend to high salinity since 1995.
• In the shallower areas of the North Sea and Irish Sea, the salinity is much more dependent on local runoff from land and local evaporation/ precipitation changes, and hence is much more variable.
• Observational evidence suggests significant freshening of the mid-high North Atlantic between the 1950s and 1990s (Dickson et al., 2002, Curry et al., 2003; Josey and Marsh, 2005), which has been attributed to changes in atmospheric circulation. Recent observations in the North Atlantic show that the trend in the last decade (1995-2005) has been of warming and increasing salinity in the upper layers of the ocean (ICES, 2006)

Level of Confidence

LOW

Key sources of Information

See Supporting Evidence

Please acknowledge this document as: Gommenginger, C. (2006). Impacts of Climate Change on Ocean Salinity in Marine Climate Change Impacts Annual Report Card 2006 (Eds. Buckley, P.J, Dye, S.R. and Baxter, J.M), Online Summary Reports, MCCIP, Lowestoft, www.mccip.org.uk