Temporal and spatial variability of the sea surface salinity in the Nordic Seas

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Furevik, Tore, Bentsen, Mats, Drange, Helge, Johannessen, Johnny A., Korablev, Alexander
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union 2002
• Subjects: Oceanography; Greenland; Norwegian Sea; Iceland; Nordic Seas
• Online Access: https://hdl.handle.net/1956/642; https://doi.org/10.1029/2001jc001118

In this paper, the temporal and spatial variability of the sea surface salinity (SSS) in the Nordic Seas is investigated. The data include a Russian hydrographical database for the Nordic Seas and daily to weekly observations of salinity at Ocean Weather Station Mike (OWSM) (located at 66°N, 2°E in the Norwegian Sea). In addition, output from a medium-resolution version of the Miami Isopycnic Coordinate Ocean Model (MICOM), forced with daily National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data, is used to complement the analysis of the temporal and spatial fields constructed from the observational data sets. The Nordic Seas show a strong seasonal variability in the vertical density stratification and the mixed layer (ML) depth, with a weak stratification and a several hundred meters deep ML during winter and a well-defined shallow ML confined to the upper few tens of meters during summer. The seasonal variability strongly influences the strength of the high-frequency variability and to what extent subsurface anomalies are isolated from the surface. High-frequency variability has been investigated in terms of standard deviation of daily SSS, calculated for the different months of the year. From observations at OWSM, typical winter values range from 0.03 to 0.04 psu and summer values range from 0.06 to 0.07 psu. Results from the model simulation show that highest variability is found in frontal areas and in areas with strong stratification and lowest variability in the less stratified areas in the central Norwegian Sea and south of Iceland. Investigation of the interannual variability over the last 50 years shows a marked freshening of the Atlantic Water in the Norwegian and Greenland Seas. Moreover, the strength of the southern sector of the Polar front, as defined by the 34.8–35.0 psu isohalines along the western boundary of the inflowing Atlantic Water, undergoes significant interannual variability with gradient stretching reaching up to 300 km. In ...