Stratification and circulation in Sognefjorden
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The winter time stratification and circulation above sill depth in Sognefjorden is studied from CTD and ADCP data from February 2002-2004. The year to year variability in distribution of temperature and salinity has been related to variations in Sognesjøen and offshore wind field, although the exact relationship is unknown. The circulation in the fjord is correlated with the vertical distribution of temperature and salinity. The variability in flow structure follows the variability in the vertical distributions. In 2004 there is a four layered circulation, while in 2002 there is a three layered circulation. Both circulation and stratification show cross fjord variations, which most likely is due to rotational effects. The fjord is found to be wider than the baroclinic Rossby radius. From the cross fjord variations of the stratification, geostrophic flow has been calculated. The geostrophic flow is divided in similar layers of inflow and outflow as the flow measured by ADCP, although the magnitudes are different. Sognefjorden is statically stable, but velocity shear may induce turbulence where the stratification is weak.