Evidence for Hydraulically Controlled Outflow of Brackish Water from Holandsfjord, Norway

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  • 1 Department of Oceanography, Göteborg University, Göteborg Sweden
  • | 2 Norwegian Institute for Water Research, Oslo, Norway
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Abstract

A large number of historical vertical salinity profiles from the deep Holandsfjord are analyzed to investigate properties of the brackish surface layer. It is found that the mean salinity and mean thickness of the brackish layer in the fjord are almost horizontally homogeneous. By statistical regression it is shown that the freshwater content in the brackish layer, measured as the freshwater height H1f varies with the freshwater supplyQf as H1fQ2/3f This result is predicted by a simple two-layer model, with a thin active brackish surface layer upon a thick passive layer of seawater, subject to baroclinic hydraulic control in a contraction at the fjord mouth. The observed freshwater height, however, is ∼50% greater than predicted. It is suggested that this, at least partly, is an effect of vertical stratification in the lower layer of seawater, focusing the estuarine compensation current toward the pycnocline.

Abstract

A large number of historical vertical salinity profiles from the deep Holandsfjord are analyzed to investigate properties of the brackish surface layer. It is found that the mean salinity and mean thickness of the brackish layer in the fjord are almost horizontally homogeneous. By statistical regression it is shown that the freshwater content in the brackish layer, measured as the freshwater height H1f varies with the freshwater supplyQf as H1fQ2/3f This result is predicted by a simple two-layer model, with a thin active brackish surface layer upon a thick passive layer of seawater, subject to baroclinic hydraulic control in a contraction at the fjord mouth. The observed freshwater height, however, is ∼50% greater than predicted. It is suggested that this, at least partly, is an effect of vertical stratification in the lower layer of seawater, focusing the estuarine compensation current toward the pycnocline.

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