Hydrographic response of Holandsfjord to changed freshwater runoff

• The observed hydrographic conditions in the upper layers of the Norwegian Holandsfjord are analyzed as functions of the location and strength of the freshwater discharge. The data sets were sampled over 21 years and consist of mostly fortnightly observations of salinity and temperature at several stations along the fjord and daily estimates or observations of the freshwater supply. The freshwater runoff to Holandsfjord was regulated and relocated to a hydroelectric power plant at the innermost end of the fjord in 1993, and by transfer of water from neighboring watersheds the yearly average freshwater discharge increased by a factor greater than 2. Before the regulation the freshwater content in the fjord was hydraulically controlled somewhere in the outer part of the fjord, and this control remains after the regulation and has been located. When the power plant is in operation a hydraulic control appears at Enganes, the narrow contraction between the outer and inner parts of the fjord. The present investigation also shows that the surface layer responds to the regulated freshwater supply with a decreased surface layer salinity, an increased freshwater content, and an increased rate of flushing. The mean value of the wind power mixing buoyancy in the surface layer is estimated to be 6-7 mW m(-2).

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences (hsv//eng)

Nyckelord

surface layer dynamics

hydraulic control

freshwater regulation

fjords

Publikations- och innehållstyp

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