The Norwegian Coast Water Chapter VIII of “The Norwegian Sea” by Helland-Hansen and Nansen Presented by Steinar Orre,

Salinity and Temperature (I) Definition: regard waters along the coast with salinity below 35.0 ‰ as coast water In general, a sharp boundary between Atlantic waters and coast waters in the surface However, the boundary may alternate due to vortex movements or displacements of surface layers due to winds

Salinity and Temperature (II) Observations of Norwegian coast water in the summer of 1904 shows that: Surface salinity increases from Skagerak (28.3 ‰) to the Barents Sea (34.3 ‰) Salinity is everywhere increasing from the surface downwards Difference of salinity vertically, surface and 100 m depth, decreases from Skagerak (6-7 ‰) to the Barents Sea (0.2 ‰) In the Barents Sea, the waters were almost homohaline

Salinity and Temperature (III) Atlantic water is getting fresher northwards, while Norwegian coast water is getting more salty. Reasons? Lateral mixing from vortex movements Vertical convection currents in winter (Still uncertainties regarding exchange processes, total amount of freshwater export, latitudinal variations etc.)

Salinity and Temperature (IV) Surface temperature varies much according to meteorological conditions and geographical positions In intermediate strata, coastal water in Skagerak influenced by the Baltic Sea is much colder than farther to the west and north - due to the effect of Atlantic water inflow

The movements of the Norwegian Coast Water From a few observations of currents in the Skagerak region: Velocities of surface currents > 1 m/s The coast water moving in the same direction (parallel to the coast) as the underlying Atlantic water Tidal currents undetectable in the upper layers, but could easily be observed near the bottom.

Current Measurements off Jæren

Currents off Jæren (St. 111), July 1908

Currents off Jæren (St. 147), July 1908

Surface currents off Jæren (St. 147), July 1908

Currents off Jæren (St. 147), July 1908

Some final remarks on the movements of Norwegian Coastal waters “The observations made so far indicate that the coastal current chiefly follows the edge of the continental shelf, in the same way as the Polar current runs along the edge east of Greenland” “The main body of the coastal current runs alongside and parallel to the Atlantic current” “… the coast water has a component seawards in summer and towards land in winter”

Currents in Hjøsenfjorden, August 1908

Currents in Byfjorden (Bergen)

Oceanography of Norwegian fjords

Annual and seasonal variations (at Feje, entrance to Sognefjorden) Variations of coast water are of different kinds and have many causes, e.g. fresh water input from Northern and Central Europe, Atlantic water inflow, air temperature, winds …

Annual variations of salinity

Area of coast water related to rainfall I: Area of coastal water Annual rainfall anomaly in II: Christiania (Oslo) III: Bergen IV: Germany V: Norway

Area of coast water and catches of fish

Seasonal variations of temp and saln

Summary of chapter VIII: Surface salinity of Norwegian coast water increase northwards (in contrast to Atlantic waters) Coast water propagates along the Norwegian coast Surface waters in Norwegian fjords are moving out of the fjords, while there is a net inflow from the depths There seems to be a link between area of coast water and rainfall the year before Also a link between area of coast water and catches of fish => predict catches of fish with the amount of rain? The coast water is wide but shallow in summer, and narrow but deep in winter Seasonal variations far greater than annual variations