Oceanography and fluorescence at the shelf break off the north Norwegian coast (69°20'N-70°30'N) during the main productive period in 1994
Nordby, E.; Tande, K.S.; Svendsen, H.; Slagstad, D. (1999). Oceanography and fluorescence at the shelf break off the north Norwegian coast (69°20'N-70°30'N) during the main productive period in 1994. Sarsia 84: 175-189
In: Sarsia. University of Bergen. Universitetsforlaget: Bergen. ISSN 0036-4827; e-ISSN 1503-1128, more
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| Authors | | Top |
- Nordby, E.
- Tande, K.S.
- Svendsen, H.
- Slagstad, D.
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| Abstract |
Data on hydrography, fluorescence, wind and currents from shelf studies on the Norwegian shelf between 6930'N and 7030'N are presented. The sampling was performed along five transects, covering a narrow shelf break site, a trench, and a bank. The sampling programme was conducted during cruises of 4-5 days duration each month from March until October 1994. Three distinct water masses were identified: 1) Coastal Water (S < 35; 4 < T > 12 °C) above the shelf and the shelf break (0-300 m depth), 2) Atlantic Water (S > 35; 5 < T > 10 °C) off shelf (0-400 m depth) and below the Coastal Water in the trenches (300-400 m depth), and 3) Norwegian Sea Deep Water (S < 35; T < 0 °C) off the shelf break, below 700 m depth. Wind direction between southeast and northwest prevailed during all cruises, except in May, when northeasterly wind was most frequent. Typical wind speeds were in the order of 7-12 m s -1, but the wind exceeded 15 m s -1 frequently during the whole investigation period. Current regime above the shelf, as obtained by Acoustic Doppler Current Profiler (ADCP) in April, June and September, demonstrated a strong off-shelf flow along the northern side of the trench Malangsdjupet, while a more irregular pattern was found along the southern margin of this trench. Above the bank area Nordvestbanken a clockwise turn in the flow field from east to west was found. This clockwise turn in flow field coincided with modelled flow fields of the major tidal component during most of the cruises. Residual currents were determined subtracting the modelled M2 from the ADCP-measurements. Fluorescence profiles indicated a higher standing crop of phytoplankton above the trench area than above the bank area. No distinct spring bloom was found, but a seasonal maximum in June in surface integrated fluorescence was detected. In June highest values were recorded in shelf waters (34.2 < S > 34.4) when the pycnocline was about to be established, while the August and September maxima were found in more saline waters (34.8 < S > 35.1) often below the pycnocline in off-shelf waters. |
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