3. Wochenbericht FS POSEIDON Reise POS503

Reykjavik - Tórhavn - Tórshavn, 01. – 19. August 201

2. Wochenbericht FS POSEIDON Reise POS503

Reykjavik - Tórhavn - Tórshavn, 01. – 19. August 201

3. Wochenbericht FS POSEIDON Reise POS503

Reykjavik - Tórhavn - Tórshavn, 01. – 19. August 201

1. Wochenbericht FS POSEIDON Reise POS503

Reykjavik - Tórhavn - Tórshavn, 01. – 19. August 201

Present-day manifestation of the Nordic Seas Overflows

Dense Nordic waters enter the North Atlantic through passages in the Greenland-Scotland Ridge at a mean rate of 6 Sv. Subsequent entrainment of ambient water into the sinking plumes downstream of the sills approximately double this flux. Decade-long observations show these fluxes to be stable with no discernible trends. Hydraulic control of the overflows and the buffering effect of the Nordic basins effectively filter out short-term variability of dense water production associated with white noise North Atlantic Oscillation forcing. Simulations with directly forced and coupled atmosphere-ocean models show, under present climate conditions, overflow variability on multi-decadal time scales but no longterm trends

Somali eddy formation during the commencement of the southwest monsoon, 1978

Also published as: Journal of Geophysical Research 85 (1980): 6654-6660An early stage of the Somali eddy circulation was mapped in the period May 29 to June 13, 1978, using expendable bathythermograph data at closely spaced stations. By this time the SW monsoon had been blowing at 5°N for about 4 weeks and the large anticyclonic eddy in the northern Somali Basin was clearly discernible between 3°N and 10°N. It is estimated that the offshore transport at this time was approximately half of that occurring during the period when the eddy reaches maximum size and strength during August and September. A smaller southern eddy was observed just offshore between the equator and 3°N.Prepared for the Office of Naval Research under Contracts N00014-74-C-0262; NR 083-004 and N00014-79-C-0071; NR 083- 004

On simultaneous measurements with rotor, wing and acoustic current meters, moored in shallow water

In two closely spaced moorings in the Kiel Bight, four different current meterstwo rotor current meters (Aanderaa and Vector averaging), an acoustic current meter (designed by Gytre), and a pendulum current meter (designed by Niskin) were moored for 22 days. The Vector averaging current meter (VACM) was used as reference instrument on one mooring with the floatation at 7 m depth. The floatation of the second mooring was at 5 m depth in the first 17 days of the experiment, but in 2.7 m depth in the last 5 days to make their mooring more effected by surface waves. The Niskin wing current meter was most effected by wave-induced mooring motion. The Gytre instrument showed the smallest surface-wave effects. The vector variances of this instrument in 7.4 m depth on the surface-wave effected mooring and those of the VACM in 10 m depth on the reference mooring were about equal

Monitoring the flow of Atlantic water through the Faroe-Shetland Channel

This report presents results from an experiment, carried out in 2011-2012 within the EU-THOR project to investigate whether future monitoring of the Atlantic water transport through the Faroe-Shetland Channel might be more efficiently achieved on another section than the traditional Munken-Fair Isle section. The new section is less affected by meso-scale activity and narrower, allowing better horizontal resolution of the mooring array, but the experiment revealed that moving to the new section involved other drawbacks. The experiment also confirmed an earlier conjecture that data from satellite altimetry might provide better estimates of transport variations than estimates based on in situ measurements, solely. Previous efforts to determine the average volume transport of Atlantic water through the channel and its variations have been hampered by lack of information on the thickness variations of the Atlantic layer. Re-evaluating the historical data set, we find that the transport estimates are not significantly affected by assuming that the lower boundary of the Atlantic layer is fixed, equal to the average 5°C-isotherm. Based on the conclusions of this report, we recommend that future in situ monitoring in the channel is re-focused