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The Inflow of Atlantic water to the Nordic Seas

MAIA. The Inflow of Atlantic water to the Nordic Seas. By Bogi Hansen and Svein Østerhus. Faroese Fisheries Laboratory. ?. Green-. I-AI:. land. Norwegian Sea. EGC. 66. °. N. Iceland. F-AI:. DS-Ov:. 64. °. N. IFR-Ov:. Faroes. S-AI:. 62. °. N. FBC-Ov:. FB. Shet-. land.

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The Inflow of Atlantic water to the Nordic Seas

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  1. MAIA The Inflow of Atlantic water to the Nordic Seas By Bogi Hansen and Svein Østerhus Faroese Fisheries Laboratory

  2. ?

  3. Green- I-AI: land Norwegian Sea EGC 66 ° N Iceland F-AI: DS-Ov: 64 ° N IFR-Ov: Faroes S-AI: 62 ° N FBC-Ov: FB Shet- land 60 ° N WTR-Ov: Atlantic Ocean 40 ° W 30 ° W 20 ° W 0 ° 10 ° W North Atlantic Nordic Seas Exchanges Courtesy: Quadfasel and Zenk

  4. The Greenland-Iceland AtlanticinflowThe IrmingerCurrent

  5. This branch of the Atlantic inflow passes through the Denmark Strait and then eastwards, north of Iceland

  6. Newest estimates of the Atlantic inflow west of Iceland (Steingrímur Jónsson) • Total volume flux: 0.95 Sv • Atlantic water volume flux: 0.8 Sv • No seasonal variation in current speeds • but, seasonal variation in water mass properties

  7. The Iceland-FaroeAtlanticinflowTheFaroeCurrent

  8. Measurements of Iceland-Faroe Atlantic inflow 4 CTD sections / year (1978 –) 3-5 ADCP moorings (1995 - )

  9. Progressivevectordiagramsat 225mdepth

  10. ADCP profiles Top layer always missing in the ADCP measurements But, the variations are highly barotropic, which can be used to extrapolate the measurements towards the surface

  11. Average geostrophic profiles (red)match average ADCP profiles

  12. Core (Atlantic water) temperature and salinity

  13. How to determineAtlantic water fraction • Reference temperature (e.g.: All water warmer than 6°C is Atlantic) • Reference salinity (e.g.: All water more saline than 35.00 is Atlantic) • 3-point mixing model

  14. Iceland-FaroesAtlantic water fluxsummer 1997 - summer 2001 Daily means

  15. Seasonal variation ofvolume fluxes

  16. TheFaroe-ShetlandAtlanticinflowTheContinentalShelfCurrent

  17. Upper-layer circulation in the Faroese channels

  18. The Continental Shelf Current is monitored by a ADCP array across the Faroe-Shetland Channel

  19. Newest estimates for the Faroe-Shetland Atlantic inflow (Bill Turrell et al.) • Average volume flux : 3.2 Sv • Amplitude of the seasonal variation: 0.2 Sv • Maximum Atlantic inflow in summer

  20. Fluxes carried by the three Atlantic inflow branches according to Hansen & Østerhus (2000)

  21. Nordic Seas budget according to Hansen & Østerhus (2000) ¾ of Atlantic inflow return as overflow Can. Archip.: 1.5 Sv Bering Strait: 0.8 Sv 2.5 1.8 1.5 7.5 5.0 2/3-4/5 4/5

  22. Seasonal variation of total Atlantic inflow • Greenland – Iceland Gap: ? Sv (max in summer) • Iceland – Faroe Gap: < 0.1 Sv • Faroe – Shetland Gap: 0.2 Sv (max in summer)

  23. Conclusions • Total Atlantic inflow to the Nordic Seas 7.5 Sv • Heat transport ~ 250 TW • The seasonal variation in the volume transport is less than 0.5 Sv • Inter annual variations ? • Long-term variations/trends ?

  24. Thank you Svein Østerhus Bogi Hansen Faroese Fisheries Laboratory

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