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Bogi Hansen, Hjálmar Hátún, Regin Kristiansen, Steffen M. Olsen and Svein Østerhus

Thermohaline forcing maintains the Iceland-Faroe inflow of heat and salt to the Arctic. Østerhus et al., GRL 2005. Nordic Seas. Greenland. IF-inflow 40 - 45%. 3.8 Sv. 0.8 Sv. 3.8 Sv. Iceland. Faroes. Scot- land.

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Bogi Hansen, Hjálmar Hátún, Regin Kristiansen, Steffen M. Olsen and Svein Østerhus

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  1. Thermohaline forcing maintains the Iceland-Faroe inflow of heat and salt to the Arctic Østerhus et al., GRL 2005 Nordic Seas Greenland IF-inflow 40 - 45% 3.8 Sv 0.8 Sv 3.8 Sv Iceland Faroes Scot- land Bogi Hansen, Hjálmar Hátún, Regin Kristiansen, Steffen M. Olsen and Svein Østerhus

  2. Didn’t we know that already ?

  3. The Feedback Mechanism Nordic Seas + Arctic Ocean World Ocean Cooling Salt Entrainment Greenland Scotland Ridge Overflow NADW

  4. Estuarine Thermoh. The Feedback Mechanism implies: Removal of water from the Nordic Seas maintains the Atlantic inflow through sea-level forcing Nordic Seas + Arctic Ocean World Ocean But !! Atlantic inflow Greenland Scotland Ridge

  5. Maybe • Sea-level forcing maintains the average Atlantic inflow • Wind stress dominates the variations ?

  6. The IF-inflow 4 CTD cruises a year since 1988 ADCPs since 1997

  7. The Standard sectionthrough the IF-inflow Velocity (cm/s) Salinity ADCPs

  8. Monthly and annually averaged Atlantic water transport of the IF-inflow 1997 - 2008 Average: 3.5 Sv No trend

  9. The flow changes character across the Ridge It is accelerated and becomes focused This requires a local (and very stable) force Not local wind stress PVDs at 225 m depth

  10. Sea-level drop: SLHW - SLHE Bernoulli Geostrophy implies: ~ 0.2 Sv per cm + Transport SLHE Atlantic inflow and sea-level drop across the Ridge Iceland Faroes SLHW Scot- land Monthly correlation: R = 0.63 Annual correlation: R = 0.87

  11. 8.5 Sv out implies lowering of Nordic Seas SLH by 30 cm/day Iceland-Faroe Atlantic inflow Remote wind forcing could raise sea-level west of the Ridge Outflow from Nordic Seas tends to reduce sea-level east of the Ridge R > 0 Atlantic Ocean Nordic Seas To Arctic Ocean R < 0 To Denmark Str. Atlantic inflow Iceland Faroe Ridge FBC-overflow East West IFR-overflow

  12. Correlation coefficient between monthlysea-level height and IF-inflow -0.4 +

  13. Conclusions • Sea-level forcing drives the flow across the Iceland-Faroe Ridge • Processes west (upstream) of the Ridge do not dominate the forcing • Water removal east (downstream) of the Ridge generates the average IF-inflow • and its variations

  14. Thermohaline forcing dominates the outflow 70 %

  15. IF-inflow and FBC-overflow IF-flow (Sv) Negative correlation FBC-overflow (Sv)

  16. Coupling between IF-inflow and FBC-overflow U R<0 D R>0

  17. Correlation coefficient between monthlysea-level height and IF-inflow -0.4

  18. The equation of motion External forcing (wind) Sea-level forcing

  19. T and S in the core of the IF-inflow

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