The retroflection of the Faroe Current into the Faroe-Shetland Channel Karin Margretha H. Larsen, Bogi Hansen and Hjálmar Hátún Reykjavík, ICES ASC 2013

Iceland Scot- land Nordic Seas Arctic Ocean Greenland North Atlantic Greenland-Scotland Ridge Reykjavík FAROES

Monitoring of inflow The Faroe Current north of the Faroes One branch is retroflected into the Faroe-Shetland Channel How far does it progress into the channel? N E S Z Observations: Standard CTD sections ADCP moorings Altimetry (AVISO MSLA)

ADCP Mooring sites NB – 164 months EB, EC – 14 months SA(36), SX(12), SB(122) - months ZA – 10 months N E S Z EB SX SA SB ZA NB

Along track altimetry at site EB (Hátún, Thesis 2004) Altimetry The retroflection has a seasonal variability and steadily flows across section E

AVISO gridded altimetry (MSLA) EOF analysis Mode1 (Prior to analysis: Area average removed) PC1: timeserie of Mode1 PC1 is negative during winter LOW HIGH

EOF analysis: PC1 Seasonal analysis: minimum in late January

PC1 and velocity at 200m Along topography NB: R = EB: R = SX: R = Across topography NB: R = EB: No correlation SX: No correlation SA: R = (5% level) SA: R = (1% level) N E S Z NB EB SX SA MSLA – EOF Mode1 A low SSH over the Norwegian Sea strengthens along-topography flow at the slopes MSLA – EOF Mode1 A low SSH over the Norwegian Sea strengthens along-topography flow at the slopes LOW

Variability in the FSC How far does the current progress into the FSC? Longterm mooring site SB has weak correlation with PC1 Individual years: 1999/00 and 2007/08 are correlated with PC1 N E S Z ? ? The retroflected FC reaches section S in some years......but perhaps site SB is not at an optimal location The retroflected FC reaches section S in some years......but perhaps site SB is not at an optimal location SX SB

Interannual variability SB No mooring data SB

Mode1 and the NAO index NAO winter index and the PC1 winter average are negatively correlated

Ongoing work Can we estimate the fraction of the retroflected Faroe Current? – Calculate volume flux, by combining in situ measurements and altimetry (Berx et al, 2013) Atmospheric forcing and how it affects the retroflection Atmospheric forcing

The research leading to these results has received funding from the European Union 7th Framework Programme (FP ), under grant agreement n NACLIM