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The Faroe Current: T-S properties and volume, heat and salt transports
Karin Margretha H. LarsenBogi Hansen, Hjálmar Hátún,
Svein ØsterhusExtended Ellett Line Workshop, 27-28. Apr 2015
North Atlantic Gyres
SPG
STG
EEL
Faroes
Faroese Standard Sections
N
V E
S
The Faroe Current
Atlantic Water properties
Rockall Trough- From ICES IROC
Warming due to Subpolar Gyre changes(Hátún et al, 2005)
Modulation by air-sea heatflux variability (Larsen et al, 2012)
Atlantic Water properties
Increasing salinity due to Subpolar Gyre changes
Salinity variability due to changes in source water properties
Modifications in the Faroe area
TW, SW
TN, SN
Cooling/freshening
The salinity difference and Faroe Current volume transports
Low volume transports increase the residence time:- Increased amospheric influence- Increased admixture
S
Vol . tr
Atlantic water on monitoring section
ADCPs: 1997-2015
AtlanticArctic
Sea level difference across the flow
Satellite altimetry
Weekly averaged volume transport 1997-2013 based on in-situ observations
Hansen et al, 2010. Ocean Science
Combining altimetry and in-situ obs.
1. Velocity fieldusing long-term ADCP and CTD records to calibrate altimetry, we can generate daily estimates of the velocity field every day since 1st January 1993
2. Temperature and salinity field altimetry + seasonal variation + long-term Atlantic water temperature and salinityto generate daily estimates of the property fields
Monthly averaged volume transport of Atlantic water 1993 - 2013
Average volume transport of Atlantic water: 3.8 ± 0.5 Sv
Hansen et al, 2015. Submitted to OS
AW transport 1993 - 2013
Weak seasonal variationAmplitude < 10% of avg transport
± standard error
20 year trend: 9±8%
(95% confidence)
Annual mean
3-yearmean
Heat transport relative to 0°C
20 year trend: 18±8%
20 year trend: 130±30%
Salt transport relative to 34.93(≈ FBC-overflow salinity)
Conclusions• Variation of AW (T,S) is dominated the Subpolar Gyre
and modulated by source water variability and atmospheric heat loss variability
• Faroe Current volume, heat and salt transports towards the Arctic have increased in the last 20 years
The research leading to these results has received funding from the European Union 7th Framework Programme (FP7 2007-2013), under grant agreement n.308299NACLIM www.naclim.eu