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Reanalysis of the Iceland-Faroe inflow
Bogi Hansen, Karin Margretha H. Larsen,Hjálmar Hátún and Svein Østerhus
NACLIM CT2, Hamburg, January 2015
Iceland-Faroe inflow
Old methodin situ CTD and ADCP (Hansen et al, 2003)
New method Combining Altimetry with CTD and ADCP
)(ˆ)(ˆ tuUtU kkk
Isoline(combined thermo and halo)
CTD stations
Altimetry points
ADCPs
Velocity profile
Average surface velocities
Geostrophy
Altimetry
ADCP
The depth of the 4°C isotherm
• Temperature field is linked to the velocity field (Hátún et al, 2004)
• EOF analysis of the altimetry SLA– Modes 1 and 2 explain 95% of the variability
• Tried regression of observed isotherm depth on various combinations of surface velocities and PC1 and PC2– Between 42 and 65% of variability explained by Uk
+ PC1
Calculating transports
),()(ˆ),( tztUtzU kk
7
2
500
0
)(),()(k z
kkTot zWtzUtQ
),0(/),(),( tutzutz ADCPADCP
)(),( ztz
)500()0(
)500()()(
AvgAvg
AvgAvgg ugug
ugzugz
)(zWk
Total transport: Konstant (to bottom or 500m)
AW transport: To bottom or average isoline
AW transport: To bottom or simulated isoline),( tzWk
AW transport 1993 - 2013
Average transport: 3.9 Sv
12 week avg
1 week avg
Simulating the temperature distribution
),,(365/),(2cos),(),(),,( Re msMaxmAmpAvm tikTikDtikTikTtikT
Tres: variance mainly associated with thermocline movement
Tres simulated by multiple regression on:
• AW temperature and 4°C isotherm depth (N04 – N11)
• AW temperature and altimetry principal component (N02 – N03)
Explained var.Using observed AW tmp and isotherm depth
Using simulated AW tmp and isotherm depth
Heat transport (relative to 0°C)
6
2
500
0
)(),(),()(ˆ)(k z
kkkk zWtzTtztUtH
AW v
olum
e tr
ansp
ort (
Sv) 1 yr avg
3 yr r.avg
Increase in Relative Heat Transport ≥ 10%
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
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