1 ICES/NAFO Symposium Santander May 11 2011 Seasonal to interannual variability of temperature and...
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Transcript of 1 ICES/NAFO Symposium Santander May 11 2011 Seasonal to interannual variability of temperature and...
1
ICES/NAFO Symposium Santander May 11 2011
Seasonal to interannual variability of temperature and salinityin the Nordic Seas:heat and freshwater budgets
Katrin LatariusDetlef QuadfaselZMAWInstitut für Meereskunde Hamburg
Funding:Deutsche Forschungsgemeinschaft (SFB512)EU-MERSEA, EuroArgo, THOR
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Background/Motivation
Transformation on the way through the Arctic Mediterenean
Nordic Seas: 1.5 x 1012m2, -50 W/m2
Nordic Seas contribute ~25%
Atlantic inflow8 Sv, 12°C, 35.25, 26.8 kg/m3
Overflow6 Sv, 0.2°C34.92, 28 kg/m3
+near the surface2 Sv polar water
total transformation:∆T: 12°C∆S: 0.37
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Argo float data - circulation
Quasi-Eulerian mean circulation of the Nordic Seas (1000-1500 dbar)
Voet et al. ( 2010)
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Argo float data - circulation
Quasi-Eulerian mean circulation of the Nordic Seas (1000-1500 dbar)
Voet et al. ( 2010)
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Argo float data – Profiles
Greenland Sea
Lofoten Basin
Norwegian Basin
Iceland Plateau
total: 3000 profiles of T, S, and σ, 0-2000m
Argo-DK, Argo-Germany, Argo-Norway, MERSEA, SFB-512
2001 2005 2011
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0
-2
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ptemp
Hydrography – Temperature time series
Norwegian Basin
Lofoten Basin
Iceland Plateau
Greenland Sea
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35.0
34.9
34.8
34.7
sal
Hydrography – Salinity time series
Greenland Sea
Iceland Plateau Norwegian Basin
Lofoten Basin
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Heat and freshwater budget
Concept
surrounding gyre
max. conv depth
The development of the heat and freshwater content in the ocean is derived from ARGO-float profile data
Lateral exchange and vertical convective mixing is estimated as the residuumsummer: only lateral exchangewinter: lateral + vertical exchange
Seasonal cycle of heat and freshwaterfluxes,from 7 meteorological models
annual mean:-53 ± 10 W/m2 22 ± 15 mm/mon
Latarius & Quadfasel, 2010
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Greenland Sea Gyre: heat is imported laterally (50-1500m) and exported to the atmosphere and in the upper 50m freshwater is imported from the atmosphere and
exported laterally
The surrounding of the gyre between 50 – 1500m looses heat and salt by exchange with the Greenland Sea Gyre
Heat and freshwater budget – Greenland Sea
Mean annual budgets
heat (W/m2) freshwater (mm/month)
22.4± 14.6
53.4± 10.2
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Heat and freshwater budget – all basins
Greenland Seawinter-MLD: max. 1400mlateral exchange 50-600m: heat: + 70 W/m2
freshwater: - 35 mm/monthArea: 1.0 x 1011 m3
Iceland Plateauwinter-MLD: max. 250mlateral exchange 50-600m: heat: + 22 W/m2
freshwater: - 8 mm/monthArea: 0.4 x 1011 m3
Norwegian Basinwinter-MLD: max. 350mlateral exchange 50-600m: heat: + 76 W/m2
freshwater: - 31 mm/monthArea: 1.7 x 1011 m3
Lofoten Basinwinter-MLD: max. 500mlateral exchange 50-600m: heat: + 101 W/m2
freshwater: - 18 mm/monthArea: 0.9 x 1011 m3
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Heat and freshwater budget – all basins
Greenland SeaT: -0.33°C 2.6%S: -0.0084 2.3%
Iceland PlateauT: -0.04°C 0.3%S: -0.0007 0.2%
Norwegian BasinT: -0.53°C 4%S: -0.0125 3.4%
Lofoten BasinT: -0.35°C 2.8%S: -0.0037 1%
Contribution to the water mass transformation in direction to the overflow (50-600m)
In: 12°C Out: 0°C ∆T=12°CIn: 35.25 Out: 34.89 ∆S=0.37
~ 10%
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Heat and freshwater budget – all basins
Greenland SeaT: -0.33°C 10%S: -0.0084 17%
Iceland PlateauT: -0.04°C 1%S: -0.0007 1%
Norwegian BasinT: -0.53°C 18%S: -0.0125 25%
Lofoten BasinT: -0.35°C 12%S: -0.0037 7%
Contribution to the water mass transformation in direction to the overflow (50-600m)
In: 12°C Out: 0°C ∆T=12°CIn: 35.25 Out: 34.89 ∆S=0.37
Nordic Seas:~ 25/14% of total heat/freshwatertransformation∆T=3°C∆S=0.05
~ 50%west ~ 15% east ~ 35%
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Conclusion
Greenland Sea, Norwegian Basin, Lofoten Basin (and the Iceland Plateau) of the Nordic Seas transform and redistribute the water masses at least down to 600m
residence time within the basins is long winter cooling forces deep vertical mixing
~ 50% of the water mass transformation of the Nordic Seas takes please in the basins (they account for only 25% of the total area)
contribution of the Nordic Seas to the total water mass transformation from Atlantic inflow to the overflow is only approx. 25%transformation in the eastern part is dominant
climate induced increase of freshwater in the surface layer of the western part will at most influence 15% of the total tranformation!
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Thank you for your attention!
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Dataset
Dataprocessing:
Receiving data from Argos, converting from hex to decimal and real-time quality check at Coriolis Data Centre(within 1 day after profile is measured)
Quality check by eye
Delayed mode quality control for S at ARGO standard: Objective mapping procedure to compare with recent and historical CTD data (Böhme, Send, 2005), correction if difference is larger than 0.01 psu.(every ½ to 1 year)
Using only profiles within f/h contour of GS gyre
Computing monthly mean values of all floats in the gyre
Deleting extreme values
2 from 8 floats have been corrected because of distinct offset/trend in S
Reduction from 915 to 546 profiles