1. Air-sea CO 2 flux variability in the North Sea: 19 months of observations from voluntary observing ships Abdirahman Omar with contributions by Are Olsen and Truls Johannessen Geophysical Institute University of Bergen

2. Outline  Data  Basin wide flux estimate  Flux variations (seasonal, latitudinal and interannual)

3. Measurement routes and platforms Nuka Arctica Trans Carrier (Norcliff) Greenland Iceland UK Norway Nordic Seas North Atlantic Svalbard North Sea Bergen Immingham Amsterdam Northern North-East Atlantic and Nordic Seas North Sea (SST & fCO 2 ) NAC NwAC

4. 2005 2006 fCO 2 and SST data for 19 months ~60000 measurements between Jan 2005 and Sep 2006 N. Arctica T. Carrier Norcliff Julian Day / Month SST ( o C) fCO 2 @ 12 o C (µatm)

5. Basin wide estimate of the air-sea CO 2 flux Observed SST and ΔfCO 2 Climatological U 10 and SSS k-U 10 parameterization of W92 Mean annual uptake 1.24 mol m -2 yr -1 0.60 1.58 0.61 2.16 I II III IV Thomas et al. (2004)  1.68 mol m -2 yr -1, based on cruise data from 2001/2002 Takahashi climatology  3.3 mol m -2 yr -1, underestimates seawater fCO 2

6. The annual cycle of the F air-sea for northern and southern regions out in During spring the North-South gradients disappear (reverse) Atmospheric fCO 2 Latitude ( o N) CO 2 flux (mol m -2 ) Feb, Aug, Nov May

7. Interannual variations in F air-sea 2005 versus 2006 (Feb – Aug) U 10 from EKOFISK Climatological SSS Observed SST and ΔfCO 2 k-U 10 parameterization of W92 ≈ 19% reduction in 2006 relative to 2005 Ekofisk

8. ..more on the interannual variations of F air-sea After Thomas et al. (2004), based on cruise data R 2 = 0.99

9. End

10. Further work Optimize the gridd size Find appropriate statistical model(s) to analyse the variance Example: ±10 µatm  ±0.14 mol m -2 yr -1, or 11% of the annual flux