European Union integrated project no Variation in atmosphere-ocean fluxes of CO 2 in the Atlantic Ocean: first results from the Carbo-Ocean observing system in the North Atlantic Andrew Watson School of Environmental Sciences University of East Anglia On behalf of Core theme 1 of Carbo-Ocean

Thanks to… Truls Johannesen, Are Olsen, Abdiraman Omar Arne Körtzinger, Tobias Steinhoff Ute Schuster, Maciek Telzewski Jon Olafsson Antoine Corbière, Nicolas Metzl, Nathalie Lefèvre Aida Rios, Fiz Perez, Martina Alvarez Nick Bates Heike Lüger, Rik Wanninkhof …and many others

Annual flux of CO 2 across the sea surface a climatology for 2000 from Takahashi et al (2006) in preparation [mol m -2 year -1 ]

The world’s oceans “conveyor belt”

from Sabine et al (2004) Science 305: Total ANTHROPOGENIC CO 2 in the oceans by 1994 [mol CO 2 m -2 ]

The Carbo-ocean North Atlantic observing system The first co-ordinated, operational multi-ship voluntary observing network for sea surface pCO 2 and air-sea flux. Currently 5 commercial ships of opportunity and one research vessel. Co-ordinated with US and Canadian observing efforts. Aims: an accurate assessment of air-sea flux at seasonal-or-better time resolution, ~<10º latitude spatial resolution.

Sea surface measurements in the observing system

2005 Fluxes by latitude and season

First results… In 2005: –the North Atlantic was a sink for atmospheric CO 2 everywhere from 14º to 65ºN, in all seasons except summer (JJA) when it was a weak source south of 55ºN –Seasonal cycle in phase at all latitudes. –The overall sink for the region 14-65ºN was calculated at 0.24 Pg C for 2005 Compare Takahashi climatology (~1995) for the region, calculated with same assumptions: 0.40 Pg C Is there a decrease?

Measurements between the UK and the Caribbean in the mid-1990s and the early 2000s from Schuster and Watson (2006) JGR, in review

Sea surface pCO 2 [μatm] between the UK and the Caribbean in the mid-1990s and the early 2000s 30 O N 25 O N 35 O N 40 O N 45 O N 50 O N 30 O N 25 O N 35 O N 40 O N 45 O N 50 O N

Average 1994/95 Average 2002/05 The changes in sea surface pCO 2 [μatm] versus month from Schuster and Watson (2006) JGR, in review Southwest region Sea surface pCO 2 [μatm] FebAprJunAugOct Dec 280 Sea surface pCO 2 [μatm] Northeast region FebAprJunAugOct Dec 280

The changes in air-sea flux of CO 2 [mol m -2 yr -1 ] versus latitude from Schuster and Watson (2006) JGR, in review Latitude [ o N] Air-to-sea flux CO 2 [mol m -2 year -1 ] Average 1994/95 Average 2002/ /95 with 2002/05 temperature 2002/05 with 1994/95 wind speed Flux = (pCO 2 atm – pCO 2 SW ) * K * s

adapted from Corbière et al (2006) Tellus B, in press Sea surface pCO 2 in the western subpolar gyre 300 pCO 2 [µatm] Atmospheric Sea surface 2004

Sea surface pCO 2 in the western subtropical gyre near Bermuda adapted from Bates (2006) JGR in review pCO 2 [μatm] Atmospheric Sea surface

Air-to-sea CO 2 flux in the western subtropical gyre near Bermuda adapted from Bates (2006) JGR in review Air-to-sea flux CO 2 [mol m -2 year -1 ]

Change in SST [ o C] Change in air-to-sea CO 2 flux [mol m -2 yr -1 ] Change in air-to-sea CO 2 flux versus change in sea surface temperature adapted from Schuster and Watson (2006) JGR, in review 6 1,2: Schuster and Watson (2006) 3: Corbière et al. (2006) 4,5: Lüger et al. (2006) 6: Bates (2006) Assigning approximate areas to these regions we estimate a decrease in the sink, from mid 90s, to , of / Pg C yr -1 ~60% of the “climatological” flux. The North Atlantic sink is very variable on decadal time scales!

Changes in the North Atlantic Oscillation (Dec to Mar) Data from Climate Research Unit, University of East Anglia High index Lower index

from Häkkinen and Rhines (2004) Science 304: Changes in North Atlantic surface currents, e.g. the subpolar gyre 1992 to 2002 determined by altimetry data

Summary The North Atlantic sink for atmospheric CO 2 is very variable on decadal time scales: in particular, it probably declined ~50% from the mid 90s to the early 2000s. Most current ocean carbon models cannot reproduce this variability. Under Carbo-Ocean, an operational observing system has been established which, for the first time in any ocean basin, enables calculation of air-sea flux with good time and space resolution. Ongoing work: improve the estimation of fluxes determine the underlying causes of changes Use fluxes, in concert with the terrestrial and atmospheric carbon community, to constrain the overall carbon budget

Countries, institutions, and companies involved in the research

The global carbon cycle adapted from IPCC (2001) Reservoirs in Pg C (= g C) Fluxes in Pg C year - -1 Total atmosphere: 750 Surface ocean: 670 Deep ocean: 36,700 Total lithosphere: > 75,000, Plants: Soil & detritus: 1, Total land: 2, Total ocean: 38,400 Anthropogenic 6.3

The changes between the UK and the Caribbean from Schuster and Watson (2006) JGR, in review monthly sea surface pCO 2 annual air-to-sea flux

from Sabine et al (2004) Science 305: 367 – 371, supplement Anthropogenic CO 2 in the different ocean basins Column inventory [mol m -2 ] 0o0o 80 o S40 o S40 o N Latitude

from Sabine et al (2004) Science 305: 367 – 371, supplement Anthropogenic CO 2 in the different ocean basins Latitudinal inventory [mol m -2 ] 0o0o 80 o S40 o S40 o N Latitude Total laitudinal inventory [Pg C] o0o 80 o S40 o S40 o N Latitude