Air- sea CO 2 flux in the global coastal ocean: Simulated trend and anthropogenic uptake

Transcription

1 Air- sea CO 2 flux in the global coastal ocean: Simulated trend and anthropogenic uptake Timothée Bourgeois, James C. Orr, Laure Resplandy, Chris<an Ethé, Marion Gehlen and Laurent Bopp

2 INTRODUCTION METHODS ASSESS TREND CONCLUSION During the : A missing component? OCEAN EMISSIONS ATMO (Pg C y - 1 ) LAND USE LAND From Regnier et al. (2013)

3 INTRODUCTION METHODS TREND ASSESS CONCLUSION A missing component? OCEAN During the : EMISSIONS 0.2? COAST ATMO - 1?? (Pg C y ) LAND USE From Regnier et al. (2013), Wanninkhof et al. (2013) LAND?

4 Terrestrial inputs Freshwater, C, N, P, Si, Fe CO 2 The coastal ocean and its carbon cycle CO 2 Atmosphere ~ 70 km TOTAL CARBON 0.2 to 0.4 Pg C yr - 1 Chen et al. (2013) Laruelle et al. (2014) < 200 m

5 Terrestrial inputs Freshwater, C, N, P, Si, Fe CO 2 Mean shelf width = 70 km The coastal ocean and its carbon cycle CO 2 Atmosphere ~ 70 km TOTAL CARBON 0.2 to 0.4 Pg C yr - 1 Chen et al. (2013) Laruelle et al. (2014) < 200 m! Carbon cycle global model resolu]on = 100 km

6 Outline A first high- resolu@on modelling study of air- sea CO 2 fluxes (FCO 2 ) in the coastal ocean: Model evalua]on for total FCO 2 Anthropogenic carbon uptake

7 Version: Model configura]on NEMO (PISCES for biogeochemistry, LIM for sea ice) Global grid: Forcing dataset: 20 to 50 km horizontal resolu]on 5 to 30 m mean ver]cal grid spacing for the m depth Atmospheric reanalyses (DRAKKAR) Ini]al condi]ons: WOA (nutrients), GLODAP (DIC, ALK), Levitus (T, S) Fe from model River dataset: Ludwig et al. (1996) for constant river discharge 50- y spin- up Natural FCO 2 (143 years) Natural + Anthropogenic FCO year climatology

8 Simulated total FCO 2 for 2012 mol C m - 2 yr - 1 Takahashi et al. (2009) Year 2000 SOURCE SINK

9 Bathymetry (m) Zoom on the East China Sea Model - 2 mol C m - 2 yr - 1 or - 27 Tg C yr - 1 Observa]on- based mol C m - 2 yr - 1 or - 19 Tg C yr - 1 Laruelle et al. (2014)

10 The MARCATS: MARgins and CATchment Segmenta]on Laruelle et al. (2013)

11 Skills assessment for total FCO 2 SOURCE R = 0.7 RMSE = 0.9 mol C m - 2 yr - 1 Coastal total carbon uptake (Pg C y - 1 ): Model: 0.27 SINK Data es]mates: 0.2 to 0.4 Data from Laruelle et al. (2014)

12 Coastal uptake of anthropogenic carbon λ Anthropogenic carbon uptake ( ) Surface: - Global Ocean: 2.3 Pg C y km 2 Uptake of anthropogenic carbon (mol C m - 2 yr - 1 ) - Coastal Ocean: 0.1 Pg C y - 1 (4.5%) km 2 (7%)

13 A 1 st model es]mate of anthropogenic carbon uptake by the coastal ocean: 0.1 Pg C y - 1 ± 10% ( ) Future needs: - Bejer coverage for CO 2 measurements - Missing processes (e.g. sedimental/estuarine processes, ]des) - Higher spa]al resolu]on? Ongoing work: - Further enhance resolu]on - New ]me- varying river input from Mayorga et al. (2010)

14 Simplifying hypothesis & limits PISCES: Redfield ra]o (C/N/P) Implicit processes : - calcifica]on in nanophytoplancton - bacteria remineralisa]on Absence of specific coastal processes: sedimental processes, coastal currents, ]des River inputs: Contant C/N/P/Si between rivers No interannual variability Misrepresenta]on of the proximal coastal zone (estuaries, wetland, mangroves)

15 INTRODUCTION METHODS RESOLUTION 1/2 RESOLUTION TREND CONCLUSION MARCATS Global Segmenta]on Laruelle et al. (2013)

16 INTRODUCTION METHODS RESOLUTION 1/2 RESOLUTION TREND CONCLUSION Effect of spa]al resolu]on enhancement Obs Total

17 Mean surface Revelle factor for MARCATS in

18 Drivers of air- sea CO 2 fluxes