The 45th International Liège ColloquiumLiège, Belgium 13th – 17th May 2013

Primary production and the carbonate system in the Mediterranean Sea

Cossarini G., Lazzari P., Solidoro C.

OGS – National Institute of Oceanography and Experimental Geophysics

Trieste (Italy)

Touratier and Goyet, 2012

Few data on carbonate chemistry are available for the Mediterranean Sea

Intense gradients from west to east

Introduction: understanding Ocean Acidification calls for the resolution of the carbonate system and its variability

Carbonate system: DIC (CT) and Alkalinity (AT)

Introduction: Mediterranean Sea circulation and boundaries

Surface circulation Siokou-Frangou et al., 2010

Anti estuarine circulation at Gibraltar

Alkalinity profile at Gibraltar Huertas et al., 2009

Nile

Input from Dardanelles:Alk 1.15 1012 mol/yDIC 12.6 1012 gC/yChopin-Montegut, 1993

Input from rivers:Alk 0.92 1012 mol/yDIC 11.23 1012 gC/yMeybeck and Ragu, 1995; Ludwig et al., 2009

PoRhone

EbroDardanelles

Longitudinal and latitudinal transects of chlorophyll a

Integrated vertical net primary production

LEVION

TYRALB SWE

NWM

Controlling mechanism: extinction factor coefficient (k)Declining DCM moving eastward

Lazzari et al., 2012

Introduction: spatial variability of trophic conditions

• Aim: evaluate scales of variability of carbonate system (DIC and alkalinity) in the Mediterranean Sea and quantify the contribution of physical & biological processes

1. 3D physical-biogeochemical model: OPATM-BFM

2. Reconstruction of alkalinity and DIC spatial patterns & validation

3. Decomposition of physical and biological contributions on spatial and temporal variability

4. Air-sea CO2 exchanges

Method: 3D coupled OPATM-BFM-carbonate model

BFM – Biogeochemical Flux Model Carbonate system

OCMIP II modelOrr et al., 1999

Wolf-Gladrow et al., 2007

OCMIP II modelSchneider et al.1999

Wanninkhof,1992

NutrientsConsumption/production

Alkalinity:Production: denitrification

phytoplankton uptake of NO3- and PO4

3-

mineralization and realise of NH4+

Consuption: phytoplankton uptake of NH4+

nitrification mineralization and realise of PO4

3-

DIC=[CO2]+[HCO3-]+[CO3

2-]consumption:photosynthesys

production: respiration by phyoplankton, zooplankton and bacterial functional type groups

www.bfm-community.eu

Atmopheric pCO2=360-390ppmPhysical and biogeochemical setup and validation Beranger et al., 2010; Lazzari et al. 2012 & poster Lazzari et al

Results: Alkalinity – spatial patterns and validation

mol/kg

Taylor Diagram: B0, B400, B1000: Boum 2008 cruise at 0, 400 and 1000 m; M0,M400, M1000: Meteor51 cruise at 0, 400 and 1000 m; Sm0, Sm400, So0, So400 Sesame dataset at 0 and 400 m, March and October cruises; P0: Prosope cruise, Dyf0, Dyf400, Dyf1000: Dyfamed site at 0, 400 and 1000 m.

1

2

3 4 5 6

1

23

4 56

mol/kg

Taylor Diagram: B0, B400, B1000: Boum 2008 cruise at 0, 400 and 1000 m; M0,M400, M1000: Meteor51 cruise at 0, 400 and 1000 m; Sm0, Sm400, So0, So400 Sesame cruises at 0 and 400 m, March and October cruises; P0: Prosope cruise, Dyf0, Dyf400, Dyf1000: Dyfamed site at 0,400 and 1000m.

1

23

4 56

1

2

3 4 5 6

Results: DIC – spatial pattern and validation

Longitudinal transectLatitudinal transect

Results: spatial variability DIC along W-E transect and its temporal variability

Annual average DIC concentration

Amplitude of the seasonal cycle

pH = 0.1-0.2

LEVION

TYRALB SWM

NWM

Decomposition of physical and biological part of the amplitude of the seasonal cycle

variability of physical fluxes: [mmol/m3/d]

flux at air-sea interface, advection and diffusion

LEVION

TYRALB SWM

NWM

variability of biological fluxes[mmol/m3/d]

Results: biological and physical contributions on DIC

Photosynthesis - respiration

Upwelling transport and diffusion of the adsorbed atmospheric CO2

Decomposition of physical and biological annual average fluxes

Results: biological and physical contributions on DIC

Biological carbon pump

LEVION

TYRALB SWM

NWM

physical process

Photosynthesis - Respiration

Decomposition of physical and biological effects: average annual signal

Results: biological and physical contributions on DIC

Biological carbon pump

LEVION

TYRALB SWM

NWM

Seasonal cycle of phytoplankton production and community respiration

mmol/m3/d mmol/m3/d

OPATM-BFM: sink of 1.6 x 1012 mol/y (-0.65 mol/m2/y)

Results: CO2 flux at air-sea interface

molC/m2/y

From D’Ortenzio et al., 2009

Other estimates:0.35-1.85 x 1012 mol/y

Copin-Montegut, 1993

2.1 x 1012mol/y Huertas et al., 2009

Sink source

OPATM-BFM: sink of 1.6 x 1012 mol/y (-0.65 mol/m2/y)

Results: CO2 flux at air-sea interface

molC/m2/ySink source

Switching off the biology from the system

-20% of atmospheric CO2 sink quantification (€) of the role of biology (ecosystem service) in carbon cycle

Conclusions:

•Mediterranean sea has strong spatial variability of carbonate system (model can help in reconstructioning patterns)

•Physical processes impact the spatial and temporal variability

•Biology has lower effect on seasonal scale but impacts on longer time scale

• CO2 flux affected by biological pump (~20%) at the present atmospheric pCO2 conditions

THANK YOU

Reseach founded by

http://www.ritmare.it/http://medsea-project.eu/