Institut universitaire europeen de la mer (iuem) Laboratoire des sciences l’environnement marin (LEMAR) Up or down: Modeling the fates and rates of phytoplankton carbon in the North Atlantic Ocean C hristoph Stegert Laurent Memery Thomas Gorgues Julie Deshayes

MOTIVATION: Where does the carbon go? Background

MOTIVATION: Where does the carbon go? Background

P DIC MOTIVATION: Where does the carbon go?

Background P DIC fisheries MOTIVATION: Where does the carbon go? Z Fish Food web dynamics

Background P DIC Z Fish D Deep Sea fisheries Carbon export MOTIVATION: Where does the carbon go? Food web dynamics CO 2 storage

Background P DIC D Deep Sea fisheries Carbon export Remineralisation Sedimentation MOTIVATION: Where does the carbon go? CO 2 storage Z Fish Food web dynamics

Background P DIC D Deep Sea fisheries Carbon export Remineralisation Sedimentation UP or DOWN What is/ What determines this ratio MOTIVATION: Where does the carbon go? CO 2 storage Z Fish Food web dynamics

Background P DIC D Deep Sea CO 2 storage fisheries Carbon export Remineralisation Sedimentation UP or DOWN Possible consequences of climate change on the ratio What is/ What determines this ratio MOTIVATION: Where does the carbon go? Z Fish Food web dynamics

How much of Primary Production is transported to the deep ocean (carbon export)? What are regional differences in the carbon transport and how do they change during the period? What is the structure of the links of primary production and carbon export in the North Atlantic Ocean? MOTIVATION: Where does the carbon go? Specific questions I want to answer in this talk:

Besides carbon the nutrient (N,P,Si,Fe) and Oxygen cycles are simulated Model concept: Carbon cycle DIC Pdiat Pnano Zmicro Zmeso DOC POCGOC Model configuration: Physics:NEMO3.4 Biogeochemics:PISCES Area:North Atlantic 20S to 80N Resolution:1/4° Simulation: Major fluxes: 1Primary Production New Production [100m integrated annual avg.] 2+3Zoo Grazing 4+5Mortality 6-8 Plankton losses 9Nitrification 10Remineralisation 11Carbon Export [at 1000m, annual average] 11

Validation of model variables Validation: Surface Nitrate annual cycle (log 10 ) WOA09MODEL

Validation of model variables Validation: Ratio of Diatoms and Nanoplankton PHYSAT MODEL

Validation of model variables Validation: Carbon export at 100m (gC/m2/yr) Schlitzer MODEL

SPG and STG have contrasting environment UP or DOWN: regional variability STG subtropical gyre SPG subpolar gyre NECS Europ. Shelf GST Gulf Stream CUW Canary Upwelling Sea surface temperature

F-ratio shows higher pelagic production in the Northern NA and SPG UP OR DOWN: NewP : TPP (f-ratio)

Highest f-ratio in SPG, very strong correlation in Canarian Upwelling and STG UP or DOWN: regional variability STG SPG NECS GST CUW avg = 0.69 p = 0.61 avg = 0.41 p = 0.89 avg = 0.34 p = 0.99 avg = 0.38 p = 0.93 avg = 0.33 p = 0.58 New P (y) TPP (x) [MolC/m2/y]

High ratio in Labrador Sea UP OR DOWN ep-ratio: Export (1000m): TPP

Export highest in SPG, and strong correlation in CUW and STG UP or DOWN: regional variability: Carbon export at 1000m STG SPG NECS GST CUW Export (y) TPP (x) [MolC/m2/y] avg = 0.15 p = 0.02 avg = 0.09 p = 0.55 avg = 0.04 p = 0.98 avg = 0.05 p = 0.95 avg = 0.06 p = 0.71

Increased TPP is followed by increased grazing and export except in SPG UP or DOWN: interannual variability TPP PHY ZOO GRAZING EXPORT GST SPG STG NECS CIW

Provinces: Clustering Longhurst provinces based on physical/ biogeochmical variables

CLUSTER: Export (1000m) and TPP Differences in the structure compared to upper layer dynamics

CLUSTER: Grazing and TPP Regional differences in the structure of coupling to export

Background P DIC Z Fish D Deep Sea CO 2 storage fisheries Carbon export Food web Remineralisation Sedimentation UP or DOWN OUTLOOK the role of zooplankton

Background P DIC Z D Deep Sea CO 2 storage fisheries Carbon export Remineralisation Sedimentation UP and DOWN OUTLOOK the role of zooplankton Vertical migration Fish Food web

Conclusions THANK YOU for your interest. This work was done within the FP7 program Basin-Scale Analysis, Synthesis and Integration We would like to thank -TANGGO consortium: travel support Different biological processes, e.g. zooplankton behavior, can influence these ratios. How much of Primary Production is transported to the deep ocean (carbon export)? Export at 1000m is ca. 5-15% of PP in upper 100m, while New Production is highest in the northern North Atlantic. What are regional differences in the carbon transport and how do they change during the period? Dynamics in SPG are significantly different to STG and other regions. Coupling of PP and EXP in the STG and for PP and Grazing in most regions. Strong decoupling in SPG. What is the structure of the links of primary production and carbon export in the North Atlantic Ocean?

Grazing lowest in SPG, all other regions show strong correlation UP or DOWN: regional variability STG SPG NECS GST CUW Grazing TPP [gC/m2/y] avg = 1.01 p = 0.59 avg = 1.17 p = 0.98 avg = 1.38 p = 0.99 avg = 1.25 p = 0.99 avg = 1.30 p = 0.98