Fayçal Kessouri , Caroline Ulses, Claude Estournel, Patrick MarsaleixLaboratoire d’Aérologie – Toulouse, France

Fabrizio D’Ortenzio, Louis Prieur, Nicolas Mayot, Orens P. de FommervaultLaboratoire d’Océanographie de Villefranche-Sur-Mer, France

Study of the plankton ecosystem variability using Modelling and

BioArgo floats deployment in the Mediterranean Sea

5th Euro Argo Users Workshop, Brest 16, 17 Mars 2015

Objectives

BioArgo Floats deployment and objectives

Global overview of Chlorophyll Seasonal Cycle

North-Western Restratification Evolution

Biochemical Functioning of the Mediterranean Sea

NW Seasonal evolution and Mesoscale processes

DOM(C, N, P)

DIMNitrate

AmmoniumPhosphate

Silicate

POMSmall (C,N,P,Chl)Large(C,N,P,Si)

Bacteria(C)

Mortality

Messy f

eedin

gPredation

Assim

ilation

Re-Mineralisation

Exudation

Nitrification

Egestion

ZooplanktonNano (C)Micro (C)Meso (C)

Photosynthesis

Respiration

Deposition

Eco3m-S (extended version from the model described by Auger et al. (2014)) : C, N,

P, Si cycles, variable intern ratios of the phytoplankton groups, uploading the dissolved O2 and the CO2 system

Vertically-integrated benthic model (Soetaert et al., 2001)

Biogeochemical Model

PhytoplanktonPico (Chl, C, N, P)Nano (Chl, C, N, P)

Micro (Chl, C, N, P, Si)

Oxygen(Dissolved O2)

CO2 systemDIC, Alkalinity

Air – sea exchanges

Respiration

Rivers inputs :15 Rivers

(Daily data series in the Rhône river, pers. comm. P.

Raimbault)+ other rivers from Ludwig

et al. (2010)

Hydrodynamics: Symphonie S26

RESOLUTION 1/111° ~ 1 Km

HydrodynamicsNEMOMed12/PSY2V2R42000-2013/2010-2014

RESOLUTION 1/12° ~ 7 Km

Atmospheric forcingALADIN (12km)/ECMWF (1°/8, 3h)

Atmospheric forcing :ECMWF (1°/8, 3h)

Rivers inputs34 rivers

+ other runoffLudwig et al. (2010)

Bio InitializingDatasets from

MEDAR/MEDATLAS (Lavezza et al., 2011)

Initializing / Consistent physical and

biogeochemical boundaries forcing

Previous global Mediterranean model

Atlantic Open Boundary

WOA climatology datasets

Grid:3D C-grid40 levels

Grid:3D

75/50 levels

5

4km Modis Satellite productModel

Surface Chlorophyll Concentrations

Provencal Sea

Tyrrhenian Sea

Algerian Basin

Adriatic Sea

North Levantine sub basin

South Levantine sub basin

1

1

2

2

3

3

4

4

5

5

6

76

7

South Ionian sub basin

µg/L

Doming form of the surface cycle

Important peaks in spring

F. D’Ortenzio and M. Ribera d’Alcalà, 2009

Northwest

Levantine Sea

Ionian Sea

Global overview Seasonal cycle

Biochemical Functioning of the Mediterranean Sea

PART 1

Northwest Ionian Sea Levantine SeaFLO

ATS

MO

DEL

8

0

4

0

4

0

20142013 20142013 20142013

201420132014201320142013

20142013 20142013 20142013

Depth

Time

Depth

Time

Depth

Time

Summer Winter

Annual cycle

West to east deepening of the chlorophyll maximum depth (DCM)

West to east DCM intensity diminishing (assumption.. Waiting for calibrated data)

Summer / Autumn Winter

Northwest Ionian Sea Levantine SeaFLO

ATS

MO

DEL

8

0

4

0

4

0

20142013 20142013 20142013

201420132014201320142013

20142013 20142013 20142013

Depth

Time

Depth

Time

Depth

Time

DCM

Nitracline

DCM

Nitracline

DCM

Nitracline

Depth

TimeDepth

Time

Depth

Time

Depth

TimeDepth

Time

Depth

Time

Depth of the Deep Chlorophyll Max Deep Chlorophyll Max Values

SUMMER

59 %41 %

0.38 µg/l0.52 µg/l

EASTWEST

Mean CHL in the DCM

Total contribution of the DCM for the primary production of the basin

POC DOC

Role for the Carbon export and

remineralisation

Balance

Organic Matter

Inorganic Matter

North-Western Mesoscale processesPART 2

FLOAT 17BFLOAT 35B

Events experienced by the floats

1st convection

2nd

convection

Phyto. Bloom

2nd

Phyto. Bloom

StrongMistral event

1st convection

2nd

convection

Mistral event

FLOAT 35B

Chlorophyll SALINITY

Depth

Time

Depth

Time

North western Mediterranean annual analysis (surface evolution)

Autumn Winter Spring Summer

2012 2013 Time (Months)

Norm

alized v

alu

es

1st Bloom

ConvectionPreconditioning Restratification StratificationStratification

1st conv.

Strong Mistral event

2nd

Phyto. Bloom

2nd

conv.

MODEL

BioArgo 35B

BioArgo 17B

Chlorophyll (norm)

NITRATE

North CentreSouthCentre

Deep chlorophyll maximum everywhere

Travelling to the North

Restratification

BLOOMMistral

event of 18 April

N-NO3 Stock (mmoles/m²)

Time (months)

North CentreSouthCentre

Strongwind

Strongwind

Strongwind

FLOAT 17B

Approaching a Northern current

meander

Depth

Time

Depth

Time

SST (°C)SST (°C)

Approaching a Northern current

meander

FLOAT 17B

Time (months)

Assumptions:

Decreasing of nutrients caused by the restratification

Oscillations caused by Mistral wind serval events

In a cyclonic eddy

Assumption:

Increasing of nutrients caused by a front vertical advection

Approaching a Northern current meander

Physical events produced in the model between April and September with the ability to impact the biological system

Convection

Bloom

Wind forcing effect

Eddies Current fronts

A B C D

Convection February 2013

Bloom April 2013

The “lovbio 17B” float was deployed under

these conditions

PhytoBloom

9-17 April 2013

Green profiles:Deep nitracline ~

80-90 mOUTSIDE THE BLOOM AREA

Red profiles:Shallow

nitracline < 50 mINSIDE THE

BLOOM AREA

A

Wind speed and direction (m/s)

Ekman Layer (m)

Surface Chla rate of change in April from 18 to 19th (µg/l/d)

Chla across the 2nd bloom (µg/l)

Mistral Wind

forcing

18 April 2013

Nitrate across the 2nd bloom (µg/l)

Max Bloom

Convection

Mistral event18 April 2013

400 w/m2 lost in 1 day

Deepening of the Ekman layer by 25m in 1 day

Heat flux (W/m²)

B

Nitrate injectionDepth

Latitude

Depth

Latitude

Cyclonic eddies

CNitrate uptake by Phytoplankton

(mmol N/m²/d)Surface velocity (m/s)

Northern current

front

D Density gradient at 100m depth

NITRATE (colors)SALINITY (Iso-lines)

CHLOROPHYLL

Nitrate uptake by Phytoplankton(mmol N/m²/d)

Depth

Latitude

Depth

Latitude

Export of organic matter

Nutrients injection

Front strength depends also on

wind forcing (Goffart et al 1995)

Conclusions

Importance of the BioArgo floats

Validation of the models thanks to the spatial and temporal aspects of the measurements

Coupled work between models and floats for better understanding :1. Mesoscale processes2. Temporary events3. Extreme events4. Seasonal cycles in Mediterranean bioregions

Model + floats + cruises sampling represent an integrated survey of a large zones systems

1. Quantifying of the primary production and the deep export of dissolved and particulate carbon

2. Global biogeochemical functioning of the Mediterranean Sea

Main objectives

Thank you

Results will be presented at the EGU Conference in Vienna (Austria) starting from April 12th 2015

Session 1: OS2.22 Posters: The CO2 system in the Mediterranean Sea (Ulses et al) Mediterranean organic and nutrients budget (Kessouri et al)

Session 2: OS3.11 Poster : North Western winter and spring mesoscale analysis from modelling and MerMex-Dewex experiments (Kessouri et al)

Acknowledgment to Jonathan Beuvier (Mercator Ocean)