Context Events Situation

LimitsStrategy

Glider Observation of Suspended Particle Dynamics in the Gulf of Lions

Gaël MANY1, François Bourrin1, Romaric Verney2, David Le Berre2, Matthias Jacquet2

Kiel - COST Action, 6th EGO Glider Conference - June, 17th, 2014

1 21

AQUA-MODIS01/21/2014

Context Events Situation

LimitsStrategy

1

200 m

2000 m

0 m

Main processes in the sediment transport ?

River inputs

(floods)

Offshore

Exports

(storms)

Sedimentation / erosion

Atmospheric deposits

8 % of total ocean surface

90% of total ocean biodiversityLOICZ

Key area

Coastal area : an interface between continent and deep-sea

Marine particles : - Food - Contaminant- Sediment

Algal Bloom

Context Events Situation

LimitsStrategy

Marine

Wind

Coastal

Rivers

Rhône

Alongshore circulationUlses et al., 2005

Importance of the Rhône(~80% of total material inputs)

Courp et Monaco, 1990

Pro-deltas

Preferential deposit areas+ -

Bourrin et al., 2006

Our study area : The Gulf of Lions 2

Context Events Situation

LimitsStrategy

Marine

Wind

Coastal

Rivers

Rhône

Fixed buoys

Mooring lines

Slocum Coastal Glider deployments 1 – Têt shelf = 1045 km, Spring 2013 > 26 Sections 2 – Rhône shelf = 450 km, Winter 2014 > 9 Sections

TUCPA campaign - Water sampling (SSC, POC) - CTD profile - LISST measurements

MODIS pictures

3

Limited by meteorological conditions

Our Strategy

Context Events Situation

LimitsStrategy

Objectives

Main events involved in the particle dynamics of the

Gulf of Lions

Winter storm (Bourrin et al., In prep)

Spring bloom period

Winter flood event

Optical sensors calibration

Chl a (factory calibration) to Chl a (In Situ calibration)

Turbidity (NTU units) to SSC (mg/L)

done

To do

Context Events Situation

LimitsStrategy

GFF filtration = SSC (mg/L) sampling HACH turbidimeter (NTU)

Turbidity / SSC calibration

Glider NTU sensor calibration

(bb 700nm)

Filt

rati

on

sys

tem

4

Context Events Situation

LimitsStrategy

CDOM (ppm)

Spring Bloom situation

April 2013

CTD

Stratified water

Complex and small structure

CDOM

Noisy sensor signal

SSC

BNL ~ 2 to 0.5 mg/L

(cross-shore)

Thickness 15-30m mab

Chl a

surface ~ 1µg/L (Im. Sat.)

subsurface >3µg/L (Glider)

SSC (mg/L) Chl a (µg/L)

SSC (mg/L)

5

Context Events Situation

LimitsStrategy

Spring Bloom situation - Chl a (µg/L) spatio-temporal variability

0

100

Dep

th (

m)

0

100

Dep

th (

m)

0

100

Dep

th (

m)

Distance to POEM Buoy (km)

302010

April, 10-15, 2013

Distance to POEM Buoy (km)

302010

May, 7-13, 2013

6

Context Events Situation

LimitsStrategy

SSC (mg/L) Chl a (µg/L)

SSC (mg/L)

Winter flood situation

February 2014

Rhône river discharge > 4000m3/s

Plume length = ~ 55km

CTD

Plume identification

Length > 45km

Thickness : 20-40m

CDOM

Plume vs BNL

Chl a

Low in plume (~1µg/L)

Correlation with MODIS

SSC

2 structures : plume / BNL

7

Context Events Situation

LimitsStrategy

SSC (mg/L)

Dep

th (

m)

Density

Dep

th (

m)

Surface turbid cell

15-20km offshore20m thicknessSSC > 5 mg/LDensity < 25Detached from mouth

Bottom turbid cell

50-90m depthSSC > 3mg/LResuspension (?)Plume sedimentation (?)

Winter flood situation 8

Context Events Situation

LimitsStrategy

Rhône plume spatial variability - SSC (mg/L)

10 20 30 40

Distance to Roustan-Sud buoy (km)

0

2

4

6

8

10

0

100

20010 20 30 40

10-12/01/2014

9

0

100

200

De

plo

ym

en

t

0

100

200

01/30/14 to 02/12/14

Context Events Situation

LimitsStrategy

0

100

20010 20 30 40

Pre-flood event Flood event

30-31/01/2014

10-12/01/2014

0

2

4

6

8

10

30-31/01/2014

Plume length > 50km

10 20 30 40

Plume length > 15km

Rhône discharge

m3/s

~4000m3/s

Rhône River plume spatial variability 10

0

100

200

De

plo

ym

en

t

~2500m3/s

Context Events Situation

LimitsStrategy

Glider problem and deployment limits

Glider recoveryby safety guards

Ballast problem

Emergency procedure

60kmdrift

11

14/02/2014

Thank you for

your attention