Particle transport and organic carbon fluxes off NW Africa: impact of dust and carbonate. G. Fischer (1) , M. Iversen (3, 4) , G. Karakas (3) , N. Nowald (1) , P. Helmke (2) , R. Davenport (1) , V. Ratmeyer (1) , G. Wefer (1) - PowerPoint PPT Presentation
Particle transport and organic carbon fluxes off NW Africa: impact of dust and carbonate G. Fischer (1) , M. Iversen (3, 4) , G. Karakas (3) , N. Nowald (1) , P. Helmke (2) , R. Davenport (1) , V. Ratmeyer (1) , G. Wefer (1) (1) Geosciences Department and Research Center Ocean Margins, University of Bremen, Germany (2) School of Life Sciences, Arizona State University, Tempe, Arizona, USA (3) Alfred-Wegener-Institute for Polar and Marine Research, Bremerhaven, Germany (4) Max Planck Institute for marine Microbiology, Bremen http://www.rcom.marum.de/Project_B3
Transcript
Particle transport and organic carbon fluxes off NW Africa:
impact of dust and carbonate
G. Fischer (1), M. Iversen (3, 4), G. Karakas (3) , N. Nowald (1) , P. Helmke (2) , R. Davenport (1) , V. Ratmeyer (1) , G. Wefer (1)
(1) Geosciences Department and Research Center Ocean Margins, University of Bremen, Germany(2) School of Life Sciences, Arizona State University, Tempe, Arizona, USA
(3) Alfred-Wegener-Institute for Polar and Marine Research, Bremerhaven, Germany(4) Max Planck Institute for marine Microbiology, Bremen
http://www.rcom.marum.de/Project_B3
Outline
• Introduction
• Organic carbon fluxes vs dust and carbonate off NW Africa
• Sinking velocities of particles in the Atlantic and off Cape Blanc
• Advective transport off NW Africa
• Summary and outlook
http://www.rcom.marum.de/Project_B3
Primary Production in four Eastern Boundary Current Systems
(EBC‘s)
Carr, 2002
Canary Current 0.3 GT C yr-1
(carbonate production system with high dust supply)
Winter-spring maximum of particle flux in the eastern N‘Atlantic: highest values in the Cape Blanc area
1 0 °
2 0 °
3 0 °
- 3 0 ° - 2 0 ° - 1 0 °
1 0 0 0 m
4 0 0 0 m
N W -
A f ric a
C a p e
G h i r
C a p e
B la n c
C a p e
V erd e
E B C
L P
C B
E U M E L I-m e so
E U M E L I-o l ig o
C V
N A B E 3 4 °N
E S T O C /CI
ITC
Z
S A L
Su mm e r d us t plu me
t rade w
ind s
Win
ter d
us t plu
me
G u in ea D o m e
CC
N E C
N E C C
A C
1-Jan 1-Apr 1-Ju l 1-O ct 1-Jan
0
100
200
300
400
Me
an
se
aso
na
l ma
ss fl
uxe
s (m
g m
-2 d
-1)
w in ter spring sum m er fa ll
E BC 2-1
C I 7
LP 1
N ABE 34°N
E U M ELI-m eso
C B 8
EU -oligo
C V 1-2
CBi
Atmospheric – ocean coupling off NW Africa ?
aerosol index vs lithogenic fluxes
Annual fluxes and composition
Cape Verde
Lithogenics=dust/carbonatevs organic carbon off NW Africa
0 10 20 30 40 50a n n u a l ca rb o n a te flu x (g m -2)
0
2
4
6
8
an
nu
al o
rga
nic
ca
rbo
n f
lux
(g m
-2)
C org/C carb= 1.3r²=0.91
0 5 10 15 20 25a n n u a l lith o g e n ic flu x (g m -2)
0
2
4
6
8
an
nu
al o
rga
nic
ca
rbo
n f
lux
(g m
-2)
C org/lith = 0.22r²=0.62
Organic carbon and dust fluxes
at four coastal sites 1-Jan 1-Apr 1-Ju l 1-O ct 1-Jan
advection of chl-a (SeaWiFS) and deep carbon fluxes
120 m d-1
90 m d-1
~ 100 km/30 days
Helmke et al., 2005, GBC
CB9 (meso)
eu- vs mesotrophic fluxes at 1300m
1-Jan 1-A pr 1-Ju l 1-O ct 1-Jan
0
200
400
600
800
1000C Bi_1 (eu)
20032004
1-Jan 1-A pr 1-Ju l 1 -O ct 1-Jan
0
200
400
600
800
1000
Tot
al m
ass
flux
(mg
m-2
d-1
)
C B_14 (m eso)
20032004
E-W advective transport of particles of ~ 100 km / 30 days
no distinct winter/sprin
g bloom
~ 45 daysdelay
CBi_2(eutrophic site)
1-Jan 1-Apr 1-Ju l 1-O ct 1-Jan
0
500
1000
1500
Tot
al m
ass
flu
x (m
g m
-2 d
-1)
C Bi_2 upper (eu)
1-Jan 1-Apr 1-Ju l 1-O ct 1-Jan
0
500
1000
1500
Tot
al m
ass
flu
x (m
g m
-2 d
-1)
C Bi_2 low er (eu)
20042005
fluxes very low
730 m d-1
Flow velocimeter
Pellet sinking velocities (CBcoastal-2)
Larvacean pellets ?
s.v. = 730 m d-1
400 x 1000 µm (ellipsoidal-type)
1.3 g cm-3 (quartz, coccos, diatoms)
CBi_2 u #10 CBi_2 l #10
CBi_2 l #10
ROMS-simulated distributionof larger particles > 150µm of shelf origin:
s.v. = 5 m d-1
Karakas et al., JGR, 2006
‚Intermediate Nepheloid Layer (INL)‘
persistentfeature
particles> 150 µm
Cape Blanc transect (~21°N)
ROMS-simulated offshore advection of particles in 400 m
Particle cameraprofiles
sediment trap sites
Summary and outlook organic carbon is best coupled to carbonate ballast
(except Cape Verde site)
s.v. estimated from chlorophyll and flux patterns were between65 and 250 m d-1 (larvacean pellets 730 m d-1)
flux patterns and chlorophyll distributions indicate a large advective component
particles advected from the shelf and producing an INL have s.v. of only 5-10 m d-1, but are relatively large (> 150 µm)
CURRENT and FUTURE RESEARCH- define various classes of particles and their s.v. (camera, ROV sinking chamber)- in situ s.v. (ROV sinking chamber)- lab measurements of s.v. of produced aggregates (flow system)- model particle fluxes (transport–ecosystem model approach)
ROMS: Model Configuration- 3-D hydostatic ocean model
- Parent only (8 km grid)
- Initialisation with January WOA 2001 climatology (cold start)
- 3 years spin-up with monthly COADS forcing
- QuikSCAT satellite daily winds
Nested Grid Configuration
- Etopo2 bathymetry
- Child grid 2.7 km
- 32 vertical levels
Gruber et al., 2005
Coupled Ecosystem Model in ROMS
Particle distribution:observations and modelling (ROMS - ecosystem)
