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The influence of dust on ocean
biogeochemistry;
chasing Saharan dust storms
Eric Achterberg, Micha Rijkenberg, Polly Hill,
Matt Patey, Maria Nielsdottir, Mark Stinchcombe,
Jane Heywood, Duncan Purdie, Mike Zubkov,
Peter Statham
National Oceanography Centre Southampton
Claire Powell, Tim Jickells and Alex Baker
University of East Anglia
Manuel Dall’osto and Roy Harrison
University of Birmingham
Ellie Highwood
University of Reading
Overview
• Atmospheric inputs into
the ocean
• Poseidon 332 cruise
Jan-Feb 2006
• Discovery 3xx cruise
Jan-Feb 2008
Dust Inputs to the Oceans
Tg (1012) yr-1
Global Dust Production
1700
Dust Inputs To The Oceans
442
Iron Inputs To The Oceans
15.5
Soluble Iron Inputs To The Oceans
(1% solubility)
0.15
The North Atlantic: high dust inputs
N. Atlantic
receives largest
global dust load
Proximity to
Sahara
Modelled dust deposition, Tegen et al. 2005
AMT 15 Transect
Southampton, UK - Capetown, S. Africa, September October 2004
(Upwelling Data Excluded)
Polarstern Anreise cruise 2000
NEC/CC
TSM
EqUp
GG/SEC
STG/BC
1.8
Dissolved Fe (nM)
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
28
24
20
16
12
8
4
0
Latitude (°N)
-4
-8
-12
-16
-20
Sarthou, Achterberg et al., Deep Sea Res. 2003
(ii) Hydrocast section data
Dissolved iron (AMT 15)
Ussher, Achterberg, Worsfold, in prep.
Surface water (1000 m) dissolved iron and aluminium (nmol/kg) in the Atlantic
along CLIVAR A16 (2003; Chris Measures and Bill Landing)
Main hypothesis of our UK SOLAS project:
Atmospheric inputs control rates of primary production and
microbial diversity in oceanic waters where nutrients are
limiting
Poseidon Cruise POS 332
January 28 – February 23 2006
Objectives of cruise:
1. Provide improved estimate of dust
inputs to tropical N Atlantic
2. Determine influence of dust on species
diversity, nutrient cycling and N2 fixation
FS Poseidon
MODIS tau-869
Aerosol opt. depth
Surface water dissolved aluminium
nM
Surface water dissolved Fe
Surface water
dissolved free organic Fe binding ligands
nM
Rijkenberg et al., 2007 Submitted to Marine Chemistry
Conditional stability constants of Fe binding ligands in
surface water
Open circles: south of Cape Verde
Closed circles: north and east of Cape Verde
CTD FRRF profile for Cape Verde region
(typical for cruise)
Nitrogen fixation in the Cape Verde region
MODIS tau-869
Aerosol opt. depth
3 Feb. 14:25
(supplied by Steve Groom et al. PML)
MODIS tau-869
Aerosol opt. depth
4 Feb. 15:10
High volume aerosol filter
for February 4, 2006
Claire Powell, UEA
Dust particles detected during cruise using ATOFMS
2/13 0:00
2/12 0:00
2/11 0:00
2/10 0:00
2/9 0:00
2/8 0:00
2/7 0:00
2/6 0:00
2/5 0:00
2/4 0:00
2/3 0:00
2/2 0:00
2/1 0:00
1/31 0:00
1/30 0:00
1/29 0:00
1/28 0:00
1/27 0:00
ATOFMS counts / hour
140
dust_1
120
dust_2
100
Cape Verde dust
80
60
Saharan dust
40
20
0
Cruise track
1
3
2
Surface water dissolved Fe
0.3
n = 16
n = 17
[Fe_diss] (nM)
0.25
0.2
0.15
0.1
0.05
0
first transect second+third
transect
nM
Surface water
dissolved free organic Fe binding ligands
n=4
n=3
nM
Rijkenberg et al., 2007 Submitted to Marine Chemistry
Surface water microbial community
2.5e+5
80000
6000
Picoeukaryotes
Synechococcus
Prochlorococcus
5000
2.0e+5
60000
n = 14
n=7
n=8
n = 14
n=7
n=8
Feb 3-4
Feb 10
Feb 11
1.5e+5
n = 14
n=7
n=8
1.0e+5
Cells/ml
Cells/ml
4000
40000
3000
2000
20000
5.0e+4
1000
0.0
0
Feb 3-4
Feb 10
Transect dates
Feb 11
0
Feb 3-4
Feb 10
Feb 11
Transect dates
Transect dates
Discovery 314 Cruise 2007
• Cancelled due to problems
with vessel
Discovery 326 Cruise 2008
• Study spatial-temporal variability in
atmospheric dust inputs and phytoplanktonbacterial responses
Cruise Plan
Region: transect west of the N Africa into oligotrophic waters
looking for dust storms
Cruise track will be guided by satellite observations of dust
Period: 32 days-January 5-February 5
Discovery 326 Cruise 2008
Measurements and experiments:
-Dissolved and particulate Fe, Al, Mn analyses
-Nanomolar and micromolar nutrients analysis
-Microbiology (flow cytometry; FISH; labelled amino acid uptake)
-Nitrogen fixation measurements, with NIFH gene determination
-DMS measurements and UV exposure studies
-Water column light measurements
-Rain and high volume dust collection for subsequent land-based analysis
-Real-time ATOFMS measurements of aerosol particles
-Low volume dust collection with ship-board dissolution experiments (Bill
Landing CLIVAR approach)
-Bottle dust dissolution experiments with subsequent dissolved Fe/Al,
nutrient measurements
-Studies of effect of leached dust solutions on microbial communities
-Nutrient addition bioassay experiments (incl. dust additions)
Acknowledgements
Captain and crew of FS Poseidon
NERC-UK-SOLAS for funding the
research
Post-doctoral position available at
NOCS on Fe biogeochemistry in
Iceland-Irminger Basins