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 HarrisonUniversity of Birmingham

Ellie HighwoodUniversity of Reading

Overview

• Atmospheric inputs into the ocean

• Poseidon 332 cruise Jan-Feb 2006

• Discovery 3xx cruise Jan-Feb 2008

Dust Inputs to the OceansTg (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 0.15(1% solubility)

N. Atlantic receives largest global dust load

Proximity to Sahara

Modelled dust deposition, Tegen et al. 2005

The North Atlantic: high dust The North Atlantic: high dust inputsinputs

AMT 15 TransectSouthampton, UK - Capetown, S. Africa, September October 2004

(Upwelling Data Excluded)

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-20-16-12-8-40481216202428Latitude (°N)

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NEC/CC TSM EqUp GG/SEC STG/BC

Sarthou, Achterberg et al., Deep Sea Res. 2003

Polarstern Anreise cruise 2000

(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 VerdeClosed 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

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Cape Verde dust

Dust particles detected during cruise using ATOFMS

Cruise track

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Surface water dissolved Fe

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Surface water

dissolved free organic Fe binding ligands

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Rijkenberg et al., 2007 Submitted to Marine Chemistry

Surface water microbial community

Prochlorococcus

Transect dates

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Picoeukaryotes

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Transect datesTransect dates

Discovery 314 Cruise 2007

• Cancelled due to problems with vessel

Discovery 326 Cruise 2008• Study spatial-temporal variability in atmospheric dust inputs and phytoplankton-bacterial responses

Cruise PlanRegion: transect west of the N Africa into oligotrophic waterslooking for dust stormsCruise track will be guided by satellite observations of dust

Period: 32 days-January 5-February 5

Discovery 326 Cruise 2008Measurements 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