European Time-series Station ESTOC in the Eastern ...European Time-series Station ESTOC in the Eastern Subtropical North Atlantic Gyre Susanne Neuer Arizona State University OCCC Woods

European TimeEuropean Time--series Station series Station ESTOC in the Eastern ESTOC in the Eastern

Subtropical North Atlantic GyreSubtropical North Atlantic Gyre

Susanne Susanne NeuerNeuerArizona State UniversityArizona State University

OCCC Woods Hole 1-4 August, 2005

NASTNAST--WW NASTNAST--EEBATS

The North Atlantic The North Atlantic Subtropical Subtropical GyralGyralProvince (NAST)Province (NAST)

ESTOC

ICCM, ICCM, TeldeTelde, , GranGran CanariaCanaria

BuqueBuque oceanograficooceanografico‘‘TALIARTETALIARTE’’

ICCM, ICCM, TeldeTelde : : Group of Group of OctavioOctavio LlinasLlinasMariaMaria--Jose Jose RuedaRuedaAndres Andres CiancaCiancaFrancisco Francisco LuzardoLuzardoJuana Juana GodoyGodoyMarimarMarimar VillagarciaVillagarciaJavier MarreroJavier MarreroLleireLleire MorotoMorotoRosa MontanaRosa Montana

Univ. Las Palmas:Univ. Las Palmas:Group of Group of MelchorMelchor GonzalezGonzalez--DavilaDavilaMagdalena Magdalena CasianoCasianoLluisLluis LagleraLaglera

Group of Group of Joaquin HernandezJoaquin Hernandez--BritoBrito

IfMIfM Kiel:Kiel:Group of Group of GeroldGerold SiedlerSiedler

Thomas Thomas MMüüllerllerMichaela KnollMichaela KnollUweUwe KoyKoyMarkus Markus BusseBusseJJöörgrg ReppinReppinChristian HaagChristian Haag

Univ. Bremen:Univ. Bremen:Group of Group of GeroldGerold WeferWeferPeer Peer HelmkeHelmkeTim Tim FreudenthalFreudenthalHelgeHelge MeggersMeggersChristina Christina HaynHaynJens LangerJens LangerGGöötztz RuhlandRuhlandVolkerVolker RatmeyerRatmeyer

Support:

German ministry for Research and Education [BMBF]

EU (CANIGO, ANIMATE, MERSEA)Gobierno de CanariasRCOM (DFG), Germany

NASA (EOS) Co-PIs, R. Najjar, D. McGillicuddy

GeoB-Geosciences, University of Bremen; IfM-Institute for Marine Sciences, Kiel; ICCM-Canarian Institute for Marine Sciences, Gran Canaria;IEO-Spanish Institute of Oceanography, Tenerife; ULPGC-University of Las Palmas; UOL-University of Oldenburg; UBOZ-University of Bremen, Tracer Oceanography; UBCH-University of Bremen, Marine Chemistry; AWI-Alfred Wegener Institute, Bremerhaven; ETHZ: Swiss Technical University, Zürich; UHH: University of Hamburg.

Primary Production Upwelling

ESTOCSatellite StudiesICCMGeoB

- a Spanish-Germantime-series station northof the Canary Islands -

Saharan Dust

M o d e l i n g (G

eoB)

Monthly samplingMonthly samplingICCMICCMULPGCULPGC

Process studiesProcess studiesIfMIfM: : HydrographyHydrographyGeoBGeoB: Drifting traps, : Drifting traps, production rates, stableproduction rates, stableisotopes, Foraminiferaisotopes, ForaminiferaUOL: BioUOL: Bio--OpticsOpticsUHH: DOMUHH: DOMETHZ:CoccolithophoridsETHZ:CoccolithophoridsUBOZ: Tracer gasesUBOZ: Tracer gases

Moored particle studiesMoored particle studiesGeoBGeoB: Traps, Camera: Traps, CameraAWI: InfluxAWI: InfluxUBMCH: PumpsUBMCH: Pumps

ExportExportProductionProduction

Moored currentMoored currentmeasurementsmeasurementsIfMIfM

‘‘ExploringExploring--inin--spacespace’…’…..has been the has been the traditional way of ocean exploration sincetraditional way of ocean exploration sincethe first oceanographic expeditions.the first oceanographic expeditions.

But...But...

‘‘ExplorationExploration--inin--timetime’’

Few characteristics of the ocean and the seafloor Few characteristics of the ocean and the seafloor are in steady state, therefore the need is paramount are in steady state, therefore the need is paramount for sustained timefor sustained time--series investigationsseries investigations

Ideally in the combination of hypothesis-testing and development of measurement strategies and new observational tools…in the time domain, not space domain…..

oceanic carbon cycle

Silicifiers N2fixers

DMS producers

CalcifiersNano

phytoplankton

Fe NO3Si

CaCO3

DMSPO4 NH4

DOM

biological carbon pump

4944

4.5

CO2

CO2 + H2O (H2CO) +O2

Photosynthesis

90 1.8

0.5

5

PgC/yPgC/y

ExportExport

Modified after Corinne Le Queré

ESTOC

Hypothesis 1: Dust input influences primary Hypothesis 1: Dust input influences primary and export productionand export production

Hypothesis 2: Export ratio scales with input Hypothesis 2: Export ratio scales with input of of ‘‘newnew’’ nutrientsnutrients

ESTOC

The physical context and biogeochemistryThe physical context and biogeochemistry

ESTOC is located in the eastern boundary current region of ESTOC is located in the eastern boundary current region of the subtropical NA Gyrethe subtropical NA Gyre

a b

c d

Seasonal geostrophic transports for upper few hundreds meters along 29° NMichaela Knoll in John et al., 2004

Typical of a subtropical gyre station

Winter mixed layer from around 20 m in summer to up to 150 m in winter

Nitrate not measurable in upper mixed layer with standard methods

Phytoplankton biomass maximum in winter follows the break-up of the seasonal thermocline in late fall

Chlorophyll levels in winter are usually around 0.4 mg l-1, and in summer around 0.05 mg l-1 in the surface

Seasonal cycle at ESTOC TT

NONO33

ChlChl

Neuer et al, in prep.

-200

-150

-100

-50

0P

ress

ure

(dba

r)

0 0.1 0.2 0.3 0.4 0.5

1994 1995 1996 1997 1998 1999 2000

Chlorophyl a (µg/l)

Chlorophyll peaks during time of deepest mixing in winter.


Chlorophyll peaks during time of deepest mixing in winter.


Particle flux maxima in late winter following the maxima of chlorophyll and primary productivity

Strong interannualvariability concomitant with the variability in mixing depth

Yearly integrated primary production at ESTOC = 12 mol C m-2

yr-1 and integrated particulate C-export = 0.2 mol C m-2 yr-1

Particle flux and its relationship to surface water processes

Jan Jul Dec Jun Dec Jun Dec Jun Dec Jun Dec Jun Dec Jun Dec

0

40

80

120

Tota

l Flu

x

( mg

m-2

d-1 )

0.5 km1 km


18

22S

ST

(C)


0

0.2

0.4

0.6

0.8

Sur

face

chl

orop

hyll

(mg

m-3

)

Prim

ary

Prod

uctio

n (m

g m

-2d-1

)

ChlPP

1994 1995 1996 1997 1998 1999 2000


-1.6-1.2-0.8-0.4

00.40.8

Biol

C u

ptak

e (m

mol

m-2d-1

)

Neuer et al. in prepNeuer et al., in prep.

Seasonal and interannual variability in the carbon dioxide species

CT biol. calculated as difference between total NCtchange and contribution from air sea exchange and mixing.

1. Jan-March Increase of CT due to winter convection2. March-October:

CT decrease due to biol. productivity + outgassing

CT(biol) ranges between 2-4 mol/m2/yr Gonzalez-Davila et al., GBC, 2003

∆CT (total inorganic carbon) variation as difference between 2 months

Gonzalez-Davila et al. , GBC, 2003

Net CO2 fluxes at ESTOC are positive with an average value of 0.05 mol CO2 m-2 yr –1

p CO2 increases at a rate of 1.2 ± 0.3 µatm/yr

pH decreases 0.001 units/yr

CT increases at 0.9 ±0.2 µmol/kg/yr

Gonzalez-Davila et al. , GBC, 2003Neuer et al. in prep.

Seasonal and interannual variability in the carbon dioxide species

ESTOC

Hypothesis 1: Dust input influences export Hypothesis 1: Dust input influences export productionproduction

ESTOC

Hypothesis 1: Hypothesis 1: Dust input influences export productionDust input influences export production

ESTOC

Jan Apr Jul Oct Jan Apr Jul Oct Jan

0

20

40

60

80

100

Tota

l flu

x (m

g m

-2d-1

)1997 1998

0

200

400

600

800

Dust conc (µg m

-3 )

C

D

Particle fluxes at ESTOC and dust deposition determined at Gran Canaria

Neuer et al., GBC, 2004

Dust

Flux

SST MLD

ChlN-input

Neuer et al (in press, GBC)


0

40

80

120

160

200

Dus

t con

c (µ

g m

-3 )

Tota

l Flu

x (m

g m

-2d-1

)


0

40

80

120

160

200

Dus

t con

c (µ

g m

-3 )

Tota

l Flu

x (m

g m

-2d-1

)

+14 days

Do peaks in dust fluxes and traps coincide?

At ESTOC winter particle fluxes coincide with(or follow with a short lag) dust deposition

Neuer et al., GBC, 2004

OK, there is a coupling, but does that imply a causal relationship?

Rates (g m-2, Jan-March)

1997 1998

Aeolian deposition1… 3.3 8.1

Primary production2 38 33

0.76Export production3

(C org, 150 m)

1assuming mean deposition rate of 1 cm s-1 (Torres-Padrón et al. 2002); 2 Neuer et al., 2002; 3normalized to 150m (Martin et al., 1987, open ocean composite).

0.73

Dust derived N deposition (wet and dry) amounts to 4-6% of new nitrogen need at ESTOC (on an annual basis).

So, what about iron?So, what about iron?

1Torres-Padrón et al. 2002, 2 assuming Fe-content of 3.5% WT (Duce 1986); 3assuming a solubility index range of 1-10% (Fung et al. 2000); 4primary production of 12 mol C m-2 yr-1(Neuer et al. 2002) and Fe:C ratio of 10 µmol/mol (Sunda and Huntsman 1995, 1997)

Fluxes 1997 1998

Dust deposition 1

(g m-2 yr-1 )11 29

Total Fe-deposition2

(g m-2 yr-1 ) 0.38 1.03

Soluble Fe-deposition3

(mmol m-2 yr-1 )0.07-0.7 0.18-1.8

Total Fe-assimilation4

(µmol m-2 yr-1 )

Supplied/Assimilated

113 116

0.6 1.6

Iron:Highly episodic nature of dust deposition might impose feast-famine situation on the phytoplankton and eolic iron deposition may relief iron stress in winter when phytoplankton biomass is high (which might explain some of the observed temporal coupling in winter).

But: What about N2-fixation?

DIN/DIP is at Redfield ratio at ESTOC, but elevated at BATS. There is no indication of significant N2 fixation at ESTOC, i.e., stimulation by iron not relevant.

0.0 0.2 0.4 0.6 0.8Phosphate (µM)

0

2

4

6

8

10

Nitr

ate-

N (µ

M)

ESTOCBATS

Neuer et al., GRL, 2002

Winter

Summer


0

200

400

600

800

1000

Dus

t con

c (µ

g m

-3 )


0

1

2

3

Opa

l flu

x ( m

g m

-2 d-1

)

0

10

20

30

40

50

Carbonate flux ( m

g m-2 d

-1)

OK, no (major) enhancement of (new) production, what about a response on the organisms level?

Opal

Carbonate

Dust

Carbonate sedimentation is higher by a factor of Carbonate sedimentation is higher by a factor of 1.4, similar to the enhancement of 1.4, similar to the enhancement of lithogeniclithogenic

matter, in winter 1998matter, in winter 1998

Rates (g m-2, Jan-March)

1997 1998

Aeolian deposition 1… 3.3 8.1

Primary production2 38 33

Trap fluxes3

Lithogenic matter 0.94 1.4

Corg 3 0.73 0.76

Opal 0.08 0.07

Carbonate 1.6 2.3

1assuming mean deposition rate of 1 ms-1 (Torres-Padrón et al. 2002); 2 Neuer et al., 2002; 3 Corg: normalized to 150m (Martin et al., 1987, open ocean composite).

LithogenicCorgOpalCarbonate

LithogenicCorgOpalCarbonate

0.97

0.73

1.6

0.08

lithogenics15

Ballast: Despite the high lithogenic matter loading of sinking particles, carbonate is the main ballasting agent

2.65 g cm-32.71 g cm-3Density?

ESTOC

Hypothesis 1: Dust input influences Hypothesis 1: Dust input influences primary and export productionprimary and export production(nutrients, ballasting).(nutrients, ballasting).

Little influence on primary and export Little influence on primary and export production production

Feast/famine situation imposed by Feast/famine situation imposed by highly episodic iron highly episodic iron

Ballasting effect: rather smallBallasting effect: rather small

ESTOC

Hypothesis 2: Export ratio scales Hypothesis 2: Export ratio scales with input of with input of ‘‘newnew’’ nutrientsnutrients

0.2

0.4

0.6

0.8

1.0

Prim

ary

Prod

uctio

n

( g m

-2 d-1

)0.0

0.2

0.4

Surf

ace

chlo

roph

yll

( mg

m-3

)

A

B

1996 1997 1998

Jan Apr Jul Oct Jan Apr Jul Oct Jan Apr Jul Oct0

20

40

60

E-PO

C

(mg

m-2d-1

)

ESTOC MTESTOC STBATS

Seasonality of surface chlorophyll, integrated primary productionand export production at ESTOC and BATS

Chl a

PP

Epoc


Yearly integrated PP, E POC and ER (EPoc /PP) for ESTOC and BATS

PPmol C m-2 yr-1

E POCmol C m-2 yr-1

ER

BATS ESTOC BATS ESTOCa BATS ESTOCb

1996 16.3 11.9 1.4 0.24 / 0.16 0.086 0.017

1997 13.3 12.0 1.3 0.16 / 0.16 0.098 0.013

1998 13.9 11.7 0.7 -- / 0.20 0.050 0.017

AVG 14.5 11.9 1.1 0.2 0.08 0.016aShallow moored/surface tethered trap. Surface tethered trap value of 1996 and 1997composite of both years b Mean of moored and surface tethered traps.


What we would expect…

When averaged over appropriate spatial When averaged over appropriate spatial and temporal scales, new production is and temporal scales, new production is equal to export production.equal to export production.

Thus, under steadyThus, under steady--state conditions, one state conditions, one would expect the ratio of new to total would expect the ratio of new to total production (production (ff--ratio) to be equivalent to the ratio) to be equivalent to the export ratio (ER)export ratio (ER)

What does that mean…

Does a lower ER at ESTOC also imply lower Does a lower ER at ESTOC also imply lower input of new nutrients into the mixed layer input of new nutrients into the mixed layer compared to BATS?compared to BATS?

Three main sources of new nutrients: Three main sources of new nutrients: Wintertime convective mixingWintertime convective mixingMesoscaleMesoscale eddieseddiesNitrogen fixationNitrogen fixation

Mixed layer depth and Nitrate-N input at ESTOC and BATS

Cianca et al., in prep.

0

100

200

300

400

Nitr

ate-

N (m

mol

m-2

)

250

200

150

100

50

0

Mix

ed la

yer d

epth

(m)

1994 1995 1996 1997 1998 1999 2000

--- Mixed layer___ Nitrate-N

0

100

200

300

400

Nitr

ate-

N (m

mol

m-2

)

400

300

200

100

0

Mix

ed la

yer d

epth

(m)

1994 1995 1996 1997 1998 1999 2000

--- Mixed layer___ Nitrate-N

ESTOC

BATS

New Production based on nitrate draw down and mesoscale eddy

Activity at ESTOC and BATS

0.12 0.12 0.070.07-- 0.20.2BATSBATS

0.02 0.02 0.03 0.03 -- 0.20.2ESTOCESTOC

EddyEddy--inducedinducednitrate nitrate inputinputaa

(mol N/m2/yr)(mol N/m2/yr)

NitrateNitratedraw downdraw down(mol N/m2/yr)(mol N/m2/yr)

What does that mean…

Does a lower ER at ESTOC also imply lower Does a lower ER at ESTOC also imply lower input of new nutrients into the mixed layer input of new nutrients into the mixed layer compared to BATS?compared to BATS?

Three main sources of new nutrients: Three main sources of new nutrients: Wintertime convective mixingWintertime convective mixingMesoscaleMesoscale eddieseddiesNitrogen fixationNitrogen fixation

Snapshots of temperature and new production in a 0.1 degree resolution simulation of the North Atlantic (McGillicuddy et al., GBC, 2004)

New Production based on nitrate draw down and mesoscale eddy

Activity at ESTOC and BATS

0.12 0.12 0.070.07-- 0.20.2BATSBATS

0.020.020.03 0.03 -- 0.20.2ESTOCESTOC

EddyEddy--inducedinducednitrate nitrate inputinputaa

(mol N/m2/yr)(mol N/m2/yr)

NitrateNitratedraw downdraw down(mol N/m2/yr)(mol N/m2/yr)

ESTOCHypothesis 2: Export ratio scales Hypothesis 2: Export ratio scales with input of with input of ‘‘newnew’’ nutrientsnutrients

Yes, low export production at ESTOC is accompanied by a lower input of new nutrients compared to BATS (by mesoscalemesoscale eddy activity and nitrogen eddy activity and nitrogen fixationfixation)

AND: Lower input of new nutrients does not Lower input of new nutrients does not necessarily result in lower PP (or biomass) but necessarily result in lower PP (or biomass) but influences the removal efficiency (export influences the removal efficiency (export ratio) of biologically produced carbon into the ratio) of biologically produced carbon into the oceanocean’’s interior.s interior.

Conclusions

Especially by inter site comparisons can we learn Especially by inter site comparisons can we learn and test hypotheses on biogeochemical processes and test hypotheses on biogeochemical processes on a global scale and on multion a global scale and on multi--year time scales.year time scales.

TimeTime--series station ESTOC enables a view into series station ESTOC enables a view into ““the other sidethe other side”” of the subtropical of the subtropical NAtlanticNAtlanticgyre (which is different)gyre (which is different)

Andrés Cianca:

BATS and ESTOC: A comparison between Western and Eastern parts of the Subtropical

Atlantic Ocean

Peer Helmke:

Vanished without a trace: sedimentation pulses in the deep sea, can we

determine their origin?

NASA-EOS

Documents

European Time-series Station ESTOC in the Eastern ...European Time-series Station ESTOC in the Eastern Subtropical North Atlantic Gyre Susanne Neuer Arizona State University OCCC Woods