Koninklijk Nederlands Instituut voor ZeeonderzoekRoyal Netherlands Institute for Sea Research

A multi-proxy approach to time-series fluxes and coretop sediments:

A possibility to deconvolve temperature and salinity in open ocean environments?

NIOZ group: Ulrike Fallet, Isla Castaneda, Sanne Vogels, Geert-Jan Brummer, Stefan Schouten

I. Research objectives

1. Establish temperature relationships in planktonic foraminifera with Mg/Ca and δ18O

2. Verify these with satellite remote sensing SST and in situ T-S from moored CTD’s

Is it possible to eliminate salinity in this equation?

Salinity gradient in the Mozambique Channel is ~0.4‰

Calculation of salinity depends on accuracy of

satellite remote sensing

Mg/Ca and δ18O measurements

Intraspecies variation

3. Determine foraminifera fluxes to the channel floor

4. Apply results to coretop foraminifera to calibrate proxies

II. Research objectives

5. Compare Mg/ Ca and δ18O from planktonic foraminifera with

Coral proxies (Sr/Ca) off the coast of Madagascar

Organic matter proxies (Tex86, Uk37)

Downward particulate matter fluxes

Eddy transport through the channel (nutrient distribution by frontal upwelling, nutrient transport from coastal margins to the open channel, etc.)

Study area: The Mozambique Channel

Anti-cyclonic eddies passing through the channel at 70 days frequency

Eddies induce frontal upwelling and might bring nutrients to the surface

Enhanced foraminifera production in cooler frontal zones?

Implications for recorded temperature signal?

40 40.5 41 41.5 42 42.5 43

longitude [ºE ]

-3000

-2500

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0

dep

th [

m]

sedim ent trap

m ulticore

CTD

ADCP

current m eter

piston core-3000

-2500

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dep

th [

m]

MadagascarMozambiqe

Juan de Nova

DaviesRidge

lm c4 lm c5 lm c5A lm c6 lm c7 lm c8 lm c9

trap

Satellite remote sensing SST: quality and averaging problems

Foraminifera fluxes to the channel floor

SST = red

Ruber = black

Trilobus = blue

Ruber has highest production rates in January and February (SST ~ 28 – 30⁰C)

Trilobus in June (SST ~ 26 – 27⁰C)

Application for coretop sediments!11

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First results on Mg/Ca from trapped planktonic foraminifera

Foraminifera follow SST but show a continuous offset of about +/- 1.0⁰C

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SST

M g/C a tem p ruber

M g/C a tem p tril

TEX 86

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SST

M g/C a tem p ruber

M g/C a tem p tril

TEX 86

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SST

M g/C a tem p ruber

M g/C a tem p tril

TEX 86

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[° C

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SST

M g/C a tem p ruber

M g/C a tem p tril

TEX 86

Satellite remote sensing has an error of about 0.5 ⁰C

TEX86 varies little having a slight anti-correlation with SST (Does eddy velocity keep OM in suspension? δ13Corg correlates well with eddy passage.)

Mg/Ca from trapped planktonic foraminifera

Black = ruber

Blue = trilobus

Ruber and trilobus as surface dwellers follow SST but show a distinct offset

Temperatures were calculated with calibrations from Elderfield (ruber) and Nuernberg (trilobus) 3 4 5 6 7 8 9 10

M g/C a SST

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Mg

/Ca

spe

cim

en

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tem perature SST [°C ]

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tem

pe

ratu

re s

pec

ime

n[°

C]

R -sq u a red = 0 .6 4 5 9 8

Paired Mg/Ca and δ18O in coretop sediment

Equations used: Kim and O’Neill for δ18O and Nuernberg for Mg/Ca

Ruber has been corrected for vital effect with results from Somalia

Only slight range in Mg/Ca (<0.5mmol/mol = 2⁰C) corresponds to relatively large range in δ18O (1‰ = 5 ⁰C )

Black line = linear fit

Thin black line = SST calculated into Mg/Ca and δ18O with Nurnberg and Kim and O’Neill equations 1 2 3 4 5 6 7

M g/C a [m m ol/m ol]

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8 O [‰

VP

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M g/C a tem perature [N urnberg]

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d18

O te

mp

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[Kim

an

d O

'Nei

ll]

aequi

dut

rub

sacc

tril

SST ca lc w ith N uernberg equation

Cleaning artefacts or intraspecies variation?

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Mg

/Ca

[mm

ol/m

ol]

N IO Z cleaned N IO Z m easured

C am cleaned C am m easured

C am not c leaned C am m easured

Accuracy of NIOZ ICP-MS matches the Cambridge ICP-OES (less than 0.1 mmol/mol offset)

Cambridge method too rigorous for fragile trap samples?

Preferential dissolution?

Conclusions

SST data

Satellite remote sensing has an error of 0.5 ⁰C

Varies locally by up to 4⁰C

Eddy passage produces frontal upwelling (nutrients)

Collecting period of 3 weeks is too long for this fast changing system

Mg/Ca cleaning procedure

Pre-cleaning step that removes OM from fluxes sufficient for fragile sediment trap samples???

Comparison ICP-MS (NIOZ) – ICP-OES (Cambridge)

Matching is very high (within 0.5⁰C)

Precision is very high (< 0.5 ⁰C)

Conclusions

Salinity in the open ocean (=Mozambique Channel) varies only slightly (~34.8 – 35.1‰)

dutertrei from coretops (no seasonality because sub-surface dweller with vital effect correction) only leaves a very small offset which could be attributed to salinity)

Needs to be verified with time-series fluxes

16 18 20 22 24 26 28 30 32d18O tem pera ture [a fter K im and O 'N eill]

0

1

2

3

4

5

6

7

coun

ts Mg/Ca

δ18O

δ18O with vital effect

Temperature [ ⁰C] after Nuernberg

Outlook

Finish Mg/Ca measurements on time-series fluxes

Analyse time-series fluxes for δ18O

Paired Mg/Ca - δ18O can be used to check for salinity effect

Obtain satellite remote sensing temperatures that have been quality checked and calculate tri-weekly averages for trap location

Use SST and altimetry data to estimate frontal upwelling in eddies (temperature difference?)