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 δ 18 O  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 δ 18 O 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 δ 18 O from planktonic foraminifera with  Coral proxies (Sr/Ca) off the coast of Madagascar  Organic matter proxies (Tex 86, Uk 37 )  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?

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 – 30 ⁰ C)  Trilobus in June (SST ~ 26 – 27 ⁰ C)  Application for coretop sediments!

First results on Mg/Ca from trapped planktonic foraminifera Foraminifera follow SST but show a continuous offset of about +/- 1.0 ⁰ C Satellite remote sensing has an error of about 0.5 ⁰ C TEX 86 varies little having a slight anti-correlation with SST (Does eddy velocity keep OM in suspension? δ 13 C org 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)

Paired Mg/Ca and δ 18 O in coretop sediment  Equations used: Kim and O’Neill for δ 18 O 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 = 2 ⁰ C) corresponds to relatively large range in δ 18 O (1‰ = 5 ⁰ C )  Black line = linear fit  Thin black line = SST calculated into Mg/Ca and δ 18 O with Nurnberg and Kim and O’Neill equations

Cleaning artefacts or intraspecies variation?  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 ⁰ C  Varies locally by up to 4 ⁰ C  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 0.5 ⁰ C)  Precision is very high (< 0.5 ⁰ C)

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 Mg/Ca δ 18 O with vital effect Temperature [ ⁰ C] after Nuernberg

Outlook  Finish Mg/Ca measurements on time-series fluxes  Analyse time-series fluxes for δ 18 O  Paired Mg/Ca - δ 18 O 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?)