Presentation on theme: "Koninklijk Nederlands Instituut voor ZeeonderzoekRoyal Netherlands Institute for Sea Research A multi-proxy approach to time-series fluxes and coretop."— Presentation transcript:
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?)