Debaille, Vinciane

Eiler, John M.

Erambert, Muriel

Trønnes, Reidar G.

Conference on Goldschmidt 2010 - Earth, Energy, and the Environment, Knoxville, TN, JUN 13-18, 2010International audienceno abstrac

Tripati, A.

Eagle, R.

Eiler, J.

Beaufort, L.

HAL-INSU

Glacial ocean temperatures from `clumped isotope' thermometry in foraminifera and coccoliths

Archive Ouverte en Sciences de l'Information et de la Communication

Primitive off-rift basalts in Iceland and Jan Mayen sample subcontinental lithospheric mantle (SCLM) in addition to the

Iceland plume with recycled oceanic crust (ROC) and meltdepleted or primitive lower mantle material [1]. The

SCLM/ROC-ratios are high at Jan Mayen (high La/Sm and ^(87)/^(86)Sr and low ^(206)/^(204)Pb, ^(187)/^(188)Os and ^(143)/^(144)Nd), intermediate in the Snæfellsnes Flank Zone and low in the Southern Flank Zone, including Surtsey. The fertile components are also present in tholeiites in the Icelandic rift zones and the NE Atlantic and Arctic ridges, despite larger proportions of melts from refractory asthenosphere. The SCLM/ROC-ratios are high where the distances to the nearest continental margin or the continental Jan Mayen Ridge are relatively short

Trønnes, R. G.

Erambert, M.

Eiler, J. M.

Debaille, V.

Caltech Authors - Main

Fertile components of the NE Atlantic mantle - Minor elements and O-isotopes in olivine phenocrysts

A primary goal of paleoclimate research over several decades has been to establish the magnitude and spatial patterns of temperature change in the oceans since the Last

Glacial Maximum (LGM; ~21 ka). We are using ‘clumped isotope’ thermometry to develop a global map of sea surface temperatures (SSTs) for the LGM. This thermometer is based

on the principle that ordering, or ‘clumping’, of heavy isotopes into bonds with each other in molecules is temperature-dependent due to an internal isotope exchange reaction which requires no knowledge of seawater isotope composition. We have previously calibrated the clumped isotope thermometer in foraminifera and coccoliths and shown that that the proportions of ^(13)C-^(18)O bonds in these biogenic carbonates are not subject to non-equilibrium biological fractionations, and are independent of the composition of the water in which the mineral precipitated (Tripati et al., in revision). Here we present the first record of Pleistocene and Holocene temperatures that is purely thermodynamically based, based on clumped isotope measurements of samples from the West Pacific warm pool. The warm pool is the warmest oceanic region and a benchmark for climate models. Reconstructions of the glacial-interglacial change in SSTs in the region vary from 1 to 6°C, differing systematically between methods. At

the LGM average SSTs in the region were 25.5°C (~3.9°C cooler than today), and the δ^(18)O_(SMOW) of surface waters was 0.9‰. Assuming these results are representative for the

region, then SSTs derived from alkenones, transfer functions, multi-proxy syntheses (i.e. MARGO) are systematically underestimating glacial cooling in this region. Mg/Ca SSTs

appear to be the most accurate empirical proxy of SST in the region. Salinity-corrected Mg/Ca SSTs, and some terrestrial reconstructions, are indistinguishable from clumped-isotope derived temperatures. The predicted LGM temperature difference, defined as the difference in annual mean SSTs between LGM and pre-industrial simulations, generated by

PMIP2 models for the region ranges from 1.0 to 2.4°C. All models predict less warming in the warm pool than our reconstruction. This mismatch could arise if there are

problems in modelling tropical processes (e.g. if the models were not simulating changes in ENSO correctly), if the LGM simulations were incomplete (e.g. not including dust changes), and/or if these models systematically underestimate climate sensitivity

Glacial ocean temperatures from ‘clumped isotope’ thermometry in foraminifera and coccoliths

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HAL AMU

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Fertile components of the NE Atlantic mantle - minor elements and O-isotopes in olivine phenocrysts

https://hal.archives-ouvertes.fr/hal-01458315

Fertile components of the NE Atlantic mantle - minor elements and O-isotopes in olivine phenocrysts

Abstract

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Archive Ouverte en Sciences de l'Information et de la Communication

Caltech Authors - Main

Caltech Authors - Main

Caltech Authors - Main

HAL Descartes

HAL AMU

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