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TEMPORAL RELATIONSHIPS AMONG PROXY SIGNALS IN MARINE SEDIMENTS (TRAMPOLINE)

English title TEMPORAL RELATIONSHIPS AMONG PROXY SIGNALS IN MARINE SEDIMENTS (TRAMPOLINE)
Applicant Eglinton Timothy
Number 175823
Funding scheme Project funding (Div. I-III)
Research institution Departement Erdwissenschaften ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Geochemistry
Start/End 01.01.2018 - 31.01.2021
Approved amount 271'500.00
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All Disciplines (2)

Discipline
Geochemistry
Other disciplines of Earth Sciences

Keywords (5)

alkenone; sea surface temperature; proxies; climate; carbon cycle

Lay Summary (German)

Lead
Alkenone sind organische Verbindungen dessen Signaturen die Bestimmung von früheren Änderungen der Meeresoberflächentemperatur (MOT) ermöglichen. In marinen Sedimenten sind Alkenone mit feinkörnigen Mineralpartikeln assoziiert, welche leicht mobilisiert und von Meeresströmungen transportiert werden können. Wir stellen die Hypothese auf, dass lateraler Partikeltransport Alkenonsignaturen verlagert und daher einen Einfluss auf die mittels Alkenonen berechnete MOT haben kann, was schliesslich zu Unsicherheiten in den daraus abgeleiteten Interpretationen früherer Klimaveränderungen führen kann.
Lay summary

Inhalt und Ziel des Forschungsprojekts

Das übergeordnete Ziel ist Assoziationen zwischen Alkenonen und Mineralpartikeln zu untersuchen um zu bestimmen ob hydrodynamische Prozesse räumliche oder zeitliche Offsets der Alkenonsignaturen verursachen und potentielle Auswirkungen auf die Rekonstruktion vergangener MOT einzuschätzen. Dabei werden wir uns auf Sedimente aus bedeutenden Meeresgegenden konzentrieren, welche im Fokus von intensiven Paleo-Klimauntersuchungen stehen.

 

Wissenschaftlicher und gesellschaftlicher Kontext des Forschungsprojekts

Die Ermittlung der Ursachen und des zeitlichen Verlaufs von früheren kurzzeitigen Klimaveränderungen ist auch durch das wachsende gesellschaftliche Interesse hinsichtlich möglicher gegenwärtiger Konsequenzen eines schnellen und unvorhergesehenen Klimawandels zum Gegenstand intensiver wissenschaftlicher Untersuchungen geworden. Seit ihrer Entdeckung im Jahre 1986 sind Alkenone zu einem der am meisten angewandten und etablierten Werkzeuge geworden, um frühere Veränderungen der MOT zu bestimmen. Ein umfassendes Verständnis der Einflussgrössen auf Alkenonsignaturen ist daher von entscheidender Bedeutung für robuste Paleo-Klimarekonstruktionen.

Direct link to Lay Summary Last update: 17.05.2018

Responsible applicant and co-applicants

Employees

Associated projects

Number Title Start Funding scheme
184865 Climate and Anthropogenetic PertubationS of Land-Ocean Carbon tracKs (CAPS-LOCK3) 01.04.2019 Project funding (Div. I-III)

Abstract

Since the discovery of alkenones in 1986 [Brassell et al., 1986], these organic biomarkers have become one of the most applied and well-established paleoclimate proxies, allowing estimation of sea surface temperature (SST) and pCO2 variations in most oceanographic settings. We know now that much of the organic matter (OM) preserved in marine sediments is physically associated with mineral surfaces by sorption. Specifically, OM tends to concentrate within fine grain-size fractions (i.e. clay (<2 µm) and fine silt (2-10 µm)), which have higher surface area. Considering that mineral particles might behave in a cohesive or in a sortable manner depending on their size, alkenone-mineral associations and the governing hydrodynamic conditions may determine the transport pathways of alkenones. Consequently, we hypothesize that hydrodynamically-driven sediment sorting processes might introduce biases in autochthonous climate signal, compromising the spatial and temporal reliability of the derived proxy records. Similarly, we expect hydrodynamic processes to exert significant control on the transport pathways of other proxy-bearing particles represented in the finer-grained sediment fractions (< 63 µm) (e.g. nannofossils), which are more prone to resuspension than those represented in coarser-grained sediment fractions (> 63 µm) (e.g. microfossils). In the proposed investigation, we aim to determine alkenone-grain size-14C age interrelationships in surface sediments retrieved from diverse environmental settings: Bermuda Risa, Santa Barbara Basin, Namibian Margin, NW African Margin, and SW Iberian Margin. These different regions are strategic benchmark areas for high-temporal-resolution paleoclimate investigations where pre-existing evidence suggests temporal de-coupling of proxy records due to lateral transport. We aim to assess possible spatial and temporal offsets by specific radiocarbon dating of the alkenones contained within each grain-size fraction and identify the plausible factors that cause them. We also aim to evaluate possible asynchronous signals between alkenones, coccoliths, and planktonic foraminifera by means of radiocarbon dating of each of these sedimentary components. Complementary geochemical and sedimentological analyses will be performed to constrain OM distribution and provenance, and associated lateral sediment transport processes. We then plan to apply derived information and our novel measurement strategy to a sediment core retrieved from the so-called Shackleton Sites in the SW Iberian Margin in order to assess the role of hydrodynamic processes impact on the paleotemperatures estimated from proxies residing in different grain size fractions. In this way, we will develop the first proxy-specific radiocarbon chronology for a sediment core. Since the Shackleton Sites represent one of the few regions in the world where direct correlation of ice-marine-terrestrial signals are feasible, constraining the provenance and temporal fidelity of proxy records is of crucial importance. Given the importance attached to molecular fossils as proxies for the study of past climate variations, and the attention focused on these strategic regions, this investigation is expected to expand horizons in the field of paleoceanography and deepen our understanding of paleoceanographic records.
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