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Detecting carbon cycle changes during Antarctic Ice Sheet Instabilities of the Oligocene-Miocene based on coccolithophore geochemistry

Applicant Stoll Heather
Number 182070
Funding scheme Project funding (Div. I-III)
Research institution Departement Erdwissenschaften ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Other disciplines of Earth Sciences
Start/End 01.01.2019 - 31.12.2022
Approved amount 999'976.00
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All Disciplines (2)

Other disciplines of Earth Sciences

Keywords (3)

coccolithophorids; CO2; climate

Lay Summary (German)

Dieses Projekt untersucht wie die atmosphärische CO2 Konzentration in der Vergangenheit Einfluss auf das Klima genommen hat und wie die Erde auf eine mögliche Klimaveränderung in der Zukunft reagieren könnte.
Lay summary

Das Projekt wird 3 Aspekte im Zusammenhang mit der Entwicklung des atmosphärischen CO2 Gehaltes untersuchen:

  1. Wir untersuchen wie Meeralgen unter kontrollierten Laborbedingungen auf eine Veränderung im atmosphärischen CO2-Gehalt reagieren um so Rückschlüsse auf CO2 Konzentrationen in der Vergangenheit machen zu können.
  2. Wir möchten herausfinden wie CO2 Gehalt und Temperatur die Bildung der charakteristischen Kalkschalen dieser Algen beeinflussen und ob der pH-Wert des Ozeans einen Einfluss auf die zellinterne Kalkbildung ausübt.
  3. Das Oligozän/frühe Miozän ist bekannt für ein rasches Wachstum und Abschmelzen des Antarktischen Eisschildes. Wir erforschen den Grad der Veränderung bei Aufnahme und Abgabe von CO2 aus der Atmosphäre während dieser Zyklen. Wir wollen herausfinden wie hoch die Temperaturen des Ozeans in den hohen Breiten war, welche eine so dramatische Instabilität des Antarktischen Eises bewirkten.

Wissenschaftlicher und gesellschaftlicher Kontext des Forschungsprojekts

Die Untersuchung von ozeanischen Sedimenten aus vergangenen Warmzeiten wird Auskunft darüber geben, wie das System Erde auf die zukünftigen anthropogenen CO2 Schwankungen reagieren wird.

Direct link to Lay Summary Last update: 20.11.2018

Responsible applicant and co-applicants


Project partner


Over a mere few centuries, human activities may bring atmospheric CO2 to levels last seen millions to tens of millions of years earlier in the Cenozoic. These major changes in atmospheric CO2 will have far-reaching impacts on climate, sea level, and ecosystems. The current proposal integrates research on three frontiers related to evolution of atmospheric CO2. First, we propose to produce a new, experimentally-supported model of the carbon concentrating mechanism in coccolithophorid algae, a group of marine phytoplankton with a significant role in global biogeochemical cycles. We propose a series of experiments using isotopically labeled carbon to track how the cell adjusts carbon acquisition strategies to compensate for sub-optimal CO2 concentrations. In combination, we conduct a series of laboratory culture experiments under variable CO2 and alkalinity, using natural isotopic abundances in coccoliths and photosynthetically fixed organic matter, to establish controls on the carbon concentrating mechanism in conditions of growth similar to those in the ocean. These approaches will test the controversial “reallocation hypothesis” which proposed that under C limitation, coccolithophores reallocate intracellular HCO3- transport from calcification to photosynthesis. In addition, they will provide new framework to apply isotopic fractionation in coccolithophore organic matter and coccolith to identify past changes in carbon limitation and CO2 concentrations.In the second objective, we evaluate evidence for long term selective pressures on biocalcification of coccolithophores. In laboratory experiments, conflicting conclusions have been drawn regarding the influence of CO2 and temperature elevation on coccolithophorid calcification and growth. We will implement novel techniques to characterize the degree of cellular calcification , and then measure how it varied between 30 and 17 Ma during a period of inferred CO2 decline, in a sediment sequence with exceptional preservation of coccoliths. This study will provide the first data on the cellular calcification of the full population of coccolithophorid algae from the fossil record. In conjunction with data on productivity, it will enable us to test the role of CO2 and other ecological factors on the degree of biocalcification. In the third objective, we explore the potential for changes in the carbon cycle and temperature during the Oligocene and Early Miocene. This period shows evidence for dramatic orbitally paced variation in climate and the cyclic growth and decay of the full East Antarctic Ice Sheet, likely causing sea level oscillations in excess of 50 m. This period may represent a warm-climate analogue to the high amplitude glacial cycles of mid-latitude ice growth and decay of the last 1 million years. We propose to provide the first estimates of the high latitude ocean temperatures which conditioned this very dramatic instability of the Antarctic ice sheet. In addition, we will evaluate whether changes in atmospheric CO2 concentration were a key amplifier of orbital climate variations, as during the late Pleistocene ice ages. A better estimation of the range of CO2 variations can be made using improved understanding of phytoplankton isotope proxies produced in Objective 1.