January 16, 2017

Investigating Bering Sea oceanographic controls on the Milankovitch orbital cycle climatic shift during the middle Pleistocene

Investigating Bering Sea oceanographic controls on the Milankovitch orbital cycle climatic shift during the middle Pleistocene 400 x 400 px

Collaborative Awards in Science and Engineering (CASE) sponsorship secured with BGS. “The transition of Earth’s glacial-interglacial cycles from 40 kyr to 100 kyr periodicity during the middle Pleistocene (the Mid-Pleistocene Transition, MPT, ~1.2–0.6 Ma) marks one of the largest climate events of the Cenozoic, but the causes of this cooling transition remain unclear. This is because the emergence of the 100 kyr Milankovitch orbital ‘eccentricity’ in climate records occurred without a long term change in external orbital forcing. Hypotheses for this transition have so far remained largely untested due to a lack of detailed, high resolution climate proxy information from critical regions on the planet. Major hypotheses infer (a) changes to North American Ice Sheet dynamics, (b) an early expansion of subpolar sea ice, and (c) decreasing CO2. However, high resolution MPT CO2 and sea ice proxies remain unavailable.

The student will develop the first MPT climate proxy records of ice sheet instability (IRD) and sea surface conditions (sea ice and other parameters) from pristine Integrated Ocean Drilling Program Bering Sea cores in order to test these various hypotheses with the following objectives:

1. Uncover the history of NAIS growth and instability over the MPT, by generating a millennial-scale IRD record and benthic foraminiferal δ18O stratigraphy, to test the changing relationship between glaciations and North American Ice Sheet (NAIS) instability.

2. Uncover the history of Bering Sea sea-ice, sea surface temperature, productivity and salinity over the MPT, by generating an orbital-scale microfossil assemblage and isotope record, and millennial-scale organic matter δ13C record (including total organic carbon and C/N ratio) to constrain surface water nutrients, productivity and surface water CO2 changes.

The student will have access to state-of-the-art laboratory facilities at Nottingham and the BGS, will present results at international conferences, and will obtain training in microfossil and sediment isotope geochemistry and marine micropalaeontology (in Nottingham and in Portugal).

References: Elderfield H et al. 2012. Science 337, 704-709; Asahi H, Kender S et al. 2014. Deep Sea Research II

Eligibility: Applicants must have a BSc (first or upper second class) or M-level degree in Geoscience, Geography/Geology or Environmental Science. For further details please contact Dr. Sev Kender (