Eocene and Cretaceous Oceanography: Disentangling the roles of geography and temperature on deep ocean circulation in past greenhouse climates

ended

Ocean circulation plays a dominant role in distributing heat over the planet and in providing oxygen for life in the deep sea. The thermohaline circulation will likely be affected by global warming, in particular the current areas of deep water formation at high latitudes. The thermal maxima of the Cretaceous (94 million years ago) and the Eocene (51 million years ago) are the two most important greenhouse climate phases of the last 100 million years and are seen as analogues to current climate change. For the Cretaceous and Eocene, mechanisms of deep-water formation and the role of ocean circulation on heat transport are poorly understood. This research aims to disentangle the controls of geography and temperature on deep circulation in past greenhouse worlds to identify ocean circulation dynamics fundamental to climates warmer than the present-day. This research has a three-fold approach: 1) To generate neodymium isotope signatures from a range of sites in the Southern Ocean to identify and track deep-water masses under two different circulation regimes: - the opening of gateways in the Eocene and - an episode of sudden warming in the mid-Cretaceous, which led to a widespread lack of oxygen in the world's oceans. 2) To identify the source regions of deep water formation, the geochemical signatures (neodymium isotopes, rare earth elements, mineralogy) of past seawater and detrital sediment contributions will be compared and contrasted to reconstructions of paleotopography. 3) To test scenarios of modelled ocean circulation in past greenhouse worlds, the Nd-isotope data will be integrated with coupled ocean-atmosphere climate models. The candidate will develop new competencies in geochemical techniques and climate modelling. Broadening her scientific skills base, whilst training transferable skills and reaching professional maturity, will ideally position the candidate to draw the disciplines of oceanography, sedimentology and climate modelling together.