« Events

Speaker: Heather Ford, NERC Independent Research Fellow, Senior Lecturer in Environmental Science, Queen Mary University of London

Host: Yuko Okumura

Title: Paleo-reconstructions of Pacific climate – the global pacemaker and Achilles heel of climate projections

Abstract: Studying past ocean dynamics is vital for constraining future climate change. I use the geochemistry of fossil shells found in marine sediment to reconstruct past ocean conditions. During the mid-Pliocene warm period (~3 million years ago), global temperatures were 2-3°C warmer than today and CO₂ is estimated to be similar to higher to today, making it a pseudo-analog for future climate change. In this talk I will present two data-model comparisons looking at Pacific deep ocean carbon cycling and tropical dynamics. Today in the North Pacific no deep water forms because of a strong halocline, but North Pacific Deep Water may have existed during the mid-Pliocene warm period. New results combined with previously published carbon isotope records show a spatial pattern consistent with a North Pacific Deep Water ventilating the deep ocean. Although the modelled Pliocene ocean maintains a carbon budget similar to the present, the change in deep ocean circulation configuration causes pronounced downstream changes in biogeochemistry in the tropical Pacific. Proxy data show the tropical Pacific had a reduced zonal temperature gradient and a deep thermocline; because this configuration looks similar to a modern El Niño event, this mean state is called “El Padre”. Models that best match with the proxy data dynamically link the eastern tropical Pacific sea surface temperature and thermocline. Future work includes using carbon models to understand deep ocean carbon storage and exploring climate transitions during the Northern Hemisphere Glaciation, mid-Pleistocene Transition and mid-Brunhes Event.