Reconstructing intermediate and deep ocean circulation during the Pliocene warm period

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The ocean is absorbing much of the heat and carbon dioxide emissions introduced to the climate system today by human activity. However, long-term impacts of the 'experiment' we are currently carrying out with our planet earth are poorly understood. Approximately three million years ago, during the Pliocene warm period, temperatures were elevated over modern levels and atmospheric carbon dioxide levels were similar to today. This past era could present clues to future climate change and a key response we would like to understand is how ocean circulation will function in a warmer world. Today, surface waters in the North Atlantic become denser than the surrounding water and sink to the ocean's interior forming a deep-water mass as part of Atlantic Meridional Overturning Circulation. This Atlantic Meridional Overturning Circulation plays a major role in global climate and climate/weather in the United Kingdom. The North Pacific on the other hand is too fresh, and hence no deep waters are formed there today. The configuration of deep ocean circulation during the Pliocene is unclear: some fossil evidence suggests that Atlantic Meridional Overturning Circulation was strong, whereas climate models suggest Atlantic Meridional Overturning Circulation was weak and a Pacific Meridional Overturning Circulation occurred in the North Pacific. This disagreement has profound implications for heat transport and the cycling of carbon, oxygen, and nutrients throughout the oceans. To address this data-model mismatch, this project aims to reconstruct intermediate and deep-water circulation in the Atlantic and Pacific during the Pliocene warm period using the chemistry of microfossils found within marine sediment. These records will then be compared to state of the art climate models for the Pliocene to help understand the climate dynamics important in maintaining Pliocene warmth. These records will help characterize heat transport, carbon cycling and intermediate to deep ocean circulation during a globally warm climate state and may help identify some of the long-term consequences of global warming.