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During the middle Miocene Earth’s climate transitioned from warm to cold with the development of permanent ice sheets on Antarctica. The middle Miocene climatic optimum (MCO; 17-14.7 million years ago) was a peak warm phase characterized by global mean sea surface temperatures ~3-4°C warmer than in the modern ocean. Surprisingly, only a few surface ocean temperature records have been generated for this important climate transition and essentially none for the North Atlantic, where deep water is generated. The aim of this Aresty project is to reconstruct surface conditions in the North Atlantic during the MCO and subsequent major cooling (14.7-12.8 millions years ago) using stable isotopes in planktonic foraminifera from Deep Sea Drilling Project Site 558. Planktonic foraminifera are amoeba like, single celled organisms that secrete a sand-sized, calcium carbonate shell. Planktonic foraminifera are depth stratified in the water column; therefore, studies of different species of planktonic foraminifera can give information about the water masses they inhabited. Previous work in the North Atlantic has used benthic foraminiferal δ18O and δ13C tracers to study deep water and isolate temperature versus ice volume signal for the Miocene. This Aresty project will augment existing records of benthic foraminifera by performing stable isotopic analysis (δ18O and δ13C) on planktonic foraminifera. The project will require using a microscope to pick multiple species of planktonic foraminifera in different size fractions, targeting thermocline and surface dwelling taxa. Overall, this research is significant in providing insights into the thermal history of the North Atlantic during the middle Miocene.
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