Collaborative Research: Sea level induced hydrothermal activity as a trigger for glacial terminations

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The last million years of earth's history are characterized the growth and decay of continental ice sheets that covered large portions of North America and Europe. Growth of the ice sheets transferred water from the ocean to the continents and caused sea level to drop by nearly 400 feet. While it has long been known that the pacing of the ice ages is related to changes in the Earth's orbit around the sun, the triggering mechanism for the end ice ages, known as terminations, has yet to be fully explained. Lowering of sea level releases pressure on the global mid-ocean ridge system, a nearly continuous chain of submerged volcanoes that span 30,000 miles of the sea floor. The pressure release should drive enhanced submarine volcanism, which may in turn influence climate by introducing heat and carbon dioxide into the deep ocean. The aim of the proposed work is to assess magmatism along mid-ocean ridges in the eastern South Pacific using geologic archives of volcanic activity. Sediment cores retrieved from the East Pacific Rise (EPR) and Pacific Antarctic Ridge (PAR) will be used to assess hydrothermal plume activity near the ridge crest. Hydrothermal plumes are created through superheating of cold deep ocean water by hot oceanic crust, which is itself heated by magma. Thus, sedimentary archives can be used to assess glacial-interglacial changes in magmatism and test whether enhanced submarine volcanism occurs during glacial terminations. The proposed work will focus on a series of cores from 10°S to 40°S along the EPR and PAR. Preliminary oxygen isotope data indicates that sediments in this region accumulate at a rate sufficient to constrain glacial-interglacial timescales. Hydrothermal activity will be inferred by estimating the flux of Fe, Mn, V, and As to ridge crest sediments. All fluxes will be constrained using the 3He normalization technique. A finding of coherent variations in metal flux at multiple sites would indicate there were regional changes in magmatic activity. Additionally, the timing of anomalous metal fluxes will be compared with climate proxies to assess the feasibility that mid-ocean ridge magmatism acts as a negative feedback on ice sheet size. Finally, a petrologic model will be used to simulate the impact of sea level variations on CO2-bearing melt production in the upper mantle. Simulations of carbon flux from the global mid-ocean ridge system will be used to assess whether variations in carbon flux could have feasibly driven atmospheric CO2 on glacial-interglacial timescales. The proposed work could transform our understanding of the climate system by constraining the interactions between the fluid and solid earth on glacial-interglacial timescales. The broader educational impacts of the proposed work includes the participation of a postdoctoral scholar and two undergraduates at the University of Connecticut, plus an additional undergraduate at Caltech.