The influence of land-surface reactivity on atmospheric carbon dioxide during past hyperthermals

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In this study, marine sediments were analysed for magnesium and lithium isotopes to create a time-series of chemical and physical silicate weathering in the Earth’s geological past. The purpose is to elucidate the response of silicate weathering, which experts a major control on atmospheric CO2 concentration, to regional and global warming. A warmer, wetter climate should provide more energy and fluids for silicate weathering reaction at the Earth’s surface to occur, consuming atmospheric CO2 and reversing the global warming trend. However, if the products of silicate weathering remain in the surficial system for too long before being deposited in marine sediments, they are converted back to silicates (reverse weathering), remitting the consumed CO2 leading to no net change on climate.During the past fiscal year, 200 sediment samples from several International Ocean Drilling Program (IODP) and Ocean Drilling Program (ODP) cores collected from deep ocean basins as well as the Amazon margin were ordered, dried, crushed and chemically processed to extract the carbonate, iron oxide and silicate phase. Magnesium is currently being purified from these phases with further purification Li still to be conducted. Magnesium and Li isotopes with then be measured via inductively coupled plasma mass spectrometry. This work will provide records of past weathering during periods of regional (Amazonian) and global warming over tens of thousands to millions of years to help understand the silicate weathering capacity to reverse global warming.