SONNE SO321/2

Time series represent the archives of Earth System Science and their acquisition plays a central role in identifying and understanding Earth processes. One important time series is the climate (sea level) record that documents transitions between ice ages and warm periods, involving vast mass transfer between the continents (ice load) and oceans.
Modeling has suggested that mid-ocean ridge (MOR) volcanism (crustal thickness, lava chemistry and hydrothermal activity) is sensitive to such pressure changes and thus has been influenced by changes in sea level, but this has yet to be proven by data, primarily due to the difficulties in obtaining MOR time series.
Because of their key role, time series are the central element of the ERC Synergy Grant T-SECTOR, which aims to obtain geochemical, geophysical, and paleo-oceanographic time series on exemplary fast- to slow-spreading MOR systems.
Here we propose to create time series of crustal thickness, magma chemistry and hydrothermal activity over the past 1.5 Ma at the intermediate-spreading Cleft segment of the Juan de Fuca Ridge off the NW coast of the USA. Through a section of closely spaced gravity coring and seabed drilling (perpendicular to the ridge axis), we plan to construct high-resolution time series of variations in mantle melting (from the chemistry of volcanic glasses preserved in the sediments and at the margins of drilled pillows and sheet flows) and hydrothermal activity (from metal concentrations and isotope compositions of the sediments). Seismic techniques will be used to determine variations in crustal thickness over time. Integration of these unprecedented 1.5 Ma time series will allow us to characterize the temporal evolution of ocean crust production at an intermediate-spreading-rate MOR and to test the controversial link between climate (glacial cycles, i.e. sea level changes) and solid-Earth (ocean crust generation) processes.