During glacial periods, lower sea level (due to storage of seawater in glaciers on land) results in less hydrostatic pressure on the ridges, thus there is enhanced decompression melting creating thicker oceanic crust and more volcanism and hydrothermal activity. During interglacials, sea level is higher and we have the opposite effect.
Testing requires innovative integrated time-series data across multiple glacial cycles. Although this is now possible, it has never been accomplished previously.
Is this study feasible? Yes! Pilot studies and models (see references below) show melt & carbon flux and crustal thickness can vary up to 15% and hydrothermal activity by a factor of four.
Is T-SECTOR novel?
• First high-resolution and integrated time series of lava (crustal) volume, chemistry and hydrothermal activity, opening up an entirely new dimension of mid-ocean ridge studies
• Definitive tests and development of the relationships between climate and the solid Earth
• New understanding of MOR processes (e.g. implications for ore forming processes and upper mantle heterogeneity)
T-SECTOR aims to literally open a new time dimension to ocean ridge studies, and to provide definite tests of the hypothesis, backed by theory, that sea level change influences ridge volcanism. Using data on the composition MORBs obtained from sediment hosted glasses, we aim to obtain time-series at an unprecedented resolution of 5-10ka over ≥1.5Ma, uniquely combined with records of hydrothermal activity in the same sediments and with data on crustal thickness and seafloor morphology. The project also proposes a novel approach to construct time series of MORB composition through seabed drilling, which will enable investigation of crustal production and other magmatic (volcanic and plutonic) processes at an unprecedented level. Once established, these approaches can also be used to construct time series of other seafloor spreading systems. These time series have the potential to transform our understanding of seafloor spreading processes and the scale of heterogeneities in the underlying mantle. They will help us understand the feedback between glacial/interglacial climate and earth processes, providing new insights into enhanced magmatism during glacial cycles and the linked emission of CO2 into the atmosphere. We will test new approaches for determining oceanic crustal thickness at high-resolution on time scales of climatic variations without the necessity of 3-D seismic studies. Finally, the closely-spaced sediment and basalt drill core profiles taken by German and U.S ships along the ~1.5Ma profiles will be stored at the GEOMAR Helmholtz Center and U.S. repositories respectively and will be available for study by other scientists with different questions than those we plan to address, e.g. looking at variations in non-traditional isotope systems (e.g. Mg, Fe, Zn isotopes) both in MORBs and the hydrothermally influenced sediments.