Orbitally paced variability of Mediterranean outflow water on the West Iberian margin through the Late Pleistocene
Abstract
Mediterranean outflow water (MOW) provides a significant salt source for North Atlantic circulation, particularly during Greenland Stadials. Yet, its evolution through the late Pleistocene glacial cycles is poorly understood. Integrated Ocean Drilling Programme (IODP) Site U1391 (1085m water depth) on the West Iberian margin has been studied to investigate MOW downstream from the Strait of Gibraltar (283m water depth) and to further understand its relationship with North Atlantic water masses. Here, we take a multi-proxy approach to detecting MOW variability, employing anisotropy of magnetic susceptibility (AMS, a magnetic grain fabric proxy signifying the mode of deposition and nature of the palaeocurrent), x-ray fluorescence (XRF) core scanning and physical grain size. We transfer the well-established synthetic Greenland age model from IODP Site U1385 to Site U1391 by close correlation of ln(Ca/Ti) XRF data at the two sites. Apparent relationship between AMS data and glacial-interglacial cycles, alongside differing levels of orbital (mainly precession) and suborbital variabilities in grain size, suggest two distinct regimes of MOW behaviour over the last 400 kyrs. Between marine isotope stages (MIS) 5 and 10, MOW appears to have been at a generally shallower depth near the west Iberian margin and changes in MOW strength were dominated by precession at this time. In contrast, MOW appears to have deepened following MIS 5, and changes in its strength were dominated by millennial-scale variability rather than longer-term orbital variations. These differences likely reflect changes in the significance of North African hydroclimate and sea level forcing on the MOW, and highlight that MOW may have had significantly different impacts upon North Atlantic overturning prior to MIS 5.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMGP31B0726N
- Keywords:
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- 0419 Biomineralization;
- BIOGEOSCIENCES;
- 1512 Environmental magnetism;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 1522 Paleomagnetic secular variation;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 1540 Rock and mineral magnetism;
- GEOMAGNETISM AND PALEOMAGNETISM