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handle: 10261/101067
It is well established that orbital scale sea-level changes generated larger transport of sediments into the deep-sea during the last glacial maximum than the Holocene. However, the response of sedimentary processes to abrupt millennial-scale climate variability is rather unknown. Frequency of distal turbidites and amounts of advected detrital carbonate are estimated off the Lisbon–Setu´ bal canyons (core MD03- 2698, at 4602 mwd), within a chronostratigraphy based on radiometric ages, oxygen isotopes and paleomagnetic key global anomalies. We found that: 1) higher frequency of turbidites concurred with Northern Hemisphere coldest temperatures (Greenland Stadials [GS], including Heinrich [H] events). But more than that, an escalating frequency of turbidites starts with the onset of global sea-level rising (and warming in Antarctica) and culminates during H events, at the time when rising is still in its early-mid stage, and the Atlantic Meridional Overturning Circulation (AMOC) is re-starting. This short time span coincides with maximum gradients of ocean surface and bottom temperatures between GS and Antarctic warmings (Antarctic Isotope Maximum; AIM 17, 14, 12, 8, 4, 2) and rapid sea-level rises. 2) Trigger of turbidity currents is not the only sedimentary process responding to millennial variability; land-detrital carbonate (with a very negative bulk d18O signature) enters the deep-sea by density-driven slope lateral advection, accordingly during GS. 3) Possible mechanisms to create slope instability on the Portuguese continental margin are sea-level variations as small as 20 m, and slope friction by rapid deep and intermediate re-accommodation of water masses circulation. 4) Common forcing mechanisms appear to drive slope instability at both millennial and orbital scales. Marine Geology Research Unit, Laboratório Nacional de Energia e Geologia, Portugal Departamento de Investigación y Prospectiva Geocientífica, Instituto Geológico y Minero de España, España Unitat de Tecnologia Marina, Centre Mediterrani d’Investigacions Marines i Ambientals, España University of Bremen, Alemania Institute for Earth Sciences, VU University Amsterdam, Países Bajos Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement, Francia
millennial climate variability, Portugal, bulk delta18 O carbonate, Geología Glacial, Portuguese margin, Heinrich, turbidite, sediment, AMOC, Dansgaard-Oeschger, cambio climático
millennial climate variability, Portugal, bulk delta18 O carbonate, Geología Glacial, Portuguese margin, Heinrich, turbidite, sediment, AMOC, Dansgaard-Oeschger, cambio climático
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