HR: 0800h
AN: PP31D-0656    [Abstracts]
TI: Hydrological forcing and circulation responses in a miniature ocean
AU: * Marino, G
EM: G.Marino@uu.nl
AF: Laboratory of Palaeobotany and Palynology, Utrecht University., Budapestlaan 4, Utrecht, 3584 CD, Netherlands
AU: Rohling, E J
EM: E.Rohling@noc.soton.ac.uk
AF: National Oceanography Centre, Waterfront Campus, European Way, Southampton, SO14 3ZH, United Kingdom
AU: Sangiorgi, F
EM: f.sangiorgi@uu.nl
AF: Laboratory of Palaeobotany and Palynology, Utrecht University., Budapestlaan 4, Utrecht, 3584 CD, Netherlands
AU: Brinkhuis, H
EM: H.Brinkhuis@uu.nl
AF: Laboratory of Palaeobotany and Palynology, Utrecht University., Budapestlaan 4, Utrecht, 3584 CD, Netherlands
AU: Schouten, S
EM: schouten@nioz.nl
AF: Department of Marine Biogeochemistry and Toxicology, Royal Netherlands Institute for Sea Research (NIOZ), P.O. Box 59, Den Burg (Texel), 1790 AB, Netherlands
AU: Sinninghe Damste, J S
EM: damste@nioz.nl
AF: Department of Marine Biogeochemistry and Toxicology, Royal Netherlands Institute for Sea Research (NIOZ), P.O. Box 59, Den Burg (Texel), 1790 AB, Netherlands
AB: The Mediterranean Sea is often referred to as a miniature ocean as it has many processes in common with the world ocean with respect to its circulation, albeit at smaller temporal and spatial scales. Specifically, the basin s freshwater and heat budgets, tied to the high vs. low latitude climate interactions over the region, drive an efficient thermohaline circulation (THC). Variations in the freshwater budget are especially dominated by processes that act in the eastern Mediterranean. During periods of precession minima, enhanced river discharge along North African margin due to intensified African summer monsoon circulation weakens the eMed THC, leading to widespread seafloor anoxia (sapropels). The eMed thus represents an ideal target to test the sensitivity of a THC system to changes in the net freshwater input. At the same time, the anoxic sedimentation allows high-resolution study of the basin s responses to high latitude climate variability during periods of monsoon maxima. Here we present highly resolved Aegean (NE eMed) records of foraminiferal stable isotopes, census counts, dinoflagellate cysts, and organic biomarkers through two key sapropels from the last (S5) and the current (S1) interglacial periods. During the last interglacial period, a severe monsoon-fuelled freshwater discharge into the open eMed promoted a virtually immediate (within 40 yr) collapse of the Aegean deep overturning system, a key source of eMed deepwater. This THC shut down was accompanied by a burial of exceptionally high amounts of organic carbon (up to 14% Corg) in the SE Aegean site of core LC21. These changes were followed (within few centuries) by the expansion of euxinic conditions toward the photic layer first in the Aegean and subsequently throughout the eMed. During the early to mid Holocene interval of S1 deposition, the monsoon-fuelled freshwater discharge into the eMed was less extreme than its S5 counterpart, leading to a somewhat muted response of the eMed THC and less enhanced carbon burial (up to 2% Corg). Superimposed, we identify two sharp episodes of intense Aegean winter cooling between ~9.8 and ~7.9 ka BP in central Aegean Sea core SL21. These cold spells are found to match changes in Greenland ice cores, pointing to meridional displacements of the atmospheric polar vortex as a connecting mechanism. The timing of these two cold events is discussed within the context of recently reconstructed re-ventilation events punctuating S1. Combined with the instrumental records of recent changes in the basin s THC, our findings hint at an exceptional sensitivity of the eMed to decadal- to millennial-scale hydrological perturbations in the tropics/subtropics. Changes in both the high and low latitude climates are found to profoundly affect heat, freshwater, and carbon budgets of this miniature ocean.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1050 Marine geochemistry (4835, 4845, 4850)
DE: 4952 Palynology
DE: 4954 Sea surface temperature
DE: 4962 Thermohaline
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting