Multi-decadal-scale records of North Atlantic climate variability during the last and present interglacials: Climate sensitivity and the AMOC
Abstract
North Atlantic climate sensitivity plays a crucial role in understanding current and future developments of the Atlantic meridional overturning circulation (AMOC). A shifted configuration of Earth's orbital parameters about the Sun caused an approximate 3% higher radiative forcing during the Last Interglacial (LIG, MIS5e; 129-115kyr) and drove climate to measurably warmer conditions than during the Present Interglacial (PIG, Holocene, 11-0Kyr). Paleoceanographic time series of surface ocean climatology from Ocean Drilling Program (ODP) Site 976 in the Alboran Sea, westernmost Mediterranean, reflect the climatic variability during the LIG and PIG. The site receives climate signals from the advection of Atlantic inflow waters confirming its quality to monitor North Atlantic climate variability. Elevated rates of sedimentation deposition at the site enable resolving variability at multi-decadal resolution (60-90 yrs). Sea surface temperature (SST) time series were established from element concentrations (Mg/Ca) in the planktonic foraminifera Globigerina bulloides. SST from alkenones were also measured for comparison purposes. Planktonic oxygen isotopes from G. bulloides allow direct comparison with speleothems and ice cores. LIG SST are between 3°- 6°C warmer than PIG SST and multi-decadal-scale variability by 4°C and more is indicated by highly variable Mg/Ca ratios. This variability persisted during the LIG climatic optimum, confirming that SST and climatic variability were independent of large ice sheets. The high variability is contrasted by more stable SST in the Uk37-derived SST record, plausibly alluding to differential SST recording by the molecular biomarker proxy. Correlation with δ18O records from European speleothems suggests the SST pattern reflects climate of the western North Atlantic region. The LIG SST pattern at ODP 976 differs from that at open North Atlantic settings where maximum SST during the LIG climatic optimum remained some 6°C below that at ODP976 while converging with levels at ODP976 in the later stages of the LIG. The ODP976 SST record suggests more variable climatic conditions and together with similar variability seen in benthic δ13C records at Atlantic sites bears implications for AMOC stability and variability. This is a contribution of the European Commission FP7 Collaborative Project "Past4Future".
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFMPP33A2078J
- Keywords:
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- 0473 BIOGEOSCIENCES / Paleoclimatology and paleoceanography;
- 3030 MARINE GEOLOGY AND GEOPHYSICS / Micropaleontology;
- 4901 PALEOCEANOGRAPHY / Abrupt/rapid climate change;
- 4954 PALEOCEANOGRAPHY / Sea surface temperature