HOLOCENE OCEAN INSTABILITY: Climate variability - how unusual is the Holocene

• Research unit: EU RFP
• Project number: 97.0415

Key words (English)

Climate change; paleoceanography

Alternative project number (English)

EU project number: ENV4-CT97-0643

Research programs (English)

EU-programme: 4. Frame Research Programme - 3.1 Environment

Short description (English)

See abstract

Partners and International Organizations (English)

Coordinator: University of Cambridge (UK)

Abstract (English)

The ocean thermohaline circulation in the Atlantic (THC) is a major component of the climate system. It is thus essential to document and understand the variations of the THC, especially during the Holocene period (0-10 kyr BP) for which paleoceanographic proxies show a dominant periodicity at 1--2 kyrs. Recently the ratio between two radionuclides (231Pa/230Th, PT henceforth) in Atlantic sediments was proposed as an indicator of the strength of the THC. We have examined, in cooperation with the Woods Hole Ocean Institution, the potential of PT to document THC changes on century-to-millennial time scales (Marchal et al., 2000). A simple description of trace metal scavenging was embedded into our latitude-depth, circulation-biogeochemistry ocean model. The model was first calibrated from water column and Holocene sediment data of 231Pa and 230Th. Numerical experiments of transient circulation changes were then conducted. We found that the response of PT to the fast THC changes is largest in the North Atlantic, lowest in the South Atlantic, and intermediate in the Southern Ocean. The peak-to-peak amplitudes in the North Atlantic amount to 0.016-0.030, increasing with the severity of the THC change. These amplitudes are larger than, respectively, about 75% and 90% of the analytical uncertainties reported for Holocene sediments. Considering that recent measurements based on inductively-coupled, plasma-mass spectrometry, typically constrain PT to about 0.0025, our results thus suggest that high-resolution PT records from the North Atlantic could document the fast changes of the THC that could have punctuated the Holocene and (more probably) the last glacial period.

References in databases (English)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
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Swiss Project-Number: 97.0415