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

• Unité de recherche: PCRD EU
• Numéro de projet: 97.0415
• Titre du projet anglais: HOLOCENE OCEAN INSTABILITY: Climate variability - how unusual is the Holocene

Mots-clé (Anglais)

Climate change; paleoceanography

Autre Numéro de projet (Anglais)

EU project number: ENV4-CT97-0643

Programme de recherche (Anglais)

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

Description succincte (Anglais)

See abstract

Partenaires et organisations internationales (Anglais)

Coordinator: University of Cambridge (UK)

Résumé des résultats (Abstract) (Anglais)

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.

Références bases de données (Anglais)

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