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Glacial greenhouse-gas fluctuations controlled by ocean circulation changes.
Andreas Schmittner1, Eric D Galbraith
1College of Oceanic & Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA. aschmitt@coas.oregonstate.edu
Nature
|November 21, 2008
Summary
Ocean circulation changes drove fluctuations in atmospheric carbon dioxide (CO2) and nitrous oxide (N2O) during glacial periods. These changes influenced millennial-scale climate shifts, impacting Greenland and Antarctic temperatures.
Area of Science:
- Paleoclimatology
- Biogeochemical cycles
- Climate modeling
Background:
- Earth's climate and greenhouse gas concentrations (CO2 and N2O) fluctuated significantly on millennial timescales during glacial periods.
- Large, rapid warming events in Greenland correlated with N2O, while Antarctic temperature shifts correlated with CO2.
Observation:
- Abrupt changes in the Atlantic meridional overturning circulation (AMOC) were previously linked to Dansgaard-Oeschger climate oscillations.
- The precise mechanisms driving greenhouse gas variations and their connection to AMOC remained unclear.
Findings:
- Simulations using a coupled glacial climate and biogeochemical model, forced by AMOC changes, reproduced characteristic Dansgaard-Oeschger temperatures and CO2/N2O fluctuations.
- Millennial-scale CO2 variations were primarily driven by slow changes in deep ocean carbon stores, linked to Antarctic temperatures and Southern Ocean stratification.
- N2O covaried more rapidly with Greenland temperatures due to quick adjustments in the thermocline oxygen budget.
Implications:
- Ocean circulation changes are identified as the primary driver of glacial CO2 and N2O fluctuations on millennial timescales.
- This research clarifies the linkage between ocean circulation, greenhouse gas dynamics, and abrupt climate change during glacial epochs.
- The findings enhance our understanding of Earth's climate system sensitivity to oceanographic forcings.
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