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According to the research, stable isotope analyses of benthic foraminiferal oxygen and carbon, indicators for climate-cryosphere and carbon transfers, documented these historic climate and carbon cycle changes. Earth's orbital factors, including eccentricity, obliquity, and precession, notably influenced global climate-cryosphere changes and the marine carbon cycle, with the 405,000-year cycle displaying a particularly strong effect.
Historically, as the Antarctic region developed unipolar ice sheets during the Oligocene and Miocene, climate-cryosphere and marine carbon cycle changes showed a synchronized pattern on eccentricity scales. However, the study reveals a moderate phase lag of about 19.2 thousand years in the marine carbon cycle relative to climate changes, attributed to carbon's prolonged oceanic residence time.
During the Miocene Climate Optimum, approximately 17 to 14 million years ago, marine carbon cycle variations began leading climate changes by an average of 17 thousand years, corresponding with the Columbia River Flood Basalt and intense global seafloor spreading. This period marked the release of substantial deep-sourced carbon into the atmosphere. Model simulations and sensitivity analyses conducted by the researchers suggest that increased atmospheric CO2 levels enhanced the low-latitude hydrological cycle, speeding up marine carbon cycle responses to eccentricity forcing through increased chemical weathering and organic carbon burial.
This research underscores the significant influence of prolonged tectonic events on orbital-scale changes in Earth's surface system.
Research Report:Accelerated marine carbon cycling forced by tectonic degassing over the Miocene Climate Optimum
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