Sea level fall during glaciation stabilized atmospheric CO2 by enhanced volcanic degassing

Abstract

Paleo-climate records and geodynamic modelling indicate the existence of complex interactions between glacial sea level changes, volcanic degassing and atmospheric CO2, which may have modulated the climate system’s descent into the last ice age. Between ∼85 and 70 kyr ago, during an interval of decreasing axial tilt, the orbital component in global temperature records gradually declined, while atmospheric CO2, instead of continuing its long-term correlation with Antarctic temperature, remained relatively stable. Here, based on novel global geodynamic models and the joint interpretation of paleo-proxy data as well as biogeochemical simulations, we show that a sea level fall in this interval caused enhanced pressure-release melting in the uppermost mantle, which may have induced a surge in magma and CO2 fluxes from mid-ocean ridges and oceanic hotspot volcanoes. Our results reveal a hitherto unrecognized negative feedback between glaciation and atmospheric CO2 predominantly controlled by marine volcanism on multi-millennial timescales of ∼5,000–15,000 years.

The Effect of Obliquity‐Driven Changes on Paleoclimate Sensitivity During the Late Pleistocene

“…It has recently been deduced, from ice core data covering the last 800 kyr, that the multimillennial trend of atmospheric CO 2 concentration and Antarctic temperature diverge when obliquity decreases (Hasenclever et al, 2017). It has recently been deduced, from ice core data covering the last 800 kyr, that the multimillennial trend of atmospheric CO 2 concentration and Antarctic temperature diverge when obliquity decreases (Hasenclever et al, 2017).…”

“…It has recently been deduced, from ice core data covering the last 800 kyr, that the multimillennial trend of atmospheric CO 2 concentration and Antarctic temperature diverge when obliquity decreases (Hasenclever et al, 2017). Hasenclever et al (2017) suggested that the combination of marine volcanism at mid-ocean ridges and at hot spot island volcanoes might react to decreasing sea level and be a potential cause for this ΔT g -CO 2 divergence. Solid Earth modeling experiments have indicated that falling sea level might lead to enhanced magma and CO 2 production at mid-ocean ridges (e.g., Lund & Asimow, 2011).…”

“…Furthermore, the model-based ΔT g -CO 2 divergence observed during times of decreasing obliquity is partially in antiphase to the proxy-based results (phases C and S), suggesting highly synchronous variations in CO 2 and simulated ΔT g while a strong divergence to CO 2 persists in the reconstructed ΔT g (Figure 3b). Interestingly, the temperature-CO 2 divergence during the MIS 5/4 transition, around 75 kyr BP (phase B) which motivated the study of Hasenclever et al (2017), is one of the largest in EDC but rather weak in K2015. Interestingly, the temperature-CO 2 divergence during the MIS 5/4 transition, around 75 kyr BP (phase B) which motivated the study of Hasenclever et al (2017), is one of the largest in EDC but rather weak in K2015.…”

“…Our calculated ΔT g -CO 2 divergence, based on ΔT g of Snyder or F2016, contains qualitatively similar dynamics related to obliquity as that based on EDC ΔT or K2015 but differs from the model-based simulations ( Figure S1). Based on these findings, the analysis of Hasenclever et al (2017) needs to be expanded: decreasing obliquity seems to be a necessary but not a sufficient condition for the ΔT g -CO 2 divergence. Furthermore, tests have shown that if new insights into polar amplification (Stap et al, 2018) are used for an improvement of the model setup used in K2015, only small changes in ΔT g are generated, but the general difference to the model-based simulations persists.…”

Deeply buried ancient volcanoes control hydrocarbon migration in the South China Sea

“…EAGE SUN et al to shallower levels within basins and may even be expelled into the ocean or atmosphere (e.g., Hasenclever et al, 2017;Lee et al, 2016;Moussallam et al, 2017). For example, the synchronous and widespread extrusion of substantial volumes of methane-rich hydrothermal fluids, emanating from the tips of intruding igneous sills, may have triggered or contributed to ancient climate change events (e.g., Iyer, Schmid, Planke, & Millett, 2017;Jamtveit, Svensen, Podladchikov, & Planke, 2004;Reynolds et al, 2017;Svensen, Corfu, Polteau, Hammer, & Planke, 2012;Svensen et al, 2004).…”