Modeling the Role of Volcanism in the Past 20 Million Years of Global Cooling
Abstract
During the Mid-Miocene Climatic Optimum, globally averaged temperatures were up to 12 degrees celsius warmer than today (Herbert et al. 2016). A period of long-term global cooling followed this maximum, culminating in the modern climate, yet the forcing of this trend remains unclear. On million year timescales, the carbon-silicate cycle is a primary regulator of Earth's climate through its effects on changes in atmospheric pCO2 and temperature. Recent work has shown that the seafloor spreading rate was nearly 18% higher during the Mid-Miocene Climatic Optimum and decreased sharply in late Miocene (10-5.35 Ma) time (Dalton et al. 2018, in prep). As seafloor spreading rate is a proxy for mantle degassing of CO2, we propose that this variable degassing is the forcing mechanism behind the climate trend observed in the last 20 million years. In this work, we design a carbon cycle box model that couples atmospheric fluxes with the oceanic calcium carbonate cycle through weathering. In the ocean, we track DIC and alkalinity to model carbonate records so that the deep ocean carbonate record can be compared to the model as an additional constraint. Specifically, we model changes in the lysocline depth and CCD as atmospheric pCO2 rises due to increased degassing. We demonstrate that the variable seafloor spreading rate generates a greenhouse effect consistent with warming of 12 degrees during the Mid-Miocene Climatic Optimum. Further work is needed to better constrain key model parameters, but our results tighten the link between global climate change, ice volume, and carbon dioxide levels in the past.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMPP14A..01S
- Keywords:
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- 1055 Organic and biogenic geochemistry;
- GEOCHEMISTRY;
- 1620 Climate dynamics;
- GLOBAL CHANGE;
- 4914 Continental climate records;
- PALEOCEANOGRAPHY;
- 4928 Global climate models;
- PALEOCEANOGRAPHY