Magmatic Forcing of Cenozoic Climate?

Established theories ascribe much of the observed long-term Cenozoic climate cooling to atmospheric carbon consumption by erosion and weathering of tectonically uplifted terrains, but climatic effects due to changes in magmatism and carbon degassing are also involved. At timescales comparable to those of Milankovitch cycles, late Cenozoic building/melting of continental ice sheets, erosion, and sea level changes can affect magmatism, which provides an opportunity to explore possible feedbacks between climate and volcanic changes. Existing data show that extinction of Neo-Tethyan volcanic arcs is largely synchronous with phases of atmospheric carbon reduction, suggesting waning degassing as a possible contribution to climate cooling throughout the early to middle Cenozoic. In addition, the increase in atmospheric CO2 concentrations during the last deglaciation may be ascribed to enhanced volcanism and carbon emissions due to unloading of active magmatic provinces on continents. The deglacial rise in atmospheric CO2 points to a mutual feedback between climate and volcanism mediated by the redistribution of surface masses and carbon emissions. This may explain the progression to higher amplitude and increasingly asymmetric cycles of late Cenozoic climate oscillations. Unifying theories relating tectonic, erosional, climatic, and magmatic changes across timescales via the carbon cycle offer an opportunity for future research into the coupling between surface and deep Earth processes. Plain Language Summary Among the most fascinating contemporary developments in the Earth Sciences is the idea that plate tectonics and climate changes are coupled through complex cycles. More than four decades of study have revealed tantalizing examples of relationships between processes near the Earth's surface and deeper within. Accounting for such a surface-deep Earth process coupling has improved our understanding of major climate and tectonic events for virtually all timescales. So far, however, the role of magmatism was overlooked. Magmatism exerts a strong influence on the amount of greenhouse gasses in the atmosphere because of volcanic outgassing. In turn, tectonic and climatic changes control the transfer of rocks, water, and ice masses at the Earth surface and within the Earth's interior, thereby affecting the production, transfer, and eruption of magmas. Unravelling the interactions between surface and deep Earth processes accounting for magmatism will help managing natural resources and mitigating natural hazards. Even more importantly, understanding how climate is naturally related to plate tectonics and magmatism will allow scientists to assess the anthropogenic perturbations to the Earth system and anticipate ongoing and future climate changes.