Sensitive Dependence of Global Climate to Continental Geometry. Issue 11 (4th June 2022)

• Record Type: Journal Article
• Authors: Baum, Mark; Fu, Minmin; Bourguet, Stephen
• Is Part Of: Geophysical research letters. Volume 49:Issue 11(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-06-04
• Subjects: climate -- tectonics -- weathering; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2022GL098843
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Over its multibillion‐year history, the Earth has experienced a wide range of climates. The long‐term climate is controlled by the atmospheric carbon dioxide concentration, which is regulated by marine sequestration through chemical weathering. This chemical weathering sink is strongly linked to the distribution and composition of the continents. However, the effect of continental distribution has never been studied within a general framework. Here we show that the global weathering rate is sensitive to the size and shape of the continents, but is not well explained by the amount of land in the tropics. We construct synthetic continental configurations and use an ensemble of global climate model simulations to isolate the expected effect of continental arrangement on weathering and carbon burial. Runoff patterns are complex, sensitive to detailed features of continental geometry, and poorly predicted by continental latitude. These results help explain the long‐term variability and irregularity of Earth's climate. Plain Language Summary: Chemical weathering of the continental crust draws down atmospheric carbon dioxide and regulates the global climate on geological timescales. The weathering process is thought to be controlled primarily by temperature and runoff. Therefore, a concentration of continental landmasses in the tropics has long been considered a factor leading to higher weathering rates and global cooling. We rigorously test this hypothesis by running a large ensemble of climate simulations with random continental configurations. Surprisingly, we find that tropical land fraction and mean continental latitude are poor predictors of global weathering rates. We also find that although the size of the continents is important, it is not a dominant factor either. A significant fraction of weathering variability is driven by precipitation and runoff patterns, which are sensitive to detailed aspects of continental geometry. This sensitivity indicates that factors other than the latitudinal position of the continents (such as continental breakup or crustal composition) are important controls on the Earth's long‐term climate. Key Points: We simulate climate and weathering with an ensemble of randomly generated continental configurations Tropical land fraction and continent latitude are poor predictors of weathering rates, but degree of continental breakup is better Half of the weathering variability is produced by complex, hard to predict interaction between continent geometry and atmospheric dynamics