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Abstract The geography of the Southeast Asian Islands (SEAI) has changed over the last 15 million years, as a result of tectonic processes contributing to both increased land area and high topography. The presence of the additional land area has been postulated to enhance convective rainfall, facilitating both increased silicate weathering and the development of the modern‐day Walker circulation. Using an Earth System Model in conjunction with a climate‐silicate weathering model, we argue instead for a significant role of SEAItopographyfor both effects. SEAI topography increases orographic rainfall over land, through intercepting moist Asian‐Australian monsoon winds and enhancing land‐sea breezes. Large‐scale atmospheric uplift over the SEAI region increases by ∼14% as a consequence of increased rainfall over the SEAI and enhancement through dynamical ocean‐atmosphere feedback. The atmospheric zonal overturning circulation over the Indo‐Pacific increases modestly arising from dynamical ocean‐atmosphere feedback, more strongly over the tropical Indian Ocean. On the other hand, the effect of the SEAI topography on global silicate weathering is substantial, resulting in a ∼109 ppm reduction in equilibriumpCO₂and decrease in global mean temperature by ∼1.7ºC. The chemical weathering increase comes from both enhanced physical erosion rates and increased rainfall due to the presence of SEAI topography. The lowering ofpCO₂by SEAI topography also enhances the Indo‐Pacific atmospheric zonal overturning circulation. Our results support a significant role for the progressive emergence of SEAI topography in global cooling over the last several million years. 

Volcanic highlands in the tropics increased global weatherability ~0.9–1.6 Ma before onset of Cryogenian Snowball Earth. 

One of the hypothesized effects of large igneous provinces (LIPs) is planetary cooling on million-year timescales associated with enhanced silicate weathering of freshly emplaced basalt. This study combines reconstructions of the original surface extent and emplacement ages of LIPs, a paleogeographic model, and a parameterization of LIP erosion to estimate LIP area in all latitudinal bands through the Phanerozoic. This analysis reveals no significant correlation between total LIP area, nor LIP area in the tropics, and the extent of continental ice sheets. The largest peaks in tropical LIP area are at times of non-glacial climate. These results suggest that changes in planetary weatherability associated with LIPs are not the fundamental control on whether Earth is in a glacial or non-glacial climate, although they could provide a secondary modulating effect in conjunction with other processes. 

Steep topography, a tropical climate, and mafic lithologies contribute to efficient chemical weathering and carbon sequestration in the Southeast Asian islands. Ongoing arc–continent collision between the Sunda-Banda arc system and Australia has increased the area of subaerially exposed land in the region since the mid-Miocene. Concurrently, Earth’s climate has cooled since the Miocene Climatic Optimum, leading to growth of the Antarctic ice sheet and the onset of Northern Hemisphere glaciation. We seek to evaluate the hypothesis that the emergence of the Southeast Asian islands played a significant role in driving this cooling trend through increasing global weatherability. To do so, we have compiled paleoshoreline data and incorporated them into GEOCLIM, which couples a global climate model to a silicate weathering model with spatially resolved lithology. We find that without the increase in area of the Southeast Asian islands over the Neogene, atmosphericpCO₂would have been significantly higher than preindustrial values, remaining above the levels necessary for initiating Northern Hemisphere ice sheets. 

Changes in the geological sulfur cycle are inferred from the sulfur isotopic composition of marine barite. The structure of the³⁴S/³²S record from the Mesozoic to present, which includes ∼50- and 100-Ma stepwise increases, has been interpreted as the result of microbial isotope effects or abrupt changes to tectonics and associated pyrite burial. Untangling the physical processes that govern the marine sulfur cycle and associated isotopic change is critical to understanding how climate, atmospheric oxygenation, and marine ecology have coevolved over geologic time. Here we demonstrate that the sulfur outgassing associated with emplacement of large igneous provinces can produce the apparent stepwise jumps in the isotopic record when coupled to long-term changes in burial efficiency. The record of large igneous provinces map onto the required outgassing events in our model, with the two largest steps in the sulfur isotope record coinciding with the emplacement of large igneous provinces into volatile-rich sedimentary basins. This solution provides a quantitative picture of the last 120 My of change in the ocean’s largest oxidant reservoir.