Earth's climate state is set by the presence or absence of arc-continent collisions in the tropics
Abstract
Over geological history, Earth has experienced three distinct climate states: glacial-interglacial, non-glacial, and Snowball Earth. Through the Phanerozoic Eon, Earth's climate has been predominantly non-glacial ( 75%), with relatively brief, 1-70 Myr intervals of glacial climate. Similarly, aside from Snowball Earth events, much of the preceding Proterozoic Eon was also characterized by a non-glacial climate state. Given that a warm, non-glacial climate is the most common climate state for Earth, what processes have caused cooling trends on million year timescales resulting in glacial-interglacial climates and Snowball Earth?
It has previously been proposed that long-term cooling trends are caused by decreases in volcanic outgassing or increases in global weatherability, and that short-term perturbations to albedo or the biological carbon cycle could push the Earth to a runaway ice-albedo catastrophe. Here we explore how CO2 sinks and global weatherability have changed through time and correlate with cooling trends. CO2 sinks are the product of variables such as lithology, paleolatitude, and uplift rates, which can be constrained with geological data. Given that mafic and ultramafic rocks are highly soluble in the warm and wet tropics, emplacement of large igneous provinces (LIPs) and arc-continent collisions at low latitude should increase global weatherability. How often are major low-latitude LIPs and arc-continent collisions not associated with global cooling and in what context? To this end, the paleogeographic position of all major Neoproterozoic and Phanerozoic large igneous provinces and ophiolite-bearing sutures associated with arc-continent collisions was reconstructed and compared to the record of glaciation. This analysis reveals that whenever extensive arc-continent collisions have been ongoing in the tropics, the Earth has experienced a glacial climate, and otherwise, the Earth has been in a non-glacial climate state. Global weatherability has provided the first-order control on Earth's climate through changes in rock-type and topography in the tropics. It remains unknown if increased global weatherability solely caused the Neoproterozoic runaway ice-albedo catastrophes, or if Snowball Earth was initiated by a combination of weatherability and perturbations to albedo or the biological carbon cycle.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMPP51B..02M
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCESDE: 0473 Paleoclimatology and paleoceanography;
- BIOGEOSCIENCESDE: 1030 Geochemical cycles;
- GEOCHEMISTRYDE: 5225 Early environment of Earth;
- PLANETARY SCIENCES: ASTROBIOLOGY