Paleogeographic controls on Phanerozoic weathering rates and implications for climate regulation
Abstract
Earth’s climate has remained habitable for billions of years, a stability usually attributed to a negative feedback from silicate weathering – the chemical breakdown of silicate rocks on land, which consumes atmospheric carbon dioxide faster as climate warms. However, whether temperature or hydrology primarily drives this feedback remains uncertain. Here we show the two controls leave geographic fingerprints: in an ensemble of climate simulations with randomized continents, temperature-controlled weathering depends on tropical land fraction, whereas hydrology-controlled weathering depends on continental fragmentation. Stronger weathering removes more carbon dioxide, cooling the planet, so each regime predicts anti-correlation between temperature and its controlling geography. Reconstructed global temperatures spanning 480 million years are anti-correlated with tropical land fraction, except from roughly 295 to 200 million years ago – overlapping the supercontinent Pangea – when they anti-correlate with continental fragmentation. The mechanism stabilizing Earth’s climate may thus have evolved, with temperature control apparently dominant for most of this period. Simulations with randomized continents show that temperature- and hydrology-controlled weathering results in climates that track different features of continental geometry. The Earth’s record suggests the control may have shifted over 480 million years.