Geology

Weathering Is Not Under the Weather

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Science  01 Jun 2001:
Vol. 292, Issue 5522, pp. 1611-1613
DOI: 10.1126/science.292.5522.1611e

Chemical weathering of silicates is thought to help regulate Earth's atmospheric temperature, because weathering removes CO2 from the air. Higher temperatures speed the rate of chemical weathering, and thus warmer climates should decrease positive radiative forcing by CO2 and ultimately act to lower temperature. The rate of chemical weathering is difficult to determine, however, so it has been hard to test whether this temperature regulation hypothesis is correct.

Riebe et al. determined chemical weathering rates at the sites of 22 mountainous granitic catchments from measurements of the concentrations of insoluble elements in soils in eroding landscapes and from estimates of physical erosion rates derived from cosmogenic nuclides. They show that recent chemical weathering rates, over the relatively short time scales of soil formation at these locations (thousands of years), are related primarily to physical erosion rates and that the effect of climate is minor in comparison. This relation implies that tectonic uplift, which strongly influences the rate of erosion, is an important control of climate over long time scales. Chemical weathering in lowland areas and floodplains could be more dependent on climate, however, and thereby increase the strength of the weathering-temperature feedback loop. — HJS

Geology29, 511 (2001).

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