Direct evidence of the feedback between climate and weathering

• Published in: Earth and planetary science letters Vol. 277; no. 1; pp. 213 - 222
• Main Authors: Gislason, Sigurdur R., Oelkers, Eric H., Eiriksdottir, Eydis S., Kardjilov, Marin I., Gisladottir, Gudrun, Sigfusson, Bergur, Snorrason, Arni, Elefsen, Sverrir, Hardardottir, Jorunn, Torssander, Peter, Oskarsson, Niels
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.01.2009
• Subjects: basalt; chemical weathering; climate moderation; CO 2 flux; CO2 flux; Earth sciences; Geovetenskap; global carbon cycle; NATURAL SCIENCES; NATURVETENSKAP; ANE, Atlantic, Iceland; chemical weathering; CO 2 flux; basalt; climate moderation; global carbon cycle
• ISSN: 0012-821X; 1385-013X; 1385-013X
• DOI: 10.1016/j.epsl.2008.10.018

Long-term climate moderation is commonly attributed to chemical weathering; the higher the temperature and precipitation the faster the weathering rate. Weathering releases divalent cations to the ocean via riverine transport where they promote the drawdown of CO 2 from the atmosphere by the precipitation and subsequent burial of carbonate minerals. To test this widely-held hypothesis, we performed a field study determining the weathering rates of 8 nearly pristine north-eastern Iceland river catchments with varying glacial cover over 44 years. The mean annual temperature and annual precipitation of these catchments varied by 3.2 to 4.5 °C and 80 to 530%, respectively during the study period. Statistically significant linear positive correlations were found between mean annual temperature and chemical weathering in all 8 catchments and between mean annual temperature and both mechanical weathering and runoff in 7 of the 8 catchments. For each degree of temperature increase, the runoff, mechanical weathering flux, and chemical weathering fluxes in these catchments are found to increase from 6 to 16%, 8 to 30%, and 4 to 14% respectively, depending on the catchment. In contrast, annual precipitation is less related to the measured fluxes; statistically significant correlations between annual precipitation and runoff, mechanical weathering, and chemical weathering were found for 3 of the least glaciated catchments. Mechanical and chemical weathering increased with time in all catchments over the 44 year period. These correlations were statistically significant for only 2 of the 8 catchments due to scatter in corresponding annual runoff and average annual temperature versus time plots. Taken together, these results 1) demonstrate a significant feedback between climate and Earth surface weathering, and 2) suggest that weathering rates are currently increasing with time due to global warming.