『Abstract
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
CO2 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℃ 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, 2) suggest that
weathering rates are currently increasing with time due to global
warming.
Keywords: climate moderation; chemical weathering; basalt; CO2 flux; global carbon cycle』
1. Introduction
2. Materials and methods
2.1. Measurement of discharge
2.2. Determination of dissolved concentrations and fluxes
2.3. Determination of SIM concentration and fluxes
2.4. Mean annual temperature and annual precipitation measurements
2.5. Statistical analysis
3. Results and discussion
3.1. Climate and rivers of north-eastern Iceland
3.2. River fluxes
3.3. Correlations between river fluxes and climate
3.4. Weathering rates and climate change from 1964 to 2004
3.5. The effect of glaciers on weathering rates
4. Conclusions
acknowledgements
Appendix A. Supplementary data
References