CONTROLS ON THE VARIABILITY IN CALCITE DISSOLUTION RATES IN SURFACE STREAMS ACROSS THE CONTIGUOUS UNITED STATES

Most studies on the effects of karst on the global carbon cycle have been limited to denudation rates calculated for broad climatic zones. In contrast, little work has been done at a finer scale, such as characterization of dissolutional incision into soluble bedrock by streams. Here we calculated surface reaction limited dissolution rates using water quality data from 875 USGS gaging stations distributed throughout the contiguous US, including stations on carbonate and non-carbonate bedrock. These data were compared against potential controls on average rates and at-a-site variability in rates: including discharge, climate, land use, and percent carbonates in the drainage basin. Rates and interquartile range variation are strongly correlated with ET (r=0.64 and r=-0.52, respectively), regardless of discharge, land use or percent upstream carbonates. As carbonate dissolution acts as a carbon sink, this suggests that wetter karst areas have a greater effect on the global carbon cycle. An important implication is that dissolution rates in surface streams flowing over carbonates are more strongly controlled by climate rather than any other factor.