Investigations On The Impacts Of Land-Cover Changes And/Or Increased Carbon Dioxide Concentrations On Four Regional Water Cycles And Their Interactions With The Global Water Cycle

Abstract

A suite of simulations that combine reference (355ppmv), doubled and tripled CO2 concentrations alternatively without and with land-cover changes in four similar-sized study regions, the Yukon, Ob, St. Lawrence and Colorado basin and adjacent land, are performed with the fully coupled Community Climate System Model to investigate the impact on global and regional water cycles and the interaction of these regional water cycles with the global water cycle. The relative changes in water-cycle quantities caused by increased CO 2 enhance with latitude and CO2 concentrations. Regional and global water cycles interactions are more pronounced in a warmer climate, but regional precipitation and evapotranspiration is affected differently in high-latitudes (Yukon, Ob) than mid-latitudes (Colorado, St. Lawrence). Land-cover changes can have comparable impacts on regional water cycles than increased CO2 concentrations do. Land-cover changes substantially alter the high-latitude water cycles through enhanced snow-albedo feedback and mid-latitude water cycles through vegetation activity in the warm season. The land-cover changes in different regions interact with each other through heat and moisture advections and secondary effects. This interaction enhances with increasing CO2 concentrations. Interactions between land-cover changes and increasing CO2 concentrations enhance with increasing CO2 due to the high sensitivity of regional water cycles to temperature changes.