Abstract: The hydrolysis of Na,K,Ca feldspar and carbonate in surface runoff consumed a mass of H⁺,which would cause atmospheric CO₂ to sink. In the glacier area,the CO₂ flux at the gas-liquid interface was usually analyzed using the method of hydrochemical mass balance.In recent years,the eddy covariance systems have been used to analyze energy balance,CO₂ flux and moisture flux in the areas of complex terrain.In this study,the CO₂ flux was monitored by eddy covariance system in the Koxkar glacier of the Western Tianshan,Xinjiang,China from 2015 to 2017,and the results showed that the CO₂ fluxes were ranged from -17.99 to 3.59 g·m^-2·d^-1 with an average of -2.58 g·m^-2·d^-1.The CO₂ flux values were negative in the January (-0.21 g·m^-2·d^-1).It indicated that atmospheric CO₂ sank on the glacier area because of the dissolved CO₂ in the water when the interaction between the water and the rock occurred during precipitation/snow and ice melting.Further analysis suggested that the net glacier exchange (NGE) of CO₂ was decreased as the daily temperature increased.There was a significant negative correlation between NGE and daily temperature.For precipitation,almost no effect on the NGE was found when the precipitation was less than 8.8 mm.However,the daily NGE was decreased exponentially with the increase of precipitation when the precipitation was greater than 8.8 mm.The effect of precipitation on CO₂ absorption was mainly reflected in the following two aspects.One was the CO₂ sink at the gas-liquid interface slow down resulting from the weakening of the water chemical erosion caused by the reduction of the ice melting,which caused by continuous heavy rain reducing the temperature.The other was the CO₂ sink at the gas-liquid interface was decreased due to the increasing dissolving CO₂ in the atmosphere because of increasing of the precipitation.Finally,there were significant linear relationships between the NGE and the runoff.However,the slopes of linear relationships between the NGE and the runoff varied during different periods,which were due to changes in the type of hydrochemical reaction caused by changes of effective ablation area,and changes in hydrochemical reaction time effected by the hydrological channels below the ice.

Key words: CO₂ flux, eddy covariance, runoff, Koxkar glacier