关键词: 化学风化, 碳汇, 水化学, 全球变暖, 育空河

Abstract: The feedback of silicate weathering to climate change and tectonism may play an important role in regulating longterm climate change, quantitative evaluation of this feedback process will help us to more accurately understand how Earth’s carbon cycle works. It is generally believed that there are two weathering types called “supply-limited” and “kinetic-limited”. Global warming may accelerate chemical weathering in the basin under the “kinetic-limited” regimes, however, it remains poorly constrained. The Yukon River Basin is a typical “kinetic-limited” regime. Studying the response of Yukon River weathering to climate warming will help us to deeply understand the interaction between climate and continental weathering. Forward modeling is an important means to distinguish end-members of river weathering. This study estimates the decadal variations in chemical weathering rates in Yukon River Basin with a forward model based on a dataset of major ion composition of the riverine dissolved from 1975 to 2019. The results show that the water chemical properties of the Yukon River basin are mainly controlled by carbonate weathering and silicate weathering. The average annual CO2 consumption rates by silicate weathering and carbonate weathering are 2.1×10¹¹ mol/yr and 4.1×10¹⁰ mol/yr, respectively, which are in the middle level of the world’s large rivers. More importantly, during the same period, with a 2.2℃ temperature rise and an increase in discharge by 13.7%, the total flux of cation in the basin is increased by 35.7%. And the cation flux of silicate and carbonate weathering increased by 41% and 35% respectively, the sensitivity of cation flux/weathering rate to climate is in good agreement with the results from Iceland. Corresponding to the accelerated weathering rate, the carbon flux of silicate weathering increased by 59.6%. Although the increase of carbon sink is insignificant in terms of absolute flux compared with anthropogenic carbon emission by contemporary fossil combustion, the additional CO₂ sequestration may have an important impact on global climate during Earth’s history, given the increased rates of global silicate weathering within the tectonic scale, especially in the relatively cold high latitude area.

Key words: chemical weathering, carbon sink, water chemistry, global warming, Yukon River