Drivers of Warming in Lake Nam Co on Tibetan Plateau over the Past 40 Years

The lake surface water temperature (LSWT) on Tibetan Plateau (TP) is sensitive to climate change. Based on a 1-D lake model, we have investigated the interdecadal variation and long-term trend of LSWT in Lake Nam Co (LNC) on TP during 1980-2018 and quantified the relative contributions of atmospheric factors to the LSWT trend. Results show LNC was warmed with a rate of 0.29°C decade–1, which is smaller than the warming of ambient air (0.45°C decade–1). The weakened wind speed, rising air temperature, increased downward longwave radiation, and decreased shortwave radiation contributed about 35%, 30%, 20%, and -15% of the estimated long-term LSWT trend during 1980-2018, respectively. The contribution rate of 32.5% was from the interactions among all forcing variables. The primary warming was completed before 1997 (0.30°C decade–1) and was followed by a hiatus that the LSWT jumped to a warm level with a slightly negative trend (-0.08°C decade–1) after 1997. During this hiatus, the wind speed recovered from decrease and the deceleratingly increased downward longwave radiation slowed down the LNC warming. Particularly, the specific humidity shifted from increasing to decreasing trend played a key role in the hiatus of LNC warming after 1997, despite its slight contribution (-2.5%) to the LSWT trend during 1980-2018. The results showed the particularity of warming for a TP lake compared to the other ice-covered lakes worldwide and provided a quantitative perspective for understanding the relative contributions of atmospheric factors to the long-term trend of LSWT. This article is protected by copyright. All rights reserved.