**5. Conclusions**

Compared to our observations, the salinity-extended lake model demonstrated a good ability to represent lake–air interactions and the thermal regime in both a freshwater lake and a saline lake. The newly introduced salinity parameterization significantly improved the model performance for a saline lake in winter.

The simulated long-term increasing rates of the annual LSWT in NL, HSP, and a shallower hypothetical freshwater lake amounted to more than 0.6 ◦C/decade, mainly due to meteorological forcing. Increasing LWD and Ta, weakening wind, and increased air humidity had positive effects on the warming trend of TP lakes in decreasing order, while solar radiation dimming counteracted the warming. The LWD and Ta contributed the most to lake warming in the sensitivity experiment; although it was overlooked in previous studies [3,15], increasing atmospheric humidity over TP should be considered a significant climatic factor.

The shallow lakes in experiments S-D1F and S-HSP lacked seasonal thermal stratification and were well-mixed vertically, revealing similar long-term warming trends across their depths. Comparing to a fresh water lake with 1 m depth, the 17-m-deep NL experienced a 0.06 ◦C/decade faster surface warming and a slower MLT rise of 0.35 ◦C/decade.

High salinity prevented ice cover formation in HSP and induced more heat release in winter and lower MLT and BLT than in freshwater lakes NL and D1F. However, the high salinity made the annual mean LSWT 2.6 ◦C higher and resulted in a 0.02 ◦C/decade stronger warming trend than in the freshwater lake with the same depth. The salinity effect on the freezing point contributed most to this difference, inducing a 90% higher LSWT compared to the freshwater D1F. The salinity effect on evaporation caused a 31% higher LSWT in HSP. The opposite salinity effect on the lake surface albedo cooled the lake surface and decelerated the warming trend.

The monthly mean LSWT differences between Ngoring Lake and the Hajiang Salt Pond were induced by salinity effects in cold periods and lake depth in the unfrozen period. The LSWT in ice-free Hajiang Salt Pond increased rapidly from January to April due to climate change, whereas the LSWT of Ngoring Lake increased faster in the first and last months of the ice-cover period due to later ice-on and earlier ice-off.

**Author Contributions:** L.W. initiated this work, carried out modeling experiments, analyzed the results and wrote the original draft; C.W. and S.C. collected the data, Z.L., L.Z., S.L., M.L. and G.K. gave constructive suggestions on the design and modification of the manuscript. All the authors contributed to the writing and editing of the manuscript. All authors have read and agreed to the published version of the manuscript.

**Funding:** This study was supported by the National Key Research and Development Program of China (2019YFE0197600), CAS "Light of West China" Program (E129030101, Y929641001), the National Natural Science Foundation of China (41975081, 41930759).

**Data Availability Statement:** ITPCAS dataset is available in the Third Pole Environment Database (https://data.tpdc.ac.cn/en/). Maduo data could be downloaded from http://www.tpdc.ac.cn/ zh-hans/data/52c77e9c-df4a-4e27-8e97-d363fdfce10a/. MODIS data could be downloaded from https://modis-land.gsfc.nasa.gov/MODLAND\_grid.html.

**Conflicts of Interest:** The authors declare no conflict of interest.
