Tibetan Plateau Ice-Covered Lakes Influencing Heat Transfer in Land, Atmosphere

Tibetan Plateau is the highest and largest plateau in the world, where the largest alpine lake system is located. Scientists have studied how the ice-covered lakes in the plateau influence the heat transfer between the atmosphere and the soil, affecting the temperature and rainfall within the area.

According to American Geophysical Union, not much is known of the thermal dynamics that happen during the winter months when the lakes are covered with ice. Researchers demonstrated in their study how these icy lakes release heat when it melts, driving changes in temperature that could potentially have global impacts.

Icy Lakes of Tibetan Plateau Act as Solar Collector

Researchers of the new study focused their research on China's Ngoring Lake. According to experts from Qinghai Normal University's Department of Geographic Sciences, Ngoring Lake is also called Cuoelang in Tibetan. It is the largest freshwater lake on the Qinghai-Tibet Plateau, located in Madoi county in Qinghai.

The lake is usually covered with ice from December until mid-April during the winter season. However, data on the thermal properties of this ice-covered lake is scarce.

AGU reported that researchers observed the atypical warming temperatures after the ice on the lake melted as solar radiation at the icy surface warmed the upper water under the ice. They noticed that Ngoring Lake had a mixed water temperature due to the strong convective mixing when it was covered with ice.

The team pointed out that by the middle of the winter season, the water temperature was higher than the expected maximum density temperature, which accelerated the melting of ice by the end of the season.

Water temperatures decreased by nearly one degree Celsius as the ice melts and releases approximately 500 watts per square meter of heat into the atmosphere in just two days.

The study demonstrates that unlike most ice-covered lakes with water temperatures that remain below the maximum density temperature, the icy lakes in the Tibetan Plateau do not lie dormant under the ice.

The effects cause thousands of lakes across the Tibetan plateau to hot spots of heat flux after ice melt, which releases the heat absorbed from solar radiating and changing convection, temperature, and water mass flux that affects the globe.

Land, Air Heat Transfer

According to UCAR Center for Science Education (UCAR SciEd), conduction, convection, and radiation play an important role in the moving heat between the soil and atmosphere. Most energy transfers occur on the surface as the atmosphere is a poor conductor.

Sunlight heats the earth during the day, which then heats the air directly above it via conduction. The earth cools at night, and heat convects from the warmer air directly above the cooler ground.

While air temperature near the ground can be significantly higher than just a few feet above, there is little to no wind on bright, sunny days. The poor conductivity of air limits heat transfer from the surface to the air above even though the sunlight warms the surface. Air temperature drops as it rises in altitude.

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