Lake Puma Yumco

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Lake Puma Yumco (centre) and Lake Yamzho Yumco from space, November 1997

Puma Yumco in winter. The north-south white line is a possible ice ridge, formed by east-west winds subsequently highlighted by snow.

Lake Puma Yumco is a lake located at 5030 meters (16,503 feet) above mean sea level on the southern Tibetan Plateau. It is 32 km (20 miles) long, and is 13 km (8 miles) wide. Streams of water from the snow-capped surrounding mountains feed the lake, but the lake has no outlet. Some sediment can be seen entering the lake at its western end.

Puma Yumco literally means The Blue Jewel which is floating in the sky. The lake freezes in winter and is crossed by shepherds with their sheep. Since the climate is warming, the ice is becoming thinner and thus creates a problem for the 120 people living off and around the lake.

The lake is considered ultraoligotrophic, meaning that nutrient concentrations in both the water column and lake sediments are extremely low. Water in such lakes tends to be blue to blue-green and to have high clarity due to low levels of photosynthesizing organisms such as phytoplankton.

During the winter, the lake develops intricate ice block patterns on the surface, ranging from less than ten to hundreds of meters in diameter. The ice pattern is caused by repeated cycles of freezing, fracturing, and refreezing of the ice due to variations in temperature and wind-induced ice motion.