Merzbacher Glacier Lake is located at the very border of Kyrgyzstan, China and Kazakhstan, 3200 m on the huge Tien San massif and the great Engilchek glacier. This lake is often called the “disappearing lake” because it dries up every year as the ice melts.

For reasons not fully understood, the lake releases its entire volume almost every year. Numerous ice blocks floating on its surface are formed by icebergs calving from the Southern Inylchek Glacier and from small side glaciers hanging above the lake. After the total discharge of Lake Merzbacher in late summer, these icebergs sink to the lake bottom and freeze to ground during the winter. As Lake Merzbacher fills up again in the summer, these icebergs sometimes rapidly “jump” to the lake surface, producing a high spray fountain. What follows is a summary of Lake Merzbacher ’s regular outbursts and the consequent glacier lake outburst floods.

The release of the lake water begins when the ice dam of the advancing Southern Inylchek Glacier buoys upwards. As a consequence, a system of englacial channels in the damming glacier opens and the lake water discharges through the main Inylchek Glacier westwards into the Inylchek Valley. Once the englacial channels start opening, they quickly increase in diameter because of the kinetic energy and slightly higher temperature of the water flow. After the lake has emptied, the ice dam lowers, the englacial channels are blocked, and the lake begins to fill again.

The emptying and filling cycle happens once or twice a year, usually in August or September.