The puzzling features are most easily seen from above, but they pose real risks at the surface.
For several decades, scientists and astronauts observing Lake Baikal have noticed giant rings in the spring ice on one of the world’s oldest and deepest lakes. Russian researchers first spotted them in satellite images in the early 2000s, but it was after astronauts on the International Space Station photographed two ice rings in April 2009 that the phenomenon become a topic of international study and fascination.
While the rings have attracted speculation and a few conspiracy theories, decades of satellite data and field-based studies have shed light on why they form. “Results of our field surveys show that before and during ice ring manifestation, there are warm eddies that circulate in a clockwise direction under the ice cover,” explained Alexei Kouraev, a hydrologist at the University of Toulouse. “In the eddy center, the ice does not melt — even though the water is warm — because the currents are weak. But on the eddy boundary, the currents are strong and warmer water leads to rapid melting.”
During field work, Kouraev and his colleagues from France, Russia, and Mongolia drilled holes near ice rings and deployed sensors capable of measuring the temperature and salinity of the water column to a depth of 200 meters (700 feet). Typically the water in the eddies was 1 to 2 degrees Celsius (2 to 4 degrees Fahrenheit) warmer than the surrounding water.
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Image via NASA Earth Observatory
