Hey Mr. Kipling, Never Say Never

“Oh, East is East, and West is West, and never the twain shall meet...”

How things have changed in the world since Rudyard Kipling wrote those words—even high above the Indian subcontinent, birthplace of the celebrated author and poet.

There, east and west likely met throughout the 1950s and ‘60s, in the form of radioactive fallout from the testing of atomic weapons in places like Nevada. Scientists know winds carried that fallout around the world before it eventually settled out of the atmosphere, including onto the ice that drapes much of the Himalayas.

In fact, researchers who drill into glaciers and ice fields around the globe have long and reliably turned up traces of that radioactivity, typically finding it buried beneath the snow and ice piled on in the years since A-bomb testing ceased. The strontium 90, cesium 136, and other isotopes have provided those experts with a clever way of dating their core samples—an atomic-age benchmark, if you will. Since the ice sullied by the radioactivity must date to the era of atmospheric testing, everything above that level had to have accumulated in the years and decades since, and in depths and volumes that are measurable.

But scientists who recently drilled into an ice field high in the Himalayas came up empty-handed, at least when it came to finding similar benchmarks. A joint U.S.-Chinese team last year pulled four ice core samples from the summit of Naimona'nyi, a large glacier 6,050 meters (19,849 feet) high on the Tibetan Plateau. But none contained any trace of the radioactivity found in virtually every other ice core extracted worldwide.

Was the glacier never dusted with radioactive fallout? Unlikely. Instead, any isotope-sprinkled layer of ice probably melted away sometime in the last 50 years. That means the Tibetan ice field is shrinking—and probably has been for quite some time, scientists reported in their findings at the fall meeting of the American Geophysical Union in San Francisco, California.

That’s bad news for one in six people on Earth, as the largest concentration of ice outside the polar caps is locked in the Himalayas. Glacial melt from the region feeds the Ganges, Indus, Mekong, Yangtze, and other major rivers, which roughly a billion people in China, India, Nepal, and other countries rely on.

While melting glaciers mean an abundance of water in the short term, eventually they will shrink away to nothing. When that happens, the flood will turn to a trickle — and choke off the water supply for a large chunk of the world.