Glacier melts are erasing climate record

Throughout the world, glaciers are on the retreat. Within just a few decades, some that used to flow kilometers down the side of mountains have been reduced to vanishing remnants near summits. And not just in polar regions. The glaciers that long capped peaks within alpine reaches at tropical latitudes such as in Peru and East Africa are also drying up, and at a double-time pace.

GLACIER THEN … Here’s the Qori Kalis glacier when Lonnie Thompson first visited it in 1978. At this time, it was still healthy. Ohio State Univ.
SAME GLACIER NOW Here’s the same view of that tropical Peruvian glacier photographed when Thompson returned in 2000. A lake of meltwater now occupied what 22 years earlier had been a deep field of flowing ice. Ohio State Univ.

Most news accounts have focused on these retreats as an early symptom of global warming and make no mistake, they are that. They’re also a warning that downstream communities could soon find themselves catastrophically strapped for the meltwater they’ve assumed would always be there for drinking, crop irrigation, and hydroelectricity. Once these frigid water reservoirs vanish they may not be replaced for a thousand years.

But for science, glacial melts represent a compounded loss. These ancient solid rivers hold clues not only to when the ice in them had been deposited, but also to how long these ice fields have persisted at particular altitudes. As such, their melting away constitute nothing less than an irreplaceable loss of the climate record, notes Lonnie Thompson of Ohio State University.

The glaciologist kicked off a climate-change conference for journalists at his school, this afternoon (an event sponsored by OSU’s Kiplinger Program in Public Affairs Journalism and by the Chicago-based McCormick Foundation).

For more than three decades, Thompson has been trekking to some of the least accessible spots on the globe. In some cases, he took photos of the moving streams of ice and compared them to ones taken up to a century earlier. In other cases, his crew embedded long poles deeply into glaciers and returned at regular intervals to see how much of each stick’s footing had been revealed as the glacier thinned.

The results have been disquieting. Glaciers like Peru’s Qori Kalis, which had been retreating 6 meters per year, are now shrinking back at a rate 10 times that fast.

More troubling to scientists like Thompson: These losses are erasing the very media that might explain the processes controlling glacial births and deaths. Currently, he’s in a race against time to glean as much data as he can before our planet’s subtle and risingfever melts all traces away.

His OSU group is among teams around the world that have been regularly drilling into deep, ancient ice fields. Like rings in a tree trunk, the narrow cores of ice that they have been extracting quantitatively illustrate the amount of precipitation deposited season by season. Some cores that Thompson’s group have extracted from Mt. Kilimanjaro, for instance, reveal snow-deposition records going back more than 11,000 years.

These cores also hold chemical clues to the environment through the years, such as the annual deposition of dust, volcanic ash even fallout from nuclear tests in recent years.

But at Kilimanjaro (as elsewhere around the globe), glacial ice is in hot retreat. What once used to dazzle tourists as a long and broad river of ice is now largely a field of rock and rubble. Only the mountain peak maintains any relics of its glacial majesty. Thompson showed a recent aerial photo of Kilimanjaro’s summit, in Tanzania, that was mere patchy glacial remains. They confirm that no glacial growth has occurred in recent history. Within 12 years, he says, Kilimanjaro will likely be glacier-free.

The largest glacial ice cap in the tropics, Quelccaya, lies in Peru. As it’s been retreating, it occasionally uncovers surprises that had been buried as the glacier grew. Melting recently uncovered one wetland region that had been buried under ice for more than 5,000 years, revealing some 50 different members of the botanical community that once thrived there.

Two months ago, Quelccaya’s continuing retreat revealed another 11 plants. Within the next day or two, Thompson says he expects to date how long it’s been since their vicinity was ice-free.

If Earth’s warming isn’t halted quickly, he says, humanity may just have to accept that for a very long time our planet will look different than the one that we grew up with. Because glacial melt is just a prelude to massive sea level rise, Earth’s landmass will shrink.

If you think cities are tight and resources strapped now, Thompson warns, imagine feeding and housing countless more on a substantially smaller and diminishing piece of real estate.

Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.

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