Andre said:
Maybe it also works in the opposite direction: sinking temperatures could cause less precipitation in certain areas. So less ice, less glaciers.
This type of behavior is common in tropical glaciers, such as the one on Mt. Kilimanjaro's Kibo Peak (Tanzania), and the Quelccaya ice cap in the Peruvian Andes.
Glaciologists Mote & Kaser write in a 2007
American Scientist article:
But the commonly heard—and generally correct—statement that glaciers are disappearing because of warming glosses over the physical processes responsible for their disappearance. Indeed, warming fails spectacularly to explain the behavior of the glaciers and plateau ice on Africa's Kilimanjaro massif, just 3 degrees south of the equator, and to a lesser extent other tropical glaciers. The disappearing ice cap of the "shining mountain," which gets a staring role in the movie, is not an appropriate poster child for global climate change. Rather, extensive field work on tropical glaciers over the past 20 years by one of us (Kaser) reveals a more nuanced and interesting story. Kilimanjaro, a trio of volcanic cones that penetrate high into the cold upper troposphere, has gained and lost ice through processes that bear only indirect connections, if any, to recent trends in global climate.
http://www.americanscientist.org/issues/feature/the-shrinking-glaciers-of-kilimanjaro-can-global-warming-be-blamed/
What? Only indirect
if any trends in global climate? What?
Weather balloon summit altitude data indicates monthly average temperatures have fluctuated from -4 to -7 degrees since 1958, and no significant warming trend is seen. This is a problem for the argument that rising air temperature is responsible for the melting of this glacier. If the air temperature never rises above -4 degrees Celsius,
the air cannot warm the ice to melting. (http://www.americanscientist.org/issues/feature/the-shrinking-glaciers-of-kilimanjaro-can-global-warming-be-blamed/5)
The researchers propose an alternative explanation, based on a keener understanding of how glaciers work.
Tropical glaciers occur when mountain summits penetrate the subzero air of the upper troposphere. Snow precipitation helps them grow, and melting makes them retreat. Retreat is due to sublimation, or solar radiation in conditions of very light wind, which allows a warm layer of air to develop just next to the ice.
As these forces whittle away at the glacial edges, steep walls are created. "Once developed, the near-vertical edges will retreat until the ice is gone, since no snow can accumulate on these walls." They see the steep walls and
sharp peaks as evidence against the role of "smoothers"—diffuse heat sources.
Penitents at Kilimanjaro.
Observers have been tracking the shrinkage of Kilimnajaro's glacier ever since Europeans first scaled the peak in the 1880s, but the ice cap at that time may have been unusually large following several decades of above-normal precipitation. Judging from Lake Victoria's water level, the climate in the region has gotten progressively drier since the 19th century. "Overall, the historical records available suggest that the large ice cap described by Victorian-era explorers was more likely the product of an unusually wet period than of cooler global temperatures."
Ironically, if smoothers strengthened, if the air temperature rose occasionally above 0˚, the slopes would smooth out and sharp corners would gentle, allowing the ice cap to hold on to more snowfall. If precipitation could accumulate to a level that it would well cover the dark volcanic ash, and not melt by next season, the glacier's retreat would reverse.
