Permanent ice fields are resisting global warming

May 16, 2007
Permanent ice fields are resisting global warming
Researchers from the Glaciology Laboratory taking an ice core sample on top of Mont Blanc, in 2005. © C. Vincent, CNRS 2007

The small ice caps of Mont Blanc and the Dôme du Goûter are not melting, or at least, not yet. This is what CNRS researchers have announced in the Journal of Geophysical Research. At very high altitudes (above 4200 meters), the accumulation of snow and ice has varied very little since the beginning of the 20th century. But if summer temperatures increase by a few degrees during the 21st century, the melt could become more marked, and could affect the "permanent" ice fields.

Alpine glaciers, which are mainly at an altitude between 2000 and 4000 meters, shrank considerably during the 20th century and particularly during the past twenty years, losing an average of 1 to 1.5 kilometers in length. However, the situation is different above 4200 meters.

At the altitude of the Dôme du Goûter (4300 m) or the summit of Mont Blanc (4810 m), all precipitation is solid, falling as snow. The ice fields melt very little, and only in extreme conditions such as the 2003 heatwave. Variations in the mass of glaciers only depend on the accumulation of snow and the downward flow of the glacier, as the ice is deformed under its own weight.

In order to study these mass balance fluctuations, the research team measured the rate of accumulation of snow on the Dôme du Goûter since 1993, and the thickness and flow rate of the glacier. They also used meteorological data from Chamonix, from 1923 to the present day, to calculate the rate of accumulation of ice during the 20th century. Or, more precisely, they used data on the precipitation in Chamonix, altitude 1036 meters, to extrapolate for quantities of snow fallen on the glacier, and so to calculate the mass balance.

Based on this data, the glaciologists have shown that at these very high altitudes, the ice mass balance has remained almost constant over the last 100 years. They have also used old topographical maps to show that the thickness of these small ice caps on Mont Blanc and the nearby Dôme du Goûter has only changed by a few meters from 1905 to 2005. By comparison, at a lower altitude (1800 meters), the thickness of the Mer de Glace has decreased by 120 meters over the same period.

So the Mont Blanc and Dôme du Goûter ice fields have not yet been affected by climate change. However, during exceptional climatic events like the 2003 heatwave, positive temperatures caused some of the surface ice to melt. If episodes like this were to occur more often, this partial melting would no longer be negligible, and would have a significant effect on the ice mass. So there is no guarantee that "permanent" ice fields will stay that way in the future.

Source: CNRS

Explore further: First eyewitness accounts of mystery volcanic eruption

add to favorites email to friend print save as pdf

Related Stories

Recommended for you

First eyewitness accounts of mystery volcanic eruption

37 minutes ago

New light has been shed on one of the biggest volcanic eruptions in the last 500 years—the so-called 'Unknown eruption'—thanks to an unusual collaboration between a historian and a team of earth scientists at the University ...

Scientists monitoring Hawaii lava undertake risks

8 hours ago

New photos from the U.S. Geological Survey's Hawaiian Volcano Observatory give a glimpse into the hazardous work scientists undertake to monitor lava that's threatening to cross a major highway.

NASA sees Odile soaking Mexico and southwestern US

19 hours ago

Tropical Storm Odile continues to spread moisture and generate strong thunderstorms with heavy rainfall over northern Mexico's mainland and the Baja California as well as the southwestern U.S. NASA's Tropical ...

NASA sees Tropical Storm Polo intensifying

19 hours ago

Tropical storm warnings now issued for a portion of the Southwestern coast of Mexico as Polo continues to strengthen. Infrared imagery from NASA's Aqua satellite showed powerful thunderstorms around the center ...

User comments : 0