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Fountain pens and climate change, two great tastes that go well together
November 12, 2007 4:28 PM   Subscribe

Why is Mont Blanc's height so stable? The pen company has been marking 4810 on their nibs since at least the 1930s. Just this year, it measured 4810m tall.
posted by b1tr0t to Science & Nature (9 answers total)
 
I'm not sure why the article you linked to didn't answer your question. Did you read it?
The summit of Mont Blanc is a thick, perennial ice and snow dome whose thickness varies, so no exact and permanent summit altitude can be determined. But accurate measurements have been made. For a long time its official altitude was 4,807 m. Then in 2002, the IGN and expert surveyors, with the aid of GPS technology, measured it to be 4,810.40 m.
So the height isn't stable in the short term. Just because the height a pen company rounded to was close to the current official measurement doesn't mean anything.
posted by chrisamiller at 4:39 PM on November 12, 2007


This Slate piece may also be of interest to you if you have not seen it.
posted by veggieboy at 4:45 PM on November 12, 2007


So the height isn't stable in the short term

Sure, but many glaciers have been shrinking dramatically in the last hundred years. If you measured some random other ice-covered peak to the nearest 10m 70 years ago, I would expect to find a very different number today.
posted by b1tr0t at 5:23 PM on November 12, 2007


Also, my question isn't about how the peak is measured, but why the thickness of Mont Blanc's ice cap has been relatively stable over the last 70+ years.
posted by b1tr0t at 5:24 PM on November 12, 2007


Sure, but many glaciers have been shrinking dramatically in the last hundred years. If you measured some random other ice-covered peak to the nearest 10m 70 years ago, I would expect to find a very different number today.

Glaciers are generally not found on the top of mountains. A glacier is not the same as a dome or covering of ice.

Sure, many glaciers world wide are shrinking, and a lot of ice and snow is melting and not being replaced. The shrinking of glaciers (and other ice) is in the news a lot because we expect them to stay relatively stable, but many aren't. That doesn't mean that every pile of ice in the world is getting smaller.

Also, Mont Blanc only has ~40m of ice on it, which isn't all that much. It isn't particularly surprising that it only has been measured to vary by a few metres. I'd also suspect that the relatively high altitude would mean that the rate of change would be much less than at lower altitudes.
posted by ssg at 5:56 PM on November 12, 2007


If you search Google on Mont Blanc and microclimate, there are a number of hits. This might explain local weather stability.
posted by Blazecock Pileon at 5:57 PM on November 12, 2007


Glaciers would typically melt at the bottom. On a tall mountain, it could warm up enough to melt away quite a bit of a glacier before enough of it was gone to change the movement of ice and snow near the top.

Until it warms up a bit more, climate change would be more likely to affect the height of Mont Blanc by changing the amount of snow that falls on it. I've heard that in some places the patterns of precipitation have changed, but I've no idea if there's been any such change in that region.
posted by sfenders at 6:20 PM on November 12, 2007


Something else to consider: 4810m above what?

You could dig a trench from the ocean all the way to Chamonix and after the water level was stable, measure how high the peak was above it. That's a little impractical; how about a geometrical answer? To calculate sea-level correctly you'd have to figure out the mass of the crust in the Alps etc. -- also impractical. Instead we have a model of the earth where latitude, longitude and elevation are pinned to points on the ground -- this is called a datum. Usually each country has its own, sometimes more than one; and they differ from each other by tens of meters. In areas where there are multiple datums to choose from, the coordinates assigned to a point on the ground (like the top of Mont Blanc) depend on the datum chosen.

So 4810 is as good a number as any.
posted by phliar at 11:50 PM on November 12, 2007


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.
posted by sfenders at 4:14 AM on November 13, 2007


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