Jakobshavn, the glacier widely thought to have spawned the iceberg that sank the Titanic, reaches record speeds.
Greenland’s fastest glacier reaches record speeds
A Greenland glacier named Jakobshavn Isbrae , which many believe spawned the iceberg that sank the Titanic , has hit record speeds in its race to the ocean. Some may be tempted to call it the king of the glacier world, but this speedy river of ice is nothing to crow about.
A new study published February 3 in the journal Cryosphere finds that Jakobshavn's averaged annual speed in and was nearly three times its rate in the s. Its flow rate during the summer months was even faster. Other glaciers may periodically flow faster than Jakobshavn, but Greenland's most well known glacier is the bellwether of climate change in the region and likely contributes more to sea-level rise than any other glacier in the Northern Hemisphere—as much as 4 percent of the global total, Joughin and his colleagues found in an earlier study.
Read about glacial meltdown in National Geographic magazine. When glaciers flow into the ocean, their floating edge, or terminus, slows the river of ice behind it.
Where the terminus is grounded on the seafloor, it can act like a doorstop, slowing the glacier's flow even further. When a blaring siren moves toward us, its sound waves get bunched up, resulting in a higher pitch. Radar guns like the kind used by the highway patrol exploit this phenomenon, called the Doppler Effect, by bouncing radio waves off a car moving toward them to measure its speed.
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The faster the car is moving, the more the returning waves get bunched, reducing their wavelength. They began by splitting a laser beam into two. One beam bounces off the slow-moving target whose speed is to be measured, a glacier for example, shifting its wavelength very slightly via the Doppler Effect. This color-shifted beam is then combined with the second beam inside a liquid crystal consisting of long, helical-shape molecules mixed with a dye.
The dye molecules change their shape when they interact with the light, slowing it down to a speed less than one millimeter per second. At full speed, the very small wavelength difference between the two light beams could not be detected. In the lab, Bortolozzo and his coworkers have been able to detect speeds as slow as 20 millionths of a billionth of a meter per second 20 femtometers per second with a measurement lasting only one second.
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This is more than sufficient for glaciers, which, on average, move on the order of a few millionths of a meter each second. Unlike other slow-light techniques, that require cryogenic temperatures, this light-slowing method is easier to turn into practical use because it can be done at room temperature. That means any technology derived from these methods could be taken into the field without the need to carry liquid helium and bulky refrigeration units.
Researchers hope this equipment can one day be loaded into an airplane that would circle the Greenland glaciers. Select and download SAR data online using Vertex.
EGU - News & press - Greenland’s fastest glacier reaches record speeds
Glacier Speed. Glacier surface-velocity map of the Alaska Range.
Light grey glacier outlines indicate missing data. Image credit: Evan Burgess, Glacier surface-velocity map of the Wrangell and St. Elias Ranges.