Glacier meal in the Greenland skies
Glacier meal in the Greenland skies
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Dust is probably the last thing that comes to mind when you think of Greenland, an island covered in ice.
Although the dust events of Greenland do not look anything like the huge clouds of dust and sand that can darken the skies above the sky. the Sahara desert for days, the winds in Greenland are occasionally strong enough to send plumes of sediment flowing from dry lakes, river valleys and plains the plains along the coasts. The dust in Greenland is mainly glacial flour, a fine-grained silt formed by glaciers that crush and pulverize rocks.
For more than a century, researchers have sporadically reported high-latitude dust events in expedition records and scientific publications. But only during the last decade have scientists I tried to study them systematically. The Arctic and high latitudes can be difficult to study even with satellites, and a recent study He noted a shortage of observations of Greenland dust.
No more. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite and a sensor in the European space agency Sentinel-2 On September 29, 2018, images of a plume of considerable silt flowing from the east coast of Greenland were collected. The source was a braided stream valley about 130 kilometers (80 miles) northwest of Ittoqqortoomiit, a town at a latitude of 73 degrees North. That puts the town north of the north coast of Alaska.
The series of Landsat and Sentinel 2 images above and below, captured on September 21, 23, 29 and 30, shows the floodplain where the current flows to the Scoresby sound. As the floodplain floor dried up (two first images), the floodplain became increasingly gray. The northwest winds on September 29 were strong enough to lift the glacial flour in the air.
"This is by far the largest event detected and reported by satellites I know," he said. Santiago gassed, an atmospheric scientist at NASA's Goddard Space Flight Center. The noticed for the first time The storm of October 3.
"We have seen some examples of small dust events before this, but they are quite difficult to detect with satellites due to cloud cover, "he said. Joanna Bullard from the University of Loughborough. "When dust events occur, field data from Iceland and western Greenland indicate that they rarely last more than two days."
The glacial flour was probably produced by several glaciers higher up in the valley, and then swept southward by streams of meltwater and deposited in the floodplain. As the water levels of the stream decreased in autumn, the floodplain dried up and became susceptible to wind erosion. In this case, Bullard said, the winds were caused by the combination of a low pressure system that crosses the Greenland ice sheet followed closely by a high pressure ridge.
Since dust events at high latitudes are poorly understood, they are usually not included in atmospheric and climatic models. Gasso hopes that they will eventually be included because they could have effects on air quality, snow reflectivity and even marine biology.
Images from the NASA Earth Observatory by Joshua Stevens, using Landsat data from the United States Geological Survey and modified data from Copernicus Sentinel (2018) processed by the European Space Agency. Story of Adam Voiland.
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