Glacial Flour in Greenland Skies .
Winds in Greenland are occasionally strong enough to send plumes of sediment streaming from dried-out lakes, river valleys, and outwash plains along the coasts. The dust in Greenland is mainly glacial flour, a fine-grained silt formed by glaciers grinding and pulverizing rock.
For more than a century, researchers have sporadically reported high-latitude dust events in expedition logs and scientific publications. But only during the past decade have scientists studied them systematically. The Arctic and high-latitudes can be tough to study even with satellites, and there is a dearth of Greenland dust observations.
No longer. The MODIS instrument on NASA’s Terra satellite and a sensor on the European Space Agency’sSentinel-2 collected imagery on September 29, 2018, of a sizable silt plume streaming from Greenland’s east coast. The source was a braided stream valley about 130 kilometers (80 miles) northwest of Ittoqqortoomiit, a village at a latitude of 73 degrees North. That puts the village north of the northern 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 stream flows into Scoresby Sound. As the soil on the floodplain dried out (first two images), the floodplain became increasingly gray. Northwesterly winds on September 29 were strong enough to lift glacial flour into the air.
The glacial flour was likely made by several glaciers farther up the valley, then carried south by meltwater streams and deposited in the floodplain. As stream water levels dropped in autumn, the floodplain dried out and became susceptible to scouring by the wind. In this case, the winds were triggered by the combination of a low-pressure system crossing the Greenland ice sheet followed closely by a ridge of high pressure. .
Credit: NASA images by Joshua Stevens and Copernicus Sentinel data (2018) processed by ESA. Text by Adam Voiland. .
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