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article imageNew mechanism found for Arctic warming and melting ice

By Karen Graham     Oct 13, 2018 in Science
A new atmospheric mechanism by which warm dust travels from the Sahara Desert across the eastern side of the North Atlantic Ocean towards the Arctic, resulting in a warming Arctic and ice melting in southeast Greenland has been found.
Researchers at NYU Abu Dhabi, along with other global scientists published their findings in the peer-reviewed Journal of Geophysical Research: Atmospheres, on October 10, 2018.
Their findings highlight the role the meandering polar jet stream and associated atmospheric circulation plays on the transport of mineral dust from the Sahara Desert and the resulting consequences.
Not only is dust being transported north, but warm, moist air masses from the subtropics and mid-latitudes are caught up in the northward movement into the Arctic, where at least half of the warming we are seeing now is being attributed to increased moisture and heat fluxes transported to the region.
Meandering polar jet stream visible in red colors  upper-level trough visible in blue. European Cent...
Meandering polar jet stream visible in red colors, upper-level trough visible in blue. European Centre for Medium-Range Weather Forecasts.
NYU/Abu Dhabi
The Saharan Cyclone of 2011
According to the authors, the "dust emission was associated with an intense Saharan cyclone that formed over Northwest Africa in early April 2011. The formation of the cyclone was caused by the intrusion into the subtropics, of a high‐latitude‐upper‐level trough, linked to the meandering polar jet.
But because of the blocking effect of the southern side of the Atlas Mountains, the meandering polar jet stream led to the formation of a cut‐off low further south with which the Saharan dust‐cyclone merged 2 days later and moved northward with the main stream.
As the mineral dust in the atmosphere was transported northward, the warm and moist air masses accompanying the Saharan dust caused a rise in surface temperature of 10 degrees Celsius for more than three consecutive days upon reaching southeastern Greenland, according to Science Daily.
Of course, an increase in the melting of ice in the region was also observed and documented. The Saharan dust storms, typically at their peak in April, even without the help of a cyclone, are becoming a regular event. In April 2015, "Blood rain" fell on the UK, brought on by Saharan dust blowing northward caught in a rainstorm.
"The polar jet stream has been identified as the main driver for such events leading to the transport of large amounts of dust to high-latitudes," said Diana Francis, an atmospheric scientist at NYU Abu Dhabi and lead research scientist in this study.
 An ice sheet covers almost all of Greenland—about 1.7 million square kilometers (650 000 square m...
"An ice sheet covers almost all of Greenland—about 1.7 million square kilometers (650,000 square miles). It holds so much ice that if it were to melt away entirely, global sea level would rise 7 meters (23 feet)," as NASA writes.
"If the polar jet is set to slow more frequently due to the changes in the Arctic climate system and to the Arctic Amplification, such events are expected to become more frequent."
"The impact of dust deposition on ice in Greenland, such as darkening ice and formation of algae on ice or cryoconite, as well as the link between Saharan dust transport and the Arctic heat dome must be investigated further in collaboration with scientists in UK and Germany," Francis emphasized.
More about Science, polar jet circulation, Sahara desert, Greenland, Arctic ice melt