Dark Snow
Most of Greenland’s interior is covered by a thick layer of ice and compressed snow known as the Greenland Ice Sheet. The size of the ice sheet fluctuates seasonally: in summer, average daily high temperatures in Greenland can rise to slightly above 50 degrees Fahrenheit, partially melting the ice; in the winter, the sheet thickens as
additional snow falls, and average daily low temperatures can drop 12to as low as 20 degrees.
Typically, the ice sheet begins to show evidence of thawing in late 13summer. This follows several weeks of higher temperatures. 14For example, in the summer of 2012, virtually the entire Greenland Ice Sheet underwent thawing at or near its surface by mid-July, the earliest date on record. Most scientists looking for the causes of the Great Melt of 2012 have focused exclusively on rising temperatures. The summer of 2012 was the warmest in 170 years, records show. But Jason 15 Box, an associate professor of geology at Ohio State believes that another factor added to the early 16 thaw; the “dark snow” problem.
According to Box, a leading Greenland expert, tundra fires in 2012 from as far away as North America produced great amounts of soot, some 17of it drifted over
Greenland in giant plumes of smoke and then 18fell as particles onto the ice sheet. Scientists have long known that soot particles facilitate melting by darkening snow and ice, limiting 19it’s ability to reflect the Sun’s rays. As Box explains, “Soot is an extremely powerful light absorber. It settles over the ice and captures the Sun’s heat.” The result is a self-reinforcing cycle. As the ice melts, the land and water under the ice become exposed, and since land and water are darker than snow, the surface absorbs even more heat, which 20is related to the rising temperatures.
[1] Box’s research is important because the fires of 2012 may not be a one-time phenomenon. [2] According to scientists, rising Arctic temperatures are making
northern latitudes greener and thus more fire prone.[3] The pattern Box observed in 2012 may repeat 21itself again, with harmful effects on the Arctic ecosystem. [4] Box is currently organizing an expedition to gather this crucial information. [5] The next step for Box and his team is to travel to Greenland to perform direct sampling of the ice in order to determine just how much the soot is contributing to the melting of the ice sheet. [6] Members of the public will be able to track his team’s progress—and even help fund the expedition—through a website Box has created. 22
12.
Which choice most accurately and effectively represents the information in the graph
A) NO CHANGE
B) to 12 degrees Fahrenheit.
C) to their lowest point on December 13.
D) to 10 degrees Fahrenheit and stay there for months.
13.
Which choice most effectively combines the two sentences at the underlined portion
A) summer, following
B) summer, and this thawing followsC) summer, and such thawing followsD) summer and this evidence follows
14.
A) NO CHANGEB) However, C) As such,D) Moreover,
15.
A) NO CHANGE
B)Box an associate professor of geology at Ohio State,
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