Questions 12-22 are based on the following
passage.
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 Q12 to as low as 20 degrees. Typically, the ice sheet begins to show evidence of thawing in late Q13 summer. This follows several weeks of higher temperatures. Q14 For 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 Q15 Box, an associate professor of geology at Ohio State believes that another factor added to the early Q16 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 Q17 of it drifted over Greenland in giant plumes of smoke and then Q18 fell as particles onto the ice sheet. Scientists have long known that soot particles facilitate melting by darkening snow and ice, limiting Q19 it’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 Q20 is 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 Q21 itself 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.Q22
