COVER STORY

The Ice Detectives

Columbia researchers go to the ends of the earth to crack the coldest case of all.

by Paul Hond Published Fall 2017
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Though Greenland holds just 10 percent of the world’s ice, increasing rates of ice loss make it the fastest-growing contributor to sea-level rise. Last year, it accounted for a quarter of the average global rise of slightly more than one-tenth of an inch. (Sea level is unevenly distributed; some areas see more rise than others.) Tedesco believes that Greenland has been caught in a feedback loop, which is accelerating the melt: warm temperatures melt sea ice (formed by the freezing of the ocean) and land ice (such as Greenland), exposing more seawater and darker ice layers (from trapped impurities like soot and dust, as well as algae and bacteria). These darker surfaces, in turn, absorb more solar radiation, which generates more warming, which melts more ice.

The Greenland ice sheet holds enough frozen water to raise sea levels by twenty-two feet. But just a tiny fraction of that rise can cause problems. “If you have storms hitting low-lying cities,” says Tedesco — cities like New York — “two or three inches of sea-level rise makes a huge difference.”

The summers of 2012 and 2015 were exceptional melt seasons in Greenland, and Tedesco was there both years. He calls 2012 “the Goliath” melting year, because it broke records for surface melting and total mass loss, just when sea ice was also shrinking to a record summer low. The conditions in 2015 were different, “though still alarming,” Tedesco says. In a paper published last year in Nature Communications, he noted the odd kinks that summer in the polar jet stream, the meandering river of atmospheric winds that loops around the northern latitudes, separating warm air from cold. In July 2015, the jet stream reached farther north than scientists had ever seen for that time of year, allowing a billow of warm air to intrude on northwest Greenland.

“We’re trying to understand the basic topography of the earth.”

But why was the jet stream doing this — “going nuts,” as Tedesco says? One theory that Tedesco is investigating suggests that the decreasing temperature differential between the mid-latitudes (the earth’s temperate zones) and the Arctic can slow the jet stream, causing wild arcs, which carry warm, moist, mid-latitudinal air called “atmospheric rivers.” Tedesco wants to know how the melting events are connected to this transport of moisture, which has energy and heat.

“If we can make that link,” he says, “we can better understand the potential increase of surface melting — and link what happens in Greenland to the rest of the warming world.”

To get data, of course, you have to be in the field, up close and personal. “The fieldwork helps us understand the processes,” says Tedesco. “If we don’t understand them, we can’t put them into our model, and so we cannot do projections.”

This spring, Lamont scientists performed more fieldwork when Jonathan Kingslake went to the Great North. Kingslake’s six-week trip began in Schenectady, New York, at the New York Air National Guard base, which provides aerial support for government-funded polar expeditions. There, Kingslake and twenty others — researchers, support staff, and crew — boarded a ski-equipped LC-130 loaded with gear and tents for the six-hour flight to Greenland.

To get data, you have to be in the field, up close and personal.

Kingslake spent four weeks in the field (the average temperature was in the single digits, with a low of -36°F), taking radar measurements and drilling for ice-core samples.

“When you use radar to look through the ice, you’re sending out a pulse and listening for the echo back,” Kingslake explains. “You get an echo from the bottom of the ice. This tells you the depth of the ice. If you want to predict what the ice sheet will do in the future, you need to know where the ground is — it’s totally fundamental.

“But we can also use radar to look at complex structures within the ice that help us understand many important processes.”

The ice cores, cylinders of condensed ice that show the bands of past seasons, are another way to read the ice sheet. Kingslake was looking for “ice lenses” — layers of ice that are formed by melted spring snow that refreezes.

“Meltwater that refreezes in the snow can create hard layers that are impermeable to water,” Kingslake says. “They impede the water’s flow, causing it to run horizontally. We always assumed it was fine if there’s melting at higher elevations, since there’s this huge sponge — the snow — to soak up the water.

“But if there’s a layer of ice just under the surface, the water simply runs off the ice sheet. Then the whole system changes.”

The Mystery of the Buried Mountains

Robin Bell was born in 1958 — or, as she likes to say, during the International Geophysical Year (IGY). The IGY, from July 1957 to December 1958, was a global scientific project devoted to the earth sciences — inquiries into the physical processes of land, ocean, and atmosphere, involving sixty-seven countries and providing a brief thaw in the Cold War.

For Bell, one of the more fascinating IGY discoveries occurred in Antarctica, where a Soviet expedition set foot atop the Antarctic ice sheet, ten thousand feet above sea level. To measure the thickness of the ice, the Soviets set off seismic charges and recorded the echoes, and took gravity readings. Since rock and ice produce different signals, they could detect where the ice had thinned — and where rock had risen. They soon realized that they had found, buried under the ice, an improbable, arresting formation.

The emerging picture shook the geophysical world. Encased in a two-mile-deep cover of ice stood an immense mountain range, more than seven hundred miles wide, with peaks of some nine thousand feet — as tall as the Alps. The explorers named the mountains after Grigory Gamburtsev, a Soviet seismologist.

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ICE DETECTIVES

The Ice Detectives by Paul Hund (Columbia Magazine, Fall 2017) describes how leading polar investigator Robin Bell (‘89GSAS, geophysicist at Columbia’s Lamont-Doherty Earth Observatory), and other distinguished Columbia polar scientists, have been building our observed scientific knowledge about the unexpected complexity of Antarctic and Greenland ice sheets, a critically important part of our "planet yet to be explored and understood” according to Bell.

Comments attributed to the Columbia scientists leave little doubt that their open minds, in the tradition of Galileo and Kepler, are making detailed studies based on their own quantitatively precise observations, following Francis Bacon’s revolutionary idea that to understand the world we must study the world, instead of relying on sacred consensus.

Regrettably the article is sprinkled with distracting random climate alarmist jargon unrelated to the primary research described. Why is it necessary to mention the thoroughly discredited projection of 8.2 feet of sea level rise by the end of the century (= 30.1mm/year)? This editorial insert starkly contrasts with Bell's lucid statement about future sea level rise, “My belief is that we don’t know yet.” Elsewhere in the article the scientists say historic and current sea level rise is between 2.5 and 3.2 mm/year vs the editorially inserted alarmist projection of over 10 times that rate.

Similarly the author uses the non-science word “consensus” as evidence that CO2 is the “…main driver of warming” and “caused unusual weather events.” Unambiguously Earth’s CO2 atmosphere concentration has increased dramatically since 1897. But equally unambiguously primary data from NASA's satellite measurements of global average surface temperature shows no statistically relevant global temperature increase in 18 years. Likewise for 100 years there has been no statistically significant increase in extreme weather events (frequency has declined) . While correlation does not prove causality, lack of correlation disproves it.

Hats off the Columbia scientists for important, extensive primary polar research. Columbia Magazine should not, however, contaminate objective information with editorial bias.

Peter Spiller, SIPA 1968
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