White-knuckle atmospheric science takes flight

Moore, chair of the Department of Chemical and Physical Sciences, is heading to Greenland from Feb. 18 to March 11 as part of the Greenland Flow Distortion experiment (GFDex), an International Polar Year research project involving Canadian, British, Norwegian and Icelandic scientists. Moore, a professor of atmospheric physics, is leading the Canadian contingent.

GFDex will provide the first evidence of the role that Greenland plays in distorting atmospheric flow around its massive land and ice mass, affecting European and Asian weather systems. Moreover, the findings may reveal how sea and atmospheric interactions in the Arctic and North Atlantic areas influence climate.

At the heart of GFDex are wind patterns known as “tip jets”. Greenland, an icy obstacle more than three times the size of Texas, forces air to go around its bulk and creates regions of high windspeeds. Tip jets travel east from the tip of Greenland towards Iceland, at speeds of 30 to 40 metres per second. Just as wind blows heat away from the body, making windy winter days feel even colder, tip jets blow heat away from the surface of the ocean. This now-cooler, denser water sinks, affecting currents of circulating warm and cool water within the ocean.

About two years ago, Moore discovered a different kind of tip jet, one that blows west towards Labrador. Now known as reverse tip jets, these also force circulation of water over the Labrador Sea to the west of Greenland. “We’ve seen these things in satellite imagery, but no one’s ever actually observed them,” says Moore. “We’ll be making the first in situ observations of these jets. It’s kind of exciting.”

The data will help scientists understand how the flow of air around Greenland affects weather downwind. “If things are happening near Greenland today, probably two days from now that [air mass] will move down over Europe,” says Moore. “Two or three days after it’s affected Europe, it affects Asia and then ultimately comes around and affects North America. So Greenland ultimately affects the whole Northern Hemisphere…our knowledge will potentially help improve forecasts.”

Moore is also hoping the findings will clarify the climate processes affecting Greenland’s glaciers, which have shrunk significantly in the past few years. “There’s evidence that the ice cap is retreating quite dramatically. In 2003, a cyclone came up on the east side of Greenland and there was a huge melting event,” says Moore. “It’s one of my hopes that we’ll be able to understand a bit more about the processes that determine the mass balance of the Greenland ice cap.”

Making these observations requires both advanced technology and a cast-iron stomach. Moore and his colleagues, along with graduate students and post-doctoral fellows, will be making 17 flights into the tip jets in a British research aircraft called FAAM (Facility for Airborne Atmospheric Measurements). Pods and sensors stud the outside of the aircraft. Most of the seats have been removed, creating space for racks of instruments measuring the presence of ice in the clouds, temperature, pressure and humidity. On-board radar gathers information on precipitation, and helps Moore—who, as a mission scientist, will sit in the cockpit—to direct the pilots where to fly. At the same time, “sondes”—paper towel tube-sized devices on small parachutes—are dropped from the back of the plane. Equipped with a barometer, thermometer, global positioning system and humidity sensor, each sonde radios its measurements back to the plane and provides a profile of conditions below the aircraft.

In order to get the best data, the researchers need to fly just 100 feet above the heaving seas, in winds of more than 140 kilometres per hour. “In these conditions and at these levels, the turbulence will be quite severe,” says Moore. “Once, on a similar flight in the Arctic, the lens of my glasses popped out!”

The GFDex experiment is funded by the U.K.’s Natural Environment Research Council, the Canadian Fund for Climate and Atmospheric Sciences, the European Fleet for Airborne Research and EUCOS, the Composite Observing System program of 21 European meteorological services.