An Arctic phenomenon that puzzled atmospheric scientists for almost 20 years has finally been explained by a joint U.S.- Russian expedition -- led by an LBL physicist -- into an area that until recently has been off-limits to Westerners.
What was thought to be a massive plume of methane gas, bubbling up from a frozen repository under the floor of the Russian Arctic Ocean, is simply an unusual cloud formation, says Tony Hansen of the Engineering Environment Division.
A longtime expert on Arctic air quality, Hansen made his observations from a Russian airplane chartered by the National Oceanic and Atmospheric Administration (NOAA). On leave from LBL to participate in the three-week-long project in April, the Russian-speaking Hansen may be the first U.S. scientist ever to fly aboard a Russian aircraft for atmospheric research purposes.
For years, satellite photographs showed large plumes, sometimes hundreds of miles long, emanating from the New Siberian Islands off the northeast coast of Russia. Soviet and other scientists postulated that solid ice-like structures called clathrates -- physically bound methane and water frozen into place by a combination of low temperature and high pressure -- were melting and releasing methane gas, which bubbled to the ocean's surface and formed the plumes.
"Every two to three weeks a huge cloud -- a hundred miles long and lasting a day or so -- would be seen from a weather satellite," Hansen says. "They thought that a frozen fizz called clathrate, resulting from the decomposition of submerged tundra, was being brought to the surface, where it came up like a geyser and made a huge cloud."
Scientists had dismissed the possibility that the clouds were a meteorological phenomenon for two reasons. The 1,000-foot high Bennett Island -- pinpointed as the source of the plumes -- was thought to be too low to cause orographic clouds, which form when air is forced up the side of a mountain and cools. Second, if the clouds were meteorological, why would they only come from one of the several islands in the area?
"A tiny, frozen speck," the uninhabited Bennett Island is eight time zones east of Moscow, Hansen says, and 600 miles from the nearest town, Cherskiy, an air base on the banks of a giant river that can only be sailed in the summer months. A town of 14,000, Cherskiy is a regional air center and served as home base for the LBL scientist and his crew. "In the days of the Soviets, the whole area was off-limits," Hansen says.
Hansen has worked for seven years on air pollution studies in the Russian Arctic under the auspices of the U.S.-Russian intergovernmental "Working Group 8." His familiarity with Russia enabled him to pull the project together and equip the research plane in short order. The cost for plane and crew was about one percent of what it would have been in the United States, Hansen says. Russell Schnell, the NOAA project director who recruited him for the job, wrote in a letter to LBL Director Charles V. Shank: "Tony Hansen did an excellent job in what was, until a month ago, 'terra incognita' in terms of scientific collaboration. Cherskiy is not on most maps (69 degrees north latitude, 161 degrees east longitude), but the aircraft flew its first mission only 2-1/2 days after their arrival with all the equipment in packing cases."
With Moscow scientist Sasha Polissar, Hansen made eight nine-hour flights to Bennett Island on a large twin-engine plane. Luckily, a special phone line between Alaska and far eastern Russia, set up so that native people could call back and forth, allowed colleagues from NOAA in Alaska to call Hansen when the plume was visible from their satellite images. The plane got to Bennett Island twice when the plume had just disappeared and once when it was still there.
"There was no methane coming out of the ocean," Hansen says. "Clouds were spontaneously forming at 10,000 feet because of the ripple put into the atmosphere by the shape of this island."
Hansen explains the meteorological phenomenon this way. "The atmosphere in the Arctic is highly layered. The air is so cold, the layers slide around on top of each other. If you fly up and down you see a sequence of bands, because the layers are at different temperatures.
"Nothing in the central Arctic stirs it up -- there are no mountains -- so it tends to lay there and move around horizontally. The air is primed to form a cloud; some layers may have sufficient moisture and particles, but it may not be quite cold enough. "Bennett Island is a little bumpy island," he says, "distinctly different from the other islands. The shape of the mountains puts a scoop in the layers, the air gets kicked up about 1,000 feet, and that puts a ripple in the atmosphere all the way up. The 1,000-foot lift triggers the formation of the cloud above the island; at maybe 10,000 feet up, a layer nucleates, condenses, and forms a cloud." The idea that the plumes might have been evidence of large underwater methane reserves was not farfetched; there were "plausible arguments of temperature and pressure," Hansen says. Such reserves of natural gas might have been a source of plentiful fuel, but their sudden release into the atmosphere could have had serious climatic effects. "It's believed that there's enough methane locked up in clathrates to have a major effect on global warming if it were all released into the air," Hansen says. If methane been present, flying into the plume would have been dangerous. The crew could have been asphyxiated, an engine could have stalled, or the plane might even have exploded. "We had a clear plan that if we saw stuff bubbling out of the ocean we would be really careful and probably not get within miles of it," Hansen says. As it was, there was "not one squeak of methane. Analysis of the flasks showed exactly the normal amount of methane for the Arctic atmosphere -- about one part per million." The mission had two objectives. In addition to solving the mystery of the plumes, Hansen was asked to take air pollution measurements and compare them with simultaneous measurements NOAA scientists were making in the Arctic over Alaska, several thousand miles west. "Smoke from factories and cities in Russia and eastern Europe gets into the Arctic circulation, swirls around and around, and doesn't go anywhere," Hansen says. "It builds up over the winter. You can see brown bands in the sky." At Bennett Island, besides catching air in flasks to measure the methane, he measured "classical Arctic haze" with instruments including an aethelometer, a device he invented at LBL to measure black carbon (soot) particles in the air. The results showed Arctic haze in the Russian sector, similar to what has been measured for years in the western Arctic; comparison of the data is expected to improve estimates of the possible global climatic effects of this Arctic-wide pollution. caption Tony Hansen of LBL's Engineering Division, perhaps the first U.S. scientist ever to fly aboard a Russian aircraft for atmospheric research purposes, led a research team into airspace that was once off-limits to Westerners.