The crystal fuel

Natural History, May, 1997 by Kevin Krajick

Some scientists theorize that hydrates could accelerate global warming, for they harbor 3,000 times more methane a powerful "greenhouse" gas--than the air does at present. The atmosphere already receives some methane from bacteria operating in rice fields and wetlands, as well as from termites and ruminant livestock like cows, which harbor bacteria in their guts. National Oceanic and Atmospheric Administration experts believe that slowly decomposing gas hydrates are currently of only minor significance in natural emissions--accounting for no more than 3 percent. But what if even a few big deposits suddenly fell apart?

There is evidence that this has happened in the past. The northern Alaska coast is carpeted with signs of old underwater landslides exactly matching calculated hydrate zones. Huge scars mark the sea floor near the Blake Ridge, where landslides have also occurred. Some seem to have formed 18,000 years ago, toward the end of the last glacial age. Charles Paull says that glaciers, at their highest point, locked up enough water to lower the seas by about 400 feet from their current levels. This would have decreased pressures at the sea bottom and caused built-up hydrates to decompose--perhaps triggering the unexplained temperature spikes that follow most cool periods.

However, changes in temperature, not pressure, might also release hydrate masses in sufficient quantities to change climate. Ian MacDonald, an oceanographer at Texas A&M University, is examining whether local temperature changes in Gulf of Mexico currents cause gas hydrates to quickly form and decompose on the ocean floor. German researchers have studied plumes of methane gas rising from the water off the northern coast of Norway--the result, they believe, of seasonal temperature variations that warm currents and cause gas hydrates to decompose. They warn that further warming may create unpredictable currents that could set off a widening gyre of such decompositions by sending more methane into the atmosphere. James Kennett, an oceanographer at the Marine Science Institute of the University of California at Santa Barbara, is completing a study of sediments off the coast of California; it suggests that in the last 70,000 years, warm local waters have repeatedly caused large hydrate decompositions, which are associated with global warmings.

Of course, what exploration companies and governments want to know about hydrates is whether they can be exploited for energy. U.S. companies have considered pumping hot water or chemicals into deposits to destabilize them, but no one has actually tried. Conventional gas deposits from Appalachia to Texas are still plentiful and easier to get at than hydrates buried under sea floors or permafrost. Japan, however, imports 95 percent of its natural gas and pays three times more for it than the United States does. In 1995 the Japanese government and a consortium of ten companies launched a five-year plan of exploration and extraction. Preliminary surveys indicate substantial hydrate deposits off Japan's coasts. Hydrates may become "one of the most important domestic energy resources left around Japan in [the] twenty-first century," Yoshihisa Okuda, of the Geological Survey of Japan, told an international hydrate conference last year. USGS officials have agreed to allow Japan to drill two prototype wells on the hydrate-rich north slope of Alaska in 1998 in return for some usually proprietary Japanese technological data, and they have met with delegations from Russia, South Korea, Indonesia, Britain, and Germany. Indian scientists also have consulted with the USGS about exploring their country's continental margins. (So far, the main interest of U.S. companies in hydrates has been the possible danger. Occasionally, when crude petroleum is pumped through pressurized pipelines in cold climates, there is enough water and methane in the mix to form hydrates, which can plug the line. When dislodged, the plug may travel at the speed of a bullet, causing pipes to rupture or explode, and sometimes killing workers.)