The term “frozen” often connotes “immune to change.” Perhaps no land is so firmly tied to that word as Siberia. Of all parts of Siberia, no place so richly deserves this connection as the grand Lena River Valley. The ninth-longest river in the world, the Lena flows through one of the world’s iciest lands, where the sun is seldom seen during winter. Nearly 80 percent of the watershed is continuous permafrost – earth that never thaws fully, even in summer.
However, climate change is reaching this remote outpost; this may have consequences not just locally but for the rest of the world as well.
Perhaps the most striking effect of global warming is that it attacks the very foundation of the Lena Basin: permafrost. Permafrost has long been the bane of Siberians. Digging anything from wells to basements or simply laying a foundation requires cutting through many feet of ice. As Siberia warms, though, the permafrost is going the way of the disappearing Arctic ice cap. As permafrost melts, the earth gives way underneath buildings and roads. A United Nations Environment Programme report says that 300 buildings in Yakutsk, the regional capital, have been damaged by permafrost melt. UNEP predicts that over 70 percent of apartment buildings built between 1950 and 1990 will fail by 2010. By 2030, that total reaches 100 percent.
The natural landscape is being transformed as well. Dr. Robert Holmes, a researcher at the Woods Hole Research Center in Massachusetts, reports that in some areas of the Arctic, new lakes and marshes are being formed. “As the permafrost thaws, the ground surface drops somewhat,” says Holmes, “causing a depression that when filled with water creates a lake.” Existing lakes are also deepening due to the thaw. Holmes notes that in Alaska, and perhaps elsewhere in the Arctic, the permafrost below some existing lakes has been pierced, draining them completely. Similarly, the New York Times reports that the freeing up of coastal ice is threatening an entire village in northeastern Russia, as the coastline erodes away at a rate of 15 to 18 feet a year.
Dr. Holmes and his colleagues have discovered another change affecting the Lena, this one perhaps even more profound. As they reported in an article in the December 13, 2002 issue of Science, the amount of water flowing to the Arctic from the Lena has increased seven percent in the last seven decades (abstract here). With a river as large as the Lena, that is a significant amount.
One might think Siberia’s great ice melt is to blame, but Dr. James McClelland, another researcher on the team, says that Eurasia simply doesn’t have enough ice stored in glaciers to account for the Lena’s swelling. “We have calculated that it would have taken a much larger change in permafrost thaw depths than anyone has observed to account for the change in river discharge.”
The actual story begins far away. “In the tropics, high temperatures and intense sunlight evaporate huge amounts of water, and the atmosphere transports much of this moisture away from the tropics and toward the poles,” explains Holmes. “Warmer air can hold more moisture, so as the Earth warms, there is more moisture in the atmosphere. So we think that global warming is causing more atmospheric moisture to enter Siberia, leading to more precipitation.”
One important local effect may be that increased volume of the Lena will exacerbate the river’s devastating seasonal floods. Any snowmelt-fed river rises in the spring, but the Lena and other Russian rivers are unusual in that they flow north. In most other rivers, the headwaters high in the mountains thaw last, but the Lena’s source, a thousand miles south of its delta, thaws first. Ice floats downstream and jams the river, causing flooding. In 2001, a giant ice dam submerged Yakutsk and Kirensk and destroyed much of Lensk.
The biggest change, though, could be international. “The ironic part,” says McClelland, “is that global warming could actually lead to the cooling of Northern Europe.” The mechanism is complex. “It has been hypothesized that increases in Arctic river discharge (including the Lena) could slow or stop North Atlantic Deep Water (NADW) formation in the Greenland-Iceland-Norwegian (GIN) Seas and Labrador Sea,” he explains. “The combination of salinity and cold temperatures in the GIN and Labrador seas lead to formation of very dense water that sinks and flows southward along the bottom of the ocean. This water is replaced by warmer (less dense) water flowing north at the ocean’s surface. This warm water flowing from south to north in the Atlantic, mainly via the Gulf Stream, keeps Northern Europe warmer than it otherwise would be.” Without the NADW, this stream of warm water bathing Northern Europe would cease.
McClelland continues: “Increasing river inputs work against NADW formation [because] fresh water is much less dense than saltwater. By adding more fresh water to the NADW formation regions, the surface waters become less dense and therefore less likely to sink and move southward.”
Global warming may amplify itself as Siberia thaws. “There is a huge amount of organic matter (dead plants and animals) locked up in permafrost, frozen and preserved for thousands of years,” writes Holmes. “As the permafrost thaws, this organic matter is ‘removed from the freezer,’ and much of it may then be decomposed and converted to carbon dioxide. More carbon dioxide leads to more warming, causing more permafrost thaw, releasing more ancient organic matter, leading to more carbon dioxide, etc.”
“The potential consequences of changes in discharge from the Lena River warrant conservation measures,” says McClelland. However, neither he nor Russian environmental experts queried knew of any conservation projects specifically targeting the Lena. Russia has ratified the Kyoto Treaty, putting it into effect among signatory nations, but that is only a modest beginning.
The Lena River region is a case study in
the complexity of global warming. Warmer temperatures caused by
industrial activity thousands of miles from the Lena are causing rising
temperatures in the tropics, leading to more rain in Siberia, perhaps
eventually cooling Northern Europe. It is truly a global phenomenon
with enormous local consequences. Even what was frozen in the icebox of
Siberia will change.
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