Siberia Losing Lakes at Alarming Rate
MELISSA BLOCK, host:
The Arctic has been suffering from a persistent heat wave. Temperatures have climbed by about five degrees in the past few decades. Sea ice has diminished, and now scientists report that many Siberian lakes are simply disappearing. As NPR's Richard Harris reports, scientists increasingly view these changes as symptoms of global warming.
RICHARD HARRIS reporting:
It's hard to get an overarching picture of how the Earth is changing, but Larry Smith at UCLA says Earth-observing satellites are proving increasingly useful for spotting trends.
Ms. LARRY SMITH (UCLA): We sort of think of satellite data as being very new and whizbang, but in fact, they've been up there long enough now--you know, over 30 years--to start treating them in a historical context.
HARRIS: Smith and colleagues looked at photos of Siberia from NASA's Landsat satellite taken back in the early 1970s. He then compared them with photos taken in the past few years. He saw a dramatic difference. In one large swath of Siberia, 125 large lakes have disappeared completely, and a thousand more have shrunk dramatically. That's 10 percent of the lakes in his study area.
Mr. SMITH: Ten percent is a dramatic number in just 25 years.
HARRIS: He says these are not simply ponds that come and go from year to year. These are substantial lakes, at least a hundred acres each. And even though they are remote for most people, we would notice their absence.
Mr. SMITH: If the lake abundance declined substantially, this would impact many species of migratory birds that use them for their feeding and breeding grounds in the summer.
HARRIS: Smith says what's odd about the disappearing lakes is how spotty the phenomenon is.
Mr. SMITH: We see cases where a lake or several lakes will disappear abruptly right alongside undisturbed neighbors.
HARRIS: It's as though someone simply pulled a plug and drained them.
Mr. SMITH: So this suggests that rather than a regional climate mechanism causing these things to disappear that something else is going on.
HARRIS: In the latest Science magazine, Smith suggests an answer. These lakes sit on top of frozen ground, permafrost. This permafrost is apparently getting thinner as the Arctic gets warmer. And once it disappears entirely from under a lake, the water simply vanishes into the ground below. This actually is not what climate studies had anticipated. Most projections predict more standing water in the Arctic as rainfall increases and as the permafrost melts.
Mr. SMITH: But what our study has shown is that that increase in lake abundance and their growth, in fact, maybe is just a temporary initial response to climate warming. And as the warming continues, in fact, the reverse will happen, and the lakes will drain into the ground.
Mr. MARK SERREZE (University of Colorado): We know that the arctic climate has been changing. Now we see that the very landscape is changing.
HARRIS: Mark Serreze studies the Arctic from his lab at the University of Colorado. He says these disappearing lakes are not merely a sideshow in the bigger story of arctic warming. They could potentially play an important role.
Mr. SERREZE: So much of how the Arctic functions depends on the freshwater cycle. So to understand the freshwater cycle is, in large part, to understand the Arctic as a whole.
HARRIS: And understanding the Arctic, in turn, helps us understand weather and climate that affects us thousands of miles to the south. Both Serreze and Smith are attending a scientific meeting in Seattle where these issues are being batted around. One of the big questions is: To what extent is Arctic warming part of a regular cycle, and how much is it the result of human activities, global warming?
Mr. SERREZE: A lot of us, including myself, 10 years ago were fence-sitters on this problem. Even five years ago, I was a fence-sitter. But I've definitely tipped to the other side now.
HARRIS: Serreze says he's increasingly convinced that we're witnessing real evidence of global warming. And in addition to the disappearing lakes, Serreze says this year will probably set a new record for minimal sea ice in the Arctic Ocean. Richard Harris, NPR News.