|Clues to Understanding Climate Change in the Rivers of the Arctic|
|Contact: Dan Krotz, [email protected]|
As soon as Berkeley Lab's Christopher Guay stepped out of the schoolhouse and onto the streets of the small Siberian village, he knew something was up. It was late May 2004, and the hardy folks who live above the Arctic Circle on the banks of the Lena River were abuzz. The river ice was breaking. Spring had come.
For the villagers of Zhigansk, Russia, the car-sized chunks of ice floating downstream hastened the start of the fishing season. For Guay, a chemical oceanographer in the Earth Sciences Division, it meant the clock was ticking. He had been there since mid-May, drilling through the ice and measuring the river's concentrations of various dissolved metals, including barium, cadmium, and copper. On this day, he and his fellow scientists were taking a break from their work and visiting a person who teaches English at the local school. Now it was time to get back to the river, and the sooner the better. With the spring thaw comes a surge in runoff and a renewed influx of metals.
Guay's work is part of a multinational project to analyze the chemistry of the six largest rivers that drain the vast watershed of the Arctic Ocean: Alaska's Yukon River, Canada's Mackenzie River, and Russia's Kolyma, Lena, Ob', and Yenisey Rivers. The project is called PARTNERS, which stands for Pan-Arctic River Transport of Nutrients, Organic Matter, and Suspended Sediments. Launched in 2002 and funded by the National Science Foundation, it's led by Bruce Peterson of the Marine Biological Laboratory in Woods Hole, Massachusetts, and includes two dozen scientists from institutions in the U.S., Canada, and Russia.
The goal of the five-year effort is to catalog each river's unique mix of metals, nutrients, microbes, and oxygen isotopes. This information, a sort of chemical fingerprint, will allow scientists to track how the rivers' freshwater runoff impacts the Arctic Ocean.
"This is important, because what happens to the Arctic Ocean plays a major role in what happens to the rest of the world," says Guay.
Computer models indicate that global climate change could lead to an increase in precipitation and melting ice at high latitudes. If this happens, more fresh water from waterways like the Lena River will course into the Arctic Ocean, which already receives 10 percent of the globe's continental runoff even though its area accounts for only 2 percent of the Earth's oceans. Add even more fresh water to the Arctic Ocean, and some scientists believe that a string of feedback mechanisms could alter the planet's ocean circulations, which in turn will impact the planet's climate. This engine of change is already running. Scientists estimate that freshwater runoff from the six rivers increased 7 percent from 1936 to 1999.
"The Arctic Ocean is relatively small and remote, but it is a major player in the planet's climate," says Guay. "And it is an early indicator of what may happen elsewhere."
Which is why Guay hurried to the banks of one of Russia's longest rivers last spring and obtained samples of its dissolved metals. Right now, the group is trying to establish a baseline of each river's biogeochemical fingerprint from season to season and year to year. The metals and other chemicals that compose these fingerprints can be used as tracers that allow scientists to "see" a specific river's freshwater contribution to the Arctic Ocean and neighboring oceans. For example, the Mackenzie River's barium-laden waters are easily detected and can be used to track oceanic flows for thousands of miles, from the river's mouth to the North Atlantic. If these barium levels change, perhaps the ocean current is changing a possible harbinger of climatic changes to come.
"We need to know if the tracer signals are changing," says Guay. "And if there are changes, how much of it is due to natural variability or anthropogenic causes."
So for a few weeks last spring, while other scientists involved in the project worked the banks of the Yukon and other rivers, Guay took daily samples before, during, and after Lena's spring thaw. This information will help fill a void surrounding what's known about the chemistry of Russian rivers that drain into the Arctic Ocean, which is currently based on outdated and possibly inaccurate measurements.
Ultimately, the data he collected will be a small part of a much larger puzzle that includes metal measurements taken at other times of the year and at other rivers, as well as measurements of microbes, nutrients, and oxygen isotopes. When completed in 2007, the group will have compiled a database of river biogeochemistry encompassing six arctic rivers and spanning four years.
"We can compare this time series of metals and other tracers to future data and see how the rivers are changing over time," says Guay. "This could help us determine how climate change affects arctic watersheds, and how this affects the Arctic Ocean and beyond."