Sea ice covering the Arctic Ocean near Alaska breaks up as spring approaches. Credit: Peter West, National Science Foundation

Frozen carbon dioxide, or dry ice, has found many uses in science experiments as well as popular culture, including as a special effect at rock concerts, magic shows and ice-skating spectacles. As it warms, the unique substance transforms directly from solid ice to a smoky gas, without ever becoming a watery liquid in between.

Severely cold Arctic temperatures have locked enormous amounts of carbon dioxide in the frozen northern permafrost for thousands or years. In a multi-pronged effort, NSF-funded scientists are studying whether a well-documented Arctic warming trend will release more of the gas from the permafrost and what may happen as a result. Any change in the current carbon-dioxide balance could affect air temperatures and the amount of sea ice covering the Arctic Ocean. For example, changes in that balance might cause some species to flourish that currently cannot and sufficiently change the habitat of others to make it impossible for them to survive in their present ecological niche.

Currently, the ocean basins act as carbon-dioxide reservoirs, or sinks, locking up some of the gas and preventing it from escaping into the atmosphere. The Arctic Ocean, for example, receives some 28 million tons of dissolved carbon each year, released from far-northern bogs and other soils. As part of the Western Shelf-Basin Interactions (SBI) project, scientists are carrying out a series of research cruises to study how Arctic warming may already be changing the carbon balance, how it may affect the plants and animals that live there—as well as the people who depend upon them—and what measures might be taken to compensate for any change.

During SBI research cruises aboard the U.S. Coast Guard icebreaker Healy, scientists will deploy water- and sediment-sampling devices and gather and study samples of microscopic life as well as larger organisms. Scientists aboard the research vessel, Nathaniel B. Palmer, are conducting surveys of the deep-ocean basins to map the distribution of salinity, temperature, nutrients and other characteristics over the outer shelf to the deep- basin region of the Chukchi and Beaufort seas off northern Alaska.

Jackie Grebmeier of the University of Tennessee, co-chief scientist for the SBI project, carefully prepares samples fresh from the ocean bottom for transport to the ship's lab. Credit: Peter West, National Science Foundation

According to James Swift, the Scripps Institution chief scientist for the Palmer summer cruise, mapping the various characteristics of the waters in the SBI will provide a reference grid for other SBI cruises in this three-year field program. "We hope, once the cruise is over, to be able to produce a very good map of the physical, chemical, pigment and other variables in the SBI study region," Swift said. "When we’re finished we will know where exactly this property or that is highest or lowest."

Meanwhile, SBI scientists have already produced findings about the Arctic carbon balance. An international team of U.S. and German scientists last spring reported that they used carbon-14 dating techniques to determine that most carbon transported to the Arctic Ocean by northern rivers is fairly new in global time scales, and not likely to affect the balance of the Earth’s climate. Nevertheless, they caution that a warming trend could result in a reservoir of ancient carbon—currently locked into peat bogs—to be released and contribute to the well-documented Arctic warming trend.

Previously, scientists had not known the age of the carbon that reaches the ocean. Was it recently derived from contemporary plant material, or had it been sequestered in soils for hundreds or thousands of years and therefore not part of Earth's recent carbon cycle?

The new findings complement work by Laurence C. Smith, an NSF-funded researcher at the University of California, Los Angeles, indicating that massive Siberian peat bogs, widely known as the permanently frozen home of countless square miles of moss and untold hordes of mosquitoes, also are huge repositories for gases thought to play an important role in the Earth's climate balance.

Even though the incriminating gases, carbon dioxide and carbon-containing methane, are known to trap heat in the Earth's atmosphere, scientists have not yet calculated the impact of large amounts of these gases in climate change models.

Stephane Plourde, right, of Woods Hole Oceanographic Institution, fends off ice flows with the help of Coast Guard personnel in order to retrieve a sampling net. Long hours and hard work are elements of any scientific research cruise. Credit: Peter West, National Science Foundation

"Traditionally, we had thought these areas were simply a gradually varying source of methane and an important sink for atmospheric carbon," Smith said. "They've been viewed as a stable thing that we always count on. The bottom line is Siberian peat lands may be a bigger player in climate change than we knew."

Scientists have debated the origin of the methane spike, variously attributing it to sources in tropical wetlands and offshore sediments. New research conclusively points for the first time, to Siberia as a likely methane source, where bogs arose suddenly between 11,500 to 9,000 years ago—much earlier than previously thought. The appearance of the bogs coincides with an abrupt and well documented spike in atmospheric methane recorded in ancient climate records. The finding counters previously held views that the bogs were largely unchanged—and unchanging—over millennia.

But researchers also point out that the bogs, which collectively cover an area of roughly 233,000 square miles, have long absorbed and held vast amounts of carbon dioxide while they released large amounts of methane.

"There are natural sources of greenhouse gases out there that are potentially enormous that we need to know about," Smith said. "One of the concerns is that up until now, the bogs have been more or less a sink for CO₂, absorbing carbon dioxide from the atmosphere. In an extreme scenario, not only would they stop taking up CO₂, they would release a lot of the carbon they have taken up for centuries."