NASA scientists have made a discovery described as unexpected as finding a rainforest in the middle of a desert. They discovered massive phytoplankton blooms beneath Arctic ice in the Chukchi Sea. Scientists say the find is an effect of global warming.
NASA reports that the finding reveals "a new consequence of the Arctic's warming climate and provides an important clue to understanding the impacts of a changing climate and environment on the Arctic Ocean and its ecology." According to Paula Bontempi, NASA's ocean biology and biogeochemistry program manager in Washington, "...this is like finding the Amazon rainforest in the middle of the Mojave Desert. We embarked on ICESCAPE to validate our satellite ocean-observing data in an area of the Earth that is very difficult to get to. We wound up making a discovery that hopefully will help researchers and resource managers better understand the Arctic."
The 2011 ICESCAPE (Impacts of Climate on EcoSystems and Chemistry of the Arctic Pacific Environment) cruise sponsored by NASA, was led by Stanford environmental Earth system science Professor Kevin Arrigo. NASA reports the expedition explored Arctic waters in the Beaufort and Chukchi Seas along Alaska's western and northern coasts on board a U.S. Coast Guard icebreaker, and studied the impacts of environmental variability and change in the Arctic on the ocean biology, ecology and biogeochemistry. The study was launched to improve NASA's remote monitoring of the changing Arctic environment.
Stanford News reports that unlike previous Arctic research teams, ICESCAPE went deep into the Chukchi Sea ice pack, north of the Bering Strait. According to NASA, the expedition punched through three-foot thick sea ice to find waters richer in microscopic marine plants than any other ocean region on Earth.
The Christian Science Monitor reports the scientists discovered a massive under-ice bloom that extended for more than 60 miles into the ice pack on the Chukchi Sea continental shelf. Expedition leader Kevin Arrigo, biological oceanographer at Stanford University, California, said: "Our results show clearly that the Arctic Ocean is a much more biologically productive place than we previously thought." The scientists found that productivity in the area they covered may be more than 10 times estimates.
Phytoplankton are bright green blooms of microscopic plantlike organisms that possess the green pigment chlorophyll that plants use for manufacturing food in sunlight. Phytoplankton are at the base of the marine food chain and account for about half of the total oxygen produced by all plant life and are thus essential for marine life.
While phytoplankton blooms arise in the Arctic waters in summer, scientists had generally assumed that the growth of phytoplankton beneath Arctic ice was negligible. The Christian Science Monitor reports that Arrigo, said: "As someone who has been studying polar marine ecosystems for 25 years, I had always thought that the idea of under-ice phytoplankton blooms was nonsense. There is simply not enough light getting through the ice into the ocean for them to grow." He added: "The idea that phytoplankton can not only bloom under 3-foot-thick ice but that they can reach numbers that put their open-water counterparts to shame was a complete surprise. It means we have to rethink many of our ideas about how the Arctic Ocean ecosystems function."
Arrigo described the moment their instruments sensed the phytoplankton bloom: "As the ship moved from the open water into the ice pack, the instrument that tells us how much phytoplankton are in the water started to produce very high numbers. I thought this was odd since there shouldn't be phytoplankton under the ice. I actually feared that our instrument was malfunctioning."
Stanford News explains that sea ice and snow cover reflects incoming radiation leaving no sunlight for plankton in water. Based on this fact, previous models of biological production in the Arctic Ocean assumed a value of zero below pack ice. But Arrigo said, "Not only was the value not zero, production was higher there than it was in open water."
After comparing samples collected from nearby sources with the phytoplankton species found in the Chukchi Sea ice pack, the scientists concluded that the Chukchi bloom had not drifted under the ice from another location. They concluded that changing climate conditions were now allowing light to penetrate deep into Arctic sea ice. The researchers found that "multi-year ice" that accumulates over several seasons was on the decline with warmer temperatures favoring thinner "first-year ice." They also found that melt pools that now commonly form on top of Arctic sea ice decrease the ice pack's ability to reflect sunlight.
According to the scientists, the phytoplankton bloom was because thinner ice due to warmer temperatures associated with global warming lets in light but protects the algae from harmful ultraviolet radiation.
Stanford News reports Arrigo said: "Grow rates under the ice are higher than I thought was possible for Arctic phytoplankton." He said that algal cells that normally take three days to divide were now doubling more than once a day.
The scientists pointed out that the conditions that allow for the Chuckchi Sea under-ice bloom exist over a large area of the Arctic. Arrigo explained: "We suspect that this is a lot more widespread than we realize."
The appearance of under-ice blooms in the arctic may lead to wholesale shifts in the ecosystem of the Arctic, scientists say. Production of phytoplankton in cold water may cause organic matter to fall to ocean floor, benefiting bottom-feeding species at the expense of species that feed in the water column.
The Christian Science Monitor reports Arrigo said: "It is often assumed that when it comes to biological food production, more is better. However, a more productive Arctic is not necessarily an improved Arctic or a better Arctic. If the Arctic becomes increasingly more productive, some members of the ecosystem will benefit while others will not. There will be both winners and losers. It's too early to tell who these winners and losers will be."
Standford News reports that scientists say that a potential benefit from the projected ecosystem shift is that it may lead to an increase in the Arctic's ability to sequester carbon. An increase in the Arctic Ocean's productivity should lead also to an increase in carbon capture rate. But according to Arrigo, the effect on the global scale is not likely to be significant. He said: "Even if the amount of CO2 going into the Arctic Ocean doubled, it's a blip on a global scale."
The Christian Science Monitor reports researchers now want to determine how widespread the under-ice blooms are and determine their impact on the polar marine ecosystems. Arrigo, however, said: "this will be difficult because the Arctic can be a pretty inhospitable place and sampling deep within the ice pack, which is what this research would require, is challenging, even for an icebreaker."
According to NASA, the discovery has implications for the broader Arctic ecosystem, including migratory species such as whales and birds. Arrigo said: "It could make it harder and harder for migratory species to time their life cycles to be in the Arctic when the bloom is at its peak. If their food supply is coming earlier, they might be missing the boat."
The paper announcing the find was published in the journal Science.