Climate researchers have long warned that the Arctic is particularly vulnerable to global warming. The dramatic shrinking of sea ice in areas circling the North Pole highlights those concerns.
A new report finds that the disappearing ice has apparently triggered another dramatic event — one that could disrupt the entire ecosystem of fish, shellfish, birds and marine mammals that thrive in the harsh northern climate.
Each summer, an explosion of tiny ocean-dwelling plants and algae, called phytoplankton, anchors the Arctic food web.
But these vital annual blooms of phytoplankton are peaking up to 50 days earlier than they did 14 years ago, satellite data show.
“The ice is retreating earlier in the Arctic, and the phyto plankton blooms are also starting earlier,” said study leader Mati Kahru, an oceanographer at the Scripps Institution of Oceanography in San Diego. Kahru published the work in the journal Global Change Biology.
Drawing on observations from three American and European climate satellites, Kahru and his international team studied worldwide phytoplankton blooms from 1997 through 2009. The satellites can spot the blooms by their color, as billions of the tiny organisms turn huge swaths of the ocean green for a week or two.
The blooms peaked earlier and earlier in 11 percent of the areas where Kahru’s team was able to collect good data. Kahru said the affected zones cover roughly 1 million square kilometers, including portions of the Foxe Basin and the Baffin Sea, which belong to Canada, and the Kara Sea north of Russia.
Ecologists worry that the early blooms could unravel the region’s ecosystem and “lead to crashes of the food web,” said William Sydeman, who studies ocean ecology as president of the nonprofit Farallon Institute in Petaluma, Calif.
When phytoplankton explode in population during the blooms, tiny animals called zooplankton — which include krill and other small crustaceans — likewise expand in number as they harvest the phytoplankton. Fish, shellfish and whales feed on the zoo plankton, seabirds snatch the fish and shellfish, and polar bears and seals subsist on those species.
The timing of this sequential harvest is programmed into the reproductive cycles of many animals, Sydeman said.
“It’s all about when food is available,” he said.
So the disrupted phytoplankton blooms could “have cascading effects up the food web all the way to marine mammals.”
Last week, the National Snow and Ice Data Center in Boulder reported that in February, Arctic sea ice covered a smaller area than ever seen in that month, tying with February 2005 as the most ice-free February since satellites began tracking Arctic ice in 1979.
