Whales, Walruses and Arctic seabirds are moving north as reduced sea ice and warmer water push their primary prey – bottom-dwelling mollusks and invertebrates – farther north toward the North Pole.
The year-to-year maximum extent of Arctic ice varies, but the average winter coverage has hit historic lows. Less ice accelerates the loss of more ice, according to a June 9, 2016, paper in Nature Communications.
A video accompanying the paper also shows a dramatic weakening of the jet stream circling the polar region. The jet stream acts as an atmospheric wall that blocks warm air from moving north toward polar latitudes, but as the jet stream has slowed, warmer air intrudes farther north. If it continues as scientists predict, Greenland’s massive glaciers could melt.
“I don’t know if you can call it a surprise,” said Marco Tedesco, first author of the paper and an atmospheric scientist at Colombia University’s Lamont-Doherty Earth Observatory. “This is the first year that the climate community is approaching the Arctic system in this rigorous way, and there is very fast progress.”
‘ARCTIC AMPLIFICATION’ HEAT WAVE
Tedesco said a huge intrusion of warm air that covered Greenland in winter supports the “Arctic amplification” theory. That theory is based upon a multiplication effect of melting Arctic sea ice: as millions of square miles of white, heat-reflecting ice are replaced by dark, heat-absorbing open water the warming process actually accelerates, enhancing the polar-warming effect.
If Greenland’s ice sheet were to melt entirely, a scenario that is now predicted to be likely, average global sea level would rise by about 7 meters (23 feet), the researchers said.
However, before that happens, other studies show that the marine ecology of the north will be transformed.
Indeed, warmer seas and shrinking Arctic sea ice are already reconfiguring the ecology of Arctic seas. Prodigious communities of bottom-dwelling mollusks and invertebrates form the bottom of the food web and support an array of marine animals. As the invertebrates retreat north, the animals must follow if they can.
THE SPECTACLED EIDER STORY
Large sea ducks called Spectacled Eiders have recently shifted 2 of their 4 molting areas as much as 56 miles (90 km) northeast over the past 20 years, according to a June 1, 2016, paper in The Condor. The shift reflects the more northerly abundance of bottom-dwelling mollusks.
Scientists implanted small radio transmitters under the skin of dozens of eiders. During September when the birds are briefly flightless, they congregate at the richest beds of mollusks. They dive for food and fatten up while waiting for their new feathers to grow. Walruses and whales also are moving north.
“Telemetry data of apex predators is allowing us to use them as indictors of prey availability,” said Matthew Sexson, a wildlife biologist with the U.S. Geological Survey’s Alaska Region and lead author of a June 1, 2016, report in The Condor. “Spectacled Eiders, Walrus, Gray Whales and other predators of sea-bottom invertebrates are moving north to match the distribution of prey.”
SHRINKING ‘MAXIMUM EXTENT’ ICE
The National Snow and Ice Data Center reported that Arctic sea ice reached its 2016 maximum on March 24. At that point, the ice covered 14.52 million square kilometers (5.6 million square miles) of ocean, which is 1.09 million square kilometers (410,000 square miles) less than the 1981-2010 average. The shrinking ice is particularly apparent in the Bering Sea where Spectacled Eiders, Walruses, seals and other marine mammals spend the winter at the edge of the ice.
However, the Arctic amplification phenomenon could reduce the maximum extent of winter ice in the Bering Sea, reduce the thickness, and lead to earlier melting.
“As an exclamation point on the unusual warmth, there was a brief weather event at the very end of December 2015 when air temperatures near the Pole nearly reached the melting point,” said a report by the National Snow and Ice Data Center.
The Spectacled Eider is the Spencer Tracy of the bird world, with what looks like large black-rimmed glasses. The birds dive for coin-sized clams during winter days. At night they often huddle on the ice like penguins to conserve body heat.
Males and females form breeding pairs in the Bering Sea, and in May and June the females lead their mates to isolated wetlands, lakes and bogs in northwest Alaska and a vast area of coastal northeast Russia. In the late-1980s and early-1990s, the eider population in Alaska unexpectedly plummeted 90 percent. A similar collapse may have occurred in the Russia population, but it’s not known.
Wildlife biologists had no idea what happened. Most other waterfowl that nests in northwest Alaska were doing fine, but most don’t rely on mollusks to the extent that eiders do. Native subsistence hunters collect eider eggs, and female eiders fly in low circles above their nests when disturbed. This makes them easy targets for hunters. To make matters worse, young eiders often ingest highly toxic lead shot while foraging in shallow water, become ill and die.
However, Sexson said the most important factor in the eider decline was probably ecological, but unraveling the exact cause is not yet possible.
‘MARINE SNOW’ MANNA
When winter ice melts, the Bering, Chukchi, Beaufort and East Siberian seas bloom with photosynthetic algae. Late in the season, massive die-offs of algae fall as “marine snow” to fertilize beds of mollusks and other invertebrates on the sea floor. The carbon-rich snow is the primary ecological driver of the food chain.
However, as ocean temperatures have warmed, zooplankton, which can’t tolerate cold water, have moved in to consume more algal snow before it can reach the sea bottom.
Fish move in next to eat the zooplankton. The net result is more fish and fewer bottom invertebrates. Spectacled Eiders, Walruses and Gray Whales must move farther north to find ample food.
SEA DUCK SENTINALS
“With warm temperatures, the fish and zooplankton move in and are partially consuming the detritus that historically settled to the bottom,” Sexson said. Satellite images show the algal blooms, but they don’t reveal how much falls to the bottom. The eiders can reveal what satellite images can’t.
Molting eiders spend September above the richest beds of mollusks. Sexson and his colleagues radio-tagged eiders and followed their year-to-year northward shift during the molting season. Sanctuaries have been established in large bays historically used as molting and feeding grounds for eiders, but Sexson said the birds are moving away from these areas.
“We can’t say that this is a threat, because the birds are naturally going to acclimatize to the location of the prey,” Sexson said. “However, if the availability of prey is less or at greater depth, we could see a potential threat, and they could abandon previously used areas.” In addition, the new areas used by eiders could have more oil exploration and other commercial activities that are known to threaten sea animals.