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Waning Sea Ice Threatens Fragile Arctic Food Web

Faced with the grim reality that this year’s Arctic sea ice may once again hit the all-time record lows of 2012, scientists weigh up the subsequent risks.

Written by Randall Hyman Published on Read time Approx. 7 minutes
Divers from Norwegian Polar Institute research vessel R.V. Lance pull gear across pack ice at 82 degrees north latitude to dive and collect plankton specimens in Svalbard, Norway.Randall Hyman

Dragging plastic sleds filled with scuba gear across the vast sea ice at 82.3 degrees north latitude, a team of scientists from the Norwegian Polar Institute (NPI) prepares to dive under the ice, roughly 1,000km (600 miles) from the North Pole. A diver bends over a seal-breathing hole in the ice and enlarges it with an ice saw. If he loses his grip, it will drop more than 3,800m (12,500ft) to the seafloor.

It is late July 2013, and we are searching for the tiny bits of life that bloom beneath the sea ice each summer. These ice algae flourish in the brine-filled channels in the sea ice and are an important cornerstone of the Arctic food chain. They will be devoured by zooplankton (tiny drifting animals), which are, in turn, eaten by birds, fish and marine mammals. They also capture vast quantities of carbon dioxide (a greenhouse gas) and help replenish the Earth’s oxygen.

We have been sailing for nearly a week aboard the research vessel Lance in search of the ice that stretches to the North Pole, and are now farther north than any of the team has ever ventured. At one point, frustrated by how little ice we have found, NPI marine biologist Rupert Krapp recalls something a colleague once wrote about disappearing sea ice.

“He said that people like me might be out of a job in the next 15 years if this continues,” Krapp says. “And here I am. It looks like the [ice] we were supposed to sample isn’t to be found. He just meant it as a joke, but maybe he was right.”

Now that we’ve found the ice, Krapp slides through the hole into frigid seas. While we wait for his return, a rifle-toting colleague patrols the area for polar bears. When Krapp finally surfaces, he pumps his fist in joy. He has found the tiny copepods, amphipods and other plankton that kick-start the Arctic food web. Our mission is a success.

German diver and marine biologist Rupert Krapp, of the Norwegian Polar Institute, pumps his fists in victory after surfacing with plankton samples from under the ice at 82 degrees north, 800km (500 miles) from the North Pole. (Randall Hyman)

German diver and marine biologist Rupert Krapp, of the Norwegian Polar Institute, pumps his fists in victory after surfacing with plankton samples from under the ice at 82 degrees north, 800km (500 miles) from the North Pole. (Randall Hyman)

A Minimum Maximum

Arctic sea ice coverage ebbs and flows on an annual cycle. It usually expands to its winter maximum in March and shrinks to a summer low in September. But as ocean and air temperatures rise, its routine is being disrupted.

Since satellites first began tracking Arctic sea ice in 1979, summer coverage (a yardstick for the health of the Arctic) has declined by almost 50 percent. It has also become thinner. Some climate models predict the North Pole may be free of continuous pack ice before midcentury. As this rich zone of life retreats farther each year, many species are becoming increasingly stressed. Ice provides not only food but a platform for breeding and hunting.

In April 2015, I return to nearly the same spot in the Arctic Ocean. The sea ice had reached its maximum extent only weeks earlier, on February 25. Not only was it the earliest maximum ever, it was the smallest maximum sea ice extent ever recorded, at 14.54 million square km (5.61 million square miles).

Norway’s icebreaker, the K.V. Svalbard, has plowed north from the Svalbard archipelago through winter ice for three days. We are leading the Lance on its third attempt since January to stay frozen in pack ice at 83 degrees north, part of NPI’s effort to track the natural drift of Arctic sea ice. Norwegian explorers had performed a similar feat 120 years earlier at this same latitude and stayed locked in ice for three years. But in the two prior attempts, the Lance has lasted six weeks each time, pushed back into open waters by winds driving the relatively thin ice southward. Now we sit surrounded by ice in all directions, ready to leave Lance beset one last time before summer.

Arctic sea ice has changed dramatically in the past 30 years. The 2015 winter sea ice maximum was 7 percent below the 1981–2010 average, and the subsequent 2015 summer minimum registered 29 percent below average. It has also become younger, or thinner. Sea ice used to grow to several meters thick as it drifted across the Arctic Ocean over a period of 10 years. This thick, multiyear or perennial ice constituted 25 percent of the ice pack in the 1980s, but now accounts for barely 10 percent of the total. Young sea ice may look extensive in winter, but in summer, it melts rapidly.

Based on the characteristics of the winter sea ice, scientists at the Alfred Wegener Institute (AWI) have predicted that the 2016 summer minimum may break the all-time negative record of 2012. In addition to reaching a new record low, this past winter’s ice thickness was similar to the winter of 2012. “In some places, the ice is even thinner,” says AWI sea ice physicist Marcel Nicolaus. If the majority of thick, perennial ice north of Greenland and Canada is carried into the Fram Strait between Greenland and Svalbard, it will leave behind much thinner ice that will quickly melt this summer.

From Plankton to Bears

Pea-sized sea angel (Clione limacina) is a shell-less cold water gastropod, one of many zooplankton collected beneath polar sea ice at 82 degrees north, near Svalbard, Norway. (Randall Hyman)

Pea-sized sea angel (Clione limacina) is a shell-less cold water gastropod, one of many zooplankton collected beneath polar sea ice at 82 degrees north, near Svalbard, Norway. (Randall Hyman)

Vanishing sea ice has other consequences. Ice algae is an important food for fatty zooplankton, such as copepods, that are a vital spring food for fish, seabirds and other zooplankton, including krill. As sea ice and ice algae become scarcer, zooplankton-loving predators such as seabirds, fish and whales can suffer.

Bearded and ringed seals, the two most common seals in Svalbard, hunt from ice and look for areas where fatty fish, such as Arctic cod, and seafloor prey, including shrimps, clams and whelks, are most plentiful. That often means the ice along the shore, but in Svalbard that habitat is disappearing. Ringed seals, wholly dependent on snow-covered sea ice for digging out birthing dens, have increasingly abandoned the southwest coast of Svalbard, where sea ice has become scarce year round. Fewer seals and less ice make life tough for polar bears, which are dependent on seal blubber to get through the harsh Arctic winter.

Bearded seal (Erignathus barbatus) rests on an ice floe in Kongsfjorden, Svalbard. (Randall Hyman)

Bearded seal (Erignathus barbatus) rests on an ice floe in Kongsfjorden, Svalbard. (Randall Hyman)

After leaving Lance marooned in the sea ice, we headed south to rendezvous with NPI polar bear scientists. “The Barents Sea is the fastest changing area [in the Arctic] for sea ice, and modeling predicts faster changes are coming,” says Jon Aars, an NPI polar bear scientist, after he arrived by helicopter aboard the Svalbard. “We have always had variability. The difference now is we’re having more bad ice years than good years.”

Svalbard bears number around 3,000 in winter, but the permanent local population is only in the hundreds. A recent paper correlated disappearing sea ice with a steady increase in polar bears plundering Arctic seabird colonies. Jouke Prop, a biologist from the University of Groningen, in the Netherlands, first noticed predation at his study site in southwest Svalbard in 2004. A decade later, not a single chick had survived the breeding season.

Prop has watched a lifetime of study gobbled up in a few short seasons. A hungry bear can raid 50 nests in an hour and a half, consuming 200 eggs, akin to a 20kg (44lb) omelet. According to Prop, a small number of bears have learned when and where to return each year for the best meals; such intense predation may eventually destroy ancestral breeding sites.

University of Groningen/Jouke Prop

A polar bear eats eggs in a breeding colony of barnacle geese on Spitsbergen. (University of Groningen/Jouke Prop)

“We are becoming more like bear scientists, and less like bird scientists,” says Norwegian biologist Borge Moe, Prop’s co-author, as we survey a plundered eider duck colony farther north.

“What we’re really in is a sort of transition from an ice-covered ecosystem in these areas to an ice-free ecosystem,” says Andrew Derocher, an Arctic ecologist at the University of Alberta who used to run the Norwegian Polar Institute’s polar bear study. Killer whales, for example, normally avoid ice-covered areas but are increasingly showing up in Canada’s Arctic waters, preying on seals and even whales.

“Killer whales will do fine,” says Derocher. “The problem is a lot of species like the narwhal and beluga won’t – that’s not the type of system they evolved to exploit.”

In the northern ecology course he teaches, Derocher now omits his standard lecture on the effects of climate change and the future of the Arctic.

“It’s just too depressing,” he says. “It is pretty grim.”

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