The Great White Bear (27 page)

Each September, researchers at the National Snow and Ice Data Center (NSIDC) in Boulder, Colorado, watch the daily images from the SMMR, and two other satellites that have been launched in subsequent years, with particular intensity. Over the course of the summer, the sea ice in the Arctic gradually decreases, until, by roughly the midpoint of the ninth month, the onset of fall arrests its demise. For a while, it may alternate, one day growing a little in extent, the next day shrinking again, responding to variations in the weather as summer fights to keep its last tenuous grip on the Northern Hemisphere. Finally, after the sea ice cover expands clearly, even if slightly, for several consecutive days, NSIDC releases information on the lowest extent it had reached to that point, which it dubs the sea ice minimum.

From the time NSIDC began to monitor SMMR imagery, the overall picture was of a decline in sea ice extent. But even as it trended downward, it did so arrestingly: for the first twelve years, even a poor summer ice year was generally followed by a recovery to average, or near-average, conditions over the winter. That all changed in 2002.

That year, the summer sea ice minimum fell to a record low 2.3 million square miles, more than 400,000 square miles below the 1979—2000 average and almost 66,000 square miles less than the previous record low. The following year, the rebound, such as it was, was a mere 7,700 square miles above the pre-2002 record. In 2005, sea ice extent fell to another low, 2.15 million square miles.

Then, in 2007, a high-pressure system hovered over the central Arctic Ocean for much of the year, opening the sea ice to the sun's rays, which beamed uninterrupted through clear blue skies. Those same atmospheric conditions brought warm winds into the Arctic, prompting further melt and pushing ice away from the Siberian coast. The combination of sunlight and warm winds was too much for an ice cap that was thinner than usual after recovering poorly the previous winter from its September minimum.

The result was a massive drop in sea ice cover, well below even the 2005 level, to 1.65 million square miles, shattering the previous record by 23 percent, some 39 percent below the 1979—2000 average and, reckoned NSIDC, half of what it had been in the 1950s.

The following year was little better, even without the same perfect storm of conditions that had prevailed in 2007. The minimum extent, 1.8 million square miles, was lower than in every year except the previous one, prompting NSIDC's Julienne Stroeve to observe, "I find it incredible that we came so close to beating the 2007 record—without the especially warm and clear conditions we saw last summer. I hate to think what 2008 might have looked like if weather patterns had set up in a more extreme way."

There was a recovery of sorts in 2009, largely because wind patterns spread ice around instead of compacting it as had been the case two years previously. But even so, sea ice extent was the third lowest on record, and of particular concern was the fact that not only was sea ice, on average, far lower in area than it had been only a few years previously, but it was also thinner and younger.

In 1987, 57 percent of the ice pack was at least five years old, and a quarter of that ice was at least nine years old. By 2007, only 7 percent was at least five years old, and virtually none was nine years old or more. In 2009, only 19 percent of the ice cover was over two years old, the least in the satellite record. That same year, researchers from NASA and the University of Washington published satellite data showing that ice thickness had declined by 2.2 feet between 2002 and 2008; ten years earlier, another study had shown that sea ice thickness had already decreased by about 4 feet between the 1950s and the 1990s.

Even as the ice thinned and melted, currents continued to flush some of it south through the Fram Strait, and that ice's removal, combined with the melting of the ice that remained and the diminishing albedo caused by that melting, threatened to push the Arctic ice pack past a tipping point, after which thinning ice would lead to further thinning ice, melting to more melting, until eventually there would be little or no summer sea ice remaining in the Arctic at all.

At the same time NSIDC announced the 2009 sea ice minimum, the
Arctic Sunrise
was grinding its way through the ice edge of the Fram Strait, carrying a team of scientists investigating sea ice thickness and melt rate. In the ship's mess, the research team's chief scientist, Peter Wadhams of the University of Cambridge, briefed the crew in stark, almost apocalyptic, terms.

"We are entering a new epoch of sea ice melt in the Arctic Ocean due to climate change," he said. "In five years' time most of the sea ice could be gone in summer with just an 'Alamo of ice' remaining north of Canada's Ellesmere Island. In twenty years' time, that will also be gone, leaving the Arctic Ocean completely ice-free in summer. In the last few years, there has been an unprecedented retreat of the sea ice in the Arctic Ocean during summer months, but this starts during the winter. So there's a decline in the rate of growth of sea ice during the winter, an increase in the rate of melt in the summer, and now the thickness of Arctic sea ice has diminished much more rapidly than it had in previous decades. At some point, the ice will not grow enough in winter to match summer melting, and the summer ice will disappear, all in one go."

As sea ice disappears, so, too, do the algae that it contains and that support the very foundations of the Arctic marine ecosystem. Because ice floes extrude salt as they form, they are fresher than the ocean that surrounds them; studies in the Beaufort Sea have suggested that, as floes have melted at a greater rate and extent, they have created a layer of relatively fresh surface water fully 100 feet deep, one-third deeper than was the case twenty years ago. As a consequence, some of the larger algae species that provide fuel for the biological engine that drives the Arctic marine ecosystem have diminished, replaced by smaller species more commonly associated with freshwater environments.

Changes in the composition of algae beneath the ice threaten the productivity of the Arctic marine system, as does the disappearance of the ice itself. The ice edge zone, the most biologically productive area in the northern polar ocean, is especially productive close to shore, above the shallow waters atop continental shelves. For walruses, these areas are a veritable smorgasbord, the ice floes on which they rest providing the perfect platform from which to dive to the bottom, where they graze on clams and other shellfish that they suck from the sea floor. As the sea ice retreats from the shore, the ice edge becomes located above deeper waters, forcing walruses to travel progressively longer distances, and expend progressively more energy, to reach their food source—until eventually, if Wadhams's bleak assessment is correct (and there are many others who propose a more conservative timeline, but who nonetheless agree with the notion of partially or wholly ice-free Arctic Ocean summers sometime around mid- or late-century), they will not even have any ice floes from which to launch their assault on benthic bivalves or on which to roam the frigid waters of the north.

Not only that, but in a warming Arctic the benthic buffet may be relatively barren.

"In the Bering Sea, for example, the spring phytoplankton bloom accounts for much of the primary production and makes for a very, very rich ecosystem," says Brendan Kelly of the University of Alaska. "It used to be the case that a lot of the phytoplankton would essentially fall out of the water column to the benthos. And part of the reason that was happening was that bloom happened at a time when the water was cold enough that the zooplankton community couldn't mature fast enough to eat all that phytoplankton before it sank. Hence it was delivered to the bottom, which is why you have this rich benthic community. Now what's happening is that it's becoming warm enough that the zooplankton community can in fact mature and consume most of that production. So now you're shifting the system away from the benthos. So bearded seals are in trouble, walruses are in trouble. But fin whales and humpback whales, the pelagic-feeding consumers, they're going to do great. What we're likely to see is a huge shift in which species are favored and which are disadvantaged."

That assessment was shared by the authors of a 2008 study in the journal
Ecological Applications
; seasonally migrant Arctic species such as fin, minke, humpback, and killer whales, they noted, are likely to find increased opportunities in a warming Arctic, not only because of a shift to a more pelagic ecosystem but also because dwindling sea ice cover would grant them easier access to that ecosystem. But at the other end of the spectrum, they continued, are four "ice-obligate" species that depend on sea ice as a platform for hunting, breeding, and resting, and for which future prospects are dim indeed. They listed the walrus as one of those species; bearded and ringed seals were two of the other three. For ringed seals in particular, the adaptation to ice is profound, an essential element of their very existence. They alone have evolved sharp claws for digging holes through floes, have turned what is to most others an obstacle to be hurdled into a niche to be exploited. Every aspect of their lives is tied to sea ice. They need a stable platform on which to haul out and rear their young in spring and ample snow cover over that platform in order to build lairs in which to give birth to those young. Should the ice break up, or the snow melt, earlier in the year, newborn pups could drift away from their mothers or be left exposed on the surface of the ice, at the mercy of the ringed seal's chief predator.

Such a development would not, however, be to the benefit of the predator, which has less to gain from eating ringed seals when they are vulnerable, newly born, and small, no matter how easy the pickings, than from hunting them when they are vulnerable, newly weaned, and fat. It is to take advantage of the abundance of ringed seal pups in their latter state that the predator's young are born at a particular time of year; in the harsh Arctic environment, a shift of just a few weeks, or a decrease in the number of pups that even make it to the fat, weaned stage, could prove disastrous. For in the same way that ringed seals have evolved specifically to take advantage of the conditions provided by ice floes, so this one predator has evolved specifically to take advantage of ringed seals. That predator, the fourth member of the aforementioned "ice-obligate" club, is, of course, the polar bear.

In 1988, when Ian Stirling wrote his definitive monograph on polar bears, he included, naturally enough, a chapter on conservation concerns. The chapter covered the rise and fall of commercial hunting and the development of the polar bear agreement. It considered the possible impact of toxic pollutants such as mercury and PCBs. And it dwelled briefly on issues of habitat modification and disturbance from such activities as seismic testing and oil drilling. As Stirling explained then, and as subsequent studies have served to confirm, the impact of all these on polar bears is uncertain.

Heavy metals such as mercury, and artificial compounds known collectively as persistent organic pollutants (POPs), are carried by winds from the industrialized world into the relatively pristine Arctic realm and deposited by precipitation over the ocean, where they enter the marine food web. Their concentrations become larger as they travel up the food chain, from planktivorous fish to carnivorous fish, to seals and thence to the apex of the Arctic marine ecosystem, the polar bear.

Polar bears in some parts of the Arctic have been found to contain mercury in levels greater than those shown to cause severe neurological ailments and death in humans, but whether such high levels have similar effects in the bears remains unclear. There is some evidence to suggest that polar bears are somehow able to metabolize mercury in their bodies into a relatively harmless form, and thus spare themselves from its worst impacts; contamination by POPs, however, may be another matter. One study has shown a strong correlation in polar bears between high levels of contaminants known as polychlorinated biphenyls (PCBs) and low levels of antibodies, and other studies have suggested the same contaminants may cause reproductive and hormonal abnormalities—such as reduced fertility in females and smaller testes in males.

As the authors of one study laconically observed, however, there remains "a substantial knowledge gap."

Such a gap exists, also, when considering to what extent polar bears are affected by nearby human activities; the particular concern is for those bears that cannot simply move away from any noise or disturbance—specifically denning mothers and cubs.

Although numerous studies of bears in dens have suggested that all but the very closest and loudest of noise sources are of little concern to them, that they show signs of anxiety only on relatively rare occasions and feel impelled to abandon their dens only in situations of extremis, the fact does remain that their immobility creates a degree of vulnerability. There is also consideration that the audio frequencies of industrial activity could interfere with what, to human ears, are unheard vocalizations between mother and cubs, a subject of ongoing research.

But polar bears are also smart and adaptable animals, and there is much circumstantial evidence that, once they have ascertained that an activity is not obviously harmful to them, they tend to simply avoid, ignore, or even exploit it.

That said, to dismiss the potential negative impacts of oil development and industrial activity in polar bear territory would be cavalier, and researchers do not do so. Even if direct impacts of a particular activity may appear to be limited, there are possible secondary considerations: the fact that development often begets development; the prospect that polar bears that become accustomed to human activity may be more likely to have encounters with the humans concerned, almost certainly leading to an unhappy ending for one or both; the potential, in the case of oil exploration and extraction, for a blowout or even a relatively small spill that could contaminate bears directly or via oiling of ice and water and the seals thereon and therein.