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THE INCREDIBLE SHRINKING SEA ICE David Barber, Louis Fortier, and Michael Byers In the disaster blockbuster, “The Day After Tomorrow,” the shrinking of polar ice caused by climate change unleashes an extreme weather Armaggedon which, among other things, sees the Statue of Liberty engulfed by a tidal wave. The predictions offered here by David Barber, Louis Fortier and Michael Byers are less cataclysmic but equally compelling. In relaying the scientific evidence and outlining the ecological, economic and political impacts of polar climate change, Barber, Fortier and Byers present a chilling case for heading off doomsday. Dans The Day After Tomorrow, la fonte de la calotte glaciaire provoque un raz-de- marée sans précédent qui engloutit notamment la statue de la liberté. Certes moins catastrophiques, les prédictions que font ici David Barber, Louis Fortier et Michael Byers n’en donnent pas moins froid dans le dos. S’appuyant sur des observations scientifiques, ils inventorient les répercussions écologiques, économiques et politiques des changements du climat polaire et brossent de ses conséquences un tableau franchement alarmant. or centuries, significant resources have been expend- culation driven by the seasonal global balance in net ener- ed in search of the Northwest Passage, or as Pierre gy. An oscillating planetary energy balance is established F Berton once called it; the “Arctic Grail.” Franklin, with net positive surplus at the equator and net loss at the Davis, Ray, Baffin, Amendment, Blot, Monk, and Perry are poles. Seasonal modulation of this general pattern is driven just a few of the names that have gone down in history for by the fact that the planet’s axis of rotation is 23.4° offset their quest for the shortest route from Europe to Asia. It was from the perpendicular. This means that solar insolation is sea ice that foiled the best laid routes and provided the sus- much larger at the equator than at the poles, and this sets pense and intrigue we are all now familiar with. The waxing up (at least in a first order fashion) the seasons that create and waning of sea ice movement in the northern hemi- polar sea ice. It also results in an overall planetary energy sphere has long created seasons when a ship could sail easi- balance with opposing signs at each pole, which helps to ly through Baffin Bay, while in other years “rivers” of ice establish a planetary-wide circulation of heat from the equa- flushed down from the Lincoln Sea towards the Labrador tor poleward and vice-versa. coast. The high variability experienced by these explorers In the Arctic, sea ice forms annually throughout most of was the norm of the day. the area north of the Arctic Circle whenever the ocean dips However, things do appear to be changing, and these below -1.8°C. Maximum volume of ice occurs around the trends are cause for concern. In recent years, scientists, end of March, with an area of about 14 million km2. through the media, have been informing the public about Perennial ice occurs throughout the Canada and Arctic developments concerning sea ice in our northern hemi- basins in the summer, and annual ice grows over the shal- sphere. Articles such as “As Polar Ice Turns to Water, Dreams low continental shelves northward to meet the southern of Treasure Abound” (the New York Times) recall the eco- advance of the perennial pack. Reduction in this maximal nomic forces at play several centuries ago, while making a extent occurs throughout the summer season until a mini- scientifically based prediction that the Arctic ocean may mum of about 7 million km2 is reached, sometime around become the next, and likely one of the last, of our great the end of September. oceans to exploit, conserve and protect. Climate models converge on a single feature: they pre- dict the first and strongest signals of global-scale climate ea ice occurs at both poles as a result of large scale vari- change to occur in the high latitudes of our planet. These S ations in solar insolation (incoming solar radiation or models predict a reduction in sea ice extent over the next the sun’s rays) and changes in oceanic and atmospheric cir- several decades, resulting in a seasonally ice-free Arctic as 66 OPTIONS POLITIQUES DÉCEMBRE 2005 - JANVIER 2006 The incredible shrinking sea ice early as 2050. Observational studies, ice will be less of a problem for nurse their pups in dens built inside based on the passive microwave satel- marine vessel transport if the current sea-ice ridges. Juvenile Arctic cod, lite record, confirm these predictions trends continue. which live in the anfractuosities of the for both rates of reduction and, to a Many researchers believe that the pack where they are protected from certain extent, geographic location. Northeast Passage will be one of the their predators and find abundant crus- We lose, on average, about 74,000 first to open, since the remnant pack tacean prey, synthesize antifreeze pro- km2 of sea ice extent each year, and we tends to shift toward North America teins that prevent their blood from have lost about 2,000,000 km2 since under current forcing. Two of us were freezing at the sub-zero temperatures 1979. The record of minimums has in fact aboard a Russian ice-breaker in prevailing in the ice. Key Arctic cope- become rather common in the instru- September 2005, and there was no ice pods have developed sophisticated mental record, with the minimum on of any significance to shipping along reproduction strategies to match the hatching of their eggs with Climate models converge on a single feature: they predict the the short season of produc- first and strongest signals of global-scale climate change to tion of ice algae. In addition to microalgae, bacteria occur in the high latitudes of our planet. These models dwell in the high-salinity predict a reduction in sea ice extent over the next several brine channels among the decades, resulting in a seasonally ice-free Arctic as early as sea-ice matrix and are active 2050. Observational studies, based on the passive microwave at temperatures as low as -22 C. Life in the Arctic seas satellite record, confirm these predictions for both rates of begins in mid-spring, when reduction and, to a certain extent, geographic location. the snow covers become sufficiently thin to allow record being that of 2005. It is impor- the entire route of the Northeast enough sunlight to reach the base of tant to note that this reduction repre- Passage (between Norway and Alaska). the ice. The light reaching the ice-water sents a switch from perennial ice (i.e., The situation with multiyear sea interface triggers the growth of ice- multiyear ice) to annual ice (i.e., first- ice in the Northwest Passage is some- dwelling microalgae. As the ice cover year ice). The issue of a reduction in ice what more complex. Historically, mul- breaks up in early summer, sunlight thickness (volume), although more tiyear ice has moved into the penetrates deeper into the ocean and difficult to measure, also suggests an archipelago through the channels on free-floating microalgae known as phy- overall reduction. Recent results pro- the western side of the archipelago toplankton start blooming. Minute vide compelling evidence for an over- (e.g., Amundsen Gulf, McClure Strait crustaceans called copepods (from 0.2 all northern hemisphere volume and small channels on the western to 2 cm long) emerge from hibernation decrease of 32 percent, most of which edge of the QEIs). When the multiyear at depth to graze on the ice algae and resulted from a reduction in thickness pack regularly extended southwards to phytoplankton. The copepods are of ice over 2 m (i.e., multiyear). This the Tuktoyuktuk Peninsula we could preyed upon by the ubiquitous Arctic coincided with an increase in the find multiyear sea ice in Amundsen cod, a small (25-30 cm) sluggish cousin extent of open water and young ice of Gulf. In recent years, the pack ice edge of the Atlantic cod that in turn is the between 20 and 30 percent. has retreated north, and it now lies at main staple of seals, belugas, narwhals Minimum sea ice concentration the northern limit of McClure Strait. and many species of sea birds. At the (SIC) is defined as 15 percent concen- Once this edge retreats beyond the top of the food chain, the polar bear tration, and is computed for the end of entrance way to McClure Strait we can preys almost exclusively on the ring September of each year using the expect a dramatic reduction in the seal, whereas man hunts any large prey, SMMR and SSM/I passive microwave amount of multiyear sea ice moving including the polar bear. The fat record (National Snow and Ice Data into the Northwest Passage. Given the reserves accumulated in summer by the Centre [NSIDC]). current trajectory, this will likely hap- small herbivore copepods sustain them The timing of the reduction in pen in the next decade. during the long winter months and the perennial ice cover is important, sustain their predators throughout the both from biophysical and socio- fter a million years of evolution, annual cycle. As their icy habitat economic perspectives. The barriers A Arctic species present unique fea- shrinks and thins, these highly special- to navigation have historically been tures and life cycles that reflect adapta- ized organisms face the double threat caused by multiyear sea ice, because it tion to life on, in and under sea ice. of displacement by less specialized tem- is thicker and harder than first-year The polar bear is impressively suited to perate species, and extinction.

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