Background on Ice Edge Expedtion
On September 1, two prominent biologists, Dr. Brendan Kelly and Dr. George Divoky, boarded the Greenpeace ship M/V Arctic Sunrise in Barrow, Alaska, to conduct population surveys of Pacific walrus and black guillemot (a seabird) along the edge of the Arctic pack ice. They will be assisted by their research teams and the crew of the Arctic Sunrise during a three-week expedition where they will study walrus and guillemot in their natural habitat along the Arctic ice pack in the Chukchi and East Siberian Seas, and on Wrangel Island in the Russian Far East.
The population surveys will provide new data to Kelly and Divoky's studies of walrus and guillemots. Results of the 1998 surveys will be combined with past data to provide a clearer picture of the species' numbers and distribution, and at the same time, should add to the growing body of evidence about the impacts of climate change on the Arctic environment.
Due to budget cutbacks and the general lack of funding for basic research, this will be the first time in many years that the scientists have been able to conduct such surveys. Dr. Kelly's last ice-edge survey of the pacific walrus population was conducted in 1981; and Dr. Divoky's last opportunity for a ship-based survey was in 1984.
Pacific walrus and black guillemot are both ice-dependent (pagophilic) species, meaning their survival is inextricably tied to the Arctic pack ice. Satellite observations already indicate a decrease in the extent of ice cover of nearly three percent per decade since the late 1970s, with the rate of loss accelerating this decade (Johannsen et al., 1997, Cavalieri et al., 1997) As the burning of fossil fuels continues unabated and the planet continues to warm, Arctic pack ice is predicted to continue thinning and retreating. This could spell disaster for walrus and guillemot populations as well as other ice- dependent species in the Arctic such as seals, whales and polar bears.
Walruses haul out on ice to rest, molt and bear their young. Males can weigh close to two tons -- about the weight of a pickup truck -- while females can weigh nearly one ton. As sea ice thins, it is less able to support the weight of a single walrus or group of walruses, resulting in a loss of critical habitat. In addition, walruses feed almost exclusively on mollusks and other invertebrates that live on the sea floor. If sea ice retreats beyond the continental shelf waters of the Bering and Chukchi Seas, the water could be too deep for walruses to dive for food.
Changes in Black guillemot colonization and population are already among the first documented biological effects of climate change in the western Arctic. Black guillemots breed in cavity nests on the ground, and require a minimum of 80 snow- free days for laying eggs, hatching their young and for the fledglings to leave the nest. Warming temperatures in the Western Arctic from the late 1960s to the late 1980s led to an increase in spring temperatures and therefore, an increase in the number of snow-free days in northern Alaska, which in turn made it possible for Dr. Divoky to establish succesful colonies of black guillemots on Cooper Island, a barrier island in the Beaufort Sea approximately 20 miles east of Barrow. Before the late 1960s, the northern-most habitat for the black guillemot was Cape Lisburne, Alaska, approximately 250 miles southwest (150 miles south) of Barrow on the Chukchi Sea coast.
Dr. Divoky's colonies increased in the 1970s and 1980s, but have declined precipitously in the 1990s. According to Divoky, the very warming that made it possible to establish colonies of black guillemots in the far north is now responsible for the population declines in the 1990s. Divoky attributes the current population decline to a decrease in the extent of sea ice. Black guillemots fly across the sea from their nests on shore to the ice edge where they forage for food in this rich, biologically productive area of the Arctic marine environment. Guillemot feed on Arctic Cod, zooplankton and arthropods that inhabit the ice-edge ecosystem. As the ice- edge retreats, guillemots have to fly farther and expend more energy to get to their food source, resulting in less efficient feeding, increased mortality and population decline. The damping effect of the sea-ice also provides the seabirds some relief from rough waters and waves generated by storms.
The ship's route during the population survey will take it northwest from Barrow to the edge of the Arctic icepack, then west along the ice edge for approximately one week before heading to Wrangel Island.
Wrangel Island is located approximately 500 miles due west of Barrow, Alaska, in the East Siberian Sea. The island is home to Arctic foxes, lemmings, introduced musk-oxen and reindeer. More than 150 species of birds have been recorded on the island, and 50 species are known to nest there. Wrangel is also home to two species of seals -- ringed seals and spotted seals -- that are the main source of prey for Wrangel's most celebrated inhabitant, the polar bear. Wrangel Island has one of the highest concentrations of polar bear dens in the world, making it one of the best places to observe and study polar bears.
Polar bears are also vulnerable to the threats posed by climate change. In October, female polar bears build maternity dens in the snow, and use them to hIbernate during their last months of pregnancy. Cubs are born in December or January, and are then nursed in the dens until they emerge with their mothers in late-March and early-April. Increased temperatures and decreased snowfall could result in increasing numbers of dens collapsing, meaning cubs could be forced to leave their dens too early, resulting in higher mortality. Female polar bears fast during pregnancy and lactation, relying on reserves of fat they have built up through hunting and gorging on seals and other prey in the summer months. As the sea ice continues to recede and thin, it could impact polar bears' ability to hunt and build up fat reserves at critical times during the year.
Polar bears are considered marine mammals, and as such, they rely on pack ice as a platform for hunting, resting and for travel. Changes in the thickness and extent of sea ice will have profound impacts on their biology, behavior and ability to survive in the Arctic environment.
The population surveys will continue for five days while the ship is at Wrangel Island and conclude when heads back to the ice-edge and then follows it east in its return to Barrow.