The Unpredictability of Ice

Cooper Island, Alaska, July 8, 2009 — Henry David Thoreau wrote that “Ice is a fit subject for contemplation” as he monitored the formation and melt of ice on Walden Pond in the mid 19th century. He had no idea how important monitoring, studying and contemplating Arctic sea ice would become in the late 20th and early 21st century, as the increasing annual retreat of the ice became one of the more dramatic and disturbing signs of changes in global climate.

When I first began my work on Cooper Island in the mid-1970s the near shore waters north of the island had a large amount of multi-year ice. The relatively high vertical relief of multi-year ice provided a dramatic counterpoint to the relatively featureless island as the size and angle of the shadows of the irregular pressure ridges responded to the movements of the 24-hour sun. As increased annual summer ice retreat resulted in extensive areas of first-year ice in the Arctic Basin, our view to the north is now primarily of flat featureless ice, which is aesthetically less appealing but is welcome when scanning for polar bears.

Cooper Island’s lack of a picturesque seascape is the least of the problems arising from the extensive first-year ice. Since first-year ice is thinner than multi-year, it melts faster and contributes to the increases in the pace and extent of summer Arctic ice retreat. For the black guillemots breeding on Cooper Island this means that the ice that supports Arctic cod, their preferred prey, can rapidly retreat from the island while they are feeding their nestlings. Watching the timing and extent of ice retreat this summer and its effects on guillemot breeding success will be the focus of my work for the next two months. Ice conditions near Point Barrow and Cooper Island can be seen at NASA/Goddard’s MODIS Rapid Response System.

The uncertainty of the timing of ice retreat from the Beaufort Sea coast is an issue for a number of human endeavors, as well as for Cooper Island’s black guillemots. During the development of the Prudhoe Bay oil fields, the annual “sea lift” of equipment and even buildings would frequently get to Barrow and have to wait for the ice to pull offshore before making the run from Barrow. In 1975, when guillemots had high breeding success and lots of Arctic cod, the sea lift had to turn back since the Beaufort Sea never did become navigable before freezing up.

Adventurers and others wanting to traverse the Northwest Passage also have waited at Point Barrow for the ice to retreat — or not. A number of years ago, a Lindblad vessel spent a few weeks off the village of Barrow and finally had to head south with its disappointed tourist, when it became obvious that while the Arctic was becoming more accessible it was not becoming more predictable.

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