Science of the Seasons: Arctic sea ice is nice for many mammals

By Dr. David Wartinbee, for the Redoubt Reporter

My first introduction to seals came on a grainy, black-and-white TV when trained seals performed on some variety show. They were a strange animal when first seen, since they didn’t look anything like the all familiar dogs, cats, horses or cows. They were awkward on land and I never got to see their graceful swimming motions until underwater cameras became popular. It took many trips to Alaska and several years as a volunteer at the Alaska SeaLife Center before I really had any understanding about these amazing creatures.

However, many Alaskans learn the ways of seals as they grow up because seals are a normal part of the rural subsistence lifestyle. Seals are hunted on a regular basis in many Native communities as a nutrient-rich food source. Seals are not only hunted for their meat. Seal oil, which is rendered from seal blubber, can be used as an additive to other traditional foods, for waterproofing skin boats or as a traditional fuel for oil lamps. Additionally, seal furs are treasured for garments like boots, hats, gloves and coats.

Along Alaska’s north and western coasts, two of the most commonly hunted seals are the bearded and ringed seals. These are commonly referred to as ice seals because they spend most of their time on or around ice. These seals mate, give birth, raise their young, and rest on or under Arctic sea ice. Only rarely do these seals actually come to shore.

A seal relative that is adapted to a life in the sea, and spends considerable time on or near pack ice, is the walrus. A major predator of these ice-adapted mammals that is worth noting is the polar bear.

There is a major problem on the horizon. The Arctic sea ice that these animals so heavily rely upon is going away. There has been a steady and dramatic loss of pack ice in the Arctic waters of northern and western Alaska. The solid summer pack ice is melting more and more each year, and only thinner, more ephemeral ice is formed each winter. The Goddard Space Center has dramatic satellite pictures that have documented this loss of sea ice over more than 30 years. The amount of open water in the summer months has been increasing. In the past 30 years there has been an increase in summertime open water that is larger than the entire surface area of the state of Alaska. There was a huge surge of ice melting in summer of 2007, but the most open water ever recorded in the Arctic happened this past September.

This unexpected increase in ice melt has led scientists to recalculate their ice-melting rate estimates and to increase their estimates of solar energy capture by open oceans. When there is pack ice floating on the oceans, the majority of solar light energy is normally reflected back into the atmosphere. But open water absorbs most of this energy and, in turn, gets even warmer. Meteorological scientists now estimate that in the summer of 2030, just 17 years away, there will be no ocean pack ice in the Arctic Ocean north of Alaska.

That leaves us with the important question: So what? What changes can we anticipate? Will this loss of Arctic sea ice impact seals and other animals around the Arctic?

In order to try to understand the potential impacts of imminent sea ice loss, we have to understand some of the biology of the creatures found there. The next installment on this topic will look at ringed seals and how they are intimately bound to pack ice. Then we’ll look at the larger bearded seal and how they use the ice. Walruses normally float about on pack ice, and polar bears hunt all of these mammals. When we understand some of their biology, we can consider what changes might come in 2030.

David Wartinbee, Ph.D, J.D., is a biology professor at Kenai Peninsula College’s Kenai River Campus.


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Filed under ecology, science of the seasons, wildlife

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