Bering Sea researcher Jackie Grebmeier, from the University of Tennessee, Knoxville, braves this ocean frontier to study small sea creatures like worms and clams, and microscopic sea plants called phytoplankton.

"The Bering Sea can be calm as a lake but ferocious storms are common. I was once on a 400-foot ice breaker whose bridge window was smashed out by a 50-foot wave."

Thousands of grizzly bears polar bears live around the Bering Sea. Grebmeier says she's "awed" by these creatures that can be 8 feet long and weigh as much as 1700 pounds.

"When you see a polar bear you immediately know that you are not the top of the food chain. When they look at you, they're looking at food."

By studying some of the Bering Sea's smallest organisms, Grebmeier's research helps groups like WWF understand changes in the environment.

"Like all ecosystems, the Bering Sea system is dynamic. There are natural fluctuations in plant and animal populations, salinity, temperature, and current flow, but it's not obvious what role human activity plays in these changes. That's why science is so important. We need to understand the consequences of our actions so we can change our activities to keep the system healthy."

Perhaps the most important species in the Bering Sea are phytoplankton. They are the most numerous species there and the backbone of the ecosystem.

"Not everything eats phytoplankton, but virtually every creature that lives in and around the Bering Sea depends on these tiny plants one way or another. They are the reason whales migrate thousands of miles every year to feed here."

Fueled by the sea's nutrient-rich waters, phytoplankton blooms can extend for hundreds of miles across the Bering Sea and, depending on the species, turn the surface dark blue, turquoise, dark green, reddish green and other colors. Wildlife flock to the blooms to feed and fishermen use them to locate good fishing areas.

"The Bering Sea is the U.S. and Russia's largest fishery but fishermen would have nothing to catch without these tiny organisms, nor would whales and walruses."

Grebmeier also studies the small animals that live at the bottom of the sea like snails, worms and clams which are a crucial source of food for numerous species. Adult walruses, for instance, can eat up to 6,000 clams a day, finding them by sweeping the murky bottom of the sea with their sensitive whiskers. When the clams expel water, the walruses suck them from the shells.

In all these creatures, Grebmeier sees a link to the weather. Like all plants, Phytoplankton take-up carbon dioxide. When the populations of carbon-absorbing plants - and the animals that depend on them - change, the amount of carbon dioxide in the environment changes, ultimately making it back to the atmosphere where these changes affect the climate.

"My main interest is in learning how the Bering Sea ecosystem mirrors global warming. All the data suggests the Arctic will feel climate change the most. We're already seeing a thinning of the sea ice and, without the ice cover, we won't have the weather we're used to."

Although the Bering Sea ecosystem clearly shows signs of human-induced change, Grebmeier says it is still one of the last frontiers. The Bering Sea, after all, is one of the few places on Earth that is still home to more wildlife than people.