An estimated 10,000 walruses unable to find sea ice over shallow Arctic Ocean water have come ashore on Alaska’s northwest coast.

Scientists with the National Oceanic and Atmospheric Administration (NOAA) recently photographed walruses packed onto a beach on a barrier island near Point Lay, an Inupiat Eskimo village 700 miles northwest of Anchorage.

The walruses have been coming to the shore since mid-September. The large herd was spotted during NOAA’s annual aerial survey of arctic marine mammals.

An estimated 2,000 to 4,000 walruses were photographed at the site September 12. The U.S. Fish and Wildlife Service, the agency that manages walruses, immediately took steps to prevent a stampede among the animals packed shoulder to shoulder on the rocky coastline. The agency works with villages to keep people and airplanes a safe distance from herds.

Young animals are especially vulnerable to stampedes triggered by a polar bear, a human hunter or a low-flying airplane. The carcasses of more than 130 mostly young walruses were counted after a stampede in September 2009 at Alaska’s Icy Cape.

The gathering of walruses on shore is a phenomenon that has accompanied the loss of summer sea ice as the climate has warmed.

Pacific walruses spend winters in the Bering Sea. Females give birth on sea ice and use ice as a diving platform to reach snails, clams and worms on the shallow continental shelf.

As temperatures warm during the summer, the edge of the sea ice moves north. Females and their young ride the edge of the sea ice into the Chukchi Sea. However, in recent years, sea ice has moved north beyond the continental shelf and into Arctic Ocean waters that are 10,000 feet deep or more, where walruses cannot dive to the bottom.

Walruses in large numbers were first spotted on the U.S. side of the Chukchi Sea in 2007. They returned in 2009, and in 2011, scientists estimated that there were 30,000 walruses along a little more than half a mile of beach near Point Lay.

Ice kept walruses offshore in 2008 and last year.

The goal of the marine mammals survey is to estimate the number of bowhead, gray, minke, fin and beluga whales, plus other marine mammals in areas that are being considered for oil and natural gas drilling, according to NOAA Fisheries marine mammal scientist Megan Ferguson.

Environmental groups say that the loss of sea ice because of climate warming is harming marine mammals and that oil and gas development would add to their stress.

Associated Press