Chukchi Sea

• Category: Marine and Oceanic Biomes.
• Geographic Location: Arctic.
• Summary: This diverse aquatic landscape, named after the indigenous Chukchi people, connects Russia's Siberian territory to the state of Alaska; it is a focus of dramatic climate change.

The Chukchi Sea, located off the coast of northwestern Alaska, is approximately 232,000 square miles (600,000 square kilometers), with most depths not exceeding 164 feet (50 meters). North of the Bering Sea, east of the East Siberian Sea, and west of the Beaufort Sea, it connects the Arctic and Pacific Oceans. Its shallow seafloor and stratified water column are populated by a vast array of organisms due to the influx of nutrients, warmth, and freshwater from warmer Pacific waters. This water flows from the Bering Sea through the Bering Strait before breaking into three different currents under the ice of the Chukchi Sea.

As with other areas of the Arctic, the Chukchi basin is overlain by pack ice for most of the year. However, indicators of global climate change are greatly in evidence here: Sea ice is disappearing at a rate of roughly 4 percent per decade, and alarmingly, this trend may be accelerating; sea temperatures are rising; shorelines are dramatically eroding; and summer sea ice is receding to historic lows. In addition to a changing climate, overfishing and commercial interest in natural resources such as gas and oil threaten the region. Thus, while rich in nutrients, marine species, and minerals, the Chukchi is threatened, and its future remains uncertain.

Hydrology and Sea Ice

The Chukchi Sea gets its name from the indigenous Chukchi people who inhabit the Chukchi Peninsula within the Russian Federation. Despite being 193 miles (500 kilometers) wide and 309 miles (800 kilometers) long, one of the defining physical characteristics of the sea is its shallow continental shelf. The water column is highly stratified, with melting sea ice and runoff providing a fresher surface layer and denser, saltier water near the bottom. The Arctic and Pacific Oceans are bonded by the Chukchi, whose waters are an important source of nutrients, heat, and freshwater for the Arctic Ocean.

Nutrients here support Arctic ecosystems; heat influences ice-melt; freshwater can stratify the Arctic Ocean and help protect the surface ice from the warmer waters below. Freshwater through-flow is an important part of global water cycles, and the pathways of Pacific waters in the Arctic are thought to affect the entire Arctic system.

Melting sea ice constantly floating above the ocean currents is another source of nutrients, providing life to a vast array of species. Sea ice in the Arctic grows and recedes seasonally, with a peak around March and a trough typically arriving in late September that leaves the Chukchi at its sea-ice minimum. Chunks of ice, or floes, are prone to converge and form thick ridges, creating a unique landscape of extremely dense sea ice. Because of these ridge formations, sea ice in the Arctic tends to have a longer life cycle than its flatter, thinner counterpart in the Antarctic. Sea ice in the Arctic, which receives very little snow due to the region's being surrounded by land, is on average about 7 feet (2 meters) thick but can grow up to 16 feet (5 meters). Sea ice is formed by cold temperatures—a minimum of 29 degrees F (minus 2 degrees C)—acting on ocean saltwater, causing tiny ice platelets, or frazil ice, to eventually form pack ice. As it freezes, the crystals of the ice expel salt into the water, yielding crystals that consist of nearly pure freshwater.

Up until very recently, the average mean Arctic sea-ice extent (or the average annual maximum ice area) has been around 6 million square miles (15 million square kilometers), and the average minimum sea-ice extent has been around 3 million square miles (8 million square kilometers), which means that more than half of the ice melts every year. During the summer of 2012, however, the Arctic sea-ice extent fell to just over 1.5 million square miles (4 million square kilometers), surpassing the previous low set in September 2007, as reported by the U.S. National Snow and Ice Data Center. The summer of 2020 was the second lowest recorded sea ice-extend, with 2012 remaining the lowest ever recorded. The comprehensive outcome of these significant ecosystem changes will unlikely be positive for many of the organisms now sustained in the region.

Biodiversity

When sea ice starts to retreat in the spring, polynyas, which are bodies of open water in the middle of ice floes, can be formed. Polynyas are unique to the polar oceans and formed via ocean currents, wind, or upwelling. When the sunlight hits one of the approximately 20 polynyas in the Chukchi every year, a microalgae bloom occurs, creating the foundation of the marine food web. The combination of sea ice and the influx of nutrient-rich Pacific water provides for one of the most productive ecosystems in the world, with a multitude of seals, seabirds, walruses, polar bears, whales, fish, and invertebrates inhabiting its realm.

Beneath the sea ice, various species of fish, such as the capelin, Arctic cod, and sculpin live in the open water, while anemones, mollusks, and numerous other benthic organisms are common sights on the seafloor. Meanwhile, rivers and inlets along the Chukchi provide more than adequate breeding, nesting, and feeding spots for dozens of bird species. Spectacled eiders, another endangered species, feed on mollusks in shallow polynyas before migrating south for breeding.

Endangered fin, bowhead, and humpback whales, as well as the formerly endangered gray whale, feed and migrate throughout the Chukchi Sea. Beluga whales, numbering about 3,500 molt, feed, and calve along the Kasegulak Lagoon off the coast of Alaska. Many other marine mammals call the Chukchi home, with bearded, ribbon, spotted, and ringed seals as well as walrus living their lives both on and below the sea ice. Walruses, which are long-lived social animals, are considered to be a keystone species of the Arctic ecosystem, with Pacific populations spending their summers and falls in the Chukchi before migrating south to the Bering Strait for the cold, harsh winters.

Ringed seals are the most abundant, wide-ranging seals in the Northern Hemisphere, identified by the small head, plump body, and silver rings on their back, from which the seals get their name. They are the primary food source for the icon of the Arctic: the polar bear. The polar bear, now on the Endangered Species list, is a symbol of wildlife loss due to global warming.

Environmental Threats

More than half of America's polar bears inhabit the Chukchi ecoregion. They depend on the sea ice for all aspects of life, from breeding and denning to hunting. In 2007, it was reported that surveys were showing that numerous polar bears were swimming far from land and risking drowning due to record loss of sea ice. However, later studies conducted in 2018, showed a stable polar bear population of nearly 3,000 bears, a significant increase from past estimates. Further study revealed that the body size and litter size of polar bears in the Chukchi Sea have not been negatively impacted by changing conditions. Scientists concluded that the bears were adjusting to changes and thriving.

Like most of the Arctic, the Chukchi is also environmentally threatened due to commercial interests in its natural reserves. Commercial fishing and whaling are putting pressure on the fragile ecosystem, and as of August 2012, Shell Oil was seeking extended time for drilling purposes. The area is projected to contain more than 30 billion barrels (4.8 billion cubic meters) of oil. However, the oil company relinquished its leases in 2016.

For now, the Chukchi remains a diverse, pristine, and balanced ecosystem, providing a habitat for over a dozen threatened or endangered species, among others. However, with global climate change causing sea-ice extent retreat, a rise in sea level, and erosion along coasts due to thawing permafrost, legislative advocacy is at the forefront of all discussions regarding this biome. More research needs to be conducted; potential impacts and mitigation measures need to be adequately addressed.

Bibliography

Audubon Alaska. "Chukchi Sea." Audubon, ak.audubon.org/chukchi-sea. Accessed 5 Nov. 2024.

Kokh, Dmitry. "Polar Bears Settled on an Abandoned Meteorological Station in Chukotka." Russia Beyond, 3 Jan. 2022, www.rbth.com/travel/334603-polar-bears-abandoned-island-chukotka. Accessed 5 Nov. 2024.

Moore, Sue E., et al. "Cetacean Habitat Selection in the Alaskan Arctic During Summer and Autumn." Arctic, vol. 53, no. 4, 2000, pp. 432-47.

Nagel, P. A., and John F. Turner. Results of the Third Joint US-USSR Bering & Chukchi Seas Expedition (BERPAC): Summer 1988. U.S. Fish and Wildlife Service, 1992.