continental shelf

The largest iceberg runs aground

April 10, 2025 By EarthWise Leave a Comment

The largest iceberg in the world, which has been slowly drifting for nearly 5 years, has finally come to a halt. The iceberg – called the unexciting name A-23A – came into existence in 1986 when it broke off from another iceberg A-23 that had calved or torn off from Antarctica earlier that year. For decades, A-23A sat in the Weddell Sea, east of the Antarctic Peninsula. Then, in 2020, it came loose from the seafloor and began to move. By 2023, it finally left Antarctic Waters.

Late last year, it began spinning in place caught in an ocean current called a Taylor column. Finally, it headed for South Georgia, a British-owned island that is home to a couple dozen people and lots of seals and penguins. A-23A is now stuck on the continental shelf, about 50 miles from the island.

A-23A is around 1,300 square miles in area. By comparison, New York City is 300 square miles.

Four years ago, a large iceberg called A-68A also came to ground in the vicinity of South Georgia. It quickly broke apart and ultimately added 150 billion metric tons of fresh water to the ocean as well as various nutrients. A-23A is also likely to succumb to the warmer waters, winds, and currents it now encounters and will affect the flora and fauna in the area.

The climate is changing and is impacting how ice shelves melt. Calving and the creation of mammoth icebergs are a normal part of the lifecycle of polar ice sheets, but we are likely to see even more events like this in the future.

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World’s Largest Iceberg Runs Aground

Photo, posted January 29, 2011, courtesy of Drew Avery via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Polar Bears And Melting Sea Ice | Earth Wise

January 14, 2022 By EarthWise Leave a Comment

Climate change poses a major threat to polar bear survival. The polar bear, whose native range lies largely within the Arctic Circle, depends on sea ice for nearly all of its lifecycle functions. And rising temperatures are causing this sea ice to disappear.

Climate change-driven sea ice loss is the primary threat to the future of this iconic species. In fact, polar bears were the first animal listed as endangered because of the forecasted impacts of climate change.

Melting sea ice as a result of climate change continues to plague polar bear survival. According to a new study by researchers from Washington State University, polar bears in the Beaufort Sea have had to travel far outside their traditional arctic hunting grounds in recent years for food. This has contributed to an almost 30% decrease in their population.

Researchers used satellite tracking data to analyze the movement patterns of female polar bears from 1986-2016 in the Beaufort Sea area north of Alaska. Over the last two decades, they found that polar bears are having to travel farther north of their traditional hunting grounds on the continental shelf to remain on their receding sea ice habitat.

The research team also found that around 20% of the polar bear population in the Beaufort Sea is foregoing its traditional sea ice hunting grounds altogether in the summer and fall. Instead, these bears are moving inland in search of food.

Scientists estimate that 800 or so polar bears remain in the southern Beaufort Sea. Curbing global greenhouse gas emissions in order to protect polar bear habitat may be the only way to help these animals survive.

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Melting sea ice forces polar bears to travel farther for food

Photo, posted September 27, 2015, courtesy of Anita Ritenour via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Fresh Water Under The Sea

July 18, 2019 By EarthWise Leave a Comment

A new survey of the sub-seafloor off the U.S. Northeast coast has revealed the existence of a gigantic aquifer of relatively fresh water trapped in porous sediments lying beneath the salty ocean. This appears to be the largest such formation ever found.

The newly-discovered aquifer stretches from the shore at least from Massachusetts to New Jersey and extends more-or-less continuously out about 50 miles to the edge of the continental shelf. The deposits begin at around 600 feet below the ocean floor and bottom out at about 1,200 feet. If all that water was found on the surface, it could create a lake some 15,000 miles in area. The researchers estimate that the region holds at least 670 cubic miles of fresh water.

Researchers made use of innovative measurements of electromagnetic waves to map the water, which had not been detected by other technologies. It was already known that fresh water existed in places under the sea bottom as a result of oil drilling as far back as the 1970s. But there was previously no hint of the extent of the undersea aquifer.

The water probably was trapped by sediments deposited during the last ice age when sea levels were much lower. But modern subterranean runoff from land sources might also be a contributor.

If water from the aquifer was to be withdrawn, it would still have to be desalinated for most uses, but the cost would be much less than processing ordinary seawater. There is probably no need to do this in the Northeastern US, but the discovery suggests that such aquifers probably lie off many other coasts worldwide and could provide desperately needed water in places like southern California, Australia, the Mideast or Saharan Africa.

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Scientists Map Huge Undersea Fresh-Water Aquifer Off U.S. Northeast

Photo, courtesy of August 1, 2015, courtesy of Michael Vadon via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.