Cracking Antarctic Sea Ice – NASA Science

It’s the season for long, straight cracks in the sea ice of McMurdo Sound. Although natural breaks in sea ice are called “leads,” the better term for the human-caused fracture seen in these satellite images is “ship channel.”

During the austral summer, usually in January, an icebreaker makes its way through fast ice, a type of sea ice anchored to the shore, which often covers McMurdo Sound. This annual effort allows cargo ships to reach McMurdo Station, a research base operated by the United States Antarctic Program. The U.S. Coast Guard Cutter Polar Star completed the task in January 2026, arriving after cutting its way through several miles of ice between the Ross Sea and an ice pier in McMurdo. Most of the channel was cut between January 19 and 20.

The animation above, composed of images captured by the OLI (Operational Land Imager) on Landsat 8 and 9, offers satellite views of the icebreaker’s work. Images were captured on January 2, 7, 19, 20, 23, 25 and 27. The nearly 120-meter (400-foot) ship weighs 13,500 tons and has thick plate steel hulls. With 75,000 horsepower, it is the most powerful non-nuclear icebreaker in the world.

The ship sometimes also carries out search and rescue missions. On January 17, its 50th anniversary of service, the Polar Star responded to a call from an Australian cruise ship in the Ross Sea, hampered by thick pack ice, a type of sea ice that has broken away from the shore and is drifting. After making two close passes to break the ice and clear a path, the Polar Star escorted the cruise ship 4 nautical miles (7 kilometers) until it opened waters in the Ross Sea, according to the U.S. Coast Guard.

Established in 1955, McMurdo Station is the southernmost point on the planet accessible by boat. With a population that reaches 1,200 in summer, it is Antarctica’s largest research station, housing a port, two airfields and a helicopter pad. Although formerly powered by a portable nuclear reactor known as “Nukey Poo”, the base now runs on power from diesel electric generators and a wind farm on Crater Hill.

With ship passage open, McMurdo Station is expected to receive two major deliveries this summer. The Stena Polaris, an oil tanker, arrived January 20 with 5 million gallons of diesel fuel. Plantijngracht, a cargo ship, will arrive later with food, supplies and parts for a new floating pier that will replace the traditional ice pier that military engineers build each winter to allow ships to unload their goods.

The United States National Science Foundation manages McMurdo Station and much of the scientific research conducted there. NASA has also been involved in several projects on the base over the years. For example, NASA’s McMurdo Ground Station, a Near Space Network facility, is used to download data from polar-orbiting satellites such as Landsat 9 and SMAP. The agency also conducted its Operation Ice Bridge airborne campaign from McMurdo in 2013 and regularly launches research balloons from the station as part of its science balloon program.

The Polar Star typically stays in McMurdo until March to keep the ship’s passage clear and returns to its home port of Seattle in April.

NASA Earth Observatory images by Michala Garrison, using Landsat data from United States Geological Survey. Story by Adam Voiland.

• Atlas Obscura (March 20, 2024) McMurdo Ice Pier. Accessed February 2, 2026.
• Cruise Industry News (January 24, 2026) Panoramic statement regarding Scenic Eclipse II Ross Sea operations. Accessed February 2, 2026.
• Defense Visual Information Distribution Service (January 30, 2026) MSC chartered ship completes fuel delivery for Operation Deep Freeze 2026. Accessed February 2, 2026.
• Defense Visual Information Distribution Service (2026, January 21) USCGC Polar Star (WAGB 10) escorts the motor ship Stena Polaris across the ice-covered Ross Sea to McMurdo Station during Operation Deep Freeze 2026. Accessed February 2, 2026.
• Defense Visual Information Distribution Service (January 21, 2026) First MSC chartered vessel arrives at McMurdo Station in Antarctica in support of Operation Deep Freeze 2026. Accessed February 2, 2026.
• Defense Visual Information Distribution Service (January 7, 2026) MSC completes cargo operations in Southern California in support of Operation Deep Freeze 2026. Accessed February 2, 2026.
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• NASA Earth Observatory (2025) A world of change: Antarctic sea ice. Accessed February 2, 2026.
• U.S. Antarctic Program (April 29, 2025) Preparations underway for a new barge pier at NSF McMurdo Station. Accessed February 2, 2026.
• U.S. Coast Guard (January 23, 2026) U.S. Coast Guard Cutter Polar Star celebrates 50 years of service and begins Operation Deep Freeze 2026. Accessed February 2, 2026.
• United States War Department Navy (January 6, 2026) Reservists support Operation Deep Freeze 2026.
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