After being stuck for the second time in nearly four decades, the planet’s current-largest iceberg (A-23A) again floats free.
Initially stuck in the Weddell Sea for decades, Iceberg A-23A was eventually caught in a Taylor column after regaining mobility. It remained trapped for several months, showcasing the dynamic and unpredictable nature of iceberg movements influenced by oceanic and seabed features.
Iceberg A-23A’s Journey Begins
When icebergs break away from ice shelves or large glacier fronts, they become travelers in the ocean, carried by currents, spinning in eddies, shifting with the tides, and pushed along by the wind. Sometimes, these massive ice chunks get stuck — either grounded on a shallow seafloor or caught in a swirling mass of water. Iceberg A-23A experienced both.
A Lengthy Detour in the Southern Ocean
After calving from the Filchner-Ronne Ice Shelf in 1986, Iceberg A-23A spent decades immobilized on the seafloor of the southern Weddell Sea. In the early 2020s, it started to break free, and by March 2023, the iceberg, roughly the size of Rhode Island, was floating freely. However, its newfound mobility was short-lived. By March 2024, as it drifted northward, A-23A became trapped again — this time in a Taylor column, a rotating vortex of water created when currents meet an obstacle on the seafloor.
The Unpredictable Path of Iceberg A-23A
While every iceberg’s journey is unique, most follow the same general path. More than 90 percent of bergs around Antarctica enter the clockwise-flowing current of the Weddell Gyre off East Antarctica and eventually escape, shooting north along the Antarctic Peninsula and finally out across the Drake Passage into warmer South Atlantic waters—an ocean route known as “iceberg alley.”
But it’s not always a straight path to the Atlantic, even for giant bergs carrying a huge amount of momentum. For example, Iceberg A-68A, a similar mammoth-sized berg that broke from the Larsen C Ice Shelf in 2017, made some loops in the Drake Passage before continuing north and disintegrating in the Northern Scotia Sea near South Georgia island.
Trapped in a Taylor Column Vortex
The motion of A-23A, however, appears quite out of the norm. For about eight months, the berg rotated tightly within the Taylor column about 200 kilometers (120 miles) north of the South Orkney Islands. According to Jan Lieser, an ice specialist with the Antarctic Meteorological Service who has been tracking the berg, A-23A made 15 revolutions between March and November 2024. “I am not aware of an iceberg that has been trapped in such a persistent manner in such a small area,” Lieser said.
The animation at the top of this page shows the iceberg between November 5 and December 16, 2024. Notice that by about mid-November, the berg appears to “spin out,” escaping the vortex and resuming its northeastward journey. Images for the animation were acquired by the MODIS (Moderate Resolution Imaging Spectroradiometer) and VIIRS (Visible Infrared Imaging Radiometer Suite) instruments on several NASA and NOAA satellites.
Scientific Observations and Hypotheses
Christopher Shuman, a University of Maryland, Baltimore County, scientist based at NASA’s Goddard Space Flight Center, estimated that the berg drifted about 240 kilometers in one month since exiting the vortex. In other words, it traveled about 8 kilometers per day as it continued to rotate on its way to the northeast.
It is still unclear what might have nudged the berg from the vortex. “My hypothesis is that a random perturbation in the system might have triggered a slight variation of the ‘usual’ spin, such that the iceberg found an exit path,” Lieser said.
“This serves to remind us both of the mysteries of our oceans and the value of remote sensing data,” Shuman said. Cryospheric scientists will continue using satellites to observe changes to the ice in this remote part of the planet—including but not limited to icebergs.
NASA Earth Observatory images by Lauren Dauphin, using MODIS data from NASA EOSDIS LANCE and GIBS/Worldview, VIIRS data from NASA EOSDIS LANCE, GIBS/Worldview, and the Suomi National Polar-orbiting Partnership, and the Joint Polar Satellite System (JPSS). Map made using data from the Antarctic Iceberg Tracking Database and the U.S. National Ice Center(USNIC).
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6 Comments
Thank god for NASA. I’ve been worried sick about that trapped iceberg. Where can we go for the latest updates on ice, and will we ever find out how it was nudged due to climate change?
#FreeTheBerg
First There is no such scientific evidence such as climate change. The earth has changed multiple times since it’s Genesis beginning millions of years ago especially in the way it revolves around the sun. Man has only been in existence in just a miniscule time period and man has only extremely limited time to even understand the cycles of the way the earth even operates in the solar system and or how many times it’s weather pattern has changed. In the way these wacky liberal scientists try to predict the weather changes in our lives claiming that what we use in energy or as travel methods has bearing on the global weather changes are delusional. The earth does what it wants despite what we do here on earth. No I’m not a scientist, however I don’t need to be either it’s called COMMON SENCE
Do you mean common SENSE?
Thank you Mike
Can you imagine how the plant life would thrive with a higher level of carbon dioxide levels we actually would not need to use as much fertilizer that should make the oceans happy do people realize that one tambora size eruption might kill billions we might need the extra heat.
Mike’s you should not politicised comments about scientific measurements it just shows you lack common sense. I’m not a climate scientist but I can read a report by trusted sources.