World’s largest iceberg A-23A — a Reagan‑era megaberg that once was twice the size of Rhode Island — now racing toward complete disintegration
The world’s largest iceberg, A‑23A, is rapidly disintegrating in the South Atlantic after a 40‑year journey from the Filchner–Ronne Ice Shelf, and scientists warn the Reagan‑era megaberg could break apart completely within weeks, producing meltwater plumes and hazardous fragments.
- Decades-old megaberg: A‑23A calved in 1986 at ~4,000 km² — nearly twice Rhode Island — and remained grounded in the Weddell Sea for more than 30 years (Wikipedia; British Antarctic Survey).
- Rapid recent decline: After breaking free around 2020, A‑23A drifted north in 2023–24 and shed large pieces in 2025; by early 2026 its area was ~1,182 km² and collapse may be imminent (NASA; U.S. National Ice Center).
- Visible signs of failure: Satellite imagery reveals blue meltwater ponds, deep fractures, rampart–moat rims and freshwater “blowout” plumes that accelerate internal collapse (NASA).
- Scientific and operational concern: Researchers study the berg’s freshwater and minerals for Southern Ocean impacts, while authorities continue to track fragments to protect shipping (British Antarctic Survey; NOAA NESDIS).
How A‑23A began: the Reagan‑era calving
A‑23A formed in 1986 when a massive slab broke off the Filchner–Ronne (Filchner) Ice Shelf, creating an iceberg of about 4,000 km² — nearly twice the size of Rhode Island. NASA highlights the year as historical context (the Reagan era and Top Gun) while notes that parts of a Soviet Antarctic base were carried and later relocated after the calving (NASA; Wikipedia).
Grounded for decades in the Weddell Sea
A‑23A became grounded on shallow seabed features in the Weddell Sea and remained largely fixed for more than three decades, earning the “megaberg” label for its size and longevity. British Antarctic Survey records and satellite monitoring document its long residency and repeated contacts with sea ice that helped preserve it (British Antarctic Survey).
Breaking free and starting its northward trek
Around 2020 A‑23A finally freed from its grounding zone and began to drift. By late 2023 it had passed the northern tip of the Antarctic Peninsula and entered the Southern Ocean. UK teams encountered the berg in December 2023; the RRS Sir David Attenborough collected water samples to examine how the iceberg’s meltwater and dust affect plankton and local ocean chemistry (Wikipedia; British Antarctic Survey).
The Taylor column trap and delayed movement
In early 2024, A‑23A encountered a rotating ocean feature known as a Taylor column over Pirie Bank. Rather than moving steadily north, the berg spun in place for months, delaying its approach to South Georgia. Satellite and case-study analyses document that interaction and the later escape from the trap in late 2024 (EUMETSAT; Wikipedia).
From world’s largest to breaking up
By January 2025 A‑23A was widely tracked as the planet’s largest iceberg. As it moved north into warmer waters in 2025 it began shedding very large pieces; through late 2025 and into early 2026 numerous calvings and dangerous fragments were reported. Field and satellite observations in December 2025 and January 2026 revealed extensive surface melt, deep fractures and fresh plumes of meltwater streaming into the ocean (NOAA NESDIS; NASA).
What the imagery shows: blue water, fractures and “blowouts”
NASA Earth Observatory imagery (26 December 2025) shows bright blue meltwater ponds pooled in grooves and basins on the berg’s surface — a clear sign of intense surface melting. Images also reveal a rampart–moat rim that temporarily holds pooled water and a white freshwater plume or “blowout” where trapped meltwater vents to the sea, accelerating internal weakening (NASA).
Sizing up the numbers and estimates
At calving A‑23A measured ~4,000 km². By January 2025 some assessments still placed it near 3,500 km², and after heavy calvings in mid‑2025 the U.S. National Ice Center estimated its area at ~1,182 km² (456 sq mi) in early January 2026. The NIC operational iceberg table reports compatible measures in nautical units, and the berg remained larger than New York City in early 2026 (NASA; U.S. National Ice Center).
Why scientists are watching
Researchers value A‑23A as a rare natural experiment in how large ice masses behave when transported from cold polar shelves into warmer ocean regimes. Teams from the British Antarctic Survey and NASA — using field sampling and satellite remote sensing — are tracking how the iceberg’s freshwater, mineral dust and melt patterns influence Southern Ocean chemistry, phytoplankton blooms and local food webs (British Antarctic Survey; NASA).
Operational risks and navigation
Even as its main mass shrinks, A‑23A continues to generate hazardous fragments — some hundreds of square kilometers — that threaten shipping and research operations. Maritime authorities and monitoring services keep updating tracks and warnings to protect vessels and crews (NOAA NESDIS; US Ice Center).
Implications for Walla Walla, Washington
Economic impact: Walla Walla is not physically threatened by A‑23A, but global shipping connections mean iceberg-related disruptions in the South Atlantic could ripple into freight rates, scheduling and export windows for regional agricultural goods.
Political consequences: The event underscores the need for robust situational awareness and investment in satellite monitoring and international data sharing — areas where agencies such as the U.S. National Ice Center and NOAA NESDIS play key roles.
Social and cultural effects: Local businesses and exporters should monitor carrier notices; the story also offers historical resonance — a Reagan‑era berg that carried remnants of Cold War activity — and a reminder to sustain long‑term environmental monitoring.
Practical advice: Walla Walla residents face no direct danger. Exporters and policymakers should watch shipping advisories, maintain flexible logistics plans, and support resilient infrastructure and maritime data systems.
Ongoing monitoring and what to watch next
Scientists indicate A‑23A is likely days to weeks from complete disintegration as it drifts through warmer waters and currents that act as an iceberg “graveyard.” For updated imagery, operational tracking and field reports see sources below:
- NASA Earth Observatory
- U.S. National Ice Center iceberg products
- NOAA NESDIS tracking notes
- British Antarctic Survey field reports
“A‑23A offers an extraordinary, real‑time case study of megaberg decay and its consequences for ocean chemistry, ecosystems and maritime safety.”
Key references embedded in the article: NASA; Wikipedia; British Antarctic Survey; NOAA NESDIS; EUMETSAT; U.S. National Ice Center / US Ice Center.
