A massive 40-year-old iceberg, once the largest on Earth, is currently drifting into the South Atlantic Ocean, where it is expected to gradually melt away. Known as A-23a, this iceberg broke off from Antarctica in 1986 and has been closely monitored by scientists over the years. Recently, attention has been drawn to A-23a due to its striking blue pattern, as captured in NASA satellite images shortly after Christmas.
Originally part of Antarctica’s Filchner Ice Shelf, A-23a calved in 1986, forming a tabular iceberg of around 4,000 square kilometers, weighing over one trillion tonnes. After remaining relatively stationary in the Weddell Sea for years, it began its journey north along the Antarctic peninsula in 2020. Currently, it is near South Georgia island, having significantly reduced in size to approximately 781 square kilometers as a result of calving in warmer waters.
Retired scientist Chris Schuman believes that A-23a is unlikely to survive the Southern Hemisphere’s summer. The iceberg’s distinct blue appearance is attributed to accumulations of meltwater on its surface, causing cracks to expand under the weight of the water. This phenomenon is explained by Ted Scambos, a senior research scientist, as the flow of meltwater being directed by parallel ridges on the ice.
While white and blue are typical iceberg colors, green, yellow, and even black icebergs have been observed in the Weddell Sea. Emerald or jade hues could result from ice reflecting the color of phytoplankton in the water, while yellow icebergs may contain iron oxide dust picked up from Antarctica’s bedrock. The appearance of rare black icebergs, like one spotted off Labrador’s coast, remains a subject of intrigue and speculation.
As icebergs like A-23a venture into warmer waters away from Antarctica, they face disintegration in what is known as the “iceberg graveyard.” The Weddell Sea gyre, a clockwise current, pulls icebergs northward along a route that leads to their demise as they drift into the Scotia Sea and the Drake Passage. Warmer waters at these latitudes pose a significant threat to icebergs, accelerating their melting process.
The fate of A-23a is uncertain, with recent satellite imagery indicating significant breakage. As icebergs continue their journey into warmer waters, their eventual demise is almost inevitable.