A colossal iceberg known as A23a has captured the attention of scientists worldwide due to its staggering size. Recent satellite measurements have revealed that the iceberg has an average thickness of over 280m, making it one of the thickest icebergs ever recorded. With an area of 3,900 sq km and a volume of approximately 1,100 cubic km, A23a boasts a mass just shy of a trillion tonnes. This remarkable feat of nature has piqued the interest of researchers as it reaches a critical point in its journey, with its future trajectory heavily dependent on the next few weeks in the treacherous Southern Ocean.
To grasp the scale of A23a, it is akin to the height of London’s renowned skyscraper 22 Bishopsgate, standing at 278m tall. It surpasses numerous architectural marvels in the UK, including the iconic 310m Shard tower. However, what truly sets A23a apart is its expansive area, which is more than double the size of Greater London. In fact, its overall profile is strikingly similar to that of a credit card, further highlighting its monumental dimensions.
The indispensable measurements of A23a were obtained through the European Space Agency’s CryoSat-2 mission. This ground-breaking spacecraft possesses a radar altimeter that accurately determines the portion of an iceberg that remains above water. Using this information alongside ice density data, scientists can deduce the submerged section. Dr. Anne Braakmann-Folgmann from the University of Tromsø – The Arctic University of Norway explains that altimetry satellites like CryoSat-2 provide invaluable insight into monitoring iceberg thickness from space. Moreover, these satellites enable scientists to monitor changes in iceberg thickness as it encounters warmer ocean waters. With knowledge of the sea-floor topography, researchers can predict both grounding and the release of icebergs.
Prior to 2020, obtaining comprehensive thickness measurements of A23a was relatively straightforward. However, as the iceberg commenced its movement, it became increasingly challenging to collect accurate data. By assuming an average total thickness of 285m and an area of 3,900 sq km, scientists approximated a volume of 1,113 cubic km and a mass of 950 billion tonnes. Originating from a mass breakout of icebergs from the Filchner Ice Shelf in the southern Weddell Sea, A23a spent over three decades trapped in shallow bottom muds, earning its status as an “ice island.” The CryoSat data has now elucidated the reasons behind this prolonged entrapment, revealing that the iceberg is not a uniform block. Certain sections possess significantly greater thickness, with one particular segment harboring an extraordinarily deep keel. In 2018, this segment had a draft of nearly 350m, firmly anchoring A23a in place. Satellite images even depict surface crevasses directly above the keel, resulting from the iceberg’s violent collision with the sea-floor. In subsequent years, A23a gradually shed mass, eventually freeing itself and commencing its journey.
The iceberg has now reached the tip of the Antarctic Peninsula, encountering the convergence of various fast-moving water streams that circulate clockwise around the continent. Its interaction with these currents and the prevalent westerly winds in the vicinity will dictate its future path. Scientists anticipate that A23a will traverse “iceberg alley,” a route pointing towards the British overseas territory of South Georgia. This awe-inspiring iceberg’s progress will be meticulously monitored by researchers due to its substantial impact on the surrounding environment. Icebergs of this magnitude induce profound effects in the oceans by initiating deep mixing of seawater. As a direct consequence, nutrients rise to the surface, fostering phytoplankton blooms. Moreover, these colossal ice islands deposit copious amounts of dust, further contributing to the ocean’s fertilization.
In conclusion, the revelation of A23a’s true scale and massive dimensions has captivated scientists. As this monumental iceberg embarks on its perilous journey beyond the Antarctic coast, its future trajectory in the Southern Ocean hangs in the balance. The satellite measurements obtained from CryoSat-2 have shed light on the complex dynamics of this behemoth and its prolonged entrapment. The impact of such colossal icebergs on oceanic ecosystems cannot be overstated, as they induce essential mixing of seawater and nutrient enrichment. Therefore, ongoing monitoring of A23a’s progress is crucial to gaining a deeper understanding of these remarkable natural phenomena that shape our world.
