The world’s largest iceberg, A23a, has been spinning., UPSC.

Description

A23a

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Context: World’s largest iceberg A23a stuck in circles after breaking free.

What is an Iceberg?

An iceberg is a large pieces of freshwater ice that broke off from glaciers or shelf ice and is floating in open water. (This process is called calving).
To be classified as an iceberg, the height of the ice must be greater than 16 feet above sea level and the thickness must be 98-164 feet and the ice must cover an area of at least 5,382 square feet.

About Iceberg A23a

Name	A23a.
Origins and discovery	Iceberg A23a calved from the Filchner–Ronne Ice Shelf in 1986 (Part of Antarctic ice sheet).
The title of world’s largest iceberg	Its current title as the world’s largest iceberg, broke the Guinness World Record. The previous largest iceberg, A76, detached from the Weddell Sea ice shelf in May 2021 but has since broken into three pieces. One of the most notable was Iceberg A-68, which calved from the Larsen C Ice Shelf in Antarctica in July 2017. At the time of its calving, A-68 was one of the largest ever recorded, measuring about 5,800 square kilometers (2,240 square miles) in area, roughly the size of Delaware or the island of Trinidad. Over time, these massive icebergs break into smaller pieces and eventually melt.
Size and structure	4,000 sq km (1,500 sq miles) in area. 400m (1,312 ft) thick. A23a is comparable in size to major global cities. Eg-
Movement	A23a, grounded to the ocean floor for 30 years, is now drifting northwards due to wind and ocean currents. The iceberg is moving at about 30 miles per day and may enter “iceberg alley” towards South Georgia. (The iceberg is in an area of the Southern Ocean known as Iceberg Alley, a popular spot for icebergs). In November 2023, A23a was tracked moving past the northern tip of the Antarctic Peninsula and heading towards the Southern Ocean.
Erosion and transformation	The erosion process involves powerful waves hitting the iceberg’s base, creating small gaps that eventually widen into caves and arches, leading to the collapse of the ‘roof’ or the top ice layer. This leaves behind smaller stacks that eventually melt away.
Impact on the environment	It influences the oceanic currents and the marine ecosystem. Immense size acts as a floating barrier, redirecting water flows and potentially altering weather patterns. Its gradual melting process releases vast amounts of freshwater, impacting the salinity of the surrounding ocean, which can have far-reaching effects on marine life.
Scientific significance	Scientists employ satellites, drones, and ship-based observations to track its movement and study its impact. This research offers insights into the behavior of icebergs and the broader implications for global climate patterns. The data gathered helps refine models predicting the response of polar regions to climate change.
Iceberg A23a and climate change	The A23a is intrinsically linked to the narrative of global warming. The increasing rate of iceberg calving in Antarctica raises concerns about the stability of ice shelves and the potential for accelerated sea-level rise. While its contribution to sea-level rise is minimal compared to glacial meltwater, it symbolizes the larger, more pressing issue of our warming planet.

Recent Finding

The A23a iceberg is spinning nearthe South Orkney Islands, about 375 miles northeast of the Antarctic Peninsula, “maintaining a 15 degree rotation per day”.

Reason

Typically, large icebergs move through quickly and get sucked into the Antarctic Circumpolar Current.
The blocks of ice eventually get shot out eastward to warmer waters, where they begin to melt and disintegrate. (transition described as “a warm bath of water” only a couple of degrees above freezing)

However, A23a got caught in the Taylor column, a current that forms around seamounts.
The normal water flow diverges around the underwater mountain, forming a stagnant cylinder of fluid above the seamount. This causes the water to slowly rotate counterclockwise around the bump.
The bump A23a is swimming over is about 100 kilometers across (about 62 miles) and rises up from the deep sea floor to a height of about 1,000 meters (3,280 feet).

Taylor column and Sea mount

Seamount

A seamount is a large submarine landform that rises from the ocean floor without reaching the water surface (sea level), and thus is not an island, islet, or cliff-rock.
Most seamounts are remnants of extinct volcanoes.
Typically, they are cone shaped, but often have other prominent features such as craters and linear ridges and some, called guyots, have large, flat summits.

Taylor column

A Taylor column is a fluid dynamics phenomenon that occurs as a result of the Coriolis effect. It was named after Geoffrey Ingram Taylor.
Rotating fluids that are perturbed by a solid body tend to form columns parallel to the axis of rotation called Taylor columns.
Taylor Columns can also form in the air. Eg- The movement of clouds above mountains.

Currents Around Seamounts

When ocean currents flow past seamounts, they are diverted over and around the summit.
In certain cases, these flows may produce a Taylor column, which is a closed circular eddy that can persist for long periods.