The iceberg that was about to strike an island in the Atlantic …

he iceberg I was about to hit an island in the South Atlantic finally broken into several pieces. This is illustrated by the latest satellite images from the A-68A, one of the largest icebergs of all time, in which two large fragments of ice detached from the block stand out and float in the open sea.

The colossal iceberg has drifted slowly north since breaking away from the Larsen-C pack ice in July 2017. Since then, it has been floating dangerously close to the South Georgia archipelago for a month and it threatened to produce an ecological catastrophe if it struck the island of San Pedro. This risk still persists.

Marine scientists fear their presence could damage the fragile ecosystem that thrives around the island.Either by scraping the keel of the iceberg on the seabed, or by the massive discharge of cold fresh water into the surrounding ocean. The proximity of the iceberg depends on the depth of its keel.

Using data from four different satellites, scientists at the Center for Polar Modeling and Observation at the University of Leeds produced the first assessment of the changing shape of the iceberg. The team first constructed a map of the initial thickness of the icebergs from measurements recorded by the radar altimeter of ESA’s CryoSat satellite during the 12 months prior to their separation from the ice front off the coast of the Antarctic Peninsula.

This detailed map reveals that the A-68 was originally, on average, 232 meters thick and 285 meters at its thickest point. The iceberg had channels 30m deep oriented parallel to its narrow side following the direction in which the Larsen Ice Shelf poured into the sea before breaking up, a common feature linked to the melting of the ocean.

Iceberg volume fell 64%

The pictures show that the iceberg was halved from an initial area of ​​5,664 square kilometers to its current expansion of only 2,606 square kilometers. Much of this loss is due to the creation of small icebergs, some of which are still afloat.

Iceberg height profiles have also been recorded eight times, as it has drifted and circled in the ocean by CryoSat and by NASA’s ICESat-2 laser altimeter, which has been in orbit since September. 2018. The coincident satellite images made it possible to orient the altimetric height profiles in relation to the initial position of the icebergs and to calculate their change in thickness over time.

On average, the iceberg thinned 32 meters and more than 50 meters in places, or about a quarter of its initial thickness. When combined, the change in thickness and area is equivalent to a 64% reduction in iceberg volume from 1,467 to 526 cubic kilometers.

The future trajectory of the iceberg depends on the depth of its keel in relation to the surrounding ocean. The island of San Pedro is surrounded by relatively shallow shelf waters that stretch for tens of kilometers beyond its shore.

In its thickest section, the A-68A iceberg currently has a keel depth of 206 meters, so the main section is unlikely to move much closer to the island until it s thins or breaks. However, two relatively large fragments that broke off on December 21 are considerably thinner, with pins up to 50 meters shallower, posing the greatest immediate threat.

Since its release, the average melting rate of A-68 was 2.5 centimeters per day and the iceberg is now pouring 767 cubic meters of fresh water per second into the surrounding ocean.