A frosty ecological drama has come to an end with the British Antarctic Survey (BAS) declaring the giant iceberg A-68a is no more. The science mission to monitor the berg has now been wound up because A-68a has broken up into disintegrating fragments that are now too small to track.
In July 2017, one the largest icebergs on record broke away from the Larsen Ice Shelf in Antarctica. Measuring 2,187 square miles (5,664 sq km) and, on average, 761 feet (232 m) thick, it generated some scientific interest, but as it drifted out to sea, it dropped out of the public's eye.
Then, in 2020, satellite images and military recon flights showed that the giant iceberg was on a collision course with South Georgia Island in the South Atlantic, which is one of the world's largest marine nature reserves. This raised the alarm that A-68a could collide with the island or run aground in the wide shallows, tearing up the seabed, disrupting the feeding routines of the local seals and penguins, and flooding the coastline with fresh water.
Fortunately, A-68a broke up rapidly into large fragments and currents deflected it from South Georgia and back into open water. As it did so, researchers and engineers, from BAS and the National Oceanography Centre (NOC) set out aboard the research ship RRS James Cook.
The mission of this team was to monitor the impact of A-68a on the local environment whether it collided with South Georgia or not. As part of this, they deployed two oceanic gliders called "Doombar – 405" and "HSB – 439" about 124 miles (200 km) off the island to measure seawater salinity, temperature, and chlorophyll.
These robotic craft operated so near the iceberg that Doombar was run over and had to spend two weeks under the ice. Though the James Cook has returned to Southampton, UK, the gliders will continue to operate until they are retrieved in May 2021.
"The threat posed by the A-68a mega-berg to the South Georgia ecosystem was substantial given its sheer size and potential to disrupt all parts of the food web," says Professor Geraint Tarling, an ecologist at the BAS. "The glider mission allowed us to obtain unique insights into how the marine environment was affected. The extremely strong currents around South Georgia ultimately came to the island’s rescue in diverting the iceberg away from a catastrophic coastal collision. We are now eager to analyze the data to assess how the natural balance of the South Georgia ecosystem was affected by the trail of meltwater and nutrients left in the iceberg’s wake."
The video below recaps the BAS mission to A-68.
Source: BAS