One of the largest icebergs ever discovered may be shrinking but robots are helping to provide valuable insights into its likely impact on the environment.

Robots are being deployed by the British Antarctic Survey and National Oceanography Centre to investigate the impact of a giant iceberg on one of the world’s most important ecosystems. Two underwater gliders have been launched from the RRS James Cook, some 200 km off the island of South Georgia, to investigate what remains of the enormous A-68 iceberg, which broke away from Antarctica’s Larsen C Ice Shelf in 2017, stretching for 5,800 sq km and weighing an estimated one trillion tonnes.

Iceberg breaks up

Since that calving event, the iceberg has slowly travelled thousands of kilometres, spirally northwards towards South Georgia and losing about half its surface area and about two-thirds of its original volume through melting. In recent months, it has shattered into smaller icebergs, 12 of which are still large enough to be officially named and tracked. The largest remaining piece, A-68a, is 50 km long and almost 900 sq km in area, similar in size to the Isle of Mull in Scotland.

Robots aid research

The gliders – used because it is too dangerous for the vessel to get too close to the giant iceberg – will spend almost four months collecting measurements of seawater salinity, temperature, and chlorophyll. The data will help the researchers understand the impact of extremely cold freshwater from the melting ice on phytoplankton, microscopic marine organisms that float in the water, which would then affect the wider food chain, from krill to the populations of seals, penguins and whales which all eat krill and come to South Georgia to feed.

A glider in the Antarctic (Credit: David White)

If the icebergs run aground in the shallow waters near the island, they may pose a risk to penguins and seals by disrupting the breeding season as well as damaging the seabed.

Unpredictability

The progress of the icebergs can be unpredictable.

“The main remnants of the berg are sitting on an ocean front (the Southern Antarctic Circumpolar Current Front), which is quite dynamic,” explained BAS Science leader Dr Povl Abrahamsen, currently on board the James Cook.

“And, indeed, the shear across the front has probably contributed to the breakup of A-68A as the berg was straddling the front. Satellite altimetry products can be helpful in predicting the future movement of the bergs, but at times it can seem like they have a mind of their own...”

The shipping angle

Tracking the icebergs is important because not only do they yield important scientific research, but they can also pose a risk to shipping.

“Modern radars are capable of detecting most icebergs,” said Dr Martin Collins, Science Manager for South Georgia at BAS.  “It is probably the smaller pieces – so called growlers – that present the greater threat, as they may go undetected on radars.  The area is not on a busy shipping lane, but in a normal year there would be numerous cruise ships in the area.  This season, there is less shipping than normal, but there are research vessels, fishing vessels and fishery patrol vessels operating in the area.”

Whilst this is thought to be a natural calving event, models predict that future warming will lead to a greater frequency of such events, he added. This is already evident in the Arctic, where rising temperatures have had marked impacts on sea ice, glaciers and iceberg activity.  The number of icebergs moving south of 48 degrees latitude, where they can pose a threat to trans-Atlantic shipping and the oil and gas rigs offshore Newfoundland and Labrador, varies from year to year and is closely monitored.  

“Ice can be difficult to detect using conventional radar as the bounce back signal is weak and can get confused by waves and other so-called sea clutter,” said Bruce McMichael, editor of Frontier Energy, which covers shipping and offshore activities in ice-affected regions. “Mariners need to treat ice with great respect. Fortunately, cutting-edge technology is making ice more visible to vessels, with tech companies such as Canada’s Rutter Inc. and Furuno of Finland developing sophisticated radar capable of detecting and monitoring icebergs and finding the optimal route through ice in all weather conditions.”

Amy McLellan is a journalist and author. She was previously editor of Energy Day. Twitter @AmyMcLellan2