The Life of the A68 Iceberg and Why it is Exciting

It’s not very often that we get to find out about the life of an iceberg, if we even consider it at all, but recent news stories have given us the chance to get a closer look at these shimmering walls of ice which glide like ghosts throughout our more remote waters.

Fresh water which freezes on land can transform into bright blue glaciers and when a chunk of ice calves or breaks off from these glaciers and ice shelves, icebergs are formed. In the Southern Ocean, almost all icebergs originate from Antarctica and can range in size from boat sized chunks to floating masses which are the same size as small countries! Any chunk of ice smaller than five metres across doesn’t quite achieve iceberg status and is known as a ‘bergy bit’ or a ‘growler’ instead. Once free from the shackles of the glacier, the iceberg drifts with the ocean currents and can either wash up on a distant shore or travel into warmer waters where it melts into the sea. Sometimes, the warm air tickles the surface of the iceberg and melts the snow on top into ‘melt ponds’ and this water can trickle through the ice where it causes wide cracks which eventually contribute to the breakdown of the berg. Scientists have estimated that the average life of an iceberg is 3,000 years from when those first flakes of snow gently flutter to the ground right through to the iceberg calving off, roaming with the currents and finally melting into seawater.

The A68 iceberg has hit the headlines frequently over the last few months and is now in contention for the most famous iceberg in the world, losing only to the berg which sank the Titanic. The A68 iceberg calved from the Larsen C ice shelf in Antarctica in July 2017 and formed the largest iceberg in the world. Since then, researchers have been tracking its movements via satellite and with such an immense size, its journey has not been hard to follow. When the Titanic sank in 1912, 13 countries joined together to form the International Ice Patrol which uses airplanes and radars to track icebergs which float into major shipping lanes and cause a dangerous hazard. Only around one-eighth of an iceberg is visible above water so detecting some of these obstacles from a boat is incredibly tricky. Today, satellites also monitor large icebergs in remote areas and so A68 definitely made it onto the Ice Patrol’s radar.

A crack first formed in the Larsen C ice shelf in 2010 and when the A68 iceberg finally broke free, it took almost 10% of the whole ice shelf with it. This enormous iceberg broke records at 175 kilometres long and 50 kilometres wide, making it a quarter of the size of Wales. Scientists have estimated that its blue glassy walls stretched 500 feet deep whilst it weighed approximately one trillion tonnes! The sheer size of this iceberg attracted a lot of scientific and public attention whilst it posed a lot of new questions to researchers in many fields. Biologists wanted to know what would happen to surrounding ecosystems and whether new ones would appear or old ones be damaged. Climate scientists wondered whether more gigantic icebergs would break from the Larsen C ice shelf under climate change and therefore potentially destabilise the inland ice lying behind it. Oceanographers discussed how the iceberg would interact with ocean currents and if its melting would impact the salinity of the surrounding sea.

So the A68 iceberg had a lot of eager followers as it drifted up and down the coastline in the Weddell Sea but it wasn’t until February 2020 that it started drifting away from the tip of the Antarctica Peninsula and headed on a more distant voyage. From the remote edges of the peninsula, the iceberg was whisked away by the strong Antarctic Circumpolar Current which circles the continent. Excitement turned to anxiety in December however, as scientists plotted that the world’s largest iceberg was set on a collision course with the island of South Georgia. South Georgia is a wildlife haven and one of the wildest landscapes left on Earth. It is home to only a handful of humans but hundreds of thousands of penguins, as well as seals, seabirds and a small population of endangered blue whales. Despite being a relatively unknown island, it has enough biodiversity to rival the famous Galapagos Islands, especially when you consider the amount of marine life living under the cool waters. Down near the seabed live brittle stars, sea urchins, worms, sponges, fish and krill which are an essential food source for some our planet’s largest creatures, such as whales. Scientists became worried that this enormous iceberg would become grounded on the shallow undersea shelf near the island and block the path of penguins and seals travelling from breeding grounds to feeding spots on the coastal shelf. This caused biologists, in particular, to worry about the delicately balanced life of many of the species which call the remote island home. Recent satellite images however, show that the iceberg has indeed come to rest on the undersea shelf but it is now breaking up into smaller and smaller chunks and is already only a third of its original size. The smaller icebergs are circumnavigating the island and being carried north by the current and with them, the A68’s grand title and claim to fame as the largest iceberg in the world is lost too.

Whilst this melting of the iceberg means that it doesn’t have quite such a menacing presence on the island, blocking the well-worn paths of penguins and seals, the impact of the melting water is something which is debated. As the weak sun and warmer waters chip away at the ice, they cause fresh water to pour out into the ocean and impact salinity levels in the immediate surrounding area. Some scientists believe this will upset the fragile balance of life around South Georgia with algae and plankton struggling to adapt quickly to less salty conditions. If these organisms see a decline in their numbers, then larger feeders such as fish, penguins and even whales could suffer a drop in available food. Yet other scientists state that as the ice melts, nutrients from the earth which have been locked away for centuries in the ice will now be released into the sea. These nutrients could contain useful elements, such as iron, which can actually help boost productivity and cause a boom in the number of plankton and algae. Research carried out in remote frozen waters has shown that icebergs tend to have an abundance of life circling them due to the nutrients and shelter they provide and in turn they create feeding hotspots. However, the processes which play out in the icy realms of our planet are still relatively unknown and the massive complex web of natural interactions means that almost anything could happen.

With so many speculations and uncertain ideas surrounding the life of icebergs, it will be interesting to see what researchers discover from following the movements of A68. Currently, scientists are using robot submarines to investigate the iceberg to help advance our knowledge of this hidden corner of the world. The robots can be controlled remotely, even all the way from the UK, and can adjust their buoyancy so they will be able to measure temperature, salinity and chlorophyll at different depths of the ocean. They hope this data will be able to give us some more information about how the melting of icebergs impacts local sea conditions and marine life whilst also giving us an idea of what could happen under climate change. Whilst it is difficult to attribute this one event to climate change, scientists are eager to document its journey and breakdown so they can include the processes in their climate models to help increase their accuracy. With so much research going on in the Antarctic at the moment to document this enormous event, it will be exciting to follow their results and potentially witness a key scientific discovery which could go down in history.

By Neve McCracken-Heywood