British Antarctic Survey scientists lead urgent mission to South Georgia to assess impact of huge iceberg
Scientists from the British Antarctic Survey (BAS) in Cambridge will lead an urgent research mission to assess the impact of a massive iceberg on one of the world’s most important ecosystems.
They will set sail in late January for the sub-Antarctic island of South Georgia from the Falkland Islands on board the National Oceanography Centre’s (NOC) ship RRS James Cook.
Using robotic gliders, they will spend four months taking measurements to understand what effect the giant A-68a iceberg is having in the region.
It broke away from Antarctica’s Larsen C Ice Shelf in 2017 and is now 3,900 sq km in area.
The team put in a proposal to NERC (Natural Environment Research Council) to fund the mission south after satellite images from the Ministry of Defence (MoD) revealed the berg was moving towards South Georgia.
They will investigate the impact of freshwater from the melting ice on a region of the ocean that sustains colonies of penguins, seals and whales and which is home to some of the most sustainably managed fisheries in the world.
Leading the mission is BAS oceanographer Dr Povl Abrahamsen, who said: “We have a unique opportunity to visit the iceberg.
“Normally, it takes years to plan the logistics for marine research cruises, but NERC, working with the government of South Georgia and the South Sandwich Islands and the UK government’s Blue Belt Programme, recognised the urgency to act quickly, allowing us to study the iceberg during an upcoming voyage to monitor the ecosystem and climate of the Southern Ocean.
“Everyone is pulling out all the stops to make this happen.”
The waters around South Georgia are one of the most biologically rich places on the planet. There are more described marine species there than in the Galapagos, and it is one of the world’s largest Marine Protected Areas.
There are concerns that if the huge iceberg grounds near the island, it will pose a risk to penguins and seals during the breeding season.
Professor Geraint Tarling, an ecologist at British Antarctic Survey, said: “Icebergs are really interesting because they bring lots and lots of fresh water into a marine system - a salty system - and actually relatively warm water for the Southern Ocean. You have animals and plants that are adapted to those conditions that are going to be faced with an instantaneous change in their environment and that will stop them from thriving.”
The impact, he said, would be particularly felt by plants, which might not grow as well. This will leave less food for zooplankton and krill, which are in turn the food for seals and penguins. Further impacts will be caused by the grounding.
“The iceberg is going to cause devastation to the sea floor by scouring the seabed communities of sponges, brittle stars, worms and sea-urchins, so decreasing biodiversity,” he said.
“These communities help store large amounts of carbon in their body tissue and surrounding sediment. Destruction by the iceberg will release this stored carbon back into the water and, potentially, the atmosphere, which would be a further negative impact.
“However, whilst we are interested in the effects of A-68a’s new arrival at South Georgia, not all the impacts along its path are negative. For example, when travelling through the open ocean, icebergs shed enormous quantities of mineral dust that will fertilise the ocean plankton around them, and this will benefit them and cascade up the food chain.”
The researchers will deploy two 1.5-metre long untethered submersible gliders to measure seawater salinity, temperature and chlorophyll from opposite sides of the iceberg, piloted over satellite link by personnel at NOC and BAS.
They will also measure how much plankton is in the water and compare their findings with long-term oceanographic and wildlife studies around South Georgia and nearby Bird Island.
Rather than using a propeller, these autonomous gliders move by changing their buoyancy, which their wings convert into forward motion.
Their sensors collect data as they “fly” through the water and this is transmitted at regular intervals back to servers in the UK when the gliders surface to check their position by GPS and check for new instructions on where to go.
Steve Woodward, the NOC’s glider technical lead, who will be managing the National Marine Equipment Pool (NMEP) glider operation, explained:“Autonomous submarine gliders are an excellent, cost-effective and sustainable means of gathering and recording important marine data.
“In this case, we will program the NMEP gliders to get as close to the edge of the iceberg as we feel is safe and practicable, and collect the data that will be needed to enable the team to understand the implications of what is taking place with A-68a.”
In addition to underwater studies, the researchers are also monitoring the iceberg from space.
Andrew Fleming, head of remote sensing at BAS, has been tracking its journey using images from satellites, including Copernicus Sentinel-1.
“We are watching the progress of the A-68a iceberg very closely as we haven’t seen a berg of this size in the area for some time,” he said. “As it breaks up, thousands of smaller icebergs have the possibility to obstruct shipping lanes in the area, especially as they disperse.
“The European Space Agency has delivered regular Sentinel-1 images and we will use these to continue tracking in the coming months.
“The images and footage collected by MoD flight missions have helped enormously in confirming some of the features we can see in the images from space. Close-up images provide detail on how the berg is starting to break up and allow us to better understand these processes.”
The expedition to A-68a has been funded by a combination of the NERC, the Government of South Georgia and the South Sandwich Islands, and the UK government’s Blue Belt Programme. Madingley Road-based BAS is an institute of NERC.
Lord Goldsmith, the UK’s minister for Pacific and the environment, said: “We need to understand the effects that huge icebergs can have on wildlife and marine life, so I’m delighted the Blue Belt Programme, which works with British Overseas Territories to protect and sustainably manage their waters, is able to support this critically important research mission.”
A-68a is the largest remaining section of the iceberg that broke off the ice shelf. While the calving is thought to have been a natural event and not directly attributed to climate change, models predict more events like it in future as Antarctica warms and ice shelves and glaciers retreat.
Dr Mark Belchier, director of fisheries and environment for the government of South Georgia and the South Sandwich Islands (SGSSI), added: “With such events predicted to increase in frequency, understanding their impacts on SGSSI’s ecosystem is essential for informing the government’s sustainable stewardship of the territory”.
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