Giant iceberg mission begins | Polarjournal
From aboard the National Oceanographic Centre’s research vessel RRS James Cook, scientists will take a closer look at the impact of the iceberg giant. Photo: National Oceanographic Centre

A research mission to determine the impact of the giant A-68a iceberg on one of the world’s most important ecosystems departs from Stanley in the Falkland Islands today (2 February 2021). A team of scientists, led by British Antarctic Survey (BAS), will set sail on the National Oceanography Centre’s (NOC) ship bound for the sub-Antarctic island of South Georgia.

Map left: A-68a set course for South Georgia for a long time until it was deflected by currents to the southeast and later broke into several large icebergs and thousands of small ones. Source: Laura Gerrish. Image at right: Copernicus Sentinel-1 satellite image from February 1, 2021 shows the large fragments of the former giant iceberg. Photo: ESA

The giant iceberg A-68a, which broke off the Larsen C ice shelf in Antarctica in 2017 and set a direct course for South Georgia for some time, has many scientists concerned about the potential negative impact on penguins and other wildlife living there. After satellite images revealed its movement towards South Georgia, the science team put a proposal to NERC to fund an urgent mission south. Images captured from the air by the Ministry of Defense in late 2020 show that the iceberg is breaking up. It now consists of several icebergs named A68a-m. The team will investigate the impact of freshwater from the melting ice into a region of the ocean that sustains colonies of penguins, seals and whales. These waters are also home to some of the most sustainably managed fisheries in the world.
Underwater robotic gliders will be deployed from the NOC research ship RRS James Cook, which will arrive at the icebergs in mid February.

«We have a unique opportunity to visit the icebergs. 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 icebergs 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.»

Dr Povl Abrahamsen, Oceanographer with the British Antarctic Survey and mission leader
Underwater gliders are small submersible robotic vehicles, which are designed to operate autonomously for months at a time. Rather than using a propeller, they move by changing their buoyancy, and wings convert this into forward motion. While “flying” through the water, sensors can measure temperature, salinity, chlorophyll, and other parameters. At regular intervals, the gliders will surface, check their position by GPS, transmit data back to servers in the UK, and check for new instructions on where to go. Photo: David White

The two 1.5-metre long untethered submersible gliders will spend almost four months collecting measurements of seawater salinity, temperature, and chlorophyll from opposite sides of the largest sections of iceberg, piloted over satellite link by personnel at NOC and BAS. The team 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.

Waters around South Georgia are recognised as one of the most biologically rich places on the planet with more described marine species than the Galapagos, and is one of the world’s largest Marine Protected Areas. The icebergs, if they grounds near the island, pose a risk to penguins and seals during the breeding season.

«The icebergs are going to cause devastation to the sea floor by scouring the seabed communities of sponges, brittle stars, worms and sea-urchins, so decreasing biodiversity. These communities help store large amounts of carbon in their body tissue and surrounding sediment. Destruction by the icebergs will release this stored carbon back into the water and, potentially, the atmosphere, which would be a further negative impact», Professor Geraint Tarling, ecologist with the British Antarctic Survey, explains. «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.»

This satellite image taken on January 31, 2021 shows several large fragments and countless smaller icebergs in their vicinity, bringing large amounts of fresh water into the region and also posing a hazard to ship traffic. Photo: ESA

Andrew Fleming, Head of Remote Sensing at BAS, has been tracking the iceberg’s journey on images from the Copernicus Sentinel-1 and other satellites. He says: «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. 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 research expedition to A-68a has been funded by a combination of the Natural Environment Research Council, the Government of South Georgia and the South Sandwich Islands, and the UK Government’s Blue Belt Programme.

Source: British Antarctic Survey

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