Boaty McBoatface AUV successfully completes first under-ice Antarctic mission

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Last week, the National Oceanography Centre’s (NOC) Autosub Long Range (ALR) AUV —popularly known around the world as ‘Boaty McBoatface’—was successfully recovered following its first under-ice mission beneath the Filchner Ice Shelf in West Antarctica.

The AUV was deployed in the southern Weddell Sea from January to February 2018 during RV Polarstern cruise PS111, as part of the Filchner Ice Shelf System (FISS) Project, which is a collaboration that involves several leading UK research institutions, including the NOC.

The AUV plays an important role in the project that aims to investigate and describe the “current state of the complex atmosphere-ice-ocean system.”

Boaty spent a total of 51 hours under the Antarctic ice, and over the duration of its deployment, it traveled 108 kilometers.

Boaty reached water depths of 944 meters, and spent 20 hours exploring beneath a section of the ice shelf that was 550 meters thick.

“I am delighted in the success of this mission,” says Steve McPhail, Head of AUV Development at the NOC. “For the engineers involved, this was a very challenging deployment that was not without risk.”

​There were a variety of factors that made the deployment challenging, according to McPhail. There was the harsh environment, with -20 Celsius air temperatures and sea temperatures very close to the freezing point of seawater. Also, under the ice shelves there are significant tidal currents, and the AUV’s underwater navigation was challenged by the “high southerly latitudes.”

McPhail adds that once the AUV was in the shelf cavity, they had no detailed information on the thickness of the ice, or on the depth of the water.

“We had no communication with the AUV for 90% of its time in the water,” McPhail says. “Waiting for the AUV to return after a 48-hour mission into a largely unknown environment is, to say the least, exciting, and as a result I was very relieved each time the AUV turned up, on time, and in the right place, circling 900m below the ship.”

​The problems weren't over with then, though, according to McPhail, as he says, “with the surface of the sea frozen, we needed RV Polarstern’s help to create an ice hole through which we carefully navigated the AUV.”

Boaty carried two sets of CTD (Conductivity, Temperature and Depth) sensors, which measured the water’s salinity and temperature. The AUV was also equipped with a “micro-structure probe” to measure ocean turbulence, a sensor to measure the amount of phytoplankton in the water (by measuring the fluorescence of their chlorophyll) and a sensor to detect the turbidity of the water.

Acoustic instruments (ADCPs) also measured the water current up to 80 meters above and below the AUV’s position, and accurately measured the depth of the seabed, and the draft of the ice along the vehicle’s track.

According to the NOC, the Filchner-Ronne Ice Shelf is the second largest of its kind in the world. It covers an area of around 450,000 square kilometers, meaning that it holds a greater volume of ice than any other floating glacier tongue.

Climate researchers are especially interested in whether more glacial ice is currently being transported into the ocean, being that this process is related to rising sea levels. Also, so-called ‘deep water’ forms near the ice shelf, which is a key driver of global ocean circulation, and ultimately causes an impact on the climate system everywhere on the planet.

“Understanding the contribution that polar ice sheets make to global sea-level rise is recognized internationally as urgent,” says Prof Adrian Jenkins from British Antarctic Survey, who is leading the investigation.

“The data from this mission are critical for assessing the future stability of Antarctica’s Filchner Ice Shelf. The ALR has enabled us to take a small step towards our goal of producing credible sea-level projections for the next 50 years.”

Science Minister Sam Gyimah adds, “global warming is one of the greatest challenges we face today. Boaty’s maiden under-ice voyage provides scientists with a greater understanding of the changes that are occurring in Antarctica, which could have a colossal impact on our planet – but, this is only the tip of the iceberg.”