Underwater robots to examine Thwaites Glacier’s impact on sea level rise

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A research mission comprising 32 international scientists and a fleet of underwater robots has set out to determine the impact of Thwaites Glacier in West Antarctica on global sea-level rise – through measuring the temperature, salinity, current velocity, turbulence, turbidity, dissolved oxygen, chlorophyll, subsurface light levels, ambient noise and pH of the water.

The research party departed on the US National Science Foundation icebreaker Nathaniel B Palmer from Punta Arenas, Chile, on January 6. The mission forms part of the International Thwaites Glacier Collaboration (ITGC), a five-year, US$50m joint US and UK mission to learn more about the Thwaites Glacier, its past, and future weather events.

The 65-day voyage, led by scientists from the University of East Anglia (UEA), along with researchers and engineers from Sweden and the USA, will investigate atmospheric and oceanic conditions close to the glacier’s ice shelf. Boaty McBoatface, the state-of-the-art Autosub Long-Range (ALR) vehicle operated by the National Oceanography Centre, will travel under the ice shelf along with Ran, a Hugin robot, from the University of Gothenburg in Sweden, while six ocean gliders patrol the entrances and exits to the ice shelf cavity. The fleet will explore largely uncharted territory, to measure geometry and melting processes, the seafloor below, the ice thickness above and water properties in between.

Boaty McBoatface will be controlled from the Nathaniel B Palmer using the NOC-developed Command and Control system (C2), which can re-task the robot over wi-fi, via Iridium satellite or using an acoustic modem once it is submerged. The ALR will measure temperature, salinity, current velocity, turbulence, turbidity and dissolved oxygen content of the water, while surveying several transects from the edge and toward the grounding line of the ice shelf. Depending on sea ice conditions, the shortest ALR dive could be a 24-hour, 55km round trip, or, if the ice is favorable, dives could last up to three days, or a 150km round trip.

As the ALR vehicle will travel through potentially very rough submarine topography, the NOC has been developing obstacle avoidance technology to be placed on Boaty, with engineers completing trials in Loch Ness last month to ensure the success of the deployment. NOC engineers have added a forward-looking sonar to avoid steep obstacles ahead and new retreat behaviors will enable the vehicle to turn around and return to the ship if the cavity gets too tight or if the terrain is impassable.

The six ocean gliders are smaller autonomous underwater vehicles that travel slower than ALR but will operate for longer – up to a month – because they are driven by a buoyancy engine rather than a propeller. They will be controlled remotely by a team at UEA via Iridium satellite and will measure temperature, salinity, current velocity, turbulence, dissolved oxygen, chlorophyll, turbidity, subsurface light levels, ambient noise, and pH. They ‘fly’ in a sawtooth pattern and will make repeated high-resolution observations along the face of the ice shelf.

Alongside the robot teams, scientists from the University of St Andrews will tag seals to acquire ocean temperature and saltiness data around the ice shelf for the next nine months over the Antarctic winter, and researchers working on the ITGC Thwaites Offshore Research (THOR) project will collect sediment cores and survey the seabed. At the same time, researchers working on the partnering Accelerating Thwaites Ecosystem Impacts for the Southern Ocean (ARTEMIS) project will measure chemical properties of the seawater, including minute quantities of iron that are the foundation of the Antarctic marine ecosystem.

The Thwaites-Amundsen Regional Survey and Network Integrating Atmosphere-Ice-Ocean Processes (TARSAN) and THOR projects are two of the eight ITGC research projects, which study the entire glacier to establish the impacts of what is known to be one of the most unstable glaciers in Antarctica.

THOR is a ship-based and ice-based project that will examine the sedimentary records both offshore from the glacier and beneath the ice shelf, together with glacial landforms on the seabed, to reconstruct past changes in ocean conditions and the glaciers response to these changes. TARSAN is a ship-based and ice-based project studying how atmospheric and oceanic processes are influencing the behavior of the Thwaites and Dotson Ice Shelves – neighboring ice shelves, which are behaving differently. This research will help identify how variations in atmospheric or oceanic conditions may influence the behavior and stability of ice shelves in the region.

Thwaites Glacier, covering 192,000km2 (74,000 square miles) – an area the size of Florida or the UK – is particularly susceptible to climate and ocean changes. Existing computer models show that over the next several decades, the glacier may lose ice rapidly, as ice retreats. Already, ice draining from Thwaites into the Amundsen Sea accounts for about 4% of global sea-level rise. A runaway collapse of the glacier would contribute around an additional 65cm to sea-level rise over the coming centuries.

Professor Karen Heywood, from UEA and UK lead on the ITGC TARSAN project, said, “This is a massively ambitious mission that we have been planning for several years. We will deploy two big underwater robots underneath the ice to collect detailed data from this crucial area of the glacier that will enable us to understand what will happen in the future. By measuring the ocean properties in sub-ice shelf cavities, we can understand how the ocean transports heat and what impact this may have on the glacier. My team and I back at UEA are going to be remotely piloting the six ocean gliders, smaller robots, once the scientists on board launch them into the water.”

The University of East Anglia’s Dr Rob Hall, the chief scientist in charge of the voyage, said, “It’s very exciting, though also daunting, to be leading this campaign to make critical measurements of the ocean under and around this vulnerable ice shelf. The team have completed a month of quarantine to ensure everyone is safe, and now we’re looking forward to putting our wide range of scientific instruments into the water to see what we will learn about how the ocean melts the ice shelf from below. We’re already monitoring the sea ice extent carefully to devise the best way to access the area because even this powerful icebreaker ship can’t get through thick sea ice.”

Prof. Anna Wåhlin from the University of Gothenburg, part of the team responsible for the underwater robot Ran, said, “Ran will venture beneath the ice shelf to map what it’s like. It will collect samples of water for later analysis and map the seabed with unprecedented accuracy. An ice shelf cavity is like another planet – we just don’t know what we’re going to find when we explore it.”

Dr Alex Phillips from the NOC said, “Our science and engineering teams have made enormous strides in pushing the boundaries of how we explore the world’s oceans with underwater technology. Autonomous underwater vehicles are vital equipment to enable oceanic research and we’re so excited to be joining the wider ITGC team with Boaty McBoatface, which will travel further under the Thwaites Glacier than ever before. The research the ALR is supporting at Thwaites Glacier will be fantastic for the science community, marking an important change in how we collect important ocean data to understand the effects of climate change.”

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