A team of Antarctic scientists is breaking new ground – or ice at least – in scientific research.
They’ve designed a cutting-edge device to measure supercooled ocean water under sea ice.
The Kiwi-led project, funded by the Marsden Fund, is collaborating with Norwegian and US scientists to build a High Precision Supercooling Measurement Instrument (HiPSMI) that can be sent below the ice on the Icefin (a small, remotely-operated submersible robot) to precisely measure exactly how cold the water gets.
Dr Inga Smith, from the University of Otago, says sea ice usually freezes at -1.9 degrees Celsius. But that’s not the case when fresh water flows from beneath an ice shelf and mixes with the salty sea water.
“Then it becomes what’s called supercooled, so it’s still liquid but actually below the freezing point. It then snap freezes into these crystals called frazil, they attach to the sea ice and form platelet ice. That means the sea ice in this area is thicker and grows faster than it would otherwise, certainly thicker and faster than you would expect in the Arctic, for example, in a similar location.
“We’re really pushing the edge of polar engineering here, operating in these really cold temperatures and making high-precision measurements of that supercooling,” she says.
Maren Richter, a PhD student from University of Otago, says oceans under ice shelves are a large black spot in our knowledge.
“We know more about the dark side of the moon than we know about what’s going on underneath the Ross Ice Shelf!
“These measurements help to inform understanding of how the system that is the ocean, the ice and the atmosphere works together, and how that all interconnects. These are all calculated by large scale models and the more accurate we can make these models, even on really small scales like this, the more accurate it will be on larger scales like informing weather in the future in New Zealand,” she says.
To test the HiPSMI in Antarctica for the first time, the team worked out of a containerised ice camp on McMurdo Sound. Sarah Williamson, Antarctica New Zealand Chief Executive, says the containerised camp, owned by NIWA, was key for the team’s success.
“They managed to collect oceanographic and sea ice data for 17 of the 20 days at the ice camp, and HiPSMI data on eight of those days. It’s always satisfying when we can support this world-leading science so successfully in Antarctica, particularly when it has such important ramifications for the rest of the planet,” she says.
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Led by Dr Inga Smith (University of Otago), HiPSMI has truly been an international collaborative team effort. Dr Pete Russell (Ngāpuhi), Research Fellow at University of Otago, and Dan Dichek, Matt Meister and Sebastian Lopez, all from Georgia Tech, USA, designed and built HiPSMI. Dr Britney Schmidt, now from Cornell University, USA, is the Icefin Principal Investigator. Icefin is a hybrid remotely and autonomously-operated under-ice vehicle (submersible robot for research), and carries HiPSMI through the water to collect its data. Professor Lars Smedsrud (University of Bergen, Norway) worked with the Kiwi team on computer modelling and laboratory work as well as in the field. Maren Richter (University of Otago PhD student), Brett Grant (NIWA) and Icefin Specialist Operators Dr Andy Mullen (Georgia Tech), Dr Enrica Quartini (Cornell University), and Ben Hurwitz (Georgia Tech) were the other five members of the field team. Dr Greg Leonard (National School of Surveying, University of Otago) was also an associate investigator on the project and provided satellite and sea ice information to the team when they were on the ice. Other research and technical staff and students from the University of Otago and Georgia Tech contributed to the design and building of HiPSMI. During their two week, pre-departure isolation in Methven the team tested HiPSMI using the swimming pool and a wheelie bin full of icy water.
The HiPSMI fieldwork was part of the project "Supercooling measurements under ice shelves" supported by the Marsden Fund Council from government funding, administered by Te Apārangi/the Royal Society of New Zealand (contract number MFP-UOO1825). Icefin was built by Schmidt’s team at Georgia Tech with support from NASA, and is now moving to Cornell University. The Icefin team was also supported by NASA grant number NNX16AL07G (RISE UP) and NSF grant number 2053280.