By Paul Gorman
A touchstone Antarctic glacier may be melting faster due to the complicated exchange of cold glacial meltwater and warmer deep ocean water.
That’s a preliminary finding of polar geophysicist Dr Jamin Greenbaum, of the Scripps Institution of Oceanography in San Diego. A longstanding user of Seequent’s Oasis montaj, Greenbaum has been employing it to help determine where glacier ice meets sea ice, and advance human understanding of the Earth.
Greenbaum had a two-week visiting fellowship at the University of Canterbury in March after finishing his 17th expedition to the Ice aboard South Korean ice-breaking research ship RV Araon.
The Thwaites Glacier in West Antarctica, on the Amundsen Sea coast, is the focus for much of his research.
Known widely as the ‘Doomsday Glacier’, the ice mass is about the size of Florida and has lost more than 1 trillion tonnes of ice since the turn of the century. Between 1979 and 2017 it accounted for 14% of Antarctica’s contribution to global sea-level rise.
Scientists and environmentalists are worried a collapse of the glacier could trigger a catastrophic disintegration of the West Antarctic Ice Sheet and raise sea-level by more than three metres.
Dr Jamin Greenbaum, of the Scripps Institution of Oceanography in San Diego, has been using Seequent’s Oasis montaj to help determine where glacier ice meets sea ice.
Source: Seequent
In this southern summer’s expedition, Greenbaum and research colleagues worked at four locations around the fractured Thwaites Glacier ice tongue, deploying their custom-built RIFT-OX (Remote Ice Fracture – Ocean eXplorer) platform from a helicopter to collect data from otherwise inaccessible and dangerous ice rifts.
At each site, the helicopter used RIFT-OX to break through thin ice before a winch lowered water sampler bottles below 850m testing for variables including temperature and salinity. Live video and data were streamed back to the ship using Starlink satellite internet and long-range Wi-Fi, allowing scientists to decide when to close the bottles and view data in real time.
Greenbaum conducted his research from the South Korean ice-breaking research ship RV Araon.
Source: Supplied
Greenbaum said he had done a ‘first cut’ on board the ship analysing the water from different depths. The next step is to fully process and analyse the samples that were returned.
‘We now have to get our samples to the Woods Hole Oceanographic Institution, so they can use their mass spectrometer to do the noble-gas analysis that we need for final interpretation. The eventual goal is to unambiguously detect subglacial discharge using noble-gas concentrations.’
He believes subglacial freshwater may play a significant role in accelerating the melting of the underside of the Thwaites Glacier. Ironically, it seems this cold freshwater coming out of the glacier is more damaging to it than the warmer salty seawater that sits below it, closer to the seabed.
‘When it emerges under the ice shelf, it rises strongly as a buoyant plume along the underside of the ice. The freshwater plume is so buoyant and turbulent that it intensifies the plume.
‘As that plume rises, it drags in warm, relatively salty water higher up under the ice shelf into contact with much more ice, instead of it staying happily down there, stratified.
‘So, you end up melting the hell out of this ice in a way that you just wouldn’t have thought.’
The result? Substantially higher basal melting rates, increasing perhaps by as much as 50%.
Findings could be used to build more robust models of future melting and likely sea-level rise, and help with coastal and climate policy development.
Greenbaum said without Oasis montaj their research would have been much slower.
‘When you’re in the field, it’s much nicer to be able to use an environment like Oasis montaj to just quickly get the thing you need.
‘For the operational work that I do, it’s the combination of the mapping capabilities and the database. It’s just really convenient. I also like how snappy it is. It’s just fast – it works, like right now.’
Greenbaum is working at the frontier of climate research.
Source: Supplied
Oasis montaj has been invaluable for loading up flight lines and targets, and visualising them with different grids.
‘We’re collecting data where there’s no data ever collected before. To design the experiment, I need to load up everything that we know about the region, to intelligently decide where to place my lines and the line spacing, or … where we place the sensor package.
‘Oasis is great because I can quickly go back and forth between different context maps, and as I collect the data I can grid it really quickly and then add it to the map.
‘We get a new satellite image, put it in, look at where the rifts are with respect to our probes from previous years, and plan our next flight.’
Greenbaum also uses Oasis montaj’s ‘grid math’ feature to differentiate between glacier ice and sea ice in high-resolution digital terrain models acquired by satellite. He is doing that in collaboration with University of Cambridge British Antarctic Survey PhD student Siobhán Johnson, whose sea-ice cores provide a measure of density.
‘Having even ballpark-accurate density values is critical for getting a reasonable answer. When I’m programming grid math, I say if the surface elevation is higher than 10m, I’ll assume it’s glacier ice. If it’s lower than that, I’ll assume it’s sea ice with a lower density.
‘Because Siobhán was getting actual cores, she could tell me the [actual] sea-ice density, which I could then use as hard constraints in my grid math calculations.’
As well as being supported by the Korea Polar Research Institute and Seequent, their work was funded by the United States’ Fund for Science and Technology, the non-profit society The Explorers Club and the Scripps Institution of Oceanography.
Greenbaum said it had been touch-and-go whether the expedition would receive funding from the Fund but about US$500,000 came through, almost ‘at the last second’.
Dr Jamin Greenbaum talks about his work during an interview with Seequent in 2024.
Source: Seequent