A team led by UC Irvine glaciologists used satellite radar data to reconstruct the impact of rising warm ocean waters on a stranding zone that extends several miles below Thwaites Glacier, in West Antarctica.
Research, which is the subject of an article published in PNAS, will help climate modelers make more accurate projections of sea level rise as a result of melting glaciers that seal off oceans around the world. Credit: NASA/James Yungel
Satellite radar data show significant intrusion of seawater beneath Antarctica Thwaites Glaciercausing the ice to rise and fall.
Using high-resolution satellite radar data, a team of glaciologists led by researchers from the University of California, Irvine, has discovered evidence of high-pressure warm seawater intrusion several kilometers beneath the stranded ice of Thwaites Glacier in West Antarctica.
This glacier is often referred to as the “doomsday glacier” because of its key role in potential global sea level rise and the catastrophic implications such a rise would have on a global scale.
The nickname reflects the glacier’s enormous size and significant melting rate, which scientists say could contribute significantly to sea level rise if it were to collapse or melt completely.
The UC Irvine-led team said widespread contact between ocean water and glaciers — a process repeated across Antarctica and Greenland — is causing “strong melting” and could require a reassessment of global sea-level rise projections. Their study was published on May 20 in Proceedings of the National Academy of Sciences,
Data and observations
The glaciologists relied on data collected from March to June 2023 by the Finnish commercial satellite mission ICEYE. The ICEYE satellites form a “constellation” in polar orbit around the planet, using InSAR – Synthetic Aperture Interferometric Radar – to continuously monitor changes in the Earth’s surface.
Many spacecraft passes over a small defined area produce smooth data results. In the case of this study, it showed the rise, fall and curvature of the Thwaites Glacier.
“These ICEYE data provided a long series of daily observations closely aligned with tidal cycles,” said lead author Eric Rignot, professor of Earth system sciences at UC Irvine. “In the past we had sporadically available data and with only these few observations it was difficult to understand what was going on.
When we have a continuous time series and compare it to the tidal cycle, we see that seawater enters during high tides and recedes, and sometimes moves further under the glacier and remains trapped. Thanks to ICEYE, we are beginning to witness these tidal dynamics for the first time.
Screenshot of a 3D view of the tidal movement of Thwaites Glacier in West Antarctica captured by the ICEYE Synthetic Aperture Radar (SAR) constellation based on images taken on 11, 12 and 13 May 2023. Contour levels are topography bottom contours at 50 m. interval.
Each interferometric fringe color cycle corresponds to a 360-degree phase change, which is equivalent to a 1.65 cm shift in line-of-sight distance from the ice surface. The interferogram is overlaid on a Landsat 9 image taken in February 2023.
In this study, we show that the tidal flexure limit varies in kilometers over the course of the tidal cycle, indicating that pressurized seawater is capable of penetrating beneath the land ice for miles and establishing itself strongly. heat exchange with the base of the glacier.
On the right side of the screen, a clear melo pattern indicates seawater intrusion extending another 6 km beyond the protective ridge, showing that the glacier is still advancing, at a rate of one kilometer per year in this critical sector of Antarctica. Credit: Eric Rignot / UC Irvine
Advanced satellite observations
Michael Wollersheim, director of analysis at ICEYE and co-author, said: “Until now, some of nature’s most dynamic processes have been impossible to observe in sufficient detail or often enough to understand and model them.
Observing these processes from space and using radar satellite images, which provide centimeter-precise InSAR measurements at the daily frequency, marks a significant step forward.
Rignot said the project helped him and his colleagues better understand the behavior of seawater beneath Thwaites Glacier. He explained that seawater reaching the base of the ice sheet, combined with fresh water generated by geothermal flow and friction, accumulates and “has to go somewhere.”
Water is distributed through natural channels or collected in cavities, creating enough pressure to lift the ice sheet.
“There are places where the water is almost under pressure from the overlying ice, so it only takes a little more pressure to push the ice up,” Rignot said. “The water is then compressed enough to lift a column of ice more than half a mile high. »
And it’s not just any seawater. Rignot and his colleagues have been gathering evidence for decades about the impact of climate change on ocean currents, which push warmer seawater toward the coasts of Antarctica and other polar ice regions.
Deep circumpolar waters are salty and have a lower freezing point. While fresh water freezes at zero degrees Celsiussalt water freezes at minus two degrees, and that small difference is enough to contribute to “strong melting” of the basal ice, the study reveals.
Impact on sea level rise and future research
Co-authored by Christine Dow, professor at the Faculty of Environment University of Waterloo in Ontario, Canada, said: “Thwaites is the most unstable place in Antarctica and contains the equivalent of 60 centimeters of sea level rise.
The problem is that we underestimate the speed at which the glacier is developing, which would be devastating to coastal communities around the world.
Rignot said he hopes and expects the results of this project to spur new research into conditions beneath Antarctic glaciers, exhibits that include autonomous robots and more satellite observations.
“There’s a lot of enthusiasm from the scientific community about going to these remote polar regions to collect data and improve our understanding of what’s going on, but funding is lagging,” he said.
“In 2024, in real dollars, we’re operating on the same budget as in the 1990s. We need to grow the community of glaciologists and physical oceanographers to solve these observational problems as soon as possible, but right now we’re continuing to climb Mount Everest in sneakers.
Conclusion and implications for modeling
In the short term, Rignot, who is also the lead scientist on the project OURJet Propulsion Laboratory (JPL), said that this study will bring lasting benefits to the ice sheet modeling community.
“If we build this kind of ocean-ice interaction into ice sheet models, I hope we can much better reproduce what has happened over the last quarter of a century, leading to a higher level of confidence in our planet. “projections,” he said.
“If we could add this process that we described in the paper, which is not included in most current models, the model reconstructions should match the observations much better. It would be a great victory if we could achieve this.
Dow added, “We don’t have enough information at this point to say one way or the other how long it will be before ocean water intrusion becomes irreversible. By improving the model and focusing our research on these critical glaciers, we will try to get these numbers at least over decades rather than centuries.
This work will help people adapt to changes in ocean levels, while focusing on reducing carbon emissions to avoid the worst-case scenario.
Rignot, Dow, and Wollershiem were joined on this project by Enrico Ciraci, a UC Irvine assistant professor of Earth system science and a NASA postdoctoral fellow; Bernd Scheuchl, UC Irvine researcher in Earth system science; and Valentyn Tolpekin from ICEYE.
ICEYE is headquartered in Finland and operates in five international locations, including the United States. The research received financial support from NASA and the National Science Foundation.