Antarctica's ice shelves are under attack from an unexpected source: ocean storms. These storms, occurring at the subsurface level, are causing significant melting and have major implications for global sea level rise.
Researchers from the University of California, Irvine, and NASA's Jet Propulsion Laboratory have uncovered a fascinating and worrying phenomenon. By studying ocean-induced ice shelf melting events on a daily timescale, they've identified a link between these "ocean storms" and intense ice melt at Thwaites Glacier and Pine Island Glacier in West Antarctica.
The research team utilized climate simulation modeling and moored observation tools to capture detailed images of submesoscale ocean features, which are tiny in comparison to the vast ocean and ice shelves. These features, measuring between 1 and 10 kilometers across, play a crucial role in the melting process.
Lead author Mattia Poinelli explains, "Submesoscale features act like hurricanes, threatening ice shelves and causing substantial damage. They bring warm water beneath the ice, melting it from below. This process is constant throughout the year in the Amundsen Sea Embayment and is a key contributor to submarine melting."
Poinelli and his team discovered a positive feedback loop, where more ice shelf melting leads to increased ocean turbulence, which in turn causes even more melting. "Submesoscale activity within the ice cavity is both a cause and a consequence of submarine melting," he says. "The melting creates unstable fronts that intensify these ocean features, leading to further melting."
The study reveals that these high-frequency processes account for nearly 20% of the total submarine melt variance over a seasonal cycle. During extreme events, submarine melting can increase threefold within hours as these features collide with ice fronts.
The findings are supported by high-resolution observational data, which shows distinct warming and increased salinity events at similar depths and timescales. "The region between the Crosson and Thwaites ice shelves is a submesoscale hot spot," Poinelli notes. "The floating tongue of the Thwaites ice shelf and the shallow seafloor enhance submesoscale activity, making this area particularly vulnerable."
The implications of these findings are significant, especially in the context of climate change. If the West Antarctic Ice Sheet were to collapse, it could raise global sea levels by up to 3 meters. With warmer waters, longer polynya periods, and lower sea ice coverage, these energetic submesoscale fronts could become more prevalent, impacting ice shelf stability and sea level rise.
"Our study highlights the critical role of fine oceanic features at the submesoscale in driving ice loss," Poinelli emphasizes. "These short-term, weather-like processes must be incorporated into climate models for accurate sea level rise projections."
Co-author Yoshihiro Nakayama adds, "Initially, we were just trying to understand the observations. Now, with our model matching the data so well, we can extrapolate and say there are weather-like storms hitting and melting the ice."
Eric Rignot, a professor at UC Irvine, emphasizes the need for better observation tools, including advanced oceangoing robots, to measure suboceanic processes and dynamics.
This research, involving Lia Siegelman from the Scripps Institution of Oceanography, was funded by NASA's Cryospheric Sciences Program with support from the NASA Advanced Supercomputing Division.
