A new computer model from researchers at the University of California, Irvine and NASA's Jet Propulsion Laboratory predicts that Antarctica's Thwaites Glacier could raise global sea levels by as much as 30 millimeters by 2100, double earlier projections, even without additional warming of the climate. The findings, published in Nature Communications, suggest previous models underestimated the glacier's retreat because they treated the boundary between grounded and floating ice too narrowly.
The new model accounts for a broad "grounding zone," sometimes kilometers wide, where warm ocean water reaches deep beneath the ice and causes vigorous melting. The researchers say this dynamic produces twice as much ice melt and sea level rise as previously thought.
"Glaciologists have long based their assumptions of ice sheet dynamics on the 'grounding line,' a discreet, narrow and mostly stable demarcation where ice leaves the land and begins floating on water," said lead author Mattia Poinelli, who was a UC Irvine postdoctoral scholar in Earth system science when the research was conducted. "We have come to acknowledge a different arrangement beneath Earth's major ocean-terminating glaciers."
The team compared its simulations with more than two decades of observations, including synthetic aperture radar measurements from Finland's ICEYE satellite constellation. Those measurements showed seawater traveling several kilometers beneath ice that remains grounded on the seafloor, with tides repeatedly lifting the ice and exposing its underside to warm, pressurized seawater.
The model also suggests Thwaites may lose a critical underwater anchor. "The Thwaites main trunk is being temporarily stabilized by the Mouginot Ridge," Poinelli said. "Once that ridge is unpinned, the glacier will continually retreat across a predominantly retrograde seafloor toward its next topographic high, the South Ridge." The simulations give a 60% probability that Thwaites becomes detached from the ridge by the end of the century.
Co-author Eric Rignot, a UC Irvine professor of Earth system science, said the results predict greater coastal flooding risk than anticipated. "Most projections up to the present have struggled to match the rapidity of the mass loss because of missing physics; our new model with more complete physics is able to match the record and then produces projections that are twice as large as before."
Analysis
Why This Matters
- The updated projection means coastal flooding risk in coming decades could be greater than governments and planners have anticipated.
- Thwaites is a keystone glacier in West Antarctica; its destabilization could accelerate retreat of the surrounding ice sheet.
- The modeling approach, if adopted widely, could change sea level projections for other ocean-terminating glaciers.
Background
Thwaites Glacier lies in West Antarctica's Amundsen Sea Embayment and is often called the "Doomsday Glacier" because of its potential to contribute substantially to global sea level rise. Scientists have documented it thinning, retreating and flowing faster in recent decades. Traditional computer models struggled to reproduce the acceleration seen by satellites, a gap the new research attributes to missing physics at the glacier's base. Instead of a narrow grounding line, the study describes a wide grounding zone where seawater regularly reaches beneath the ice.
What to Watch
- Whether Thwaites becomes unpinned from the Mouginot Ridge before 2100, which the new model puts at a 60% probability.
- Whether other research groups adopt the grounding-zone approach and produce similar revisions to sea level projections.
- Continued satellite monitoring of the grounding zone, including data from Finland's ICEYE constellation and other missions.
Checked
12 claims in this story checked against 1 source: 10 supported.
Show each claim
- SupportedThe new model doubles earlier projections of sea-level rise from Thwaites Glacier.Latest Science News -- ScienceDaily: “That is double earlier projections, even without any additional warming of the climate.”
- SupportedThe glacier could add as much as 30 millimeters to global sea levels by 2100.Latest Science News -- ScienceDaily: “the model predicts that melting from the massive West Antarctic glacier could raise global sea levels by as much as 30 millimeters by 2100.”
- SupportedThe projected rise could occur even without additional climate warming.Latest Science News -- ScienceDaily: “That is double earlier projections, even without any additional warming of the climate.”
- SupportedThe model was developed by researchers at UC Irvine and NASA's Jet Propulsion Laboratory.Latest Science News -- ScienceDaily: “Developed by researchers at the University of California, Irvine, and NASA's Jet Propulsion Laboratory, the model predicts”
- SupportedThe findings were published in Nature Communications.Latest Science News -- ScienceDaily: “The findings, published in Nature Communications, reveal why earlier models may have underestimated the glacier's retreat.”
- SupportedEarlier models may have underestimated the glacier's retreat because they treated the grounded-floating ice boundary too narrowly.Latest Science News -- ScienceDaily: “Instead of treating the boundary between grounded and floating ice as a narrow line, researchers accounted for a much broader area where ocean water can reach beneath the glacier.”
- SupportedPoinelli said, “Glaciologists have long based their assumptions of ice sheet dynamics on the 'grounding line,' a discreet, narrow and mostly stable demarcation where ice leaves the land and begins floating on water.”Latest Science News -- ScienceDaily: ““Glaciologists have long based their assumptions of ice sheet dynamics on the 'grounding line,' a discreet, narrow and mostly stable demarcation where ice leaves the land and begins floating on water,” said lead author Mattia Poinelli”
- SupportedPoinelli said, “We have come to acknowledge a different arrangement beneath Earth's major ocean-terminating glaciers.”Latest Science News -- ScienceDaily: ““We have come to acknowledge a different arrangement beneath Earth's major ocean-terminating glaciers.””
- Partly supportedThe researchers compared their simulations with more than two decades of observations, including the ICEYE radar measurements.Latest Science News -- ScienceDaily: “the UC Irvine-led research team compared its simulations with more than two decades of observations. The researchers also analyzed synthetic aperture radar measurements collected by Finland's ICEYE satellite constellation”
- SupportedThe ICEYE measurements showed seawater traveling several kilometers beneath grounded ice, with tides lifting the ice and exposing its underside to warm, pressurized seawater.Latest Science News -- ScienceDaily: “The satellite evidence shows that seawater travels several kilometers beneath ice that remains grounded on the seafloor. As tides rise and fall, the water lifts the ice and repeatedly exposes its underside to warm, pressurized seawater.”
- Partly supportedThe simulations give a 60% probability that Thwaites will detach from Mouginot Ridge by the end of the century.Latest Science News -- ScienceDaily: “When the model includes a grounding zone measuring 4 to 6 kilometers across, it predicts a 60% probability that Thwaites will become detached from Mouginot Ridge by the end of the century.”
- SupportedRignot said, “Most projections up to the present have struggled to match the rapidity of the mass loss because of missing physics; our new model with more complete physics is able to match the record and then produces projections that are twice as large as before.”Latest Science News -- ScienceDaily: ““Most projections up to the present have struggled to match the rapidity of the mass loss because of missing physics; our new model with more complete physics is able to match the record and then produces projections that are twice as large as before.”