Ice melange, a combination of ice rack fragments, windblown snow and frozen seawater, can act as a glue to fuse large rifts in floating ice in Antarctica. Scientists at UCI and NASA JPL found that a thinning of the compound over time can trigger rifts to open, leading to the calving of large icebergs. Instead, the model showed that a thinning ice shelf without any changes to the melange worked to heal the rifts, with average annual widening rates dropping from 79 to 22 meters (259 to 72 feet). Thinning both the ice rack and the melange likewise slowed rift widening however to a lesser extent. When modeling just melange thinning, the researchers discovered a widening of rifts from an average yearly rate of 76 to 112 meters (249 to 367 feet).
” The thinning of the ice melange that glues together big sectors of floating ice shelves is another method climate change can trigger quick retreat of Antarcticas ice racks,” said co-author Eric Rignot, UCI teacher of Earth system science. “With this in mind, we might need to reassess our price quotes about the timing and level of water level rise from polar ice loss– i.e., it might come sooner and with a larger bang than expected.”
Using NASAs Ice-sheet and Sea-level System Model, observations from the agencys Operation IceBridge mission, and data from NASA and European satellites, the researchers evaluated hundreds of rifts in the Larsen C ice shelf to determine which ones were most susceptible to breaking. They picked 11 top-to-bottom fractures for extensive research study, modeling to see which of three scenarios rendered them probably to break: if the ice rack thinned since of melting, if the ice assortment grew thinner, or if both the ice rack and the assortment thinned.
” A great deal of people believed intuitively, If you thin the ice rack, youre going to make it much more vulnerable, and its going to break,” said lead author Eric Larour, NASA JPL research scientist and group supervisor.
Rather, the model revealed that a thinning ice shelf without any changes to the assortment worked to heal the rifts, with average annual widening rates dropping from 79 to 22 meters (259 to 72 feet). Thinning both the ice shelf and the melange also slowed rift widening but to a lesser degree. When modeling only melange thinning, the researchers found a widening of rifts from a typical yearly rate of 76 to 112 meters (249 to 367 feet).
The difference, Larour described, shows the different natures of the substances.
” The melange is thinner than ice to begin with,” he said. “When the assortment is only 10 or 15 meters thick, its similar to water, and the ice shelf rifts are released and begin to crack.”
Even in winter, warmer ocean water can reach the melange from below because rifts extend through the entire depth of an ice shelf.
” The dominating theory behind the increase in large iceberg calving events in the Antarctic Peninsula has been hydrofracturing, in which melt swimming pools on the surface allow water to seep down through cracks in the ice rack, which broaden when the water freezes again,” stated Rignot, who is likewise a NASA JPL senior research researcher. “But that theory fails to discuss how iceberg A68 could break from the Larsen C ice shelf in the dead of the Antarctic winter when no melt pools were present.”
He stated that he and others in the cryosphere studies community have experienced ice shelf collapse on the Antarctic Peninsula, coming from a retreat that started decades ago.
” We have lastly begun to seek an explanation regarding why these ice shelves started coming and pulling back into these setups that ended up being unsteady years prior to hydrofracturing could act on them,” Rignot stated. “While the thinning ice assortment is not the only process that could discuss it, its enough to represent the deterioration that weve observed.”
Reference: “Physical processes controlling the rifting of Larsen C Ice Shelf, Antarctica, prior to the calving of iceberg A68” by E. Larour, E. Rignot, M. Poinelli and B. Scheuchl, 27 September 2021, Proceedings of the National Academy of Sciences.DOI: 10.1073/ pnas.2105080118.
Signing Up With Rignot and Larour on this NASA-funded job were Bernd Scheuchl, UCI associate job scientist in Earth system science, and Mattia Poinelli, a Ph.D. prospect in geoscience and remote picking up at Delft University of Technology in the Netherlands.
Ice assortment, a mix of ice shelf fragments, windblown snow and frozen seawater, can function as a glue to fuse big rifts in floating ice in Antarctica. Researchers at UCI and NASA JPL found that a thinning of the compound in time can cause rifts to open, leading to the calving of big icebergs. Credit: Beck/ NASA Operation IceBridge
Thinning of rift-healing slush is recognized as a significant cause of iceberg calving occasions.
Glaciologists at the University of California, Irvine and NASAs Jet Propulsion Laboratory have examined the characteristics underlying the calving of the Delaware-sized iceberg A68 from Antarcticas Larsen C ice shelf in July 2017, discovering the most likely cause to be a thinning of ice melange, a slushy mixture of windblown snow, iceberg debris and frozen seawater that normally works to heal rifts.
In a paper published on September 27, 2021, in Proceedings of the National Academy of Sciences, the scientists report that their modeling research studies revealed melange thinning to be a major motorist of ice rack collapse. The blood circulation of ocean water underneath ice racks and radiative warming from above, they say, slowly deteriorate ice assortment throughout years.
As ice racks are thought to strengthen and prevent land-borne glaciers from more rapidly flowing into the ocean, this new understanding about rift dynamics illuminates a formerly underappreciated link in between climate modification and ice shelf stability.
