Radar scans of Greenland ice sheet reveal closure and reconfiguration of ice flows over thousands of years – ScienceDaily

Large ice flows can come to a standstill within a few thousand years and shift the rapid transport of ice to other parts of the ice sheet. This was determined in reconstructions of two ice streams based on ice-penetrating radar scans of the Greenland ice sheet, which a research team led by the Alfred Wegener Institute has just presented in the journal Nature Geoscience.

How fast sea level will rise in the future will largely depend on how dynamic or stable the Greenland ice sheet is – ice that has lost about 40 mm of mass since sea level rise since 1900. In addition to melting at its surface and base, the sheet is also losing ground Ice Streams to Bulk – Essentially conveyor belts for the rapid transport of ice from the inner slab to its rim. In the now glacier-free areas at the edge of the plate, the routes of past ice flows can now be precisely reconstructed, since the landscape forms they left behind provide clearly visible clues. However, until recently very little was known about the activity of past ice streams in the Greenland ice sheet due to the area’s poor accessibility. The answer: state-of-the-art measurement technologies such as high-resolution radar systems that can penetrate the ice to map structures several thousand meters below the ice sheet surface. As part of a project to reconstruct past ice flows in collaboration with Professor Paul Bons from the University of Tübingen, experts from the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research (AWI) used structural geology methods to analyze these images.

“Thanks to our ice-penetrating radar data, we can show how quickly the ice transport system of the Greenland ice sheet has reconfigured. Large ice flows can be ‘shut down’ within a few thousand or even several hundred years, while others appear elsewhere at a similar time. No one previously suspected that flows of this magnitude could change so quickly,” reports AWI glaciologist Dr. Steven Franke, first author of the study. Ice transport, which involves the flow of solid ice – not melting – is a component of ice dynamics that needs to be more actively integrated into projections of how much the Greenland ice sheet will contribute to sea level rise under a variety of future climate scenarios. Current ice sheet models can only depict processes that are clearly understood. However, since there are no observations on the instability of ice flows, this aspect is not considered in any model. The flow history of the ice, now made visible by radar, offers insights into the temporal and spatial development of this dynamic.

The data published in the study were collected during flight campaigns with the AWI research aircraft Polar 6 and during NASA’s IceBridge operation in central north-eastern Greenland, where only very low flow velocities can currently be observed in the ice. The research team identified two paleo ice streams that were once active and are now buried under several hundred meters of ice. Their analyzes show that these ice flows were active into the Holocene (less than 11,700 years ago) and extended well into the ice sheet in central northeast Greenland.

“The radar signature of one of the two paleo ice streams that we used to reconstruct earlier ice flow activity is remarkably similar to that of the massive and still active Northeast Greenland Ice Stream (NEGIS),” says AWI glaciologist Dr. Daniela Jansen, leader of the project on past ice flows that resulted in the publication. This discovery, she claims, could offer new insights into the future behavior of the NEGIS, the formation and stability of which are the subject of considerable debate. The observations now published will allow researchers to better understand the mechanisms responsible for the generation and formation of ice streams. This allows them to be more accurately represented in models designed to predict how our planet’s ice sheets will respond to global warming.

story source:

Materials provided by Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research. Note: Content can be edited for style and length.

Leave a Reply

Your email address will not be published. Required fields are marked *