[ad_1]
Close-up image of an esker (a sedimentary cast of a meltwater channel formed under an ice cap), discovered in a tunnel valley using new 3D seismic reflection data. Credit: James Kirkham
Spectacular Ice Age landscapes under the North Sea have been discovered using 3D reflection seismic technology. Similar to MRI (Magnetic Resonance Imaging), the images reveal in unprecedented detail huge channels of the seabed – each 10 times wider than the Thames.
For the first time, an international team of scientists can show previously undetectable landscapes that formed beneath the vast ice caps that covered much of the UK and Western Europe thousands to millions ago. years. These ancient structures provide clues to how the ice caps are responding to global warming. The results are published this week (September 9, 2021) in the journal Geology.
The so-called tunnel valleys, buried hundreds of meters below the seabed of the North Sea, are the remnants of huge rivers that were the “plumbing system” of ancient ice caps when they melted in response to the rising air temperatures.
Lead author James Kirkham, from the British Antarctic Survey (BAS) and the University of Cambridge, says:
“The origin of these canals has not been elucidated for over a century. This discovery will help us better understand the ongoing retreat of current glaciers in Antarctica and Greenland.
“Just as we can leave footprints in the sand, glaciers leave a footprint on the land on which they sink. Our new cutting-edge data gives us important markers of deglaciation.
Comparison of the resolution of the new high-resolution 3D seismic reflection data to previous 3D seismic data from this region. The new data is revolutionizing our ability to image these buried channels and their internal structures, as evidenced by the contrast between the left and right of the image. Credit: James Kirkham, BAS
BAS co-author and geophysicist Dr Kelly Hogan says:
“Although we have known the immense glacial channels of the North Sea for some time, this is the first time that we have imagined small-scale landforms there. These delicate features tell us how the water moved through the channels (under the ice) and even how the ice simply stagnated and melted. It is very difficult to observe what is happening beneath our large ice caps today, especially how moving water and sediment affects ice flow and we know these are important controls over the behavior of the ice. ice. As a result, using these ancient channels to understand how ice will react to changing conditions in a warming climate is extremely relevant and timely. “
A map of the North Sea showing the distribution of buried channels (tunnel valleys) that were previously mapped using 3D seismic reflection technology. The limit of the last ice cap covering the UK (around 21,000 years ago) has been passed. Credit: James Kirkham
The 3D seismic reflection technology, which has been provided by industry partners, uses sound waves to generate detailed three-dimensional representations of ancient landscapes buried deep below the Earth’s surface, in much the same way as satellite imagery. Magnetic resonance imaging (MRI) can image structures within the human body. The method can image features as small as a few feet below the Earth’s surface, even if they are buried under hundreds of feet of sediment. The exceptional detail provided by this new data reveals the imprint of how the ice interacted with the channels as they formed. By comparing these ancient “ice prints” to those left under modern glaciers, scientists were able to reconstruct the behavior of these ancient ice caps as they retreated.
Close-up image of an esker (a sedimentary cast of a meltwater channel formed under an ice cap), discovered in a tunnel valley using new 3D seismic reflection data. In this image, the esker is presented against the backdrop of high-resolution 3D seismic data that can be “sliced” both vertically and horizontally to reveal ancient glacial landscapes buried beneath the seabed of the North Sea. Reflections from the curved sides of the tunnel valley are visible at the top of the image. Credit: James Kirkham
Diving into the past, this work opens a window to a warmer future world where new processes could begin to alter the plumbing system and flow behavior of the Antarctic and Greenland ice caps.
Reference: “Tunnel Valley Infill and Genesis Revealed by High-Resolution 3D Seismic Data” by James D. Kirkham, Kelly A. Hogan, Robert D. Larter, Ed Self, Ken Games, Mads Huuse, Margaret A. Stewart, Dag Ottesen, Neil S. Arnold and Julian A. Dowdeswell, September 8, 2021, Geology.
DOI: 10.1130 / G49048.1
[ad_2]
Source link