Steven Gibbons’s research while affiliated with Norwegian Geotechnical Institute and other places

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Publications (2)


Fig. 1| Maximum flow velocity of the Storegga tsunami as calculated for each grid point during the 10 h simulation time. White triangles show location of marine sediment cores of the "8.2 event". Purple triangles (a, b, c and d) are additional locations of simulated time series (Supplementary Fig. 1). The white outline of the Storegga Slide is the run-out of landslide debris (Haflidason et al., 2004), the continuation of turbidites is not shown. Pixels in red-brown have maximum velocity > 5 m/s and < 20 m/s. Green circles are onshore locations of Storegga tsunami deposits (Bondevik, 2019). Depth contours are paleo-bathymetry used in the simulations. Countries are shown with their present-day coastlines.
Fig. 2 | Simulation of wave height (blue line) and flow velocity (dotted) during the Storegga tsunami at the location of marine sediment cores with an 8.2 ka layer. Paleo-water depths in brackets. For core locations, see Fig. 1. a Core site MD95-2011 at the Vøring plateau in the Norwegian Sea. b Core site LINK14 east of the Faroe Island and c Core site Troll, 28-03 in the Norwegian channel.
Fig. 3| Data from core MD95-2011 plotted according to age. a Percentage of grains > 63 μm and the number of grains > 150 μm per gram sediments. b Number of planktonic foraminifera, the blue line is for the cold-water species Neogloboquadrina pachyderma and the red line is
Confusion and contamination of 8.2 ka cold climate records caused by the Storegga tsunami in the Nordic Seas
  • Preprint
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June 2023

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204 Reads

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Steven Gibbons

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Since the end of the last ice age, no cold snap rivals the one dated to 8200 years ago. Its oceanic response has been reconstructed in part from sediments in the Norwegian Sea and North Sea. Here we show that these sediments have been reworked by currents generated by the Storegga tsunami, dated to the coldest decades of the 8.2 ka event. From a new simulation of the Storegga tsunami we calculated the maximum flow velocity to be 2–5 m/s on the shelf offshore western Norway and in the shallower parts of the North Sea, and up to about 1 m/s down to a water depth of 1000 m. We re-investigated sediment core MD95-2011, from which a large and abrupt 8.2 ka cooling had been inferred, and found the cold-water foraminifera to be re-deposited and 11,000 years of age. Oxygen isotopes of the recycled foraminifera and the content of sand grains, thought to be dropped from ice bergs, might have led to an interpretation of a too large and dramatic climate cooling. Our simulations imply that large parts of the sea floor in the North Sea and Norwegian Sea might have been reworked by currents during the Storegga tsunami.

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Confusion and contamination of 8.2 ka cold climate records by the Storegga tsunami

June 2023

·

139 Reads

Since the end of the last ice age, no cold snap rivals the one dated to 8200 years ago. Its oceanic response has been reconstructed in part from sediments in the Norwegian Sea and North Sea. Here we show that these sediments have been reworked by currents generated by the Storegga tsunami, dated to the coldest decades of the 8.2 ka event. From a new simulation of the Storegga tsunami we calculated the maximum flow velocity to be 2–5 m/s on the shelf offshore western Norway and in the shallower parts of the North Sea, and up to about 1 m/s down to a water depth of 1000 m. We re-investigated sediment core MD95-2011, from which a large and abrupt 8.2 ka cooling had been inferred, and found the cold-water foraminifera to be recycled and 11,000 years of age. Oxygen isotopes of the recycled foraminifera and the content of sand grains, thought to be dropped from ice bergs, might have led to an interpretation of a too large and dramatic climate cooling. Our simulations imply that large parts of the sea floor in the North Sea and Norwegian Sea might have been reworked by currents during the Storegga tsunami.