Iceberg ‘Doodles’ Trace Climate History

2017-05-02T14:49:17+00:00 May 2, 2017|
The part of the icberg which lies underwater can be scouring the seafloor. (Credit: AWeith/Wikicommons)

(Click to enlarge) The part of the icberg which lies underwater can be scouring the seafloor. (Credit: AWeith/Wikicommons)

It is as if a child has been doodling with large coloured crayons.

(From What you see are actually the great gouge marks left on the seafloor when the keel of a giant block of ice has dragged through the sediments.

The arcs and loops record the movement of the berg as it turns about, caught in the wind, currents and tides.

This “ice art” is from a stunning new collection of images that detail how glacial action has shaped the ocean floor in Earth’s polar regions.

The atlas is the work of more than 250 scientists from 20 countries and represents our most comprehensive view yet of what the seabed looks like at high latitudes.

“We now have a critical mass of high-resolution imagery, of the imprints left by the action of ice,” explained Dr Kelly Hogan, one the collection’s editors from the British Antarctic Survey (BAS).

“We can see where the ice has been and what it’s done, and this allows us to compare and contrast. Looking at what has happened in the past can help us understand what may happen in the future with modern ice sheets as they respond to climate change.”

The book, published as a “memoir” of the Geological Society of London, has taken four years to put together.

It contains mostly images produced from ship echosounders, which pulse the ocean bed and then build depth maps from the resulting return signal (the “false colours” will usual denote different depths).

A first version of the book came out in 1997, but comprised really only low-resolution data.

The new tome, on the other hand, benefits from 20 years of multibeam swath technology, which is capable of creating spectacular perspectives of the ocean floor, often at sub-metre resolution.

All ships now entering polar waters will routinely map the bed in this way.

“Today’s icebreakers and ice-strengthened vessels all carry these high-res systems; they are standard. No longer do we get just single points, but a whole fan of sound goes down to the seafloor to collect 3D data. And we’re finding all these weird and wonderful features,” Dr Hogan told BBC News.

As well as the iceberg ploughmarks, there are the classic forms left by marine glaciers. These include long striations, drumlins (egg-shaped mounds) and moraines (bulldozed sediment ridges).

“When the moraines are pushed close together, they’re most likely annual features, but move a bigger distance offshore and you might find moraines that are from thousands of years ago and are spread further apart. We could go date the sediments to look at how quickly ice has retreated. So, this gives you an idea of how we can use the imagery to help us understand what is going on.”

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