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Tuesday, 4 September 2018

Old BRITICE computer simulations for the Devensian glaciation


On the maximum model, there is a much reduced ice cover around 27ka.  In a decade of research, the dates on the model have been dramatically altered.  It is now thought that the Devensian MAXIMUM was around this time.

The files on the BRITICE site are not easy to get at.
https://www.aber.ac.uk/en/dges/research/centre-glaciology/research-intro/britice-model/

These have now been placed on YouTube by a mysterious benefactor, in the cause of science.  You don't need masses of computing power to look at them.

The models have no dates attached to them, but they probably date from 2008-2009, since the time sequence represented on the models is way out of step with the most recent published research. For example, at 27ka the ice is shown as retreating into its heartland in Scotland, whereas the recent work refers to that being more or less the time of maximum advance. Some corrections are needed somewhere.........  I must make some enquiries to see if the models have been revised as of 2018.

Devensian minimum model
https://www.youtube.com/watch?v=bcUpNYLUEOc

Devensian maximum model
https://www.youtube.com/watch?v=oABxYza9ELM

Devensian "most representative" model
https://www.youtube.com/watch?v=aNb5ucif584

Reference:

'Dynamic cycles, ice streams and their impact on the extent, chronology and deglaciation of the British–Irish ice sheet.'
Alun Hubbard, Tom Bradwell, Nicholas Golledge, Adrian Hall, Henry Patton, David Sugden, Rhys Cooper, Martyn Stoker
Quaternary Science Reviews 28 (2009) 759–777

2016 revisions:

Henry Patton, Alun Hubbard, Karin Andreassen, Monica Winsborrow, Arjen P. Stroeven. 2016.
The build-up, configuration, and dynamical sensitivity of the Eurasian ice-sheet complex to Late Weichselian climatic and oceanic forcing.

This all goes to show that models are only as good as the data fed into them........



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4 comments:

  1. Steve Hooker4 September 2018 at 17:02

    I ain't no mysterious benefactor ;-) Just some geezer making models of Stonehenge after being cursed by a witch.

    https://www.buystonehenge.com/witchphotography

    I'm trying to understand. And there's so much to understand around The Henge.

    ReplyDelete
  2. Steve Hooker4 September 2018 at 17:13

    One thing I'm particularly confused about is the extent on the last ice age around southeastern England.

    https://ars.els-cdn.com/content/image/1-s2.0-S0277379116304498-gr13_lrg.jpg

    Sometimes I see that it extends over the coast, in other maps it does not. I see particularly, your map on Wikipedia under Irish Sea Glacier and this stops at the coast, but comes I guess around 30 miles west of Stonehenge.

    https://en.wikipedia.org/wiki/Irish_Sea_Glacier

    Is there not yet a definitive line. Exactly this far, no further?

    And, what does 'mostly ice free' mean?

    ReplyDelete
  3. BRIAN JOHN4 September 2018 at 20:10

    Steve

    There is no definitive line -- all researchers are seeking to work out where it is. My own view is that the Irish Sea Glacier butted against the coasts of Devon and Cornwall, and maybe pressed a bit inland, where it met the ice of the Exmoor and Dartmoor ice sheets. Because of the extensive Somerset Levels embayment, the ice was able to press much further inland there -- maybe as far as Glastonbury, and maybe even further east. Ground truthing needed. We now have a range of models that are getting (we hope!) better and better.......

    "Mostly ice free" means intermittent and patchy ice cover and lots of ice free (but maybe snow-covered) ground. There might, for example, be upland ice caps as on Bodmin, Preseli, Exmoor, Dartmoor and maybe Mendip.

    ReplyDelete
  4. Steve Hooker6 September 2018 at 20:00

    So the ice edge would have been, according to your map, around 30 miles from Stonehenge. Coming nearly to Bath, overtopping Glastonbury and the Mendips.

    Oh... Nevermind. I found the map I was looking for...
    https://brian-mountainman.blogspot.com/2012/08/british-glacial-limits.html

    I had thought that it wouldn't take much to push the line much closer to Stonehenge. I don't know much about glacier theory, but I know the buggers wax and wane. An extra cold couple of decades and they could retreat or advance 30 miles.

    Job done, but I was already convinced, several years ago ;-)

    ReplyDelete

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