Glacierization intensity and duration

 Does the word "glacierization" have any meaning or relevance?  Isn't it the same as "glaciation"?  This is the thinking of the glaciology establishment:

https://www.cambridge.org/core/journals/journal-of-glaciology/article/glacierization/354F9D3447C4AE8159D984B235114DE6

Fair enough.  I agree that the word "glacierization" can be used to cover a full glacial cycle, from the initial onset of permafrost conditions, to the transformation to a snow-covered landscape and thence to landscape cover by active (moving and eroding) ice and thence through to ice wastage and the return of interglacial conditions. Glacierization might last for 80,000 years, but within that period there may be just 10,000 years of glaciation.

We need to think about this more than we have done traditionally, especially since we are now encountering the results of cosmogenic dating on rock surfaces in ice-covered and ice-free areas as researchers try to reconstruct episodes of past climate change.

Way back in the days when I was a D Phil research student, I created this model while I was trying to understand the sequence of Quaternary sediments exposed in the Pembrokeshire coastal exposures.

In a somewhat crude fashion, the columns represent the "glacierization time" at each of the four chosen locations.  This may have been 25,000 years in Southern Scotland but only 10,000 years near the southern glacial limit.  Within those time periods, full glacial conditions will have occupied a smaller and smaller percentage of glacierization time with distance from the ice sheet centre.  In reality, of course, you get climatic oscillations, topographic effects, sea level interactions and glaciological feedback mechanisms, so it all gets very complicated -- but the general principle still stands.

When the computer modelling folks arrived on the scene and started with really sophisticated modelling, we saw the arrival of rather splendid animated seqiuences in which we could watch small glaciers, ice caps and ice sheets expanding and contracting.  The BRITICE models are the latest of these, but the way was paved by Geoffrey Boulton, Alun Hubbard, Henry Patton and many others.  This was one of the images from this period of research that grabbed my attention:

It may look like a model of ice thickness over the southern part of the area affected by the Irish Sea Ice Stream -- but no, it shows the computed duration of glaciation.  This is zero at the outer ice edge, maybe just a few decades at Land's End, c 800m years near Lundy, c 1000 years at the north coast of Pembrokeshire, and c 1300 years in the southern Irish Sea proper.  The light coloured blotches on the map show areas of thin ice where glaciation time was reduced;  at times these upstanding areas will have been nunataks.

This is all of course rather wildly inaccurate -- but you have to admire the objectives and the skills of the members of the modelling team.

The ANCIENT BRITISH ISLES ICE SHEET TIME-LAPSE ANIMATION produced by the BRITICE-Chrono team is based on much more sophisticated modelling and a much greater "ground truthing" data base.  You can find it here:

https://iafi.org/ancient-british-isles-ice-sheet-time-lapse-animation/

It spans the period 31,000 yrs BP to 15,000 yrs BP, and shows parts of western Scotland being glaciated for almost the whole of that period, while West Wales experienced active ice cover for just 2,000 years and the Isles of Scilly for just a few centuries.

See also:

https://brian-mountainman.blogspot.com/2023/01/glacierized-landscapes-and-advance-of.html

This work is of great importance to the reliability of cosmogenic dating results -- measuring the "exposure time" of rock surfaces on (for example) tors or glacial erratics.  Cosmogenic dating methods are often used to measure the length of time that has elapsed since the "last disappearance of glacier ice"  -- but "nuclide inheritance" can seriously distort the results obtained, and in multiple cosmogenic dates obtained for a certain area it is sometimes difficult to isolate the "outliers".

It is also too easy to assume that in the presence of glacier ice, abrasion and surface lowering always occurs.  This is not so.  If an ice cover is thin, and glacier bed temperatures are very low, protection of bedrock or erratic surfaces may occur instead of erosion or abrasion.  Trimlines on upland slopes may not mark glacier edge positions, but the transition between warm-based (eroding) ice and cold-based (protecting) ice.  Long-term cover by snowfields can also distort results, as can periods of vegetation overgrowth.  

Lots to think about........