#22 — Aonach Beag’s six-year-old snow

On 20 August I visited the long-lying patch of snow at Aonach Beag, near Ben Nevis. The ostensible aim of the visit was to ensure the snow was still there so that it could be counted in the annual all-country survey that I’ve been doing since 2008.

When my walking companion (Al Todd) and I reached the rim of An Cuil Choire, we peered over hoping to see the snow still present. To our relief it was, and slightly larger than we thought it would be.

Our initial view. The patch is visible at the foot of the large cliffs.

When we got down to the patch (which measured 20 metres long) we could see there were a number of features about it which were highly interesting. The first one was the sheer solidity of the snow. Although the top few mm were soft, the underlying core more resembled glacial ice than Scottish snow. Walking on it without an ice axe and crampons would have been hazardous, given its angle and rocky run-out if a fall had occurred.

The second feature of note was the amount of debris that covered the right hand side of the patch.

Al stands on the snow, which is covered with rock debris from above.

It is unusual to see so much rock in such a confined area, and it is beyond doubt that this rock had come down from above over a period of time. The question we asked ourselves was ‘how long’? To us the snow looked much older than other patches that persist this late in the season.

I was fortunate in that I had been to this location many times over the last few years, and I said to Al at the time I suspected the snow we were looking at fell in 2011. If that were the case, it would partly answer the question about the amount of rock on it, and the glacial quality of the snow (the ‘snow’ was, in fact, now firn).

When large multi-year snow patches melt out, the debris that has been held in them eventually and inexorably travels downward and reaches the ground. Because the Aonach Beag snow is the smallest it’s been since winter 2011/12, all the rock that has been imprisoned is now being liberated. So it’s almost certain that the stones visible in the pictures date from a variety of years from 2012–2017.

‘How do you know the snow visible is from 2011?’

The notes and photographic records we have for this location are very good, so it is possible to look back to ascertain what was present in each year.

21 October 2012. The snow visible here fell the previous winter. The patch didn’t survive in 2011, so we know for sure this is all from one winter’s falls.

Al Todd at Aonach Beag on 29 September 2013. 2011/12 snow buried, and would remain so for the rest of the season

29 October 2014. Very large patch, a result of the huge snowfalls of winter 2013/14. The snow from 2011/12 is very well buried.

17 August 2015. An extraordinary amount of snow for the time of year. This patch would remain large right up until the new season’s falls buried it. Winter 2011/12 patch has hundreds of tonnes of snow covering it.

5 November 2016. Blair Fyffe stands at the bottom of the snow patch, with fresh snow surrounding it. Again, the 2011/12 snow is well buried.

On 31 October 2012 there was a big fall of snow that completely covered the patch from winter 2011/12, and which hasn’t seen the light of day since. For further evidence compare the rocks in the photo of 20 August 2017 with those in the photo from 21 October 2012.

20 August 2017

21 October 2012

The two photographs show the snow with a striking similarity. There is a slight difference in the upper right hand side of the 2012 image, but this can be attributed to the slight melting that happened after the photo was taken, and before the heavy falls of 31 October that buried it.

It is for these reasons that we can say with some certainty that the snow now visible at Aonach Beag is from winter 2011/12.