Wednesday, 24 August 2016

Snowpatch time again.

This little tunnel within the Observatory Gully snowpatch had melted out from below. This was probably due to air movement. 
The Point Five Gully tunnel during the Ben Nevis Survey. This is formed by the stream flowing down Point Five Gully and under the snowpatch melting it from below.  
Alison Austin doing some science in the impressive Tower Cleft during the Ben Nevis survey. Probably a nicer place to be in winter than in summer.   
Still plenty of depth in the Observatory Gully patch. 
Saturday the 20th of August was the 9th annual Scottish snowpatch survey. Various people were out and about scanning the hills to see how much snow remains.  I joined Iain, Mark and Ben to see how things were looking on Ben Nevis. Iain has recently become a bit of a TV star with his interest in snow.

I had also been up that way a week or so earlier when working on the Ben Nevis survey as part of my work for the John Muir Trust. The Ben Nevis survey is a botanical and geological survey of Ben Nevis where mountaineers helped geologists and botanists into various places on the North Face which are not very easy to get to. I did three days on the survey in some fairly sub-optimal weather conditions, and visited some fairly dank and loose places to which I suspect I will never return to in summer conditions.

A relatively warm May and June, followed by a wet July and early August meant that there is a fair bit less snow on the hills now than there was at this time last year. However last year was quite exceptional, and compared to many years this year is not looking too bad. For example the Zero Gully patch which survived last year, was small when we passed it on the 20th However, some years it has not been there at all for the snowpatch survey. There was also a noticeable difference in size of the Observatory Gully patch between my visits on the 11th;and the 20th. I suspect this might be a reflection on how wet it had been between my two visits. 

Another view of the Observatory Gully Patch. Interestingly the wall in the foreground  is absent of the ablation hollows which  you usually see in such locations. I am not sure why this is. 
Iain taking pictures of the Point Five Gully patch. It was all looking a bit unstable, so we didn't actually go any further under the tunnel.  The boundary between last years snow and older multi year snow can be seen just above Iain's head. The snow tunnel here hard enlarged significantly, and was looking a lot less stable that 9 days earlier when I had visited it on the Ben Nevis survey. 
At the end of last autumn there was a significant amount of very hard, dense, icy snow remaining at the base of Point Five Gully and in particular in Observatory Gully. This meant that although last winter was not exceptional in terms of snow build up in these locations, they had a significant head start.  Despite the significant melting between my two visits, I would say that the Observatory Gully patch in particular was looking was looking very healthy, and point five was looking okay. In places the boundary between the last winter’s snow and the old hard icy multi-year snow was very evident.

One thing that was very noticeable about both the Observatory Gully and Point Five patches is how much melting had occurred from below due to water and air. This is due to these patches sitting on scree which allows the air start circulating underneath, and lots of running water coming down the gullies and flowing below the patches. This is in contrast to other long laying patches such as Aoanch Beag (the lowest lying regularly surviving snow patch) and Britain’s most permanent snow patch, the Sphinx Patch over in the Cairngorms. These patches lie in sunken hollows, and sit on soil rather than on rock so air and water do not get underneath them, so they only melt from the top. This means that they don’t melt as quickly, but on the other hand you don’t see the create the impressive tunnels and shapes that are shown in the photos here.  

After descending from Observatory Gully, Iain and the others continued round to Aonach Mor and Aonach Beag to have a look at the snow patches there. I had to head down to start getting organised for another trip up to Svalbard, which I am sure I will write about in due course.

From what I saw last on the Ben Nevis, and from Iain’s pictures for the rest of his trip my predictions of the West coast snow patches are as follows; Observatory Gully will definitely survive, Aonach Beag is highly likely and Point Five likely to survive. I don't think however, that the other remaining Lochaber patches will make it.  I will let you know how accurate these predictions are in a few months time.....
Heading home! It will be interesting to see how much of this snow remains when next season  lasting snow arrives in October or November. 

No comments:

Post a comment