[Foxy2]

Has anybody referred to this link:

http://e360.yale.edu...g_glaciers/8/1/

Comparisons of glacier extent at present with that in the early 20th century, as observed in photographs.

If its been mentioned then accept my 'apologies'.

[ldavidcooke]

Village, on 06 March 2012 - 17:00, said:

I dont particularly like that word tolerant. Its the wrong word. I dont want people tolerating me and I certainly wont tolerate childish (you have hurt my feelings nonsense).
The word I believe is understanding. I try to understand the alternative point of view and understand the other person behind it to see their viewpoint. Its understanding which I ask for in an adult conversation.
Thats also the way to understanding the subject.

Hey Vil,

Just as long as you try to understand others as much as to be understood yourself we are okay with the difference.

(Toleration of others view points actually is more similar to agreeing to disagree. Through accepting others rights to their PoV and not requiring them to have your PoV, is being tolerant.)

[Peter H]

Foxy2, on 06 March 2012 - 17:58, said:

Has anybody referred to this link:

http://e360.yale.edu...g_glaciers/8/1/

Comparisons of glacier extent at present with that in the early 20th century, as observed in photographs.

If its been mentioned then accept my 'apologies'.

Not seen that, some impressive contrasts over time!

[John Mason]

Yes that's an impressive set of image-pairs. It's impossible to pretend that radical changes are not afoot in these. The areas where glaciers are advancing are localised to those where precipitation has cranked right up IIRC - parts of the Karakorum for instance, where the super-monsoons that slam into that corner of the world obviously involve phenomenal dumpings of snow at altitude. As per our discussions as to why Siberia largely escaped glaciation in the last glacial, temperatures alone are not the key: temperatures and precipitation-patterns most certainly are, and the two have an important relationship.

Cheers - John

[andre]

Aren't we just looking at variation, due to changes in precipitation.

Also how would glaciers melt on those pressure levels when the average temperatures rose from say -10C to maybe -8C?

This post has been edited by andre: 07 March 2012 - 18:17

[John Mason]

Andre,

This I too wondered, but the answer is to read a few expedition-books by e.g. Bonington, Scott, Boardman, Habeler, Messner et al. I was surprised to find how hot it can get at altitude during relatively calm and clear conditions during summertime. It can get seriously hot. Guess if the consequential melt-rate overtakes the replenishment-rate then retreat of glaciers is guaranteed, with heat/cold and precip trends all having an effect. From news from the Sherpa people, the Khumbu Icefall on Everest seems to be a lot more dodgy than it was too - and it was always a well dodgy place.

We see the same in the Alps. The north face of the Eiger is not attempted in summer any more, except by the suicidal, because the stonefall is much worse than it used to be. Attempts are now standard in Spring and Autumn, and for the tough dudes, in winter. But not summer.

Cheers - John

[Nigel Bolton]

The apparent heat, and believe me, it can feel torrid, is partially due to the fact that the UV's bounce off the snow and come at you from all angles. A snowy valley or glacier can seriously focus the heat, and can create an extremely high sunburn risk, even in those bits that do not see direct sunshine, such as ear lobes, chin and under the nose.

Mountaineers normally wear bright coloured cloting too, which are good at UV absorbtion. However, as soon as the sun dips below the horizon at altitude, it goes from searing heat to intense cold in seconds.

N.

[John Mason]

Out of all the books that describe this, I thing Peter Haberler's account of the first ascent of Everest without oxygen should be the starting-point, BTW. The rest are excellent writers but the detail in Habeler's account is useful. Plus, talk to some leading Sherpas, who know their country.

Cheers - John

[ldavidcooke]

Hey John,

Hmmm..., it still seems that generally overall it is a variation in precipitation driving most of the change. I would think if it were not for the recent bout of stagnant Summer ridges the normal melt would be less.

Likewise, the issue of the change in the coastal Ridge setting up in NE Asia drying out the air masses in the Bangladesh and Indian peninsula. (Afterall when was the last time massive loss of life due to flooding, due to annual monsoons dominated the evening news.)

BTW, did I understand correctly that you correspond with Sherpas in this region? Also do we really need to revisit the IPCCs erronous inclusion of images from the WWF being passed off as fact again. Circular proof is not proof... ( Sorry poor joke on my part... (:-) )

[Flatlander]

Is evaporation not much reduced at altitude too?

I suspect there will be a positive feedback with more exposed rock = more solar heating. A small precipitation change could be amplified quite significantly. Radiation is the main thing you notice on a glacier, not what the air temperature is - especially when you are advised to 'dress for the crevasse' and not the surface...

Is there any difference between N and S flowing glaciers? Be interesting to know.


The Alps are different, because it can get above freezing in the summer. The nights when the glaciers don't freeze are the ones to avoid...

[John Mason]

Good points, Tim. Indeed, glacier-travel can be hard-going on a hot day, but falling, even if roped, ten metres into a crevasse in shorts and t-shirt would be a Very Bad Thing, so sweating and cursing is the order of the day. Luckily on most Alpine routes I've done the hotter part of the day on a glacier has been spent in descent.

LDC, the point I was making is based on observations from these climbers of temperature on fine summer days reaching 30-40C in the Khumbu Ice-fall and the Western Cwm on Everest, despite sharp overnight minima, and most of these accounts date back some twenty years. The diurnal temperature range at altitude on a fine day out of the wind can be phenomenal.

I would certainly like to correspond directly with the Sherpa folk, but for now it needs to be second-hand info. Many news outlets are currently running this story:

http://news.yahoo.co...-141707761.html

If this guy says there have been big changes, then I'm prepared to take his word for it.

Cheers - John

[ldavidcooke]

Hey John,

No problem with his concern over moraine lake failures, just over assesment of reason for formation. Of course, I did not think you to be in correspondence; however your post appeared to suggest it. Finally, as to reasons for warmth, t is quite clear that clear skies have multiplied the sublimation effect combined with the solar heating due to changes in tbe large scale weather patterns. As of yet the changes in these patterns have not been linked to the change in night-time radiational reduction and increased advection, unless you have seen recent data to that effect in a paper... Even then we do no have an explanation why the advection would be centered over land in Asia when it is evident over the ocean in the N. Atlantic...

[Nigel Bolton]

Tim Prosser, on 08 March 2012 - 00:42, said:

Is evaporation not much reduced at altitude too?

I suspect there will be a positive feedback with more exposed rock = more solar heating. A small precipitation change could be amplified quite significantly. Radiation is the main thing you notice on a glacier, not what the air temperature is - especially when you are advised to 'dress for the crevasse' and not the surface...

Is there any difference between N and S flowing glaciers? Be interesting to know.


The Alps are different, because it can get above freezing in the summer. The nights when the glaciers don't freeze are the ones to avoid...

Evaporation can be significantly enhanced at altitude for two reasons.

One, the air is often very dry, i.e. low RH.

Two, Stronger winds.

The two in combination can cause a good deal of sublimation of snow and ice. However, strong winds can blow snow off of the ridges into the valleys, effectively covering glaciers in pure white.

If glaciers are retreating, and there is strong evidence that they are, how much of the acceleration of melt is due to change of albedo of cover caused by changes in the percentages of medial moraine with respect to ice?

N.

This post has been edited by Nigel Bolton: 08 March 2012 - 23:20