conceptually, I can picture circumstances where glacier melt is substantial proportion of runoff and circs where it isn’t. The Ottawa River of 10000 BP was Amazon-sized due to the recession of the Laurentide glaciation. The modern Mississippi has negligible contributions from glacier recession.

On a worldwide basis, I’m satisfied there is actual glacier recession in the 20th century and it’s idle to argue that some glaciers are advancing and others are retreating as some kind of supposed rebuttal of this.

I presume that everyone agrees that during a period of glacier recession, runoff will be larger than the annual precipitation by some amount. The practical question is whether the percentage is trivial or material.

bender argues that contribution from receding glaciers in the Canadian prairies is non-negligible. If so, in practical terms, all this suggests to me is that this particular area is experiencing a non-recurring and non-sustainable supply of water – sort of like mining an aquifer.

As far as I can tell, this may well be a real long-term problem, but one that would exist anyway. If global warming stopped and the glaciers stopped receding, the runoff would be reduced.

My guess is that the percentage contribution of receding glaciers in India is negligible and that most of the runoff is from current precipitation. However, if this is incorrect and some substantial proportion is from “mining” the meltwater, then isn’t this a potential problem whenever the recession stops for whatever reason?

The (Columbia) glacier retreated 394m between 1724 and 1924 and advanced 1km between 1966-1977. After 1975, the glacier advanced further to completely fill the large proglacial lake, a distance of approximately 800m (Ommanney, 2002).

The size of the advance since the 60s is surprisingly large, especially relative to the size of the retreat from the LIA. Some glaciers are known to periodically surge. Maybe this is one of them. As noted earlier there is no data on ice mass for this glacier.

Link

To bring this topic back on thread, the Schindler paper cannot therefore be used to argue that the decline of glacial meltwater will have a persistent adverse impact downstream.

how do you come to this wild conclusion?
a 50% loss of water in drough years is not an argument, supporting “a persistent adverse impact downstream”???

in a raising temperature scenario, as we are experiencing it at the moment?

The one comment that I would be inclined to make on this is that, if people are depending on water from glacier retreat in tropical and temperate settings, then it seems to me that their water supply would be equally diminished by glacier stabilization or advance, not just by glacier disappearance.

this is obviously false. glacier stabilization and advance could both be accompanied by the same or even more melting water.
it will only reduce melt water, if you assume a constant level of snowfall.

it looks like for us, the glaciers provide a helpful feedback during times of temperature increase: they provide the steady water necessary in dry years and with warming temperature tend to provide MORE water.
right up to the moment, when they are (sort of) gone…

it is a very good example of a climate change problem. it illustrates how nature compensates and delays the change. to judge the effect, we need to factor an increased vulnerability. people depend on the water for irrigation and electricity, which will lead to conflicts. people adjust to a slow change and will have difficulties to handle a fast one. (multi year drought, with no glacier counterbalance)

India’s and Pakistan’s economies seem to be doing pretty good now. If there is a real threat of losing the storage from the Himalayan glaciers, I would expect their government to do something about it locally.

America built most of its its surface storage during the great depression when it was practically broke, so I don’t buy the concept that India or Pakistan can’t afford to do it now.

I can’t think of any other major population as being dependent on glacier melt other than India or Pakistan. Anyone else know of any?

The general point seems simple unto being trivial. Wastage increases runoff.

But what proportion of runoff in river basins of interest is contributed by “mining” of meltwater from receding glaciers relative to annual precipitation? 1% 10% 50% ??? Let’s try to collate some facts before speculating.

As to people providing references: it would be far more helpful if you cited figures from the refs, rather than saying the refs look interesting.

Just a reminder to posters, don’t just quote the post # in your reply — it’s likely to change. Best to head your post with the OP’s name, topic, maybe a brief quote of what you’re replying to. See http://climateaudit101.wikispot.org/FAQ

Otherwise, it’s an unholy mess to try to follow — like this thread!

Try to help other readers, please.

What a pity that blog software writers ignore 30 years of Usenet experience in dealing with these issues…

Thanx in advance, Pete Tillman