Comments on: Guliya Core #2 and Mountain Glacier Flow

By: Brooks Hurd

Brooks Hurd — Tue, 02 Jan 2007 20:58:01 +0000

Lucia,

I do not disagree with your arguments. I also believe that your comments are a valuable contribution to CA.

My comments are an attempt on my part to visualize how the annual ice layers travel from the accumulation zone, into and through the flowing section of the glacier.

It appears to me that only portions of the accumulation zone would have consistent annual layers similar to ice cores which have been drilled in Antartica. This indicates to me that some parts of of the accumulation zone as well as the flowing portions of the glacier would have a complex chronological makeup. The rather steep velocity profile that Steve M referenced for Guliya in post 42 makes it appear to me that the oldest ice is in the upper and lower boundary layers, whereas the rapidly flowing portions would be much composed of much younger ice.

By: Steve McIntyre

Steve McIntyre — Sun, 31 Dec 2006 14:52:04 +0000

#43. Willis, it looks to me like Law Dome is both flatter and colder than Guliya. I don’t have time to wade through the paper – did you notice relevant parameters for Guliya circumstances?

By: Willis Eschenbach

Willis Eschenbach — Sun, 31 Dec 2006 10:42:02 +0000

Steve, I found a good paper discussing the shear characteristics at various depths at Law Dome here. w.

By: Steve McIntyre

Steve McIntyre — Sun, 31 Dec 2006 05:13:38 +0000

HEre's an interesting table from this lecture about ice properties: Temperature at the base of the Guliya glacier (Core 2) was -2.1 deg C at 300 m in depth. The gradient seems to easily be at least 5 degrees. Some of the functions seem to be very nonlinear - notice that the flow at 5 degrees slope and 0 deg C goes from 4.7 m/year at 100 m depth to 75 m/year at 200 m depth. So at 300 m depth and -2.1 deg C, there must be some pretty serious flow. THat must be why the downslope Core at Dasuopu is young to such depths - high flow rates.

By: Steve McIntyre

Steve McIntyre — Sat, 30 Dec 2006 05:57:54 +0000

#40. I presume that “ick” is a technical term in rheology. Being unfamiliar with rheological terms myself, could you expand a little?

Visually it looks to me like the glaciers emanate out from a dome and then channelize after a certain point. I must say that I’m baffled as to how uphill ice from (say) 1765 located over a km away from one another knows how to emerge at a pinch-point at precisely the 1765 level at the pinch-point within a cm or so. (I presume that it doesn’t really and that’s why they prefer to drill at summits.)

Thompson has recently said that the base of the Guliya core contains 500,000 year old ice – the oldest tropical glacier ice. It’s like the competition between 19th century paleontologists to have the oldest horse fossil.

By: lucia

lucia — Sat, 30 Dec 2006 05:42:13 +0000

Bender:
Presumably, the anwer is “yes”. You can see some rheograms at the bottom of this page.
http://www.homepage.montana.edu/~geol445/hyperglac/systems2/#flow

Unfortunately, even if we got all the data available, the glacier flows occur in complex geometries. (I also assume these things start and stop?)

Steve: with respect to the image in #33– is that glacier spreading laterally as it narrows flowing downhill? That could explain thinning of the white part. Otherwise, I could envision quite a few things cause the middle region to thicken somewhat under flow conditions.

As to the slow in figure #34, all I can say is “oh, ick!”

By: bender

bender — Fri, 29 Dec 2006 15:47:19 +0000

Has the relationship between flow speed and deformity of the core’s properties been quantified, either in theory or in practice?

By: stephan harrison

stephan harrison — Fri, 29 Dec 2006 14:45:57 +0000

Re #36
Hi Steve. 4.7m/yr seems pretty average to me for high altitude/cold-based and/or continental glaciers. The ones I usually work on are moving about this much per day (high accumulation, calving, warm-based etc) and are therefore useless for coring.

By: Steve McIntyre

Steve McIntyre — Fri, 29 Dec 2006 13:37:30 +0000

#35. Thompson et al NATO 1996 Figure 3 shows a vertical temperature profile for Gliya Core 2, in which temperatures at 10 meters are -15.6 deg C, increasing to -2.1 deg C at the ice/bedrock contact at a depth of 308.6 m (in a topographic depression.)

By: Steve McIntyre

Steve McIntyre — Fri, 29 Dec 2006 13:34:18 +0000

#35. Stephan, does 4.7 m/year qualify as “rapidly moving” in your terms? (It seems fast to me.) That’s the speed at the site of Guliya Core 2. Adding another layer of inutility to this particular site is the inconsistent dating systems applied to this site – as noted elsewhere, three inconsistent versions of this core have been used in 2006 peer-reviewed literature.