Re: The Cryosphere -- discussion clarification

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Re: The Cryosphere -- discussion clarification

Wendell Tangborn


On Wed, May 2, 2012 at 11:29 AM, wendell Tangborn <[hidden email]> wrote:
Hi William,
 
Removing the two wild points ( 5 mwe at about 2800 m elevation and 5.5 mwe at 2300 m) would drastically change the shape of the exponential curve in Figure 1, and it also would not predict 6 mwe at 3200 m elevation).  Too much weight is given to these points in comparison to the others.
 
Should I be posting these comments on Cryolist? 
 
Regards
 
Wendell
 


 
On Wed, May 2, 2012 at 9:00 AM, William Colgan <[hidden email]> wrote:

Hi Wendell -- Yes, I appreciate there has been some suspicion of the accuracy of the 1978 measurements, but Tad's post points to a new 2010 in situ dataset collected by Shad O'Neel that agrees very well with the 1978 measurements, hmm... Liam

 

----------------------------------------------------

http://cires.colorado.edu/~colganw

 

From: wendell Tangborn [mailto:[hidden email]]
Sent: May-01-12 8:29 PM


To: William Colgan
Subject: Re: The Cryosphere -- discussion clarification

 

Hi William,

 

Thanks for your response. Such high accumulation above 2000 m on the Columbia Glacier in 1978 is impossible to believe.  It has to be due a misreading of the summer surface at the  two points, either with a coring auger or in a snow pit - it was likely from a core as digging a 5 meter snowpit at this altitude would be a major manpower effort. It is unlikely that much dust collects on the surface of the Columbia Glacier at this altitude, therefore detecting a summer surface would be extremely difficult.

 

In addition, these two points are not at all compatible with the remaining balance measurements below 2000 m or with the balance-altitude curve produced wth the PTAA model.  I realize of course that the PTAA model balance results are not too credible even though they appear reasonable, and have been verified for nearby glaciers that have records of manually measured annual balances (for example, Gulkana ad Wolverine).

 

I plan to .re-run the mass balance calculation of the Columbia Glacier as part of a larger mass balance project that is briefly described on the attached document.  The PTAAGMB website will soon go on line.

 

Best Regards

 

Wendell

 



 

On Mon, Apr 30, 2012 at 10:45 AM, William Colgan <[hidden email]> wrote:

Hi Wendell, I think I will be running some low accumulation scenarios, but I imagine that there might not be sufficient mass input to maintain the pre-retreat ice geometry with the imposed pre-retreat sliding field. Re: USGS observations, I see Tad just posted a new figure on the discussion forum that seems to run counter to your sentiment.... Thanks for the citation verification. Liam

 

----------------------------------------------------

http://cires.colorado.edu/~colganw

 

From: wendell Tangborn [mailto:[hidden email]]
Sent: April-25-12 10:27 AM
To: William Colgan
Subject: Re: The Cryosphere -- discussion clarification

 

Hi William,

 

The Columbia paper that was published by BPRC is the same as the PDF that you  cite although the figures in color make it very confusing.  It is much easier to scan a paper and make a PDF now than it was in 1997 so I'll replace the one on-line with an improved copy soon.  I assume you have access to BPRC publication No 15 where this paper appears. 

 

I still feel the high accumulation measured at two stakes by the USGS  on the upper Columbia Glacier is not correct (I had several discussions with Mark Meier about this nearly 20 years ago but we never came to an agreement).  Figure 5 in my paper clearly shows the difference.  Using such a high value for accumulation above 2000 m distorts the balance-elevation curve and must create a problem with modeling the flow of this glacier.  Have you noticed this in your research?

 

Best Regards

 

Wendell

On Tue, Apr 24, 2012 at 11:28 AM, William Colgan <[hidden email]> wrote:

Hi Wendell -- I recently submitted a paper to The Cryosphere on Columbia Glacier. In an online ("open") discussion forum during review, someone referred me to your paper, which I had previously overlooked. The citation they provide suggests it is a PBRC publication, but the version I find at http://www.hymet.com/docs/columbiaglacier.pdf does not look like a PBRC publication. I would appreciate if you could clarify the confusion in our discussion forum, at http://www.the-cryosphere-discuss.net/6/893/2012/tcd-6-893-2012-discussion.html

 

The query is raised in the M. Pelto thread, but I welcome your thoughts on any aspect of the general discussion as well. The discussion board closes down in about a week (May 2). Thanks very much, Liam Colgan

 

----------------------------------------------------

http://cires.colorado.edu/~colganw

 




--
Wendell Tangborn
HyMet
13629 Burma Rd SW
Vashon Island, WA 98070
<a href="tel:206%20567%204077" target="_blank">206 567 4077
[hidden email]
www.hymet.com




--
Wendell Tangborn
HyMet
13629 Burma Rd SW
Vashon Island, WA 98070
<a href="tel:206%20567%204077" target="_blank">206 567 4077
[hidden email]
www.hymet.com




--
Wendell Tangborn
HyMet
13629 Burma Rd SW
Vashon Island, WA 98070
<a href="tel:206%20567%204077" target="_blank" value="+12065674077">206 567 4077
[hidden email]
www.hymet.com



--
Wendell Tangborn
HyMet
13629 Burma Rd SW
Vashon Island, WA 98070
206 567 4077
[hidden email]
www.hymet.com

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Re: The Cryosphere -- discussion clarification

Rod March
I'm not sure this discussion is appropriate to Cryolist, but as it appeared there to me, I am responding there. Please disregard this if you are not interested in 1978 point measurements of very large balances from the top of Columbia Glacier, their methodology and accuracies.


Wendell and William,

I'm responding In regards to suspicion about the accuracy of the 1978 balance measurements at the two highest sites at Columbia Glacier: 2640 m and 2220 m elevation, 2 km and 8 km from the head of the glacier. The balance measurements of about 5 mwe at these sites would translate into pit depths of about 10 m, not 5 m, and that is certainly too deep for a snow pit.  Measuring snow/firn depths of about 10 m is extremely difficult and hence suspicion is reasonable. I was not involved with making these measurements myself though am one of the authors of the report this data appeared in:

Columbia Glacier stake location, mass balance, glacier surface altitude, and ice radar data, 1978 measurement year; 1979; OFR; 79-1168; Mayo, L. R.; Trabant, D. C.; March, Rod; Haeberli, Wilfried (not available online at this time)

The report is a pretty stripped down data report with minimal text and no specifics about the methods used for these high balance measurements.

I was able to look up the notes for these measurements and can provide you with some information about how they were made.
Stakes were install at both sites with 2 strong magnets (roughly 1" diameter by 1' long each) installed in the tops of both stakes in August 1977. The height of the 1977 summer surface was identified on the stakes at the time of the stake installations. In August 1978 both sites were re-visited and the stakes were buried and not directly observed. Magnetometer surveys were conducted by a tech of Will Harrison's, to locate the stakes and determine the depth to the magnets from mapping the field strength. Will has published a report about the technique of using magnets and magnetometer surveys to determine snow depths. The depth to the magnets was added to the height of the magnet above the 1977 summer surface when the magnets and stakes were installed to get the depth of snow/firn remaining at the end of the 1978 balance year. It was assumed that the height of the 1977 summer surface on the stake did not change significantly over the year. Snow pits were dug to about 1.5 meter for partial density and coring was done from the pit bottom to determine the density down to about 10 m at each site. I don't know what the accuracy of the magnetometer depth surveys is or how it might be affected by a leaning stake (and magnet) without looking up Will's paper but I think it is suppose to be pretty good and not too sensitive to leaning unless the lean is fairly severe. I have not taken the time recheck all the interpretations of the coring and magnetometer surveys and stake readings.

Making balance measurements this deep is challenging and it is reasonable to be suspicious of them. Though I can't guarantee their accuracy, from a quick review of the notes, these appear to be pretty good measurements for snow this deep. And they do not depend on the visual identification of the summer surface in a core, as was suggested, which admittedly can be difficult this high in the Chugach Mts where accumulation occurs year round.

Hope this is helpful.

Rod
-- 
Rod March
US Geological Survey
3400 Shell St.
Fairbanks, Ak 99701-7245
907-479-5645 ext. 241

On 5/2/2012 12:31 PM, wendell Tangborn wrote:


On Wed, May 2, 2012 at 11:29 AM, wendell Tangborn <[hidden email]> wrote:
Hi William,
 
Removing the two wild points ( 5 mwe at about 2800 m elevation and 5.5 mwe at 2300 m) would drastically change the shape of the exponential curve in Figure 1, and it also would not predict 6 mwe at 3200 m elevation).  Too much weight is given to these points in comparison to the others.
 
Should I be posting these comments on Cryolist? 
 
Regards
 
Wendell
 


 
On Wed, May 2, 2012 at 9:00 AM, William Colgan <[hidden email]> wrote:

Hi Wendell -- Yes, I appreciate there has been some suspicion of the accuracy of the 1978 measurements, but Tad's post points to a new 2010 in situ dataset collected by Shad O'Neel that agrees very well with the 1978 measurements, hmm... Liam

 

----------------------------------------------------

http://cires.colorado.edu/~colganw

 

From: wendell Tangborn [mailto:[hidden email]]
Sent: May-01-12 8:29 PM


To: William Colgan
Subject: Re: The Cryosphere -- discussion clarification

  Hi William,

 Thanks for your response. Such high accumulation above 2000 m on the Columbia Glacier in 1978 is impossible to believe.  It has to be due a misreading of the summer surface at the  two points, either with a coring auger or in a snow pit - it was likely from a core as digging a 5 meter snowpit at this altitude would be a major manpower effort. It is unlikely that much dust collects on the surface of the Columbia Glacier at this altitude, therefore detecting a summer surface would be extremely difficult.

In addition, these two points are not at all compatible with the remaining balance measurements below 2000 m or with the balance-altitude curve produced wth the PTAA model.  I realize of course that the PTAA model balance results are not too credible even though they appear reasonable, and have been verified for nearby glaciers that have records of manually measured annual balances (for example, Gulkana ad Wolverine).

I plan to .re-run the mass balance calculation of the Columbia Glacier as part of a larger mass balance project that is briefly described on the attached document.  The PTAAGMB website will soon go on line.

Best Regards

Wendell



 

On Mon, Apr 30, 2012 at 10:45 AM, William Colgan <[hidden email]> wrote:

Hi Wendell, I think I will be running some low accumulation scenarios, but I imagine that there might not be sufficient mass input to maintain the pre-retreat ice geometry with the imposed pre-retreat sliding field. Re: USGS observations, I see Tad just posted a new figure on the discussion forum that seems to run counter to your sentiment.... Thanks for the citation verification. Liam

 

----------------------------------------------------

http://cires.colorado.edu/~colganw

 

From: wendell Tangborn [mailto:[hidden email]]
Sent: April-25-12 10:27 AM
To: William Colgan
Subject: Re: The Cryosphere -- discussion clarification

 

Hi William,

The Columbia paper that was published by BPRC is the same as the PDF that you  cite although the figures in color make it very confusing.  It is much easier to scan a paper and make a PDF now than it was in 1997 so I'll replace the one on-line with an improved copy soon.  I assume you have access to BPRC publication No 15 where this paper appears. 

I still feel the high accumulation measured at two stakes by the USGS  on the upper Columbia Glacier is not correct (I had several discussions with Mark Meier about this nearly 20 years ago but we never came to an agreement).  Figure 5 in my paper clearly shows the difference.  Using such a high value for accumulation above 2000 m distorts the balance-elevation curve and must create a problem with modeling the flow of this glacier.  Have you noticed this in your research?

Best Regards

Wendell

On Tue, Apr 24, 2012 at 11:28 AM, William Colgan <[hidden email]> wrote:

Hi Wendell -- I recently submitted a paper to The Cryosphere on Columbia Glacier. In an online ("open") discussion forum during review, someone referred me to your paper, which I had previously overlooked. The citation they provide suggests it is a PBRC publication, but the version I find at http://www.hymet.com/docs/columbiaglacier.pdf does not look like a PBRC publication. I would appreciate if you could clarify the confusion in our discussion forum, at http://www.the-cryosphere-discuss.net/6/893/2012/tcd-6-893-2012-discussion.html

 

The query is raised in the M. Pelto thread, but I welcome your thoughts on any aspect of the general discussion as well. The discussion board closes down in about a week (May 2). Thanks very much, Liam Colgan

 

----------------------------------------------------

http://cires.colorado.edu/~colganw

 




--
Wendell Tangborn
HyMet
13629 Burma Rd SW
Vashon Island, WA 98070
<a moz-do-not-send="true" href="tel:206%20567%204077" target="_blank">206 567 4077
[hidden email]
www.hymet.com




--
Wendell Tangborn
HyMet
13629 Burma Rd SW
Vashon Island, WA 98070
<a moz-do-not-send="true" href="tel:206%20567%204077" target="_blank">206 567 4077
[hidden email]
www.hymet.com




--
Wendell Tangborn
HyMet
13629 Burma Rd SW
Vashon Island, WA 98070
<a moz-do-not-send="true" href="tel:206%20567%204077" target="_blank" value="+12065674077">206 567 4077
[hidden email]
www.hymet.com



--
Wendell Tangborn
HyMet
13629 Burma Rd SW
Vashon Island, WA 98070
206 567 4077
[hidden email]
www.hymet.com


_______________________________________________
You're subscribed to the CRYOLIST mailing list
To change your subscription options, visit http://cryolist.org/member
To send a message to the list, email [hidden email]
For conference-related messages, email
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For posting guidelines, see http://cryolist.org/posting/ 



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To change your subscription options, visit http://cryolist.org/member
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Re: The Cryosphere -- discussion clarification

Wendell Tangborn
In reply to this post by Wendell Tangborn
How snow accumulation is measured makes a great difference.  Is it 25  meters deep at the end of the season or is daily accumulation summed throughout the winter to total 25 m?  At the Mt Baker ski resort  here in Washington they have reported as much as 90 feet (27 m) of accumulation by totaling the daily measurement throughout the winter.  The actual depth in the spring is much less of course.
 
Wendell

On Wed, May 2, 2012 at 8:34 PM, de la Pena, Santiago <[hidden email]> wrote:
Hi William and Wendell,

    I am not sure if this will help, but Valdez Heli Skiing keeps accurate snowfall records in the Chugach just 50 km east of Columbia. They report an average of 25 m of annual snow accumulation at an elevation of about 7,500 feet (so about 5-8 m.w.e.). Annual accumulation at Columbia at an elevation of 2000 m shouldn't differ much from 5 m.w.e.

Kind regards,

Santiago de la Peña

Byrd Fellow
Byrd Polar Research Center, the Ohio State University
1090 Carmack Road
Columbus, OH 43212




From: [hidden email] [[hidden email]] on behalf of wendell Tangborn [[hidden email]]
Sent: Wednesday, May 02, 2012 4:31 PM
To: William Colgan
Cc: Cryolist
Subject: Re: [CRYOLIST] The Cryosphere -- discussion clarification



On Wed, May 2, 2012 at 11:29 AM, wendell Tangborn <[hidden email]> wrote:
Hi William,
 
Removing the two wild points ( 5 mwe at about 2800 m elevation and 5.5 mwe at 2300 m) would drastically change the shape of the exponential curve in Figure 1, and it also would not predict 6 mwe at 3200 m elevation).  Too much weight is given to these points in comparison to the others.
 
Should I be posting these comments on Cryolist? 
 
Regards
 
Wendell
 


 
On Wed, May 2, 2012 at 9:00 AM, William Colgan <[hidden email]> wrote:

Hi Wendell -- Yes, I appreciate there has been some suspicion of the accuracy of the 1978 measurements, but Tad's post points to a new 2010 in situ dataset collected by Shad O'Neel that agrees very well with the 1978 measurements, hmm... Liam

 

----------------------------------------------------

http://cires.colorado.edu/~colganw

 

From: wendell Tangborn [mailto:[hidden email]]
Sent: May-01-12 8:29 PM


To: William Colgan
Subject: Re: The Cryosphere -- discussion clarification

 

Hi William,

 

Thanks for your response. Such high accumulation above 2000 m on the Columbia Glacier in 1978 is impossible to believe.  It has to be due a misreading of the summer surface at the  two points, either with a coring auger or in a snow pit - it was likely from a core as digging a 5 meter snowpit at this altitude would be a major manpower effort. It is unlikely that much dust collects on the surface of the Columbia Glacier at this altitude, therefore detecting a summer surface would be extremely difficult.

 

In addition, these two points are not at all compatible with the remaining balance measurements below 2000 m or with the balance-altitude curve produced wth the PTAA model.  I realize of course that the PTAA model balance results are not too credible even though they appear reasonable, and have been verified for nearby glaciers that have records of manually measured annual balances (for example, Gulkana ad Wolverine).

 

I plan to .re-run the mass balance calculation of the Columbia Glacier as part of a larger mass balance project that is briefly described on the attached document.  The PTAAGMB website will soon go on line.

 

Best Regards

 

Wendell

 



 

On Mon, Apr 30, 2012 at 10:45 AM, William Colgan <[hidden email]> wrote:

Hi Wendell, I think I will be running some low accumulation scenarios, but I imagine that there might not be sufficient mass input to maintain the pre-retreat ice geometry with the imposed pre-retreat sliding field. Re: USGS observations, I see Tad just posted a new figure on the discussion forum that seems to run counter to your sentiment.... Thanks for the citation verification. Liam

 

----------------------------------------------------

http://cires.colorado.edu/~colganw

 

From: wendell Tangborn [mailto:[hidden email]]
Sent: April-25-12 10:27 AM
To: William Colgan
Subject: Re: The Cryosphere -- discussion clarification

 

Hi William,

 

The Columbia paper that was published by BPRC is the same as the PDF that you  cite although the figures in color make it very confusing.  It is much easier to scan a paper and make a PDF now than it was in 1997 so I'll replace the one on-line with an improved copy soon.  I assume you have access to BPRC publication No 15 where this paper appears. 

 

I still feel the high accumulation measured at two stakes by the USGS  on the upper Columbia Glacier is not correct (I had several discussions with Mark Meier about this nearly 20 years ago but we never came to an agreement).  Figure 5 in my paper clearly shows the difference.  Using such a high value for accumulation above 2000 m distorts the balance-elevation curve and must create a problem with modeling the flow of this glacier.  Have you noticed this in your research?

 

Best Regards

 

Wendell

On Tue, Apr 24, 2012 at 11:28 AM, William Colgan <[hidden email]> wrote:

Hi Wendell -- I recently submitted a paper to The Cryosphere on Columbia Glacier. In an online ("open") discussion forum during review, someone referred me to your paper, which I had previously overlooked. The citation they provide suggests it is a PBRC publication, but the version I find at http://www.hymet.com/docs/columbiaglacier.pdf does not look like a PBRC publication. I would appreciate if you could clarify the confusion in our discussion forum, at http://www.the-cryosphere-discuss.net/6/893/2012/tcd-6-893-2012-discussion.html

 

The query is raised in the M. Pelto thread, but I welcome your thoughts on any aspect of the general discussion as well. The discussion board closes down in about a week (May 2). Thanks very much, Liam Colgan

 

----------------------------------------------------

http://cires.colorado.edu/~colganw

 




--
Wendell Tangborn
HyMet
13629 Burma Rd SW
Vashon Island, WA 98070
<a href="tel:206%20567%204077" target="_blank">206 567 4077
[hidden email]
www.hymet.com




--
Wendell Tangborn
HyMet
13629 Burma Rd SW
Vashon Island, WA 98070
<a href="tel:206%20567%204077" target="_blank">206 567 4077
[hidden email]
www.hymet.com




--
Wendell Tangborn
HyMet
13629 Burma Rd SW
Vashon Island, WA 98070
<a href="tel:206%20567%204077" target="_blank" value="+12065674077">206 567 4077
[hidden email]
www.hymet.com



--
Wendell Tangborn
HyMet
13629 Burma Rd SW
Vashon Island, WA 98070
<a href="tel:206%20567%204077" target="_blank" value="+12065674077">206 567 4077
[hidden email]
www.hymet.com



--
Wendell Tangborn
HyMet
13629 Burma Rd SW
Vashon Island, WA 98070
206 567 4077
[hidden email]
www.hymet.com

_______________________________________________
You're subscribed to the CRYOLIST mailing list
To change your subscription options, visit http://cryolist.org/member
To send a message to the list, email [hidden email]
For conference-related messages, email
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For posting guidelines, see http://cryolist.org/posting/ 
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Re: The Cryosphere -- discussion clarification

Roger Braithwaite
In reply to this post by Rod March

I didn’t understand these messages until I read Rod’s comment. The issue seems to be the correct measurement of accumulation and/or winter balance when it is too large to caught by a conventional snow pit. It would be a great shame if our global knowledge of observed glacier balance would be biased to low-accumulation glaciers. Indeed, some of us would argue that high-accumulation glaciers ought to be the ones that are more sensitive to climate variations.

 

 

Roger Braithwaite

[hidden email]

 

From: [hidden email] [mailto:[hidden email]] On Behalf Of Rod March
Sent: 03 May 2012 00:30
To: wendell Tangborn; William Colgan; [hidden email]
Subject: Re: [CRYOLIST] The Cryosphere -- discussion clarification

 

I'm not sure this discussion is appropriate to Cryolist, but as it appeared there to me, I am responding there. Please disregard this if you are not interested in 1978 point measurements of very large balances from the top of Columbia Glacier, their methodology and accuracies.


Wendell and William,

I'm responding In regards to suspicion about the accuracy of the 1978 balance measurements at the two highest sites at Columbia Glacier: 2640 m and 2220 m elevation, 2 km and 8 km from the head of the glacier. The balance measurements of about 5 mwe at these sites would translate into pit depths of about 10 m, not 5 m, and that is certainly too deep for a snow pit.  Measuring snow/firn depths of about 10 m is extremely difficult and hence suspicion is reasonable. I was not involved with making these measurements myself though am one of the authors of the report this data appeared in:

Columbia Glacier stake location, mass balance, glacier surface altitude, and ice radar data, 1978 measurement year; 1979; OFR; 79-1168; Mayo, L. R.; Trabant, D. C.; March, Rod; Haeberli, Wilfried (not available online at this time)

The report is a pretty stripped down data report with minimal text and no specifics about the methods used for these high balance measurements.

I was able to look up the notes for these measurements and can provide you with some information about how they were made.
Stakes were install at both sites with 2 strong magnets (roughly 1" diameter by 1' long each) installed in the tops of both stakes in August 1977. The height of the 1977 summer surface was identified on the stakes at the time of the stake installations. In August 1978 both sites were re-visited and the stakes were buried and not directly observed. Magnetometer surveys were conducted by a tech of Will Harrison's, to locate the stakes and determine the depth to the magnets from mapping the field strength. Will has published a report about the technique of using magnets and magnetometer surveys to determine snow depths. The depth to the magnets was added to the height of the magnet above the 1977 summer surface when the magnets and stakes were installed to get the depth of snow/firn remaining at the end of the 1978 balance year. It was assumed that the height of the 1977 summer surface on the stake did not change significantly over the year. Snow pits were dug to about 1.5 meter for partial density and coring was done from the pit bottom to determine the density down to about 10 m at each site. I don't know what the accuracy of the magnetometer depth surveys is or how it might be affected by a leaning stake (and magnet) without looking up Will's paper but I think it is suppose to be pretty good and not too sensitive to leaning unless the lean is fairly severe. I have not taken the time recheck all the interpretations of the coring and magnetometer surveys and stake readings.

Making balance measurements this deep is challenging and it is reasonable to be suspicious of them. Though I can't guarantee their accuracy, from a quick review of the notes, these appear to be pretty good measurements for snow this deep. And they do not depend on the visual identification of the summer surface in a core, as was suggested, which admittedly can be difficult this high in the Chugach Mts where accumulation occurs year round.

Hope this is helpful.

Rod

-- 
Rod March
US Geological Survey
3400 Shell St.
Fairbanks, Ak 99701-7245
907-479-5645 ext. 241


On 5/2/2012 12:31 PM, wendell Tangborn wrote:

 

On Wed, May 2, 2012 at 11:29 AM, wendell Tangborn <[hidden email]> wrote:

Hi William,

 

Removing the two wild points ( 5 mwe at about 2800 m elevation and 5.5 mwe at 2300 m) would drastically change the shape of the exponential curve in Figure 1, and it also would not predict 6 mwe at 3200 m elevation).  Too much weight is given to these points in comparison to the others.

 

Should I be posting these comments on Cryolist? 

 

Regards

 

Wendell

 



 

On Wed, May 2, 2012 at 9:00 AM, William Colgan <[hidden email]> wrote:

Hi Wendell -- Yes, I appreciate there has been some suspicion of the accuracy of the 1978 measurements, but Tad's post points to a new 2010 in situ dataset collected by Shad O'Neel that agrees very well with the 1978 measurements, hmm... Liam

 

----------------------------------------------------

http://cires.colorado.edu/~colganw

 

From: wendell Tangborn [mailto:[hidden email]]
Sent: May-01-12 8:29 PM


To: William Colgan
Subject: Re: The Cryosphere -- discussion clarification

  Hi William,

 Thanks for your response. Such high accumulation above 2000 m on the Columbia Glacier in 1978 is impossible to believe.  It has to be due a misreading of the summer surface at the  two points, either with a coring auger or in a snow pit - it was likely from a core as digging a 5 meter snowpit at this altitude would be a major manpower effort. It is unlikely that much dust collects on the surface of the Columbia Glacier at this altitude, therefore detecting a summer surface would be extremely difficult.

In addition, these two points are not at all compatible with the remaining balance measurements below 2000 m or with the balance-altitude curve produced wth the PTAA model.  I realize of course that the PTAA model balance results are not too credible even though they appear reasonable, and have been verified for nearby glaciers that have records of manually measured annual balances (for example, Gulkana ad Wolverine).

I plan to .re-run the mass balance calculation of the Columbia Glacier as part of a larger mass balance project that is briefly described on the attached document.  The PTAAGMB website will soon go on line.

Best Regards

Wendell



 

On Mon, Apr 30, 2012 at 10:45 AM, William Colgan <[hidden email]> wrote:

Hi Wendell, I think I will be running some low accumulation scenarios, but I imagine that there might not be sufficient mass input to maintain the pre-retreat ice geometry with the imposed pre-retreat sliding field. Re: USGS observations, I see Tad just posted a new figure on the discussion forum that seems to run counter to your sentiment.... Thanks for the citation verification. Liam

 

----------------------------------------------------

http://cires.colorado.edu/~colganw

 

From: wendell Tangborn [mailto:[hidden email]]
Sent: April-25-12 10:27 AM
To: William Colgan
Subject: Re: The Cryosphere -- discussion clarification

 

Hi William,

The Columbia paper that was published by BPRC is the same as the PDF that you  cite although the figures in color make it very confusing.  It is much easier to scan a paper and make a PDF now than it was in 1997 so I'll replace the one on-line with an improved copy soon.  I assume you have access to BPRC publication No 15 where this paper appears. 

I still feel the high accumulation measured at two stakes by the USGS  on the upper Columbia Glacier is not correct (I had several discussions with Mark Meier about this nearly 20 years ago but we never came to an agreement).  Figure 5 in my paper clearly shows the difference.  Using such a high value for accumulation above 2000 m distorts the balance-elevation curve and must create a problem with modeling the flow of this glacier.  Have you noticed this in your research?

Best Regards

Wendell

On Tue, Apr 24, 2012 at 11:28 AM, William Colgan <[hidden email]> wrote:

Hi Wendell -- I recently submitted a paper to The Cryosphere on Columbia Glacier. In an online ("open") discussion forum during review, someone referred me to your paper, which I had previously overlooked. The citation they provide suggests it is a PBRC publication, but the version I find at http://www.hymet.com/docs/columbiaglacier.pdf does not look like a PBRC publication. I would appreciate if you could clarify the confusion in our discussion forum, at http://www.the-cryosphere-discuss.net/6/893/2012/tcd-6-893-2012-discussion.html

 

The query is raised in the M. Pelto thread, but I welcome your thoughts on any aspect of the general discussion as well. The discussion board closes down in about a week (May 2). Thanks very much, Liam Colgan

 

----------------------------------------------------

http://cires.colorado.edu/~colganw

 




--
Wendell Tangborn
HyMet
13629 Burma Rd SW
Vashon Island, WA 98070
<a href="tel:206%20567%204077" target="_blank">206 567 4077
[hidden email]
www.hymet.com




--
Wendell Tangborn
HyMet
13629 Burma Rd SW
Vashon Island, WA 98070
<a href="tel:206%20567%204077" target="_blank">206 567 4077
[hidden email]
www.hymet.com




--
Wendell Tangborn
HyMet
13629 Burma Rd SW
Vashon Island, WA 98070
<a href="tel:206%20567%204077" target="_blank">206 567 4077
[hidden email]
www.hymet.com




--
Wendell Tangborn
HyMet
13629 Burma Rd SW
Vashon Island, WA 98070
206 567 4077
[hidden email]
www.hymet.com



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