GLIMS Update: GLIMS ASTER image coverage and research documentation

Mon May 25 07:39:50 MDT 2009

Hi All,

I've been tracking the progress of the GDEM. Michel Abrams made a 
presentation at the ISRSE 2 weeks ago. He said the validation report 
will be ready soon and the product will be released in June or July.  
The compositing uses all available scenes at a given location - so over 
mountains it may combine scenes with both GLIMS and non-GLIMS gain 
settings.  Also, it fills voids with other data (but there is a layer 
saying which pixels and filled and what the source.

Attached are photos I took of the slide showing coverage. Note that for 
Greenland the count is 1 scene.

SiriJodha

Graham Cogley wrote:
> I have been looking forward eagerly to the ASTER global DEM, which as Frank
> points out is a resource of enormous potential for glaciology. But it won't
> be much use to *anyone* if it relies on non-GLIMS gain settings above the
> snowline. Have the global-DEM people figured this out yet? I don't
> understand why there has to be a conflict between GLIMS and the DEM in this
> respect.
>
> Graham.
>
> J. Graham Cogley, Ph.D., Professor of Geography,
> Department of Geography, Trent University,
> Peterborough, Ontario, CANADA K9J 7B8.
>
> Tel    +1 705-748-1011-x7686
> Fax    +1 705-742-2131
> Email  gcogley at trentu.ca
> Web    http://www.trentu.ca/geography/glaciology/glaciology.htm
>
>
> -----Original Message-----
> From: Frank Paul [mailto:fpaul at geo.uzh.ch] 
> Sent: May-25-09 7:46 AM
> To: gcogley1 at cogeco.ca; Jeffrey Kargel
> Cc: GLIMS mailing list; stearns at ku.edu; Gordon Hamilton;
> william.sneedjr at maine.edu; Slawek Tulaczyk
> Subject: Re: GLIMS Update: GLIMS ASTER image coverage and research
> documentation
>
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>
> Dear Jeff and all
>
> Thank you for the extended comments on GLIMS acquisitions by ASTER. I am
> sympathetic to most of your points and would like to add a few general
> remarks that might help to constrain the issue. From my point of view the
> use of ASTER data in GLIMS can be roughly classified in three groups:
>
> (1) Glacier outline mapping for the purpose of a global glacier inventory
> (`snapshot' over a ca. 5 year period) -> must be largely cloud free & from
> the end of the ablation period/dry season
> (2) Scientific research projects (albedo, snow cover, lakes, debris, ...)
> focusing on specific regions / individual glaciers -> could be partly
> cloudy but should be taken at a specific time
> (3) Repeat imagery from rapidly changing targets (e.g. glacier
> lakes/hazard situations, Greenland outlet glaciers). -> needs frequent
> update of many but small regions
>
> I further identify three huge changes in the past 5 years that were not
> clear during the set-up of GLIMS and ASTER STARs:
> (A) freely available and already orthorectified Landsat scenes from the
> USGS archive: This makes the use of ASTER data for purpose (1) nearly
> obsolete
> (B) rapid changes of Greenland's outlet glaciers: these regions should be
> clearly specified and regionally limited for ASTER data acquisitions
> (C) massive downwasting of glaciers in many parts of the world that could
> be quantified from repeat DEMs: ASTER DEMs will provide an increasingly
> valuable resource for this purpose
>
> Two additional points have to be kept in mind regarding the sensor
> capabilities:
> ASTER has a 60 km swath with 15 m resolution while Landsat offers 180 km
> with 30 m pixels (or 15 m for ETM+ pan). In this regard I would say that
> ASTER is not the appropriate sensor for monitoring the two ice sheets and
> their outlet glaciers or ice streams. Moreover, Landsat7 data are
> available (orthorectified!) a few days after acquisition which is in my
> opinion an extremely valuable resource for the monitoring of Greenlands
> outlet glaciers (despite the scan line corrector stripes).
>
> On the other hand, the proposed annual interval for glacier mapping or
> even one good image in 5 years was maybe over-optimistic. While such a
> frequency might work well in dry regions under constant high-pressure
> systems like in Greenland, it does not work out for maritime (Alaska,
> Norway, Patagonia, New Zealand), tropical or monsoon type climates. Even
> in the Alps the frequency is not higher than every 5 years (with Landsat
> coverage!). As far as I know, after 10 years of acquisition we have now
> two strips from ASTER (23 Aug 03 & 8 Sep 04) that could be used for
> purpose (1) and maybe a dozen strips for purpose (2). Please also keep in
> mind that it took 22 years (Sep 2006) before a useful image for purpose
> (1) of Jostedalsbreen (Norway) was acquired by Landsat 5 ...
>
> To conclude, I am in favour of Jeff's suggestion to prepare an update of
> ASTER data that has been used for GLIMS so far by all RCs (indicating
> whether the purpose was 1, 2 or 3 from above) and provide information on
> the regions that are still lacking appropriate coverage. For Greenlands
> outlet glaciers (purpose C) I propose to identify a set of key regions
> (shape file polygons) that are of utmost importance for frequent
> monitoring with ASTER that are hardly covered (e.g. due to severe
> striping) by Landsat 7. Please keep in X-Qmail-Scanner-Version: 1mind that
> Landsat 7 ETM+ could
> not be used since 2003 for purpose (1) and only partly for (2).
> Hope this helps and looking forward to your feedback!
>
> With best regards, Frank
>
>
> PS: sorry for the long email :)
> PPS: The upcoming ASTER GDEM will be the most important breakthrough in
> creating a detailed glacier inventory (i.e. incl. topographic attributes)
> from all glaciers and icecaps north of the SRTM3 coverage.
>
>
>   

-- 
Siri-Jodha Singh KHALSA, Ph.D.
National Snow and Ice Data Center
University of Colorado
Boulder, CO 80309-0449 Phone: 1-303-492-1445 
http://cires.colorado.edu/~khalsa

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