GLIMS ASTER image acquisition planning
Jeffrey Kargel
jeffreyskargel at hotmail.com
Sun May 24 10:42:03 MDT 2009
Gordon (and others),
Of course ASTER Mission Operations is going to (justifiably) cite the tens of thousands of GLIMS acquisitions over Greenland, Antarctica, nonpolar glaciers. It is indeed a valued resource, along with other satellite image archives. I don't think any of us are complaining too much about the lack of satellite data to analyze. In terms of the ASTER contributions to that archive, it has been substantial, both from the Global Map program and from GLIMS STARs. So I think there's fairly wide appreciation of what data there are. However, most people in the GLIMS project (and not in GLIMS) are well aware that the image acquisitions in their area(s) of responsibility are short of what would be desired. In Alaska, some areas still have ZERO GLIMS acquisitions over the lifetime of ASTER (GLIMS acquisitions being those where the gain settings have snow is unsaturated almost everywhere), and many areas have only one or two non-GLIMS images (with saturated snow) that have low or no clouds. So my first point is that I think you have a misconception about (a) what the original GLIMS plan (approved by NASA and the peer community) was, and (b) what the record of acquisition has been. Taken together, it argues very strongly that we still need to acquire imagery of nonpolar glaciers, and in fact we need to make better efforts to improve the image coverage UNDER GLIMS GAIN SETTINGS. The same can be said for polar glaciers, given the points you and Slawek have made about 2007-2008 (2009?) imaging. I'd actually say that what we need is a RETURN to the original GLIMS plan and a further enhancement in the plan for selected high-priority glaciers. To say or suggest that nonpolar glaciers have been covered well enough already is to write from a position of not having looked at the record of acquisitions. The original goal (attempt) of GLIMS was to obtain an ANNUAL image of all the glaciers, not just one image over the lifetime of ASTER. Given ASTER's imaging capabilities, this always was (and remains) a realistic goalpost to aim for. We knew from simulations that this could not be achieved strictly speaking, because clouds would always obscure some percentage of glaciers just through stochastic variation in success stats, especially over certain mountain ranges. The goal (meaning: the plan to attempt) annual imaging was set with the recognition that if some percentage of glaciers escaped imaging in one year, they would be picked up the next year, and so we would end up the nominal 5-year mission with darned near every glacier covered at least a couple times. (Simulations showed that around 1% of glaciers still would not have coverage after 5 years of trying).
The chief failure, as far as I can tell, is that clouds have not had as good screening as might have been possible, especially during ASTER's first few years. But there would seem to be further problems in scheduling any observations at all in some regions. There are other minor failures (minor on the total scale of the GLIMS project, but impactful for individual projects), such as the failures to obtain cloud-free images during particular field activities (as an example, for my effort last year in Alaska, which was simply due to the fact that every day of scheduled observations was cloudy); that can be very impactful to individual projects, but sometimes there is nothing that can be done about it.
I and colleagues have done assessments of nonpolar versus polar glacier coverage, and over the lifetime of ASTER it is very clear that most of Greenland in particular has been extremely well covered, some nonpolar areas such as Mount Everest have been extremely well covered, but many, many nonpolar areas have had lackluster coverage by non-global-map imaging. The Global Map images, as I've mentioned, are also a useful part of the glacier imaging archive, because they cover rock-covered and slightly dirty-ice areas, lakes, and terrain adjacent to glaciers very nicely.
However, all things taken together, it seems evident to me that so many resources have gone into the Global Map program (along with other non-GLIMS priorities) that GLIMS has not gotten the quota of images that was an original part of the plan. The solution has been elusive. There have been pressures to reduce the resources dedicated to GLIMS, and I have made every effort to produce a workable plan that allows a reduction in GLIMS acquisitions while improving the cloud-free (and low-snow in cases of nonpolar ice) statistics. Nothing seems to work either for nonpolar or polar glaciers.
I would be VERY HAPPY if a series of STARs were developed that would supplement GLIMS imaging. We need more glacier and ice sheet imaging than has been taking place, that's clear. If we, the community, want a third and fifth and nth Global Map, ASTER can do it, but the projects that have been funded and approved will not meet the original goals. We already have lost SWIR, and my main focus in to be sure we have one superb, unsaturated image of every glacier in the world (99% will do), and repeat imagery (meaning two images, correct gains) of most glaciers (90% will do). Redefining GLIMS goals by saying that nonpolar glaciers have been covered WILL NOT do and will be and must be opposed. I agree that many of the most interesting and impactful changes occurring are taking place in the polar ice caps and their outlet glaciers (NOT to say that other glaciers, which provide meltwater that people actually use, or meltwater that actually kills people are somehow just sitting there in uninteresting steady state).
If you'd rephrase your statements and suggestions and say that the GLIMS goals were originally what was intended, and were well conceived, and should finally be implemented, then I'd be onboard. If there are compromises that need to be made with Mission Ops for technical reasons, then we can be realistic, which is what I have tried to be. But let's not kill GLIMS with poorly thought out and unresearched statements.
--Jeff
> Date: Sun, 24 May 2009 11:40:39 -0400
> From: gordon.hamilton at maine.edu
> To: jeffreyskargel at hotmail.com
> CC: tulaczyk at pmc.ucsc.edu; william.sneedjr at maine.edu; stearns at ku.edu; glims at flagmail.wr.usgs.gov; michael.j.abrams at jpl.nasa.gov; leon.maldonado at jpl.nasa.gov
> Subject: Re: GLIMS ASTER image acquisition planning
>
> Jeff--
>
> I am just back from East Greenland, so I am jumping into this discussion
> a bit late. Also, I will be heading back to Greenland in a few weeks, so
> regrettably I will not be at the team meeting in Kyoto. Slawek raises a
> very important point and it needs a thorough discussion.
>
> Examining the number of scene acquisitions per year over Greenland (and/or
> Antarctica) is a very crude way of determining the success of ASTER and/or
> GLIMS imaging in these incredibly important parts of the glacierized world.
> Bill just sent me a quick analysis of scene numbers/usability for the last
> few years over selected parts of Greenland. Sure, some years have a lot of
> image acquisitions (e.g., 400 scenes for the NE quadrant of Greenland in
> 2006) but the vast majority of these images are unusable for any kind of
> quantitative analysis, such DEM generation, velocity mapping, melt pond
> depth extraction, or margin mapping (e.g., for the same quadrant in 2006,
> only ~15 images out of the 400 were somewhat usable).
>
> A lot of the most important glaciers in Greenland (e.g., Kangerdlugssuaq,
> Helheim) have *no* useable images in recent years (2007, 2008), which means
> we have been unable to use ASTER to track the behavior of some of the key
> glaciers contributing to sea level rise (we have had much better success
> with ALOS data).
>
> The same is true for a lot of Antarctica outlet glaciers -- our recent work
> has relied on ALOS acquisitions to maintain data continuity.
>
> My own attempts at Greenland STARs have been a total bust. Maybe my requests
> were overrided by the GLIMS STAR?
>
> I am not sure I have any good solutions. Going back to the beginnings of
> the GLIMS program, the idea of collecting at least one usable image of each
> glacier on Earth for the ~2000-timeframe has largely been accomplished. A
> lot of these images are ASTER scenes, but the availability of high-resolution
> optical imagery has exploded since the days when the GLIMS idea was hatched,
> so a lot of the scenes are non-ASTER images. My guess is that the existing
> image archive is sufficient for a lot of GLIMS tasks (e.g., mapping changes
> in snow/ice extent) -- the small size of many mid-latitude ice masses
> necessitates the need for a long time record in order to detect change; in
> these cases, annual coverage is not required. The polar regions are different.
> The changes are bigger and happening faster, and the consequences have global
> implications. A lot of the really cool and high-profile science done by ASTER
> has been in Greenland and Antarctica (I'm trying not to be biased here!), but
> we have really been struggling to keep that science going with the current
> acquisition plan.
>
> Maybe we need to critically review the GLIMS objectives, see if the current
> image archive (be it ASTER or any other easily-available high-resolution
> imagery) is sufficient to meet that objective (and see where it does not meet
> that objective), then re-assess what key science questions we want to be
> trying to answer. The GLIMS idea is more than a decade old -- science has
> evolved, and maybe other glaciological questions provide a better use of the
> finite ASTER resource. Maybe not, but I think we need to take a close look
> to be sure.
>
> Okay, a long message, but I just wanted to echo Slawek's concerns.
>
> -gordon
>
>
>
> Quoting Jeffrey Kargel <jeffreyskargel at hotmail.com>:
>>
>> Slawek,
>> I offer this letter as an open message to the GLIMS community
>> (responding to your message below) in a bid to enlist the GLIMS
>> community's further help in evaluating the successes and failures of
>> the GLIMS STAR in the Southern Hemisphere in 2009, with recognition
>> that what elapsed there (successes and failures) is apt to be a
>> model of what will happen this year in the Northern Hemisphere over
>> the next few months. This is needed, while also recognizing that we
>> need good Greenland coverage, as you are shooting for. Perhaps
>> what we need is a one-year Greenland DAR that supplements the
>> coverage expected from the GLIMS STAR by targeting possibly
>> one-fifth of the Greenland coastline for multiple repeat imaging
>> (that's in addition to the current plan to get one image on average
>> of each part of the coastline over the course of the summer). I
>> would need to know what one-fifth to cover with greater frequency,
>> and then we could see how this idea fares with ASTER MIssion
>> Operations.
>> So far as what has actually been achieved for GLIMS STARs of
>> non-Greenland/non-Antarctic glaciers, I can say we're still
>> suffering. I don't know what it is, but there just seems to be a
>> very minimum priority given to GLIMS, or there's some technical
>> reason (the "exclusion zones" or whatever) that makes certain areas
>> very difficult to image. There are lots of images of glaciers from
>> 2008-2009, but the majority are global map or other images that have
>> saturated snow. (Those work well for debris covered areas, so we
>> don't discount the fact that we have those.) The Southern
>> Hemisphere GLIMS STAR has completed its summer season a couple
>> months ago, and the received images are fairly hit and miss
>> according to a random assessment of a few areas done in Tucson and
>> by some other GLIMS people; some really great images were received
>> in Jan-Feb-Mar 2009, but many areas have had no coverage this year
>> (or were attempted but were clouded out). So I am fairly
>> apprehensive about this summer's northern hemisphere GLIMS STARs.
>> Greenland was one big area where GLIMS was going really well, and of
>> course that was a great thing. I just wish something like the
>> Greenland coverage we had year after year (several received
>> low-cloud scenes of most parts of the coast each year) would happen
>> just once in the lifetime of GLIMS for nonpolar glaciers; or even
>> just one good image per season (with GLIMS gains) of most glaciers
>> would be a great improvement. It just has not been achieved so far
>> in 9 years of ASTER. I realize that we have acquired lots of GLIMS
>> scenes over the life of ASTER, so I am not issuing an all-out
>> complaint, but certainly there remain serious inadequacies. I have
>> not done the analysis to see whether on average the Southern
>> Hemisphere did significantly better in 2009 than in other years
>> under the old STAR. I just know that there are quite a few
>> significant glaciers that were not imaged, and some that were imaged
>> had saturated snow (gains indicative of the global map program).
>> Let me know whether you think the "one-fifth plan" will work
>> acceptably (plus an expected average of one summer image of the
>> other areas under the newly implemented STAR). We will need to do
>> something similar for Antarctica next austral summer.
>> --Jeff
>>
>>
>>> Date: Wed, 20 May 2009 13:26:45 -0700
>>> Subject: Re: US Mtg agenda
>>> From: tulaczyk at pmc.ucsc.edu
>>> To: Michael.J.Abrams at jpl.nasa.gov
>>> CC: kargel at hwr.arizona.edu
>>>
>>> Jeff,
>>>
>>> Let's talk about this. If at all possible, I would love to see more
>>> coverage of Greenland/Antarctica without subtracting from your focus
>>> on the smaller glacier systems.
>>>
>>> Cheers
>>>
>>> Slawek
>>>
>>> On 5/20/09, Michael Abrams <Michael.J.Abrams at jpl.nasa.gov> wrote:
>>>> Slawek,
>>>>
>>>> Could you also discuss this with Jeff Kargel before the meeting (He is
>>>> not attending). The GLIMS STAR was changed to reduce Greenaland
>>>> coverage. Not sure about antarctica.
>>>>
>>>> Michael Abrams
>>>> ASTER Science Team Leader
>>>> Group Supervisor, Land Surface Processes
>>>> NASA/Jet Propulsion Laboratory
>>>> Mail Stop 183-501
>>>> 4800 Oak Grove Dr.
>>>> Pasadena, CA 91109
>>>> 818-354-0937 FAX: 818-354-5148
>>>> michael.j.abrams at jpl.nasa.gov
>>>>
>>>>
>>>>
>>>>
>>>> Slawek Tulaczyk wrote:
>>>>> Dear Mike,
>>>>>
>>>>> Could we reserve time for a discussion on increased data acquisition
>>>>> over margins of Antarctica and Greenland?
>>>>>
>>>>> Cheers
>>>>>
>>>>> Slawek
>>>>>
>>>>> On Wed, May 20, 2009 at 10:29 AM, Michael Abrams
>>>>> <Michael.J.Abrams at jpl.nasa.gov> wrote:
>>>>>
>>>>>> attached is US Team meeting agenda for monday morning. let me know of any
>>>>>> changes/additions/etc.
>>>>>>
>>>>>> mike
>>>>>>
>>>>>> --
>>>>>> Michael Abrams
>>>>>> ASTER Science Team Leader
>>>>>> Group Supervisor, Land Surface Processes
>>>>>> NASA/Jet Propulsion Laboratory
>>>>>> Mail Stop 183-501
>>>>>> 4800 Oak Grove Dr.
>>>>>> Pasadena, CA 91109
>>>>>> 818-354-0937 FAX: 818-354-5148
>>>>>> michael.j.abrams at jpl.nasa.gov
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>
>>>
>>> --
>>> Professor Slawek Tulaczyk, Ph.D.
>>> Department of Earth and Planetary Sciences
>>> University of California, Santa Cruz, CA 95064, USA
>>> phone: 831-459-5207, fax: 831-459-3074, tulaczyk at pmc.ucsc.edu
>>
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>
>
>
> --
> Gordon Hamilton, Assoc. Professor
>
> Climate Change Institute
> University of Maine, Orono, ME 04469
>
> gordon.hamilton at maine.edu
> 207-581-3446 (ph/voicemail)
> 207-581-1203 (fax)
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