GLIMS Update: working group on ocean-calving glaciers (OCG)

[Jeff Kargel]

Dear GLIMS colleagues and Cryolisters,

Bob Bindschadler wrote this morning:

>I recently attended an Ocean-Ice Interaction Workshop at NYU.  To make a
>long story short, Tad Pfeffer made an excellent point that if marine-based
>ice is at the crux of near-term acceleration of sea level--and I believe it
>is--then it would behoove the glaciology community to get at least a handle
>on how much of the "glaciers and small ice caps" component of the cryosphere
>falls into this category.  Tad stated that this fraction is not known--at
>all!  I expect he's right.  It seems like a perfect tangible task for GLIMS
>to take a stab at producing at least the percentage of non-ice-sheet
>involved, if not some other metric such as volume fraction.

Bob inquired whether GLIMS and others are ready to take on this task.  In project design, we are ready; the database includes parameters about glacier terminus properties, and people are busy assessing glaciers and ice caps, including tidewater calving glaciers, and populating the database; and in our project charter we are supposed to be looking at what Bob suggested, among other things of course.  In practice, we are globally short of manpower, but we do have people working on the analysis of these glaciers, so far piecemeal.   We need something more comprehensive and consistent.

To add somewhat to what Bob (and Tad) pointed out, most of the global assessments of small glaciers avoid tidewater glaciers, because of the obvious complexities, nonlinearities, and natural dynamical oscillations inherent in these complex systems.  But most of the mass balance action probably is tidewater glaciers, because of their usual large size, proximity to oceans and hence high accumulation and discharge rates, and the important influence of oceanic thermal energy.  To a lesser but important extent, lake and river calving glaciers exhibit some similar phenomenology. The dynamics are in many ways similar to those of ice shelves and the ice sheets that feed them.

Given the special nature of tidewater calving glaciers, and Bob's suggestion, it seems high time that GLIMS and other interested colleagues form a working group to examine the long-term trending and recent mass balance record of tidewater calving glaciers.  We would isolate long-term trending from natural dynamical oscillations, and specifically try to reach an estimation on the current sealevel contributions from tidewater calving glaciers and small ice caps.  We need more manpower in this effort, but we have to start somewhere, and I think we have critical mass to forge this group, define its charter, assemble existing assessments of these matters, and move toward an answer to Bob's and Tad's challenge.

First thing is to develop a working group, then to establish its specific charter, measurement goals, reporting expectations, and timeline needed to give policy makers what they need as soon as possible.  We need more manpower, and that's money we don't have, but let's get a head start on this with what we do have.

Sorry for double listings between glims and cryolists.

Sincerely,

Jeff Kargel