Bulled emailed by different people
.-----------------------------------------------------------------------------------------------------------------Larry Smith
For my bullets I would propose two basic measurement goals:
- quantitative measurements of water outflow (for sectors with land-terminating ice)
- direct measurements of runoff R in supraglacial channels on the ice sheet to help
constrain SMB
Look forward to talking soon, Larry Smith
.---------------------------------------------------------Ian Howat
My main question would be:
Are the SMB & densification models to the point where they can reliably tell us where we
need more measurements and of what? For example, can they provide a spatially &
temporally resolved uncertainty estimate, as well as the relative uncertainties for each
parameter or boundary condition?
If yes, then it seems we should base targeted observations based on these uncertainties.
If no, then we need to get the models to that point, through targeted cal/val observations.
.---------------------------------------------------------Indrani Das
My bullets:
With ICESat2 coming up, there is an immediate need to study densification processesperhaps on a higher resolution than regional climate models provide. Climate models are
not to the point where they have incorporated or know what they need to reliably
constrain the process. Their resolution is another issue. It is useful to work on models that
are higher resolution and on a region basis that can incorporate high resolution
observations. They can then be nested in climate models.
The airborne platforms like OIB, if they fly at least twice a year, have a huge potential to
help constraining many of the processes like albedo variation, elevation change,
densification, seasonal evolution of melt water channels. It has to be targeted flights for
SMB studies, keeping at least an entire catchment/region in mind. This may provide an
initial assessment of the situation, can even be used for cal/val or the regional climate
models to see how far off they are.
.---------------------------------------------------------Isabella Velicogna
- runoff is the largest uncertainty in SMB models (based on Michiel van den Broeke
comments and on the intercomparison between the different models I can email a few
papers published and send some comparison we made, the largest discrepancy are in
runoff not in precipitation), so I would prioritize understanding sources of uncertainty in
the regional climate models (RCM) due to runoff:
- Identify main source of uncertainty in modeled runoff ( is the error due mainly to
albedo/energy balance or water retention)
- Improve firn correction for interpreting ICESat-2 data
I think that a good approach will be to monitor/measure big signals they can be the best
place to evaluate/validate the models
Bullet:
-Runoff is the largest uncertainty in model
- measure big event/big signal
Also runoff in situ only in central west Greenland, elsewhere uncertainty is unknown
derive and validate a firn compaction algorithm
.---------------------------------------------------------Harihar Rajaram
my bullets how is melt partitioned into runoff versus retention? what is the nature of retention, what
feedbacks does the nature of retention impose on future behavior and evolution of runoff
versus retention partitioning?
what are the key processes controlling retention, at what scales are they manifest (likely
small) and how can we upscale to be compatible with climate model grids?
thanks
------------------------------------------------------------------------------------------------------
13 FEB 2015 Telecon
-------------------------------------------------------------------------------------------------------------------Tom Wagner question:
Are a lot of fly hours lost due to bad weather (boomerang flights/  cost issue)? Pilots
used do not use Danish met office that Koni said is better than other for weather
forecast
--------------------------------------------------------------------------------------------------------------------What we have and what are we looking for? which are the main goals we want to
achieve?
-- Quantify uncertainty on Runoff and Accumulation estimates
-- Understand processes in the percolation zone.
-- Indrani: measurements should be done at the same time
--Question can be rephrased as (Ben):
what are the problems experienced by models now :
1- wrong amount of melt?
2- retention, how much water goes out?
-What region is the most problematic?
-outlet glacier area ok with fluxes
-inland good with altimetry
-percolation zone is most problematic
--What do we know about internal water storage in cavity? (Larry)
is this term important ? How large can this term be?
Retention/storage term:
- supraglacial/intraglacial water are not well known (Larry)
- outflow measurement are good enough (Larry)
-- We should identify critical areas in the percolation zone where to improve our
understanding of these processes.
--Would it be useful to do a densification model comparison?
Very different values in firn densification model in percolation zone
Can we compare the different densification schemes?
-- How can we evaluate how well RCMs model retention?
--How are the different RCM defining/calculating retention?
--Would an inter-comparison be useful?
Larry: If we know the total run off in a catchment (including supraglacial and intraglacial)
we could use this to compare different retention schemes.
Koni: Can the modeled retention be evaluated using shallow ice cores, how deep is the
retention zone (30 or 20 m for example)? Would this comparison be useful?
Marco Tedesco: There are some parameters that we cannot define in RCMs. Can we
use remote sensing or other measurements to evaluate these parameters?
Koni: Percolation zone is not important for overall impact on SMB, but it is important for
firn densification models.
David Bromwich: what is the largest uncertainty? Outflow or residual between melt
production and refreezing?
We have measurements of outflow and there are measurements in the bare ice zone
How do we connect with measurements in the percolation zone so we can evaluate
this?
Larry: It is not easy to make measurements in the percolation zone. We could do some
acoustic doppler measurements of surface run off/discharge in the channels that feed
up to the ablation zone to compare with SMB.
-- We should define a standard format for the available dataset. Lora has done some of
this and can provide guidance as she working on this with NSIDC.
-- We should have some discussion about potential megasites. Are they a good idea?