characterizing and predicting surface melt in antarctica
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David B. Reusch (New Mexico Tech)Derrick Lampkin (Penn State)
David Schneider (NCAR)
Characterizing and Predicting Surface Melt in
Antarctica
Funded by the Office of Polar Programs,National Science Foundation
Collaborative Research: Decoding & Predicting Antarctic Surface Melt Dynamics
with Observations, Regional Atmospheric Modeling and GCMs
OutlineOverview of the project ideasScience questionsMethods (modeling, analysis)Case study plan
Satellite-based passive microwave data tell us about surface melting on polar ice sheets
Meteorological models provide gridded temperatures, winds, energy balance components, etc.We know they’re imperfect and can be
expensiveBut still invaluable as an information source
We ought to be able to create a useful calibration between the satellite and model datasets
The Premise: Looking Backward
Assume that the recent past and future share the same physical principles…
Then calibration of satellite->atm model should be usable for predicting future surface melt from climate projections
The Premise: Looking Forward
Compare atmospheric model-based estimates of surface melt occurrence to satellite-based melt records to better understand this aspect of model skill for the Antarctic and to build confidence in our model-based predictions of the future.
Diagnose the synoptic factors, present and future, controlling Antarctic surface melt through objective classifications and analysis of synoptic-scale meteorology (from global and dynamically downscaled datasets based on regional models) and sea ice conditions.
Evaluate modern climates and surface melt estimates of CMIP5 general circulation models (GCMs) to identify best candidates for future prediction of surface melt occurrence.
Objectives
Retrospective studies help climate scientists and glaciologists better understand the relationship between surface melt and synoptic meteorology/climate, aid investigations of melt intensity and amount, and contribute to improved paleoclimate interpretations from ice core melt layers.
Prognostic results inform the climate change community about possible future changes in surface melt and ice shelf behavior. Surface melt is a significant factor in ice dynamics, a key to future ice-sheet behavior and critical for predicting the future of global sea level.
Results will both leverage and complement ongoing community evaluations of Polar WRF and CMIP5 GCMs in Antarctica.
Significance
What are the variability characteristics (existence, frequency, spatial patterns) of the satellite data?
How do our melt estimates (GCMs, PWRF) compare to the satellite data? To each other?
How dependent are PWRF results on the source of boundary condition data?
What are the synoptic controls on melt occurrence and how do they vary in space and time?
How does future compare with the recent past?
Example Science Questions
XPGR algorithm (Abdalati and Steffen, 1995) uses passive microwave data to detect changes in emissivity associated with melt
Well-established techniqueOnly detects melt presence, not magnitudeProcessing at Penn State for Nov-Feb, 1987-
200825 km pixels, daily
Methods: satellite observations
Threshold
Example Record from Greenland
(Abdalati and Steffen, 1995)
Three Days in January 1988Missing
Data
Melt
Jan 13
Jan 14
Jan 15
Periods: Recent & FutureBoundary conditions: Reanalyses & GCMsResolutions/domains (tentative)
Continental (45 km)Interior West Antarctica (15 km)Selected ice shelves (5 km)
ConfigurationUse community-identified “best practices”“Climate” so keeping options fixed
Outline of PWRF modelingCCSM3 MM5 60 km
WRF 20 km
Summarize complex datasets as generalized patterns
PMM5 December 1990-19926-hourly 2-m temperature anomalies
SOMs (Self-organizing maps)
Ross sea is upRed line is coast
Look at dates with distinct melt in West Antarctica
Compare PWRF and other datasets to try to identify synoptic conditions, etc.
Evaluate results
More at Fall AGU poster sessions Thu a.m. 12/8: C41E-0482. Characterizing and Predicting
Surface Melt in Antarctica, Reusch et al Tues p.m. 12/6: C23C-0513. Synoptic scale atmospheric
forcings on surface melt occurrence on West Antarctic ice shelves, Karmosky et al
Case studies
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