Characterizing and Predicting Surface Melt in Antarctica

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