report on ice sheet modelling activities david holland courant institute of mathematical sciences...
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Report on Ice Sheet Modelling
Activities
David HollandCourant Institute of Mathematical Sciences
New York University, NY USA
Jonathan GregoryWalker Institute, Department of Meteorology, University of
Reading, UKMet Office Hadley Centre, Exeter, UK
Arctic System Modeling WorkshopUQAM, Montreal
July 17, 2009
A Story of Two Ice Sheets
Greenland Ice Sheet:Long, narrow Fjords
Antarctic Ice Sheet:Wide expansive, ice shelves;
West Antarctica marine based
Why does it matter? What are the obstacles to progress?
What are we doing?
- Jakobshavn Isbrae retreats in 1997- Forced by the ocean
- (which was forced by the Atmosphere, the NAO)
Recent Changes: Greenland
- Larsen B collapses in 2002- Forced by the surface melt ponds
- (which was forced by the Atmosphere)
Recent Changes: Antarctica
- Pine Island thinning over last decade- Forced by the ocean warm waters
- (which was forced by the Atmosphere)
Recent Changes: Antarctica
IPCC: Summary for Policy Makers
IPCC: “Excluding future rapid…”
Why does it matter? What are the obstacles to progress?
What are we doing?
Is it Predictable?
Chaotic system?
Rate of Observational Progress?
Rate of Modeling Progress?
Russell et al, 2006
IPCC: Antarctic Circumpolar Current
(an analog for uncertainty?)
Challenges of Physics
… there remains uncertainty in the physics that controls the rate of flow of ice steams coming
from the land and feeding into the ice shelves, floating on the ocean.
Challenges of Physics
1) physics of calving at ice fronts,
2) grounding line migration,
3) buttressing effects associated with ice geometry,
4) basal melting of ice-shelves, and the associated sub-ice-shelf ocean circulation.
Challenges of Physics
… even regarding the comparatively well-understood processes determining ice-sheet surface mass
balance, there are substantial uncertainties.
Challenges of Computation
1) how to represent on the grids of relatively coarse resolution global climate models the steep
marginal areas of ice-sheets, on which any surface melting occurs, and the coastal ocean circulation
that may impinge on ice-shelves.
2) within the ice models themselves how to represent regions of rapid dynamic changes, such as at the
grounding line.
Why does it matter? What are the obstacles to progress?
What are we doing?
Ice Sheet Modeling Community
West Antarctic Ice Sheet Initiative (WAIS)
Ice Sheet Modeling Community
Forum for Research Into Ice Shelf Processes (FRISP)
Ice Sheet Modeling Community
Ice Sheet Model Intercomparison Project (ISMIP)
Recent “Sea-Level” Workshops
Evolution of the Antarctic Ice SheetRoyal Society of London, 2005
Recent “Sea-Level” Workshops
Understanding Sea-Level Rise and VariabilityParis, 2006
Recent “Sea-Level” Workshops
Toward a New Generation of Ice Sheet ModelsGFDL, 2007
Predicting Sea Level in the 21st Century:The Role of Ice-Ocean Interaction
New York University, 2008
Recent “Sea-Level” Workshops
… to stimulate activity between
the cryospheric community and clim
ate
modelers in national laboratories …
Recent “Sea-Level” Workshops
Workshop on Improving Ice Sheet ModelsSCAR, 2008
Recent “Sea-Level” Workshops
Building a Next Generation Community Ice ModelLANL, 2008
UK Efforts
Hadley Centre using HadCM3 coupled to the Greenland 3D ISM of Huybrechts
starting to use the Glimmer 3D ISM coupled to Hadley Centre AOGCMs
Glimmer is being developed (led by Payne), to include an adaptive-mesh high-resolution treatment of ice streams and the
grounding line
The Hadley Centre AGCM is being improved as regards ice-sheet surface mass balance
EU Effort: ice2sea
proposed EU Framework 7 project on estimating the future contribution of continental ice to sea-level rise
focus on key processes not included in current models, •essential observations (especially for the satellite period),
•projection of ice-sheet surface mass balance and ice-shelf basal mass balance using regional atmosphere and ocean models,
•projection of ice-sheet response over 200 years, •and synthesis including regional sea-level projection
•and risk assessment
does not include model development, two-way coupling between ice sheet and climate (only climate->ice-sheet)
LANL Efforts
developing a Community Ice Sheet Model (CISM)
implementing CISM in the Community Climate System Model (CCSM)
strategy for developing an IPCC-ready community ice sheet model in 1 to 2 years
and fully coupled model later on
Conclusions: The Good
there exists an ever-growing (?) and diverse group of researchers studying ice sheets and sea level
some detectable momentum in EU and USA efforts
Conclusions: The Bad
Conclusions: The Ugly
No existing capability to model future sea level change
The capability is not obviously going to emerge anytime soon
There is no detailed plan