Report on Ice Sheet Modelling Activities David Holland Courant Institute of Mathematical Sciences New York University, NY USA Jonathan Gregory Walker Institute,

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