Synopsis

1. Progress in climate-glacier-ice sheet modellingJeremy Fyke (LANL)Bill Lipscomb (LANL)Bill Sacks (NCAR)ValentinaRadic (UBC, Canada)

3. Synopsis • RCP8.5 Greenland Ice Sheet (GIS) sea level rise contribution predictions • Glacier model initialization on RASM model grid • Preliminary techniques for non-GIS surface mass balance evaluation • Ongoing work

4. RCP8.5 GIS sea level rise contribution predictions (Lipscomb et al., submitted) • Optimized Greenland Ice Sheet preindustiral spin up simulations forced with CESM-derived RCP8.5 surface mass balance to year 2100.

5. RCP8.5 GIS sea level rise contribution predictions • Best initial GIS configurations generate 7.3 cm of eustatic sea level rise (SLR) 1850-2100

6. RCP8.5 GIS sea level rise contribution predictions • Negative feedback between ice thickness and ice velocity strongly damps total SLR signal

7. RCP8.5 GIS sea level rise contribution predictions • Variability in ablation dominates overall SMB variability (+ increase in future variability?)

8. RCP8.5 GIS sea level rise contribution predictions • ‘Poorly’ optimized models generate different SLR curves • Due to interplay between hypsometry (area-elevation relationship) of GIS realization ice surface and ablation/discharge • Improved spinup techniques and reduction of geometry (i.e. preindustrial SMB) biases = important

9. Surface mass balance model initialization on climate model grids • Distributed glacier model component requires an initial glacier population on climate model grid • Each glacier forced with output from climate model grid-cell SMB • Recall: each glacier evolved forward using volume-area scaling • Development of initial conditions for glacier models in RASM has been latest focus

10. Surface mass balance model initialization on climate model grids • Randolph Glacier Inventory (v.2) shapefiles + 30-m SRTM/ASTER DEMs processing extended to provide global-coverage high-resolution glacial hypsometries Normalized hypsometry Normalized elevation

11. Surface mass balance model initialization on climate model grids • Randolph Glacier Inventory (v.2) shapefiles + 30-m SRTM/ASTER DEMs processing extended to provide global-coverage high-resolution glacial hypsometries Iceland

12. Surface mass balance model initialization on climate model grids • Characteristic shape of normalized hypsometries is motivating some side-line glaciological work – interesting spin-off of model development Western Canada/US

13. Surface mass balance model initialization on climate model grids • Characteristic shape of normalized hypsometries is motivating some side-line glaciological work – interesting spin-off of model development Svalbard

14. Surface mass balance model initialization on climate model grids • Characteristic shape of normalized hypsometries is motivating some side-line glaciological work – interesting spin-off of model development Scandinavia

15. Surface mass balance model initialization on climate model grids • Characteristic shape of normalized hypsometries is motivating some side-line glaciological work – interesting spin-off of model development Greenland Periphery

16. Surface mass balance model initialization on climate model grids • Characteristic shape of normalized hypsometries is motivating some side-line glaciological work – interesting spin-off of model development Arctic Canada (South)

17. Surface mass balance model initialization on climate model grids • Characteristic shape of normalized hypsometries is motivating some side-line glaciological work – interesting spin-off of model development Arctic Canada (North)

18. Surface mass balance model initialization on climate model grids • Characteristic shape of normalized hypsometries is motivating some side-line glaciological work – interesting spin-off of model development Alaska

19. Surface mass balance model initialization on climate model grids • Characteristic shape of normalized hypsometries is motivating some side-line glaciological work – interesting spin-off of model development Russian Arctic

20. Surface mass balance model initialization on climate model grids Annual-mean PDD at mean glacier elevation Annual-mean total precipitation

21. Surface mass balance model initialization on climate model grids • RGI glaciers nearest-neighbour-binned to RASM grid cells

22. Surface mass balance model initialization on climate model grids • 6% of RASM land cells contain initial glacial ice • Land-terminating, ‘non-trivial’ glaciers/ice caps cover approximately 0.3% of the RASM land surface

23. Surface mass balance model initialization on climate model grids • Individual glaciers binned on grid-cell basis

24. Surface mass balance model initialization on climate model grids • Empirically, observed ELA occurs where accumulation area=0.57*total area Accumulation ELA Ablation

25. CESM non-GIS surface mass balance evaluation • Simulated SMB fields need to be compared against against RGI-derived hypsometry • ELA (line of net 0 ice gain/loss) useful as a composite indicator of T/P conditions: give a new glaciologically-relevant metric of model performance: vertical ELA bias • Evaluation completed around Greenland peripheral glaciers in CESM

26. CESM non-GIS surface mass balance evaluation Individual glacier ranges in CESM cell Integrated grid cell hypsometry CESM SMB profile

27. CESM non-GIS surface mass balance evaluation Individual glacier ranges in CESM cell Integrated grid cell hypsometry CESM SMB profile

28. CESM non-GIS surface mass balance evaluation Individual glacier ranges in CESM cell Integrated grid cell hypsometry CESM SMB profile

29. CESM non-GIS surface mass balance evaluation melting glaciers growing glaciers

30. CESM non-GIS surface mass balance evaluation

31. CESM non-GIS surface mass balance evaluation • Conclusions • ELA bias a strict indicator of model performance • Bias integrates T and P signal: correlating ELA bias to (seasonal) T/P biases or land surface biases way forward for assessing REASON for bias • RASM grid reaches 30N: if all glaciers to be modelled well, sub-grid VIC SMB scheme should work from near-sea-level to above 5000 m, at <=100 m vertical resolution • RASM may improve on CESM significantly w/r/t ELA biases and glacier simulation due to higher resolution topography

32. Ongoing work • Topography dataset generation underway for set of CAM5.2-SE AMIP-style simulations (collab with Peter Lauritzen), using GIS topographies from Fyke (PhD thesis, 2011) • Results will guide dynamic coupling of ice sheet with atmosphere models

33. Ongoing work • Transient spin-up techniques: • CESM has been run to quasi-equilibrium under LGM/mid-Holocene/preindustrial conditions • Extensions of these simulations with SMB calculations turned on should provide end-members for a transient glacial spin-up for model using ice core isotope data as control on interpolation Holocene time LGM

34. Ongoing work • Further development of CESM SMB scheme: • Refinement of vertical SMB calculations to capture high-elevation glaciers (Fyke/Sacks) • Dynamic land units for ice sheet/glacier retreat (Sacks) • Wrapping glacier and ice sheet model into ‘glc’ land surface model component (Sacks) • Isolating climate-ELA biases (Fyke/Radic): forcing CLM model with CAM/re-analysis • Further refinement of statistical glacier scheme: • Simulation of size distribution vs. individual glaciers • Parameterization of ice retreat at terminus Thanks!