Progress in climate-glacier-ice sheet modelling Jeremy Fyke (LANL) Bill Lipscomb (LANL) Bill Sacks (NCAR) Valentina Radic (UBC, Canada)

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

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.

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

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

Variability in ablation dominates overall SMB variability (+ increase in future variability?)

‘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 RCP8.5 GIS sea level rise contribution predictions

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

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

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

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

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

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

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

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)

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)

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

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

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

RGI glaciers nearest-neighbour-binned to RASM grid cells 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

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

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

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

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

Individual glacier ranges in CESM cell Integrated grid cell hypsometry CESM SMB profile

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

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

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 CESM non-GIS surface mass balance evaluation

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

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 LGM time 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!