Constraining uncertainty in Greenland Ice Sheet surface mass balance model output and in situ validation

GrISSMB Sheffield Mtg 2015 Group PhotoGreenland Ice Sheet International Workshop Group Photo, May 2015, Sheffield, UKThe meeting took place from 19-20 May 2015 in the Ron Johnson Research Room, C Floor, Department of Geography, University of Sheffield, Winter Street, S10 2TN, UK.  The proposed CliC-sponsored workshop did:

  1. Prompt more comprehensive spatial comparisons between SMB model output from the several different SMB modeling approaches (RACMO2, MAR, SnowModel, Hanna et al. PDD approach) mentioned above. The first measurabledeliverable/output will be a new international peer-reviewed publication on SMB model intercomparison that will highlight remaining disparities and uncertainties and the best next steps forward; this will be led by EH and co-authored by members of the workshop (i.e. authors of the various SMB models), and will be produced for a leading geophysics or cryospheric science journal.

  2. Discuss how major discrepancies between GrIS SMB model estimates (e.g. relating to precipitation/snow accumulation amounts in inland south-east Greenland) can be better reconciled through the improved use and implementation of in situ validation observations, including (but not limited to) weather stations, ice radar and shallow ice cores. It is anticipated that the results of our improved/updated SMB model intercomparison can be directly used to recommend specific spatial areas and parameters for improved in situ data collection for better validating GrIS SMB models to major international (e.g. UK/European and US) funding agencies. This will be the second measurabledeliverable/output of our workshop.


Hence we plan to invite a range of participants representing not just the GrIS SMB modeling community but also the network of field-based and remote sensing glaciologists. Thus our proposed workshop aims to better link these different strands of the GrIS SMB research community and promote a more holistic approach to delineating the GrIS mass balance response to current climate change, which will help narrow remaining uncertainties in the GrIS mass budget. The results of the workshop will help raise the profiles of both ISMASS and CliC, for example by feeding into further international peer-reviewed publications leading up to the Sixth Assessment Report of the IPCC.

For more information, contact Edward Hanna.

Download the Draft ACTION PLAN arising from GrIS SMB modelling/model validation CliC/ISMASS Sheffield workshop here.


Greenland Ice Sheet (GrIS) surface mass balance (SMB) (i.e. meteorologically-driven snow accumulation minus surface meltwater runoff) changes comprise about half the total mass balance changes of the ice sheet (Rignot et al. 2008, van den Broeke et al. 2009), where the latter also include ice dynamical changes. At the same time, it has recently been established that there is a major and accelerating overall loss of mass from the GrIS (Rignot et al. 2011, Shepherd et al. 2012, Hanna et al. 2013a), and some of the strongest global warming since the early 1990s has been in Greenland, leading to record surface melting of the ice sheet (Nghiem et al. 2012, Hanna et al. 2012, 2013b). The purpose of the proposed workshop is to direct future research for reconciling the considerable differences in GrIS SMB between several different models that are currently widely used. Recent research reported in the IPCC AR5 (2013), Chapter 13, and by Box et al. (2013) and Vernon et al. (2013), has revealed significant disparities - especially in the absolute values - between several widely used SMB model estimates from different semi-independent models, e.g. RACMO2 (van den Broeke et al. 2009), MAR (e.g. Hanna et al. 2013b), Jason Box/Polar MM5 (Box et al. 2013), SnowModel (e.g. Mernild & Liston 2012) and Hanna et al. (2011) positive-degree-day (PDD)/runoff retention-based model approaches. This has important implications for accurately ascertaining the current sensitivity of the GrIS to ongoing climate change and the accompanying effects on global sea-level rise. At the same time, it has recently been realised that SMB changes comprise a significant portion, perhaps the majority, of the overall mass balance changes of the GrIS. This may especially be the case moving into the future as current Greenland tidewater glaciers loss their floating ice tongues, accelerate and retreat inland, in response to continued oceanic climate forcing, and the GrIS therefore becomes increasingly exclusively sensitive to atmospheric forcing changes (i.e. changes in precipitation and surface meltwater runoff climatology directly affecting the SMB). Published comparisons so far made between GrIS SMB model output have so far been restricted to total ice-sheet SMB values and report on several years’ old SMB model output, while the models are constantly evolving and newer/improved SMB estimates are more recently available.

Report from the meeting

The GrIS SMB workshop report is available here.


Draft agenda as of May 12, 2015

Tuesday, May 19, 2015
9:00-9:30 Arrival and workshop registration – Amy Jowett
9:30-9:35 Welcome from Head of Department of Geography - Andy Hodson
9:35-9:45 Welcome/agenda/housekeeping info – Edward Hanna & Amy Jowett
9:45-10:00 Workshop intro – motivation/wider perspective and aims/rationale, intended outputs/objectives – Edward Hanna
10:00-10:20 Use of RACMO in GrIS SMB modelling – Michiel van den Broeke
10:20-10:40           Use of SnowModel in GrIS SMB modelling – Sebastian Mernild
10:40-11:00 Danish Climate Centre GrIS SMB model – Ruth Mottram
11:00-11:30 Coffee break/informal discussion
11:30-11:50 Use of MAR in GrIS SMB modelling – Xavier Fettweis
11:50-12:05 Use of positive degree day/runoff retention approach in GrIS SMB modelling – Edward Hanna
12:05-12:20 Recent enhancements to PDD-based GrIS SMB modelling – Amy Jowett
12:20-13:00 Discussion – how can we best compare output between SMB models?
13:00-14:00 Lunch in Geography Cafe/informal discussion
14:00-14:20 PROMICE program and weather station data for validating SMB models – Andreas Ahlstrom
14:20-14:40 Greenland ice cores and their use in validating modelled SMB – Christine Hvidberg
14:40-15:00 Remote sensing of Greenland Ice Sheet and its application in SMB modelling – Marco Tedesco
15:00-15:40 Discussion of SMB validation data, their current application and suggestions for future improvements and their extended use
15:40-15:50 *Group photo in nearby Weston Park just outside Geography Building*
15:50-16:20 Afternoon tea/informal discussion
16:20-16:50 ISMIP6 and use of reanalysis data for GrIS SMB modelling; downscaling methods in GCMs – Richard Cullather
16:50-17:10 Climate modelling for GrIS SMB applications – Jonny Day
17:10-18:00 Discussion – what is the best way forward for improving GrIS SMB models and constraining their uncertainties on a common footing?
18:30 for 19:00
CliC-sponsored workshop dinner at The York Restaurant, 243-247 Fulwood Road, Broomhill, Sheffield, S10 3BA
Wednesday, May 20, 2015
9:00-9:20 Global warming, Arctic amplification and Greenland climate change influence on GrIS SMB – Edward Hanna
9:20-9:40 Atmospheric circulation changes and Greenland blocking + GrIS SMB changes until 2100: towards more reliable future predictions - Xavier Fettweis
9:40-10:00 GrIS recent dynamical changes and ice-ocean interaction – Andrew Sole
10:00-10:30 Discussion
10:30-11:00 Coffee/informal discussion
11:00-13:00 Next steps and formulate action plan for SMB intercomparison/validation publication and recommendations to wider Greenland/climate community – All (possibly split into several small groups, reviewing different aspects of the problem, then report back in plenary session)
13:00-14:00 Lunch
14:00-~17:00 Optional visit to Bradfield Environmental Laboratory in nearby part of Peak District National Park, for further informal discussion


Name Affiliation
Andreas Ahlstrom Dept. Marine Geology and Glaciology, GEUS – Geological Survey of Denmark and Greenland – representing PROMICE
Jonathan Bamber

Bristol Glaciology Centre, School of Geographical Sciences, University of Bristol, UK - GrIS SMB modelling and Arctic climate change

Michiel van den Broeke    Institute for Marine and Atmospheric research Utrecht (IMAU), Utrecht University, The Netherlands - representing RACMO
Richard Cullather NASA/Goddard Space Flight Center, USA -climate modeller and use of reanalysis data for GrIS SMB modelling
Jonny Day Department of Meteorology, University of Reading, UK - climate and sea-ice modeller
Xavier Fettweis University of Liege, Belgium - representing MAR
Edward Hanna University of Sheffield, UK - workshop chair and representing GrIS climate change/statistical-based SMB modelling
Christine Hvidberg Center for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Denmark - Greenland ice cores and SMB model validation
Amy Jowett University of Sheffield, UK and APECS member – workshop co-organiser and representing Hanna et al./ECMWF enhanced positive degree day SMB modelling
Sebastian Mernild Centro de Estudios Cientificos, Chile - representing SnowModel GrIS SMB simulations
Tom Mote Department of Geography, University of Georgia, USA – representing GrIS meteorology/climatology and remote sensing
Ruth Mottram Danish Meteorological Institute, Denmark - representing Danish Climate Centre’s GrIS SMB modelling
Bette Otto-Bliesner  National Center for Atmospheric Research (NCAR), USA - feedbacks and mechanisms of long-term changes of the Greenland ice sheet in the past and future
Andrew Sole University of Sheffield, UK - representing GrIS dynamics and interaction with ocean
Marco Tedesco The City College of New York, CUNY, and National Science Foundation, USA - representing GrIS remote sensing
Martyn Tranter Bristol Glaciology Centre, School of Geographical Sciences, University of Bristol, UK - Greenland albedo and ice-life-climate interaction
David Wilton University of Sheffield, UK – 1 km downscaled GrIS SMB modelling

Getting to the University of Sheffield and the Rutland Hotel

Getting to Sheffield
- By Air: Manchester Airport is the closest and is recommended for this meeting. From the airport in Manchester, we recommend either of the following options:

- By Coach/Bus: There is a dedicated coach stop within the bus station serving Terminals 1 and 2. National Express bus (route number NX350) departs for Sheffield from 8.05 am. The fare is about £7.90 and the journey takes 2-3 hours.

- By Rail: A covered travellator links the rail station direct to all terminals. Trains to Sheffield depart every hour during the day time – the fare is £18.80 (or £12.40 with a young person/student rail card) and the journey time is approximately 1 hour. Trains are safe and comfortable. Please note that travelling before 9.30 am can be more expensive. For information on train times please refer to

Getting to the Rutland Hotel

The Rutland Hotel is located at 452 Glossop Road Sheffield S10 2PY.

- from the Sheffield Train Station
Take a taxi from outside the train station is the easiest option, from directly outside the railway station.
- from the Sheffield Bus Station
From the bus station catch the number 30, 40 or the 120 and ask for the Rutland Hotel, it is the stop after the Hallamshire Hospital.

The hotel is within 15 minutes walk of the meeting venue Ron Johnston Research Room on C Floor of the Geography Building on Winter Street, Sheffield, S10 2TN, UK at the University of Sheffield.

Zoom out on Google map below to see route.

1. Go east on Glossop Rd/B6547 against St. Mark's Crescent
2. Turn left onto Beech Hill Rd
3. Turn right toward Claremont Pl. Turn left
4. Continue on Claremont Crescent (the street changes names at Northumberland Road)
5. Continue on Damer St
Turn left
6. Continue on Winter Street
The meeting venue is on the right hand.

View ISMASS Meeting in Sheffield in a larger map