Ice Sheet Mass Balance and Sea Level

Portland, Oregon, USA 14 July 2012

ISMASSISMASS 20122012 WorkshopWorkshop

IceIce SheetSheet MassMass BalanceBalance andand SeaSea LevelLevel Edward Hanna Francisco Navarro Frank Pattyn OrganizersOrganizers andand sponsorssponsors

Organizing and sponsoring:  Scientific Committee on Antartic Research (SCAR)  International Arctic Science Committee (IASC)  World Climate Research Programme (WCRP) with organizing support from WCRP/CliC & APECS Sponsoring:  International Council of Scientific Unions (ICSU)  International Glaciological Society (IGS)  Internat. Association of Cryospheric Sciences (IACS) ISMASSISMASS SteeringSteering CommitteeCommittee

From SCAR Buenos Aires 2010 Meeting till autumn 2011:  Kees van der Veen, University of Kansas.  Christina Hulbe, Portland State University.  Francisco Navarro, Technical University of Madrid.

Under co-sponsorship of SCAR & IASC, from autumn 2011 till present, interim SC:  Frank Pattyn, Un. Libre Bruxelles (representing SCAR).  Francisco Navarro, TU Madrid (representing IASC).  Edward Hanna, Univ. Sheffield (representing WCRP). ISMASSISMASS 20122012 WorkshopWorkshop aimsaims

 To assess the current knowledge of the contribution of the Antarctic and Greenland Ice Sheets to SLR (focus on quantifying uncertainties and understanding discrepancies).  To analyze how model-based predictions of ice-sheet discharge and melting contributions to sea-level changes can be improved (emphasis on identifying shortcomings and suggesting improvements, and on interactions with oceans and atmosphere).  To study other contributions to SLR (e.g. thermal expansion of oceans).  To analyze the impacts of SLR on coastal areas.  To determine how the renewed SCAR-IASC ISMASS group should be organized to effectively meet its objectives. OutlineOutline ofof AgendaAgenda

08:30-10:00 – Invited lectures (mass balance from remote sensing; glacial isostatic adjustment) 10:00-10:30 – Coffee break 10:30-12:30 – Invited lectures (modelling of ice-sheet dynamics; contributions to seal level rise from thermal expansion of the oceans; impacts of SLR) 12:30-13:30 – Buffet lunch 13:30-15:30 – 3 round tables, 40 min. each 15:30-16:00 – Coffee break 16:00-17:30 – ISMASS group organization session 17:30-18:00 – Presentation of conclusions, and closing FirstFirst blockblock ofof invitedinvited lectures:lectures: MBMB fromfrom remoteremote sensing,sensing, andand GIAGIA

08:30-09:00 – Overview of the Ice Mass Balance Inter- comparison Exercise (IMBIE) project findings (Erik Ivins, JPL, Caltech, USA, and Ben Smith, APL, University of Washington, USA) 09:00-09:30 – What is a GIA model, and why do we need it to determine ice-mass balance? (Pippa Whitehouse, Durham University, UK) 09:30-10:00 – Mass Balance of Antarctic Ice Sheet 1992 to 2008 from ERS and ICESat: Gains Exceed Losses (Jay Zwally, NASA Goddard, USA) SecondSecond blockblock ofof invitedinvited lectures:lectures: ISIS modelling,modelling, thermalthermal exp.exp. oceans,oceans, impactsimpacts

10:30-11:00 – Modelling the evolution of Antarctica and Greenland ice sheets: recent improvements and challenges for the future (Catherine Ritz, LGGE, France) 11:00-11:30 – Convergence of models and reality? Bothersome boundary conditions (Slawek Tulaczyk, University of California Santa Cruz, USA) 11:30-12:00 – Ocean thermal expansion and its contribution to sea-level rise over the past 40 years (1960-present) (Catia Domingues, ACE CRC, Australia) 12:00-12:30 – Global impacts of sea-level rise (Robert Nicholls, University of Southampton, UK) RoundRound tablestables

13:30-14:10 – Ice-sheet MB from remote sensing, and GIA Moderator: Edward Hanna At table: Erik Ivins, Ben Smith, Pippa Whitehouse, Jay Zwally

14:10-14:50 – Modelling of ice-sheet dynamics Moderator: Frank Pattyn At table: Catherine Ritz, Slawek Tulaczyk

14:50-15:30 – Thermal exp. of oceans, and impacts of SLR Moderator: Francisco Navarro At table: Catia Domingues, Robert Nicholls RoundRound tabletable 11 -- RemoteRemote sensing:sensing: relatedrelated ISMASSISMASS 20122012 WorkshopWorkshop aimsaims

 Poor agreement remains between various observation-based mass balance estimation methods: need to reconcile these.

 Error estimates & uncertainties - re. delta MB.

 Need to accurately discriminate 1-2% changes in Antarctic (& Greenland) mass balance (SLE)?

 Required/continuous coverage of satellite MB observations. RoundRound tabletable 1:1: RemoteRemote sensingsensing--somesome keykey pointspoints

 Acknowledged more important role of postglacial rebound model corrections in mass balance estimates. Need for more GPS measurements in data-poor regions. Integrating different satellite methods. Palaeoglaciological analogues.

 Firn compaction also important.

 Antarctic sea-level contribution reduced compared with previous estimates.

 Required coverage of satellite MB observations.

 Surface mass balance uncertain & high impact.

 Need of field data for SMB and dh/dt model validation. RoundRound tabletable 22 -- IceIce--sheetsheet modellingmodelling:: relatedrelated ISMASSISMASS 20122012 WorkshopWorkshop aimsaims

 There has been a major improvement of ice sheet models since AR4: full-Stokes, higher-order, grounding line migration, dynamic evolution, initialization (inversion).

 AR5 will incorporate a number of process studies, but a certain degree of (cross)scaling will still be necessary.

 What improvements are needed for AR6? What is needed in terms of targeted observations/datasets for modellers/process understanding? RoundRound tabletable 2:2: Process./Process./observobserv.. needsneeds

 Assessments between ARs (7 years is a long time)? Demands a lot of energy.

 ISMASS as an authority to produce these?

 LGM to present: reconstructions of the past and Melt Water Pulse 1A.

 Linking GIA models with ice sheet models linked to GL motion/ocean interaction.

 Thermal and hydrological processes; widening of ice streams and their margins. RoundRound tabletable 2:2: OtherOther remarks/recommend.remarks/recommend.

 Calving: calving laws - comprehensive observations linking calving to atmosphere/ocean processes.  Basal sliding (plastic vs viscous vs nonlinear).  Ice-ocean interactions (coupling models at different scales), observations (melting-refreezing under ice shelves), ocean measurements, cavity shapes (data).  Lack of velocity data (evolving over time) - is all data out there properly used?  Lack of bedrock data (under-resolution) - raw data are often preferred (unstructured grids). RoundRound tabletable 33 -- ThermosteticThermostetic SLRSLR && SLRSLR impactsimpacts relatedrelated ISMASSISMASS 20122012 WorkshopWorkshop aimsaims

 Need to reduce uncertainties introduced by instrumental bias corrections and mapping approaches in estimates of the global evolution of thermosteric sea level and its spatio- temporal variability.

 Need to improve the quality and consistency of the ocean subsurface measurements (temperature, salinity) to meet the more demanding climate-related requirements.

 Need to expand the current ocean monitoring system to coastal boundaries/marginal seas; below 2000 m; under sea ice coverage/nearby ice sheets (water properties, mixing and circulation changes). RoundRound tabletable 3:3: ImpactsImpacts ofof SLRSLR

 What are the impacts of different global sea-level rise scenarios? – With socio-economic developments? – With subsidence? – With and without adaptation? – With and without other climate change (storms)?  Understanding major impacts of relative sea-level rise – impacts and adaptation in subsiding areas.  What observational system is required to detect unexpected acceleration of sea-level rise due to ice loss in Greenland and Antarctica?  How to ‘avoid deglaciation’ in Greenland and Antarctica? (a temperature threshold?) Portland, Oregon, USA 14 July 2012

ISMASSISMASS 20122012 WorkshopWorkshop

ISMASSISMASS organizationorganization sessionsession Background:Background: aa briefbrief ‘‘historyhistory’’ ofof ISMASSISMASS

 ISMASS, initially established in 1993, has been for many years an Expert Group of SCAR.

 During its first decade, ISMASS focused on techniques for collection and synthesis of ice sheet mass balance data.

 During its second decade, the focus has been on addressing the inadequacies in prognostic ice-sheet models.

 A bi-polar perspective was desirable for ISMASS, and In early 2011 ISMASS became a joint group SCAR-IASC.

 2011-2012: interaction with other groups/programmes: SERCE/POLENET, AntClim21, PAIS, … WhatWhat’’ss next?next? (some(some issuesissues discussed)discussed)

 Should ISMASS continue as a group? Is there a current need for it? DISCUSSION (most relevant arguments): . Argument 1: The glaciological community is self-organizing. Under particular needs, groups arise to solve them. There is no need for additional structures. . Argument 2: ISMASS could serve as a liaison between different groups/communities (e.g. glacier and ice-sheet modelling, GIA, remote sensing, in-situ observations, climate modelling, interactions with the ocean) addressing closely related subjects. . Argument 3: SCAR & IASC would provide institutional support to sustain such group activities. CONSENSUS OPINION: . ISMASS should continue as an expert group. WhatWhat’’ss next?next? (some(some issuesissues discussed)discussed)

 Should ISMASS continue focusing on ice-sheets or should it also address mass balance of glaciers and ice caps & their contrib. to SLR? DISCUSSION (most relevant arguments): . Argument 1: Historically, the techniques for estimating the MB of IS & GIC have been very different, and this justified that ISMASS focused on IS. However, at present some of the techniques are converging (e.g. GRACE) & this makes a point for including GIC. . Argument 2: Even if some techniques are common, there remain many substantial differences. Broadening the scope of ISMASS would ‘dilute’ its focus. Moreover, there are other well-established groups already addressing GIC. CONSENSUS OPINION: . ISMASS should continue to focus on IS. Rather than including GIC, strengthen the cooperation with existing groups dealing with them (IACS, GLIMS, …). WhatWhat’’ss next?next? (some(some issuesissues discussed)discussed)

 How to organize? Suggestion (by AAD*) of creating Technical Focus Groups. DISCUSSION (most relevant arguments): . Argument 1: Such groups would allow to focus on particular aspects involved in IS MB and its contribution to SLR. . Argument 2: There exist many well-established groups already dealing with the most relevant aspects. . Argument 3: This would create an (unnecessarily) more complex ISMASS structure, not envisaged at this stage. CONSENSUS OPINION: . Rather than creating focus groups under ISMASS, strengthen the cooperation with, and serve as a liaison among, the already existing groups/programmes (SERCE/POLENET, AntClim21, PAIS, IMBIE, IACS, GLIMS, FRISP, WMO/PORS**, ...) * Australian Antarctic Division, IS group; ** Polar Observations, Research & Services WhatWhat’’ss next?next? (some(some issuesissues discussed)discussed)

 Should ISMASS generate (peer-reviewed) updates of cryospheric contributions to SLR in between successive IPCC reports? DISCUSSION (most relevant arguments): . Argument 1: There is a large time gap between successive IPCC reports, and there is (or could be) an interest by society/policymakers for more frequent updates. . Argument 2: IPCC reports provide consensus estimates, that are long to prepare. Shorter timescales do not seem feasible. The role of ISMASS is not preparing consensus reports but generating/facilitating science. . Argument 3: There is no need by policymakers for more frequent updates. The response time by policy is not so short. Society could be confounded by too frequently changing estimates. CONSENSUS OPINION: It is not the role of ISMASS to generate updates of cryospheric contributions to SLR. WhatWhat’’ss next?next? (some(some issuesissues discussed)discussed)

 Interest of extending ISMASS to the WCRP.  Need to redefine the terms of reference of ISMASS on the light of the above considerations.  Need to appoint a new Steering Committee and Chair . Not having focus groups, the SC should be sufficiently ample to cover the most relevant aspects of the IS MB & SLR. . 1 chair and 6 members, the latter representing the following specialities: IS modelling, remote sensing, GIA, in situ observations, climate modelling, interactions with oceans. • Geological constraints & palaeo IS reconstructions part of IS mod. . SC members do not need to be SCAR/IASC nat. reps., but contact person(s) in SCAR and IASC will be appointed. . Call for volunteers made. Some volunteered. A call will be made to the community to get additional members. WhatWhat’’ss next?next? (some(some issuesissues discussed)discussed)

 Deliverable from workshop (to be generated): joint SCAR/IASC/WCRP report. • This will be lead by the current Interim SC, with the support by the invited speakers to the workshop, but the draft will be circulated among all workshop participants for further input.  Additional comments: • Secretariat & Web support will be provided by the CliC Office. • The workshop website will be transformed into ISMASS website. A page will be created for (open) online membership to ISMASS. • An associated mailing list will be created, though the most relevant activities will be announced through the Cryolist.