Objectives and opportunities for shared CryoSat-2 Icebridge experiments Prof. Duncan Wingham, CryoSat Lead Investigator

CryoSat Mission Requirements “CryoSat will, in its own lifetime, determine whether the present observed changes in sea ice signal important changes in Arctic climate or merely the ephemera of inter-annual variability at short spatial scales; and reduce the uncertainty in the ice sheet contribution to sea level to a magnitude similar to that associated with other sources of sea level rise”

Mission Status Interferometer Error 0.01˚ -0.01˚ degrees -0.6˚ 0.6˚ 0.0˚ degrees 0.01˚ -0.01˚ Interferometer Error Courtesy: Marco Fornari

Mission Cross-calibration Wingham, Phil. Trans. Roy. Soc, 2006 Pritchard et al., Nature., 2009

Sources of Error Error in spatially averaged ice sheet mass imbalance. Covariance of uncertain snowfall fluctuation Covariance of uncertain near surface density Covariance of elevation trend error Post-glacial rebound error Covariance of instrument system error Radial orbit error Covariance of retrieval error Echo delay time error Tidal forcing errors Speckle-errors Time-variant penetration error Datation Error Timing (and other) drifts Echo direction error Intersatellite bias Atmospheric refraction error

Determination of surface accumulation and its variability. de la Pena et al., Cryosphere, 2010 Hawley et al., Geophys. Res. Lett, 2006

CryoSat Validation Locations

Coordination & Data Sharing • The CryoSat-2 CVRT is a group selected by an ESA AO process. Its activities are cost shared (approximately 6 M€ for CryoSat-2), approximately 1/3rd ESA and 2/3rds national agencies. • The multitude logistics and funding constraints make multi-year, detailed planning impractical. The CVRT operates through broadly agreed scientific goals, implemented through on-going, twice-per-year meetings that plan the upcoming year’s activities, taking opportunistic advantage of logistics and funding. • The CVRT operates a (non-satellite) data sharing arrangement in which the ‘ground’ observations are pooled in ‘exchange’ for the airborne data. We allow a reasonable, but not prolonged, period for individual groups to publish individual results prior to data sharing. It is generally agreed that when individuals use ‘pooled’ data the group that provided the data is credited with authorship on publications. There is no agreement, today, to make data available to any user; equally, there would probably be no objection to doing so after a reasonable (2 year?) interval. • The next meeting of the CVRT is 3 February 2011 at ESRIN (Frascati, Italy), immediately following the CryoSat-2 workshop.