The Ice sheet Mass Balance Inter-comparison Exercise (IMBIE) was established in 2011 as a community effort to reconcile satellite measurements of ice sheet mass balance. The purpose of IMBIE is to reduce uncertainties in ice sheet mass balance estimation through community efforts, in order to reconcile different satellite-based measurements of ice sheet mass balance and help constrain future projections of sea level rise.
IMBIE is an international collaboration between scientists, supported by European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA), primarily as a contribution to the Intergovernmental Panel on Climate Change (IPCC), but also to provide critical information on global sea levels for a wide range of stakeholders.
IMBIE has led to improved confidence in the measurement of ice sheet mass balance and the associated global sea-level contribution. The improvements were achieved through combination of ice sheet imbalance estimates developed from the independent satellite techniques of altimetry, gravimetry and the input-output method. Going forwards, IMBIE provides a framework for assessing ice sheet mass balance, and has an explicit aim to widen participation to enable the entire scientific community to become involved. The previous two phases led to a reduction in ice sheet mass balance uncertainties and showed a 6-fold increase in the rate of mass loss during the satellite era. In addition to continuing this exercise, the new phase of IMBIE includes new objectives designed to provide more robust and regular estimates of ice sheet mass balance and their contribution to global mean sea level rise. These new objectives are to:
• Include data from new satellite missions including GRACE-FO and ICESAT-2
• Provide annual assessments of ice sheet mass balance
• Partition changes into dynamics and surface mass balance processes
• Produce regional assessments
• Examine the remaining biases between the three geodetic techniques