The Greenland GPS Network (GNET): Geodetic constraints on climate cycles, climate change and ice mass balance in Greenland

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This 1-year award will support initial maintenance and upgrade of the Greenland GPS Network (GNET) that was originally installed during International Polar Year 2007-2009. Maintenance and upgrade activities in summer 2011 will focus on installations along the southeast coast of Greenland and along the west coast facing Baffin Bay.Intellectual Merit: The primary purpose of GNET is to study changes in ice sheet mass balance produced by climate cycles and climate change, and to provide observational constraints on models of glacial isostatic adjustment, often referred to as postglacial rebound (PGR), which provide the crucial 'PGR correction' for the GRACE (Gravity Recovery and Climate Experiment) satellite mission and any follow-on missions. The goal is to achieve a consistent set of gravity, displacement and ice mass histories with the highest possible spatial resolution. GNET will also contribute meteorological estimates of surface mass balance (SMB) by generating precipitable water (PW, i.e., integrated water vapor) solutions at all GPS (Global Positioning System) stations that can be assimilated and exploited using numerical weather models (NWM). Surface atmospheric pressure fields from high resolution NWMs will be used to correct the GPS time series for atmospheric loading effects, thereby isolating the displacement cycles associated with seasonal changes in ice mass. Broader Impacts: GNET is an international collaboration between a US team, led by Ohio State University, and international partners in Denmark and Luxembourg. It is expected that GNET will contribute to understanding of the globally significant issues of climate and sea level change, and will be able to detect the onset of runaway or catastrophic ice loss within weeks of a sudden onset. A collaboration between GNET and the NWM community could have a significant impact on general meteorological products. It is also expected that GNET will contribute to studies of the polar ionosphere, and can synergize with existing space physics networks and facilities in Greenland and northern Canada. GNET will be used as a general positioning infrastructure, for kinematic positioning of survey aircraft, GPS rovers embedded in ice flows, etc. GNET is becoming a multiple use instrument or facility, as well as a specific research project.