Greenland mass balance derived from GNET

In the context of global sea level rise and climate change related global scale phenomena, the Greenland mass balance (GMB) plays a crucial role. Estimates of the GMB are regularly updated, using three main methods. Those are based mainly on satellite data: 1) gravity variations, e.g. GRACE, 2) surface elevation changes, e.g. CryoSat-2, IceSat-2 and 3) the ice flow (input-output method) inferred from surface ice velocities.

Each of these three methods has strengths and weaknesses, and they rely on models and assumptions to infer the mass changes that cannot be measured directly. The agreement among the different estimates has improved in the last decade, thanks to the coordinated efforts of the scientific community, but there are still discrepancies.

We propose a fourth method, based on a simple methodology that uses the entire Greenland GNSS network (GNET) as a “virtual instrument” to monitor the present-day mass changes. This method is tested against GRACE-derived GMB, and we find a very good agreement. This leads to an independent methodology for monitoring present-day mass changes from GNSS, hopefully helping in reducing the overall uncertainties. Moreover, we show that within certain assumptions, which are verified in the actual available GNET time series, the method is robust and not particularly sensitive to small data gaps, and potentially allows tracking the GMB daily, also bridging the gap between GRACE and GRACE-FO in GMB estimates. This approach shows how a well-designed GNSS network is worth more than the sum of the stations it is made of.

 

Reference: Barletta, V. R., Bordoni, A., & Khan, S. A. (2024). GNET derived mass balance and glacial isostatic adjustment constraints for Greenland. Geophysical Research Letters, 51, e2023GL106891. https://doi.org/10.1029/2023GL106891