Oct 10, 2022
New method promises improved determination of ice-sheet mass changes
Synthetic GIA mass effects in Greenland (a) and Antarctica (c) were almost fully resolved within the simulation experiments (b+d). For these results it is essential that the input-data uncertainty is rigorously accounted for.
The mass losses from the Antarctic and Greenland Ice Sheet contributed about a fourth to total seal-level rise over the last 20 years, according to the sixth Assessment Report by the Intergovernmental Panel on Climate Change (IPCC). However, there is a significant spread between ice-mass change estimates from different methods. Some methods determined an ice-sheets contribution to sea level rise of about 20 % and others determined a contribution of close to 40 %. One method is satellite gravimetry, realized by the satellite missions GRACE and GRACE-FO, which measure changes of the Earth's gravity field over time. Mass redistributions on Earth cause gravity changes. An example of a mass redistribution is the loss of the ice mass in Greenland and Antarctica. Therefore, ice mass changes can be calculated from satellite gravimetry measurements. To get useful results, it is necessary to account for all other effects that lead to gravity changes. The most important effect results from mass redistributions in the Earth interior caused by glacial isostatic adjustment (GIA). In Antarctica, this effect is almost as large as the effect due to ice mass changes, but the GIA effect is poorly known. The uncertainty of this GIA effect propagates into determined ice mass changes.
A new method for an improved determination of the GIA effect was published on the 10th of October 2022 in the study „Feasibility of a global inversion for spatially resolved glacial isostatic adjustment and ice sheet mass changes proven in simulation experiments“. In addition to data from satellite gravimetry, the method applies data from satellite altimetry and from climate modelling. Satellite altimetry measures changes of the ice-sheet surface elevation. The presented methodology allows to evaluate the different data sets in combination and thus to calculate ice mass changes and the GIA effect in a single step. As an important aspect, the data is evaluated globally and does not need to be adapted to certain regions. Furthermore, the uncertainties are accounted for more rigorously than in previous approaches. Simulation experiments demonstrate the feasibility of the method (cf. figure). The results show that the knowledge on the input-data uncertainty is of crucial importance. A first application to real-world data leads to promising results. Improved estimates of ice mass changes can be expected in the near future.
The method was developed in a research project in collaboration with the University of Bonn funded by the Germany Research Foundation (Deutsche Forschungsgemeinschaft, DFG). This project is part of the DFG special priority programme „Regional Sea Level Change and Society”
© Sven Ellger
Research Associate
NameDr.-Ing. Matthias Willen
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