Nanok Expedition &
Royal Observatory of Belgium
The ROB will be able to calibrate ice sheet elevation models and satellites data in Greenland by placing a GNSS receiver on the adventurers' pulkas during their traverse of the inlandsis.
Nowadays, research on the ice mass balance of the Greenland ice sheet mainly uses the flux method, elevation change measurements, and gravity satellite measurements. However, the importance of discrepancies (> 100m) between the elevation models and satellite measurements shows the limits of such method to accurately estimate the present ice mass balance in Greenland. The GNSS (Global Navigation Satellite System, e.g. GPS, Galielo …) experiment proposes to estimate, from ground measurement, the elevation of the ice sheet during the 600 km traverse of Nanok. This will be used to calibrate the existing models and satellite data. For that we will use a GNSS receiver and antenna from the Belgian company Septentrio©.
We propose to fix a high-precision GNSS antenna on the pulka during the 600km traverse of Nanok. The data will be processed using a state-of the-art scientific software to estimate the position of the GNSS antenna every 30s 24/24. The positions will be estimated at centimetres level accuracy on the vertical component and will allow us to improve the actual accuracy (~10-100m) of the ice sheet elevation. Another aspect of the experiment is to estimate the water vapor content in polar region. The water vapor is the main greenhouse gas but is also the most difficult component to estimate continuously especially in polar region. The data acquired during the bivouac periods of Nanok will allow the estimation of the variation of the water vapor across the Greenland continent. Finally, the GNSS data will be used to estimate the Total Electron Content in the Ionosphere-Plasmasphere system. The long traverse in the sub-auroral zone, will allow a better understanding of the coupling between the ionized layer and the geomagnetic field lines.
The GNSS receiver and antenna will be placed on one pulka. The GNSS antenna will be place on a fixed structure at the back of the pulka with on the top, to avoid any mask from the package in the pulka, and to assure a constant elevation of the antenna with respect to the ground (i.e. ice sheet elevation). The receiver will be place in the pulka itself, protected as much as possible from the cold. The receiver will be connected to a battery powered by solar panels.
The Nanok people will only need to verify regularly that the receiver is alimented in power, and that the receiver is registering data files by checking the lights on the receiver itself. The material will run 24/24h acquiring data every 30s.
There is a huge gap in ground-based data across the Greenland continent. This is a fist world premiere traverse over Greenland used to measure directly the ice sheet elevation. This has been done in Antarctica in 2019 and demonstrated the importance of ground measurement such as GNSS to estimate the ice sheet elevation and to calibrate satellite-based models. Nanok is an opportunity to apply this data set for the first time in Greenland also for water vapor and space weather purposes.
Howat et al. 2014, The Greenland Ice Mapping Project (GIMP) land classification and surface elevation data sets, The Cryosphere
Xing et al. 2020, Accuracy Evaluation of Four Greenland Digital Elevation Models (DEMs) and Assessment of River Network Extraction, Remote Sensing
Brunt et al. 2019 Assessment of altimetry using ground-based GPS data from the 88S Traverse, Antarctica, in support of ICESat-2, The Cryosphere