Stand-alone single-frequency GPS ice velocity observations on Nordenskiöldbreen, Svalbard

Abstract

Abstract. Precise measurements of ice-flow velocities are necessary for a proper understanding of the dynamical response of glaciers to climate change. We use stand-alone single-frequency GPS receivers for this purpose. They are designed to operate unattended for multiple years, allowing uninterrupted measurements for long periods with a reasonable temporal resolution. We present the system and illustrate its functioning using data from 9 GPS receivers deployed on Nordenskiöldbreen, Svalbard, for the period 2006–2009. The accuracy of the receivers is 1.62 m based on the standard deviation in the average location of a stationary reference station (NBRef). Both the location of NBRef and the observed flow velocities agree within one standard deviation with DGPS measurements. Periodicity in the NBRef data is explained by the atmospheric influence on the GPS signal and by the GPS satellite configuration. A (weighed) running-average on the observed locations significantly reduces the standard deviation and removes high frequency periodicities, but also reduces the temporal resolution. Results show annual average velocities varying between 40 and 55 m/yr at stations on the central flow-line. On weekly to monthly time-scales we observe a peak in the flow velocities (60 to 90 m/yr) at the beginning of July related to increased melt-rates. No significant lag is observed between the timing of the maximum speed between different stations. This is likely due to the limited temporal resolution in combination with the relatively small distance (max. ±13 km) between the stations.