Effects of surface snow cover on gravimetric observations

A three year long absolute gravity time series from Trysil, Norway, is presented. The series shows a significant seasonal pattern, i.e. high gravity values during the winter season and low during the summer. A hydrological model was developed. The model is based on direct observations of the local ground water, snow cover and rainfall data. It successfully explains the seasonal pattern in the gravity time series and reduces the total variation in the time series by 64%. The model shows that 58% of the total variation is caused by the snow of which 90% is generated by the snow cover within 200 m from the gravity laboratory.