Volume measurements and change of Longyearbreen and Tellbreen, Svalbard

Abstract

Climate change is a comprehensive field of research. The cryosphere is only a small portion of the entire spectrum but is still a very important constituent to try and understand. Thermal expansion of the oceans is the second largest cause for sea level rise around the world after the global melting of glaciers and ice sheets combined. Even the smallest valley glaciers, with small individual volumes, can altogether on a global scale have a great impact on the ocean level at the same time as they have a much faster response to climate change than the larger ice masses do (Meier et al., 2007; Bahr et al., 2009; Bahr and Radic, 2012).

This thesis evaluates the actual changes in ice volumes measured by ground penetrating radar (GPR) and the theoretical volume-area scaling method. The GPR method collects thorough ice thickness data by 2D cross profiles of a glacier which can be interpolated to ice volume models. The method provides detailed information about depth distribution, changes between different years and englacial structures, but is limited due to time consuming field work and has therefore only been carries out on a few hundred glaciers around the world. The volume-area scaling method is an alternative approach which describes the non-linear relationship between the volume and the surface area of a glacier by using exponents and proportionality coefficients derived from theoretical and empirical studies. Due to the lack of ice thickness measurements, this method is often used for volume estimations on a large scale, regionally or globally. The field work for this thesis was carried out with GPR on Longyearbreen and Tellbreen, close to Longyearbyen on Svalbard, during five consecutive days in April 2016. A total of 86 2D depth profiles collected with 100 MHz and 50 MHz rough terrain antennas (RTAs). 46 of the profiles (all 100 MHz) were interpolated to achieve a total ice volume estimate. The ice volume in 2016 was 0.085 km3 for Longyearbreen and 0.110 km3 for Tellbreen. The results were firstly compared with reprocessed data from 2004 which showed a decreased ice volume for both glaciers by 15.8 % for Longyearbreen and 16.9 % for Tellbreen. Secondly, both GPR surveys was compared to the ice volume estimates calculated by the volume-area scaling results. The comparison shows that the volume-area scaling method is likely to overestimate the volume for small valley glaciers similarly to Longyearbreen and Tellbreen.