Natural and societal consequences of climate-forced changes of Jostedalsbreen Ice Cap
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Radar measurements reveal the hidden landscape beneath Jostedalsbreen
by Mette K. Gillespie, January 13, 2025
In this newest JOSTICE publication in Earth System Science Data, we describe findings from four field seasons on Jostedalsbreen measuring ice thickness with various radars and the subsequent modelling study of ice cap-wide ice thickness and bed topography.
Our radar measurements show that the ice thickness at Jostedalsbreen varies from a maximum of c. 630 m in the uppermost accumulation area of Tunsbergdalsbreen, to less than 50 m in narrow regions connecting the largest central parts of the ice cap with the more northern and southern regions. These critical regions of thin illustrate that Jostedalsbreen is likely to separate into three smaller ice caps if the ice continues to thin and retreat in the future.
Learn more about the radar fieldwork here! (Insert video link to: Mette explains radar)
More than 351 000 point values of ice thickness collected along c. 1100 km transects were input to an ice thickness model to produce ice cap-wide maps of ice thickness and bed topography. From these maps we calculate a mean ice thickness of c. 155 m and a total ice volume of 70.6 ± 10.2 km3 for Jostedalsbreen.
Fieldwork on Jostedalsbreen (photos: Kamilla Sjursen, Simon de Villiers, Jostein Aasen, and Mette Gillespie).
Although some measurements of ice thickness and bedrock elevation were conducted in 1980s, we now have a much better understanding of the hidden landscape beneath Jostedalsbreen. The subglacial terrain is characterised by deep glacier eroded valleys, bedrock depressions and steep valley walls. As Jostedalsbreen continues to decrease in size, these bedrock depressions are locations where we can expect lakes to form in the future. In total, we estimate that c. 14% of the current glacier area may be covered by lakes if Jostedalsbreen was to melt away completely.
The results presented in this paper is the work of a large conglomerate of JOSTICE partners. We would like to acknowledge the enormous amount of work that has gone into planning and executing the fieldwork, as well as the following data analysis, ice thickness modelling and not least the preparation of this publication. The photo collage shows pictures from some of the many field trips to Jostedalsbreen. The work we do in the office after data collection is equally important, but unfortunately less well documented by pictures!