Natural and societal consequences of climate-forced changes of Jostedalsbreen Ice Cap
Jostedalsbreen during the Little Ice Age reconstructed
by Jacob Yde, May 24, 2022 (last edited: 25 May, 2022)
A new study has reconstructed the extent and size of Jostedalsbreen during the Little Ice Age maximum, which occurred from 1740 to 1860. A comparison with digital outlines of Jostedalsbreen from 2006 and a recent digital elevation model reveals that Jostedalsbreen has lost 16% of its area and 18% of its volume since the Little Ice Age.
During the Little Ice Age outlet glaciers from Jostedalsbreen Ice Cap advanced into adjacent valleys, forming large terminal moraines. In a new study by Carrivick and co-authors published in Quaternary Science Reviews, these moraines, together with markings of glacial erosion on valley sides called trimlines, have been used to map the maximum extent of Jostedalsbreen during the Little Ice Age. The exact date of the maximum extent may have varied from glacier to glacier with a median date of 1755.
Near-horizontal lines, called trimlines, on the valley sides above Austerdalsbreen reveal significant ice loss since the maximum Little Ice Age extent (photo: E. Nielsen).
When Jostedalsbreen was at its maximum extent during the Little Ice Age, it may have covered an area of 568 km2. This area was reduced to 475 km2 (16%) in 2006 and to 458 km2 (19%) in 2019. This decrease in area is less than other glacierised regions in Norway, where the reduction since the Little Ice Age has been approximately between 30% and 40%. The largest losses of area by percentage at Jostedalsbreen occurred at Langedalsbreen (66%) and Lodalsbreen (62%).
The volume of Jostedalsbreen during the Little Ice Age is estimated to 76 km3 compared to 62 km3 in 2006, a loss of 18%. Both volume estimates are based on modelling, but since the glacier surface topography during the Little Ice Age and the bed topography beneath Jostedalsbreen are unknown the uncertainties of the estimated volumes may be +/-20%. In comparison, the uncertainties of the estimated areas are likely less than 10%.
The Little Ice Age moraine at Austerdalsbreen (photo: J. Yde).
JOSTICE has recently finished radar measurement surveying of the entire Jostedalsbreen Ice Cap. The results of this effort will likely improve the estimation of the present ice volume even further, in addition to revealing the hidden landscape beneath Jostedalsbreen. Also, JOSTICE works on geodetic mass balance models to highlight the response of Jostedalsbreen to climatic changes during recent decades.