Changes in the southeast Vatnajökull ice cap, Iceland, between ∼1890 and 2010c

Area and volume changes and the average geodetic mass balance of the non-surging outlet glaciers of the southeast Vatnajökull ice cap, Iceland, during different time periods between ∼ 1890 and 2010, are derived from a multi-temporal glacier inventory. A series of digital elevation models (DEMs) (∼ 1890, 1904, 1936, 1945, 1989, 2002, 2010) are compiled from glacial geomorphological features, historical photographs, maps, aerial images, DGPS measurements and a lidar survey. Given the mapped basal topography, we estimate volume changes since the end of the Little Ice Age (LIA) ∼ 1890. The variable volume loss of the outlets to similar climate forcing is related to their different hypsometry, basal topography, and the presence of proglacial lakes. In the post-LIA period, the glacierized area decreased by 164 km² (or from 1014 to 851 km²) and the glaciers had lost 10-30 % of their ∼ 1890 area by 2010 (anywhere from 3 to 36 km²). The glacier surface lowered by 150-270 m near the terminus and the outlet glaciers collectively lost 60 ± 8 km³ of ice, which is equivalent to 0.15 ± 0.02 mm of sea-level rise. The volume loss of individual glaciers was in the range of 15-50%, corresponding to a geodetic mass balance between -0.70 and -0.32 m w.e. a-1. The annual rate of mass change during the post-LIA period was most negative in 2002-2010, on average -1.34 ± 0.12 m w.e. a-1, which is among the most negative mass balance values recorded worldwide in the early 21st century.