Response of Eyjafjallajökull, Torfajökull and Tindfjallajökull ice caps in Iceland to regional warming, deduced by remote sensing

Abstract

We assess the volume change and mass balance of three ice caps in southern Iceland for two periods, 1979–1984 to 1998 and 1998 to 2004, by comparing digital elevation models (DEMs). The ice caps are Eyjafjallajökull (ca. 81 km2), Tindfjallajökull (ca. 15 km2) and Torfajökull (ca. 14 km2). The DEMs were compiled using aerial photographs from 1979 to 1984, airborne Synthetic Aperture Radar (SAR) images obtained in 1998 and two image pairs from the SPOT 5 satellite's high-resolution stereoscopic (HRS) instrument acquired in 2004. The ice-free part of the accurate DEM from 1998 was used as a reference map for co-registration and correction of the vertical offset of the other DEMs. The average specific mass balance was estimated from the mean elevation difference between glaciated areas of the DEMs. The glacier mass balance declined significantly between the two periods: from −0.2 to 0.2 m yr−1 w. eq. during the earlier period (1980s through 1998) to −1.8 to −1.5 m yr−1 w. eq. for the more recent period (1998–2004). The declining mass balance is consistent with increased temperature over the two periods. The low mass balance and the small accumulation area ratio of Tindfjallajökull and Torfajökull indicate that they will disappear if the present-day climate continues. The future lowering rate of Eyjafjallajökull will, however, be influenced by the 2010 subglacial eruption in the Eyjafjallajökull volcano

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

“…Here we use ρ = 900 kg m −3 in order to be consistent with the commonly used value for Icelandic glaciers (e.g. Guðmundsson et al, 2011;Pálsson et al, 2012;Jóhannesson et al, 2013). The uncertainty related to the conversion of ice volume to mass change to obtain geodetic mass balances is small for long periods (decades) of glacier retreat, and when volume loss is mainly confined to the ablation area, mostly ice is lost (e.g.…”

“…The mass balance of the larger ice caps in Iceland was generally close to zero in 1980-2000 (e.g. Björnsson and Pálsson, 2008;Guðmundsson et al, 2009Guðmundsson et al, , 2011Pálsson et al, 2012). In situ measurements show that mass balance was positive on Vatnajökull 1991-1994, but negative since then (Björnsson and Pálsson, 2008;Björnsson et al, 2013).…”

“…We base our estimates of the error for the geodetic mass balance on previous assessments of errors in DEM reconstruction and geodetic mass balance calculations for ice caps in Iceland (e.g. Guðmundsson et al, 2011), which take into account the square root of the sum of the two errors associated with each DEM and the glacier area. …”

Modelling the 20th and 21st century evolution of Hoffellsjökull glacier, SE-Vatnajökull, Iceland

“…and are highly dynamic. They are sensitive to climate variations and have responded rapidly to changes in temperature and precipitation during historical times (Björnsson, 1979;Björns-son et al, 2003;Björnsson and Pálsson, 2008;Guðmundsson et al, 2011). The recorded volume and area changes of these glaciers are therefore good indicators of climate change.…”

“…3). It is used as a reference map for co-registering the SPOT5 HRS-DEM (pixel resolution of 40 × 40 m), using the ice free areas surrounding Hoffellsjökull and the correlation method described by Guðmundsson et al (2011). This comparison revealed a horizontal shift of the HRS-DEM by 15 m and 5 m towards east and north, respectively, and a vertical offset of 2.3 m. Gaps in the HRS DEM, due to low contrast of the SPOT5 stereo image pairs at some sections in the accumulation area of Hoffellsjökull, were filled by smoothly adjusting the LiDAR DEM to the HRS DEM.…”