Jökull - 01.01.2020, Page 81

Guðmundsson and Björnsson
Figure 4. Area changes of Kvískerjajöklar outlets since the LIAmax, the North glacier (blue line), the South
glacier (orange line) and total area changes of both glaciers (green). – Flatarmálsbreytingar á Kvískerjajöklum
frá lokum litlu ísaldar, nyrðri (blá lína) og syðri (rauðgul lína) tungurnar og báðar saman (græn lína).
let glaciers were outlined, but inside the gorges and
adjacent gullies, no signs of moraines are found and
the outlines were interpolated between the neighbour-
ing identified features with the aid of the lidar DEM
elevation contours. The glacier terminal position in
Múlagljúfur gorge was based on Thoroddsen’s (1959)
description from the late 19th century, who noted that
a narrow ice tongue occupied the inner part of the
gully. Flosi Björnsson (1998) describes a steep glacier
tongue reaching down to the gully in the first decades
of the 20th century.
The delineation of the 1930 ice margin was done
by examination of a handful of photographs from this
year, taken on land and from the air, using the QGIS
Pic2Map plugin. Several landforms were identified
on high-resolution photographs captured from the air-
ship Graf Zeppelin on July 17, 1930 (Figure 5). The
ice margin and the landforms were traced to identify
several points that indicated the ice-surface elevation
at the lateral glacier margin.
The ice divides of Kvískerjajöklar are well defined
by mountain ridges. In the present study we assumed
that the glacier surface at high elevations remained
approximately the same during the period 1890 to
2011, as was proven to be the case for the neigh-
bouring Kotárjökull, another outlet of Öræfajökull by
Guðmundsson et al., 2012, 2017; Hannesdóttir et al.,
2014, 2015, who noted that the ice surface above 1600
m altitude on Öræfajökull might only have lowered by
∼5 m since the 1890s.
CONSTRUCTION OF ICE SURFACE DEMS
Three digital elevation models were constructed of the
past ice surface elevation, representing: a) the LIAmax
extent in the mid-18th century; b) the 1880s; and c)
1930. This involved vertically shifting the lidar 2011
DEM, a method previously applied for reconstruct-
ing outlet glacier elevation in Southeast Iceland by
Guðmundsson et al. (2012, 2017) and Hannesdóttir
78 JÖKULL No. 70, 2020