Jökull - 01.01.2012, Blaðsíða 99

Reviewed research article
Post-Little Ice Age volume loss of Kotárjökull glacier,
SE-Iceland, derived from historical photography
Snævarr Guðmundsson, Hrafnhildur Hannesdóttir and Helgi Björnsson
Institute of Earth Sciences, University of Iceland, Sturlugata 7, 101 Reykjavík, Iceland
Corresponding author: snaevarr@mmedia.is
Abstract – Kotárjökull is one of several outlet glaciers draining the ice-covered central volcano Öræfajökull
in SE-Iceland. We estimate the average annual specific mass loss of the glacier, to be 0.22 m (water equivalent)
over the post Little Ice Age period 1891–2011. The glacial recession corresponds to an areal decrease of
2.7 km2 (20%) and a volume loss of 0.4 km3 (30%). A surface lowering of 180 m is observed near the snout
decreasing to negligible amounts above 1700 m elevation. This minimal surface lowering at high altitudes is
supported by a comparison of the elevation of trigonometrical points on Öræfajökull’s plateau from the Danish
General Staff map of 1904 and a recent LiDAR-based digital elevation model. Our estimates are derived from a)
three pairs of photographs from 1891 and 2011, b) geomorphological field evidence delineating the maximum
glacier extent at the end of the Little Ice Age, and c) the high-resolution digital elevation model from 2010–
2011. The historical photographs of Frederick W.W. Howell from 1891 were taken at the end of the Little Ice
Age in Iceland, thus providing a reference of the maximum glacier extent.
INTRODUCTION
The first descriptions of the Little Ice Age (LIA)
glacier margins in Iceland were collected in the prox-
imity of inhabitated regions south of Vatnajökull ice
cap. Occasional reports descend from travellers pass-
ing through rural districts in the 18th and 19th centuries
(e.g. Þórarinsson, 1943; Björnsson, 2009). Less atten-
tion was paid to the smaller outlet glaciers, although
sparse observations were made during traverses on
the glaciers. A number of photographs of Icelandic
glaciers from the late 19th and early 20th century
are preserved (Ponzi, 2004; Archives of the National
Land Survey of Iceland; Reykjavík Museum of Pho-
tography; National Museum of Iceland). They pro-
vide valuable information on glacier extent, and can
be analyzed by repeat photography to deduce glacier
changes. This approach has been used world-wide,
and first practiced to document glacier variations in
the European Alps in the late 1880s (see e.g. Harrison,
1960; Luckman et al., 1999; Molnia, 2010; Webb et
al., 2010; Fagre, 2011).
In this paper we present unique historical oblique
photographs of Kotárjökull outlet glacier (Figures 1
and 2) from the first ascent of Hvannadalshnúkur (the
highest peak in Iceland) in Öræfajökull in 1891 (Guð-
mundsson, 1999). They were taken by an English
traveller, Frederick W. W. Howell (1857–1901), who
together with two companions from the farm Svína-
fell (Páll Jónsson and Þorlákur Þorláksson) reached
the summit on 17th of August. The photographs
are among the first prints of glaciers in Iceland, and
were taken during the 1890 LIA maximum stage (e.g.
Þórarinsson, 1943). His photographs are used to de-
rive the geometry of the LIA maximum glacier, by
trigonometric calculations, and by including informa-
tion from present-day photographs, geomorpholog-
ical evidence and a detailed digital elevation model
(DEM). Our findings allow quantitative estimates of
JÖKULL No. 62, 2012 97