Jökull - 01.01.2016, Blaðsíða 27

Reviewed research article
Surface and geometry changes during the first documented
surge of Kverkjökull, central Iceland
Jonathan L. Carrivick1, Fiona S. Tweed2, William M. James1 and Tómas Jóhannesson3
1School of Geography, University of Leeds, Woodhouse Lane, Leeds, West Yorkshire, LS2 9JT, UK
2Geography, Staffordshire University, Leek Road, Stoke-on-Trent, Staffordshire, ST4 2DF, UK
3Icelandic Meteorological office, Bústaðavegi 9, 150 Reykjavík, Iceland
Correspondence to: j.l.carrivick@leeds.ac.uk
Abstract — Many surge-type glaciers remain unrecognised because surge events can be short-lived and are
rarely captured by satellite or field data. This study reports the first documented surge of Kverkjökull, central
Iceland, adding a relatively short, narrow, steep and alpine outlet glacier from the Vatnajökull ice cap to the
surge-type glaciers in Iceland. The surge occurred after decades of persistent and recently accelerated terminus
retreat. The surge initiated after 2008 and immediately preceded drainage of the Gengissig geothermal lake
and a jökulhlaup in 2013. The surge was still in progress in 2013. It caused vertical surface displacements of
up to 20 m that were most prominent in parts of the glacier >100 m thick. The magnitude of surface elevation
changes, terminus advance and ice surface velocity changes probably reflect a single surge phase. Asymmetry
in the response of the glacier terminus to the surge front suggests interaction with near-stagnant ice in a part
of the glacier terminus but otherwise the trigger and mechanism of the Kverkjökull surge remain unexplained.
INTRODUCTION
Glacier surges are events of enhanced ice flow dur-
ing which ice previously stored at elevation is rapidly
discharged down glacier. Surges are important agents
of erosion and deposition, they affect the timing and
magnitude of meltwater runoff and in areas where
surging is common, e.g. Iceland and Svalbard, they
represent an important mechanism of glacier mass
transfer. Glacier surges may usually be recognised
by their distinctive surface morphological expression,
and where appropriate data are available, by changes
in terminus position, surface velocity and glacier sur-
face elevation.
The flow of a surge-type glacier is periodically
interrupted by suddenly-enhanced ice-flow velocities
for months or years (Meier and Post, 1969; Thórar-
insson, 1969). This behaviour is apparently unrelated
to climate change although climate may play a role in
determining the periodicity of surges and whether or
not a glacier will surge (Sharp, 1988; Hewitt, 2007;
Striberger et al., 2011). Surging glaciers tend to clus-
ter in a few geographical areas such as Alaska, Yukon
(especially the St. Elias Range), British Columbia,
Svalbard, Andes, Caucasus, Karakoram, Pamirs, Tien
Shan, and Iceland (Sevestre and Benn, 2015). In
contrast, the European Alps, Scandinavia and the
Rocky Mountains have very few surging glaciers.
Understanding glacier surges is important because
they can cause considerable and widespread landscap-
ing (Sharp, 1988) and they affect meltwater runoff
regimes, especially notably in Iceland (Björnsson et
al., 2003). Furthermore, surges can account for signif-
icant glacier mass transport. For example, surges have
contributed at least 10% to the total ice transport to
the ablation areas of Vatnajökull during the 20th Cen-
tury (Björnsson and Pálsson, 2008). Understanding
of surges is key to understanding glacier dynamics;
they can yield important insights into basal processes
JÖKULL No. 66, 2016 27