Jökull - 01.01.2010, Blaðsíða 185

Reviewed research article
Geomorphic implications of the retreat of Breiðamerkurjökull
in the southern part of the Skálabjörg ridge, Esjufjöll, Iceland
Maciej Da̧bski and Piotr Angiel
Department of Geomorphology, Faculty of Geography and Regional Studies,
University of Warsaw. Krakowskie Przedmieście 30, 00-927 Warsaw, Poland
mfdbski@uw.edu.pl
Abstract — The Skálabjörg nunatak, one of the summits of the Esjufjöll central volcano (SE Iceland), has been
glacially eroded by the Breiðamerkurjökull outlet glacier for thousands of years. Since the end of the Little Ice
Age, six to eight lateral moraine ridges have formed on the slopes of Skálabjörg. Ice-dammed lakes have also
developed in the southernmost part of Skálabjörg and in Fossadalur. The highest and largest moraine ridge
is situated 85–98 m above the contemporary glacier margin. Dating based on lichenometry, cartographic and
photographic documentation indicates that the initial exposure of the highest moraine ridge occurred between
AD 1896 and 1930 along its eastern margin and between AD 1915 and 1930 along its southwestern margin,
giving an average glacier surface lowering rate of 0.8–1.3 m/yr in the southern hills of Skálabjörg. Hills above
the highest moraine ridge bear imprints of earlier glaciation, most notably glacially abraded rock outcrops and
transported boulders. Small active solifluction tongues and lobes with stone-armoured fronts cover the surface
above the LIA limit. Small-scale and large-scale stripes exhibiting sorting down to c. 15 cm are abundant. The
uppermost parts of the Skálabjörg nunatak are heavily frost-weathered bedrock outcrops, and can be classified
as a typical periglacial domain.
INTRODUCTION
The Esjufjöll nunataks consist of four main mountain
ridges: Vesturbjörg, Skálabjörg, Esjubjörg and Aust-
urbjörg, running NW-SE, within the Breiðamerkur-
jökull glacier (Figure 1). Most of these nunataks
lie in the ablation zone but close to the glacier’s
equilibrium line altitude (Björnsson et al., 1998; de
Ruyter de Wildt et al., 2003; Björnsson and Páls-
son, 2008). Skálabjörg has recently been the focus
of biological, petrological and geochemical research
(Holm et al., 2003; Heiðmarsson et al., 2007; Heið-
marsson and Sigurðsson, 2008, María Ingimarsdóttir,
pers. comm.). Limited geomorphological studies have
been carried out in this region (Eyles, 1978), hence
the dynamics of relief change in this part of SE Ice-
land are relatively unknown. Although there exist nu-
merous works on geomorphic implications of recent
deglaciation in Iceland, they usually pertain to frontal
marginal zones, not the glaciers’ lateral environments
exposed by lowering of ice surfaces by ablation.
Our research hypothesis assumes that as
deglaciation proceeds, a periglacial environment
develops on the nunataks. The aim of this paper is
to assess the following research questions: What is
the geomorphological imprint of Breiðamerkurjökull
retreat in the southern part of Skálabjörg; and to what
degree have bedrock and superficial sediments on the
nunatak been altered by periglacial processes?
JÖKULL No. 60 185