Jökull - 31.12.2001, Page 28

Thorsteinsson et al.
Kvíslajökull
Múlajöl
kvislar
Satujöku
Miklafell
....
■
Þjórsárjökull
Figure 1. Landsat-image of
Hofsjökull from September
16th, 1986. The route of the
expedition (broken line),
the drilling site (X) at the
summit of Hofsjökull (1790
m a.s.l.) and the names of
major outlet glaciers are
indicated. The rims of
the subglacial caldera are
clearly visible. - Landsat-
gervihnattarmynd af Hofs-
jökli frá 16. september,
1986. Sýnd er leiðin, sem
farin var á jökulinn (brot-
in lína), borstaðurinn (X)
á hábungunni í 1790 m
y.s. og nöfn helstu skrið-
jökla. Barmar öskjunnar
miklu undir jöklinum sjást
greinilega.
accumulation area on western Vatnajökull indicate
that soluble impurities are washed out of the winter
snow during the melting season (Gíslason, 1994).
This does not exclude the possibility of obtaining
well-dated records of precipitation variations from ice
caps in Iceland. Several well-known tephra layers de-
tected in the Bárðarbunga ice core allowed the dating
of that core back to 1650 AD (Steinthórsson, 1977). It
is generally believed that detailed studies of the con-
centration of wind-blown dust, deposited on the ice
caps mainly in late summer, could allow the detection
of annual layers. If this turns out to be possible, exist-
ing mass-balance records from the ice caps could be
extended decades and perhaps even centuries back in
time. Moreover, ice-core studies of stratigraphy and
crystal textures and fabrics could add considerably to
our knowledge of the intemal structure of temperate
ice caps and glaciers, a subject of glaciology which
hitherto has received relatively little attention.
In this article, we describe an ice core drilling
project to 100 m depth carried out on the Hofsjökull
ice cap in the summer of 2001, focusing mainly on
the technical aspects of drilling and outlining possible
improvements in the existing drilling technique.
HOFSJÖKULL
Hofsjökull (Figure 1) is a temperate ice cap located
in the central part of the Icelandic highland. It has
an area of about 900 km2 and lies between elevations
of 600 m and 1800 m. The equilibrium line altitude
(ELA) has beeninthe 1200-1300 mrange since 1988.
26 JÖKULLNo. 51