Jökull - 01.06.2000, Page 14

Mcickintosh, Dugmore and Jacobsen
Figure 3. The results of the glacier survey; glacier long profile and cross sections (crosses delineate individual
sounding points +). - Langsnið og þversnið af Sólheimajökli. Mœlistaðir á yfirborði jökulsins eru merktir með
krossi.
near the snout (around Jökulhaus) where the sub-
glacial hill is expressed on the glacier surface as
transverse and longitudinal crevasses. North of the
1300 m contour, the ice surface levels off dramatically
at the transition from shallow ice on the caldera rim
to deep ice within the basin (Table 1). A comparison
between our survey results and the 1:50000 Iceland
Geodetic Survey topographic map (DMA Mýrdals-
jökull Sheet, 1812 (ii)) reveals that the glacier is 20-
80 m thicker in its middle and lower reaches and ext-
ended ~500 m further in 1996 than when the DMA
map was compiled (Figure 4). The date of compilation
for the DMA map is unknown, but it pre-dates 1990
and probably occurred before 1980 (Oddur Sigurðs-
son personal communication 1998). Between 1970
and 1995 the glacier advanced a net distance of 482
m (Sigurðsson, 1998). As the advance had just halted
at the time of our survey, Figure 4 may represent a
before and after snapshot, showing the changes in
extent and ice thickness that have occurred on Sól-
heimajökull during recent times.
DISCUSSION
There are a number of implications following from
this work. First, a comparison between the subglacial
topography map published in Lawler etal. (1996), and
our data shows very good agreement near the ice cap,
12 JÖKULLNo. 48