Jökull - 01.01.2004, Page 26

Eyjólfur Magnússon et al.
Figure 6. The water divides for Tungnaá derived from the EMISAR DEM in 1998 (solid line) and from the
DEM in 1981 (broken line). – Vatnasvið Tungnaár samkvæmt gögnum frá 1998 (heil lína) og 1981 (brotin
lína). Breytingarnar stafa af framhlaupi jökulsins 1994–1995.
tial distances along the glacier margin making it im-
possible to identify individual outlets. According to
our model, a large majority of the water draining into
Hverfisfljót is collected at a critical point marked with
a red star in the lower part of the Hverfisfljót river
basin (Figure 7). It is not possible to say on the basis
of our model (Equation 4) in which direction the water
drains from this point (south or west). The locations
of the two predicted runoff outlets draining from the
critical point are, however, in accordance with the lo-
cations of the marginal runoff outlets seen in the Pol-
SAR image (marked 1 and 2 in Figure 7). Therefore, a
substantial amount of water drains in both directions.
The locations of runoff outlets for Skaftá (number 3
to 7) seen in the PolSAR image also agree fairly well
with the predictions. Inconsistency between the pre-
dicted and observed watercourses at some locations
could be due to unknown features in the basal topo-
graphy close to the margin. Our model may also fail
because the thin ice close to the margin does not rest
26 JÖKULL No. 54