Jökull - 01.01.2005, Side 156

Þröstur Þorsteinsson et al
0.591 0.592 0.593 0.594 0.595 0.596
7.068
7.069
7.07
7.071
7.072
7.073
MD00
MD02
MD03
MD05
MD06
MD07
MD08
MD09
MD10
MD11
MD12
MD13
MD14
Easting (
b
×106 m)
N
or
th
in
g
(×
10
6 m
)
Figure 1. a) Location of the study area on the northern part of Mýrdalsjökull, S-Iceland. The area is about 4 km
x 4 km (black box). b) Locations of the stakes in UTM coordinate system, in the 28N zone. – a) Staðsetning
mælisvæðisins á norðanverðumMýrdalsjökli. b) Mælipunktarnir í UTM hnitakerfi, svæði 28N.
in June was supposed to follow exactly the same pro-
cedure as the survey in April, in order to allow an anal-
ysis of baseline length change, yielding high accuracy
strain rates. Unfortunately, bad weather, crevasses,
and equipment failure made that impossible.
Figure 2. Visiting the permanent stations in Septem-
ber was tricky due to dirt cones and crevasses. The
large amount of melting can be seen from the trian-
gular platform that was 20 cm off the snow surface
in June. – Dríli og sprungur gerðu leiðangursmönn-
um erfitt fyrir að komast aðmælistöðvum í september.
Á þríhyrningslagaða loftnetspallinum má glöggt sjá
hversu mikill bráðnun hefur átt sér stað frá júní, en
þá var hann 20 cm yfir yfirborði.
The Icelandic Meteorological Office operates a
permanent GPS station (SOHO) near the south termi-
nus of Mýrdalsjökull, about 20 km south of the sur-
vey area. Absolute base coordinates of the station are
listed as 63.55247◦N, 19.24665◦W, at 791.6 m eleva-
tion. Daily RINEX files are available on the Internet,
eliminating the need for setting up a base station for
this survey.
Three of the marks, MD00, MD11, and MD12,
were set up for semi-permanent recording (Figures 1–
4). In each case 3 poles were drilled to a depth of
approximately 8 m and fitted with a wood plug at the
bottom to prevent self-drilling. A triangular plywood
platform served as the antenna-mounting surface atop
the three poles (Figure 3). Rough solar panels mounts
were constructed of wood. A 20 amp hr battery was
used to power the three receivers. Solar panel mounts
were hose clamped to a ∼30 cm long PVC tube that
fit over one of the survey poles, allowing the panels
to subside with the surface melting (Figure 4). The
battery and receiver were tied to a similar tube or the
mount itself, in hope that they too would subside with
glacier surface ablation. A 10 m antenna cable was
coiled under the platform; allowing the receiver box
to subside relative to the fixed antenna as the surface
melted. Melt rate during the April fieldwork was be-
tween a few and up to 20 cm d−1.
156 JÖKULL No. 55, 2005