Jökull - 01.12.1970, Page 55

This map is at a scale of 1:15,000 with 10 m
contour intervals making it very accurate. It
also reveals the glacial topography on Breida-
merkursandur making it easy to estimate the
maximum advance of the glacier.
Some measurements of the glacial thinning.
During July 22—26, 1968 the author stayed to-
gether with B. Adalsteinsson at the nunataks
Esjufjöll in Vatnajökull. The lowering of the
glacier margin was measured at 15 localities.
On July 27 the author together with F. Björns-
son of Kvísker walked along the eastern margin
of Breidamerkurjökull and up to the ice-damm-
ed lake of Vedurárdalslón which at that time
was quite empty (Fig. 4) because it had bursted
some days earlier. In this trip the lowering of
the glacier margin was measured in three places
on the western flanks of Vedurárdalsfjöll. In
locating the measuring points the following
criteria were preferred. It had to be a rather
steep slope (>15° dip), where the uppermost
lateral marks of the recent iceflow were distinct
and obvious. They should form a straight line
for at least 200 m. The present ice edge should
be even and its slope along the flank almost
parallel with the uppermost flow marks. These
conditions could be fulfilled except for the
lowest measuring point on the western side of
Vedurárdalsfjöll, where it proved to be diffi-
cult to determine the elevation of the present
glacier margin, and at the middle point at the
west side of Vesturbjörg in Esjufjöll where the
uppermost marks were irregular because of less
slope (ca. 8°—10°). The measurements were per-
formed with a Paulin aneroide altimeter with
a measuring accuracy of ± 0.5 m. The air pres-
sure was very stable during these days and
repeated measurements never differed more
than ± 1 m. The results of these measurements
are represented in Table 1. The measurements
TABLE 1 - TAFLA 1
The lowering of Breidamerkurjökull from its maximum thickness at the end of the last centurv
according to the measurements performed by the author on July 23—27, 1968
Þynning Breiðamerkurjökuls frá hámarksþykkt hans í lok s.l. aldar samkvœmt þynningarmœl-
ingum höfundar dagana 23.-27. júlí 1968
Measuring locality Present elevation of the ice surface Núverandi hæð The quality of the locality Gæði Lowering, m Þynning,
Esjufjöll, Austurbjörg, NE jökuls, m y. s. 960 mælistaðar Fair m 44
,, ,, E 870 Excellent 50
}> >) E 800 Excellent 42
,, , SW 850 Good 34
„ Esjubjörg, E 840 Excellent 32
,, ,, SW 860 Fair 37
,, ,, SW 940 Good 35
„ Skálabjörg, NE 860 Good 51
,, ,, E 720 Excellent 68
„ E 650 Excellent 71
,, , SW 650 Good 57
„ Vesturbjörg, E 700 Excellent 51
,, ,, S 800 Good 23
,, „ sw 870 Fair 31
,, sw Excellent 29
Fellsfjall, NW 300 Fair 43
Útigönguháls, w 380 Excellent 49
Fauski, NW 530 Good 35
JÖKULL 20. ÁR 53