Jökull - 01.06.2000, Blaðsíða 52

Magnús T. Guðmundsson
Figure 1. Öræfajökull, location map. The site of measurement in 1993-1998, the meteorological stations of
Kvísker and Fagurhólsmýri and the location of the pit dug in 1954 at Tjaldskarð are indicated. - Öræfajökull.
Mælistaðurinn á sléttunni milli Hvannadalshnúks og Hnappa er merktur með krossi. Staðurinn þar sem gryfja
var tekin í Tjaldskarði 1954 er merktur með punkti.
Considering that the thickness of the annual layer is
more than 10 metres in all cases, the error in mass
balance due to this uncertainty is always less than 5%.
Taking other sources of error into account, the error in
the measured mass balance is conservatively estima-
ted at about 10%.
MASSBALANCE
The 1993 core was obtained at the end of July, the
1994 core (Figure 2) at the end of August and in 1995,
1996 and 1998 the coring was done in June (Table 1).
A pole was left at the measurement site in 1996, and
a reading, giving the summer balance, was taken on 1
October.
The June mass balance measurements (1995,1996
and 1998) give the winter balance at the site while the
1994 measurement, taken at the end of August (roug-
hly the end of the melt season), yields the annual net
balance for 1993-1994. The 1993 measurement gives
the mass balance for the period September 1992 - Ju-
ly 1993. The annual layer thickness ranges from 10.2
to 13.2 m and the water content from 5750 mm to
7780 mm (Table 1). These values are two to three
times higher than reported for other parts of Vatna-
jökull (Björnsson et al., 1998) and for Hofsjökull
in central Iceland (Sigurðsson, 1993). They are also
much higher than the 3230 mm obtained on Öræfa-
jökull in 1954 (Rist, 1957) at an elevation of 1810 m.
50 JÖKULL No. 48