Jökull - 01.10.1998, Blaðsíða 45

Table 4. Mass balance of drainage basins in Vatnajökull, 1992-1993. Bw and bw = winter balance, Bs and bs = summer balance,
Bn and bn = net balance, ELA = the equilibrium line altitude, AAR = accumulation area ratio. Accuracy 15%.
-Afkoma skriðjökla Vatnajökuls, 1992-1993. Bw og bw er vetrarafkoma, Bs and bs er sumarafkoma, Bn og bn ársafkoma, ELA
er hœö jafnvœgislínu, AAR er hlutfall ákomusvœöis af heildarflatarmáli jökuls. Nákvœmni 15%..
Area Bw Bs bw bs b„ ELA AAR
km3 106m3 106 m3 106m3 m a' m a' ma'1 m
Síðujökull 385 1000 0.65
Tungnaárjökull 308 580 -535 45 1.87 -1.74 0.13 1130 0.65
Dyngjujökull 1040 1665 -340 1325 1.6 -0.33 1.27 1100 0.85
Brúarjökull 1695 2760 -910 1850 1.63 -0.54 1.09 1070 0.75
Grímsvötn 160 415 40 455 2.59 0.25 2.84 1.0
Fig. 6. Mass balance measurements, 1992-93. Specific mass
balance in m water equivalent, bw: winter balance, bs: sum-
mer balance, b„: annual net balance.
- Afkoma 1992-1993 sem metrar vatns. bw: vetrarafkoma,
bs: sumarafkoma, bn : ársafkoma. Mœlistaðir eru merktir
með krossi.
400* 106 m3. This is equivalent to an average runoff of
about 12 m3 s1 which is about 80% of the average for
the years of 1967-1980 (Guðmundsson and Björns-
son, 1992). Considering the positive mass balance of
the glacier, this was a year of small meltwater contri-
bution to the glacial rivers; about 20% of the summer
runoff and 10% of the annual runoff at the discharge
gauge Maríufossar, where the glacier covers about
12% of the total drainage basin. On the other hand, the
glacial component was 70% of the discharge during
the summer in Kaldakvísl at Þveralda, where the
glacier comprises 43% of the drainage basin.
II. THE MASS BALANCE 1992-1993
The mass balance was measured at 51 points on
seven drainage basins (Table, 4, Fig. 6), the winter
balance during the period April 23 to May 12 and on
June 19 (in Grímsvötn). The summer balance was
JOKULL, No. 45, 1998
43