Jökull - 01.10.1998, Page 47

Table. 5. Meltwater runoff from drainage basins in Vatnajökull in the summer of 1993, from May 1 to Sept. 30, Ag = glacier area,
£QS = runoff during summer from the glacier, corresponding to the summer balance , Qs = mean summer discharge from the
glacier, corresponding to the summer balance, q, = specific discharge, corresponding to the summer balance, Ar = area above the
discharge gage, £Qrs = runoff during summer in the river (June 1 to September 30), Qra = mean river discharge during the year.
- Afrennsli leysingarvatns frá jökli sumarið 1993frá byrjun júní til loka september, Ag erflatarmál jökuls, ZQS er heildarrennsli
vegna neikvœðrar sumarafkomu jökulsins, Qs er meðalrennsli sumars frá jöklinum vegna neikvœðrar sumarafkomu, qs er
afrennsli áflatar- og tímaeiningufrá jöklinum vegna neikvœðrar sumarafkomu, Ar erflatarmál vatnasviðs ofan við rennslismœli
á jökulá, ZQrs er sumarrennsli í jökulá frá byrjun júní til loka september, Qm er meðalársrennsli jökulár.
River a8 £QS Qs qs Ar £Qrs Summer Qra Q7Qra Annual
km2 106 m3 a'1 m3 s'1 1 s'1 km'2 km2 106 m3 a'1 % m3 s'1 %
Tungnaá 141 331 10.5 74 1131 1328' 25 80.9' 13
Jökulsá á Fjöllum 1144 752 23.8 21 1966 8962 84 70.22 34
Kreppa and Kverká 302 333 10.6 35 862
Jökulá á Brú 1406 994 31.5 21 2090 1970’ 50 90.23 35
‘) National Power Company, vhm 096, Maríufossar.
2) National Energy Authority. Hydrological Service, 1994.
3) National Energy Authority. Hydrological Service, 1998b.
measured September 7 to 8 on Tungnaárjökull and
September 23 to October 8 on the other glaciers. On
Síðujökull, measurements were only conducted in the
accumulation area. On Dyngjujökull and Brúarjökull,
measurements were carried out along more than one
flowline in order to study the lateral distribution, i. e.
a possible east-west trend.
On the glacier snout at 700-800 m elevation, the
winter precipitation was about 1000 mm higher on the
western than on the northern outlets. The specific
winter balance was at maximum (2.4 to 3.2 m) on
Síðujökull towards the Grímsvötn area and eastwards
across central Vatnajökull (Fig. 6) and decreased
down the westem and northem outlets. The winter
balance on Tungnaárjökull increased with elevation
by 170 mm/100 m, but two times faster on the north-
em outlets (Fig.7). On Brúarjökull, the winter balance
increased considerably eastward: by 1200 mm over
30 km at 1200 m elevation (Fig. 8). A lateral trend
was also observed on Dyngjujökull, perhaps an effect
of the neighbouring mountains Bárðarbunga and
Kverkfjöll (Fig.6). Cyclonic activity was high and
winds from southwest and northeast were frequent.
The winter precipitation in Iceland was above normal,
especially in northem regions (Veðráttan, 1993).
The summer was cold (especially during June
through August) and the summer balance was posi-
tive in the uppermost accumulation areas of all the
glaciers (by as much as 1 m, Fig. 6) because of cold
spells with considerable snowfall during the summer.
The summer temperature was 1.0 °C below the aver-
age of 1930-60 (Veðráttan, 1993). In general, snow-
fall during the summer was more frequent on the
distance (km)
Fig. 8. Variations in mass balance at 1200 m elevation on
Brúarjökull 1992-93.
- Breytingar í afkomu frá vestri til austurs eftir 1200 m
hœðarlínu áBrúarjökli 1992-1993.
JÖKULL, No. 45, 1998
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