Jökull - 01.12.2007, Page 90

Eyjólfur Magnússon og fl.
7. mynd. Landslag í nágrenni Kvískerja eins og það gæti hafa verið í kringum landnám. Lega áa eftir ársléttum
er ágiskun höfunda. – The study area as it might have appeared prior to the Little Ice Age.
Þakkir
Við þökkum Kvískerjasjóði og Alþingi kærlega fyr-
ir hafa gert þessa rannsókn mögulega með fjár-
stuðningi sínum. Loftmyndir ehf. fá bestu þakk-
ir fyrir afnot af landhæðarlíkani. Einnig er SPOT
Image í Frakklandi þakkað fyrir not af SPOT5-
gervihnattamynd. Að mælingunum unnu auk Eyj-
ólfs, Haukur Elvar Hafsteinsson, Einar Ísfeld Stein-
arsson, Alexander Jarosch, Óliver Hilmarsson og Sig-
urlína Þóra Héðinsdóttir og fá þau kærar þakkir fyrir
allt streðið. Að lokum skal þakkað sérstaklega Sig-
urði, Helga og Hálfdáni Björnssonum á Kvískerjum
fyrir góð ráð um framkvæmd mælinga sem og ýmsan
annan fróðleik um jöklana í nágrenni þeirra.
SUMMARY
Radio echo sounding on Kvíárjökull, Hrútárjökull
and Fjallsjökull
Radio echo soundings were carried out on the outlets
Kvíárjökull, Hrútárjökull and Fjallsjökull, in Vatna-
jökull, flowing east from Öræfajökull, the highest
mountain in Iceland. The results show that the largest
one, Fjallsjökull, is up to 450 m thick and dug down
to 180 m below sea level. The neighbouring outlet
Hrútárjökull has maximum thickness of 300 m and
its bed reaches 10 m a.s.l. Kvíárjökull outlet is up to
350 m thick and its bed goes down to 100 m below sea
level. At present these glaciers are retreating rapidly.
Assuming that the retreat continues and the refilling of
sediment deposit is negligible while these outlets are
disappearing, the glacier lagoon, Fjallsárlón, in front
of Fjallsjökull will reach maximum size of 11 km2,
with average depth of 70 m and maximum depth of
210 m. Another glacier lagoon will appear in front
of Kvíárjökull, which will be 3 km2 when it is largest,
around 60 m deep on average and 130 m deep where it
will be deepest. We estimate that during the Little Ice
Age the outlet Kvíárjökull excavated 0.25±0.06 km 3
of sediments, assuming that the glacier margin was
above 100 m a.s.l. with a river delta below in the beg-
inning of that period. The corresponding sediment
erosion of Fjalls- and Hrútárjökull outlets during the
same period is 1.3±0.3 km3. Assuming this exca-
vation took place over four centuries, this equals an
erosion rate of !12 m/century averaged over the area
affected by the Kvíarjökull outlet and !15 m/century
88 JÖKULL No. 57