Jökull - 01.12.1972, Blaðsíða 43

the advected energy contribution could be as
much as 150 X 106 cal/sec or about 630 x 10B
watts, not taking into account latent heat o£
fusion of water.
3) If, additionally, the entire melt-water
volume is derived directly from ice by geo-
thermal heating, taking into account 79.7 cal/g
latent heat of fusion, another 120 X 106 cal/sec
(about 500 X 10° watts) should be added to
the above estimate.
4) The speculative estimates outlined above
undoubtedly do not include the full energy
contribution of steam sources characteristic of
high-temperature geothermal areas in Iceland.
Because Kverkfjöll is such an area and lieat loss
from perforations in the ice lias been observ-
ed, the amount of lieat advected through
Kverkjökull outflow tunnel is possibly consider-
ably less than the total convective heat loss
i'rom Kverkfjöll vestri.
5) Direct evidence as to the location of the
subglacial thermal sources is lacking. Three
possibilities can be mentioned: a) tliermal
waters from the northeastern end of the Hvera-
dalur geothermal area draining north-north-
east subglacially in the general direction o£
the topographic slope, and entering Kverk-
jökull between the 1200 and 1300 meter con-
tours (Figs. 2, 3, and 4); b) thermal spring
effluents beneath the outlet tongue of Kverk-
jökull (about 1/2 to 1 km south of point B,
Fig. 4), forming a continuation towards the
north-northeast of the Hveradalur tliermal
area; c) geothermal source in the subglacial
accumulation area of Kverkjökull, probably a
caldera.
Additional advective heat transfer from Hvera-
dalur and the escarpment of Kverkfjöll eystri
and estimated total heat transfer from Kverk-
fjöll geothermal area
Even less reliable estimates can be made for
advective heat flow from Hveradalur and the
thermal area of Kverkfjöll eystri than from
Kverkjökull, but a few points merit some
attention. Both 1966 and 1968 infrared images
suggest considerable thermal surface drainage
from Hveradalur through the breach in the
glacier and down tlie steep slopes to the north-
west (Figs. 4 ancl 5), not included in the Kverk-
fjöll estimates.
It is entirely possible that the total runoff
from Hveradalur above exceeds that from
Kverkjökull outlet tongue. If so, the advective
heat loss may also exceed our estimates for
Kverkfjöll.
If heat transfer from Hveradalur to north-
west-flowing surface drainage and from Kverk-
fjöll eystri to east-flowing drainage is equival-
ent to that from Kverkjökull, the total advec-
tive heat flow from the entire Kverkjökull and
Kverkfjöll drainage areas may be in the 300—
540 x 106 cal/sec range or greater.
SUMMARY
Infrared imagery and photographic surveys
of 1966 and 1968 confirm the existence of per-
sistent subglacial thermal activity at Kverkfjöll,
provide new information on the location and
number of exit points of thermal waters and
on the extent of thermal melt-water outflow
from Kverkfjöll outlet tongue. The specific
source of this thermal outflow is not readily
apparent but may be beneath Kverkjökull out-
let tongue along the north-northeast extension
of the Flveradalur volcano-tectonic line or be-
neath its accumulation area. The apparent
temperature gradient of the outflow melt-
water suggests high temperatures at its source.
Advective heat represented by Kverkfjöll
melt-water drainage is at least 20 X 106 cal/sec,
but probably represents geothermal sources
yielding more than 150 X 10° cal/sec, most o£
which is lost subglacially. Fleat advectecl
through surface drainage from Hveradalur ancl
Kverkfjöll eystri and lost by radiation, ebulli-
tion, and evaporation from more than 120
recognizable points of thermal emission, prob-
ably by concluction, convection, seepage ancl
other mechanisms, may be of a similar magni-
tude, and gives an estimate for the total thermal
yielcl from the entire KverkfjölI-Kverkjökull
subglacial drainage area which may be 300—
540 X 106 cal/sec.
The energy expended in forming the major
Kverkfjöll cauldron is estimated at 1.2 X 1023
ergs. The 1968 aerial surveys suggest a recent
diminution in thermal activity í'rom the ice
cauldron but confirm continued high-tempera-
ture thermal activity on 26 August 1968 at the
new steam vent southeast of Jökullón.
JÖKULL 22. ÁR 41