Náttúrufræðingurinn - 2004, Side 62

N áttúrufræðingurinn
son's43 and Thorarinsson's9 conclusions
about glacier maxima in the northwest-
ern peninsula (Vestfirðir) during the
middle of the 18th century and the mid-
dle of the 19th century must be viewed
with caution. Therefore, Thorarinsson's
"known facts" are not beyond doubt.
A caim built for geodetic purposes on
top of the highest peak (Sjónfríð) in the
Gláma massif in the year 1806 is still
standing (Fig. 3). This proofs that there
was no glacier during the last century of
the "Little Ice Age'' on top of the pro-
tmding peaks in the area. Therefore, the
location of any glacier must be sought in
the lower passes between the peaks or as
isolated ice masses in cirque basins. The
19th century in Iceland was a period of
expansion of glaciers, most of which
reached their maximum areal extent
about 1890. There is no reason to expect
that glaciers in the northwestem penin-
sula had a trend which was appreciably
different.
The glacier Unadalsjökull, northem
Iceland, has a similar topographic set-
ting as the postulated Glámujökull; it is
situated in a saddle between two valleys.
The time of its maximum area is not
documented but might very well be
toward the end of the 19th century, as
with most other glaciers in Iceland. Its
previous maximum extent is still clearly
visible by the dark colour of the scoured
proglacial area (see Fig. 5). During the
warm 20th century, Unadalsjökull
shrank from about 3 km2 to about 2 km2.
Many glaciers that in historical time had
a maximum area of less than 1 km2 still
exist as such despite the fact that the 20th
century was probably the mildest centu-
ry of the last millennium.
In general, masses of snow and ice
need to be about 40-50 m thick and
show some signs of flow to meet the
definition of a glacier. According to mea-
surements of Icelandic glaciers in the last
decades, annual net mass balance has
rarely exceeded ±1 m water equivalent.
Therefore, a new glacier is not likely to
form in less than about a century during
a period with a distinct trend of positive
mass balance. Likewise, it will take a
glacier, even a small one, at least a centu-
ry to disappear during a distinct and
extended period of warming. Ac-
cordingly, there is no reason to believe
that a substantial glacier, present in the
Gláma highlands as late as about 1800,
would have disappeared entirely by the
visits of Stefán Stefánsson in 1893 or
even Herrmann in 1914, taking the cool
climate of the 19th century into consider-
ation. The remnants or traces of such a
glacier would certainly still have been
easily recognized in the field.
About 10-15 km north of Gláma there
are a few cirque glaciers (Fig. 7) present
on the north side of a mountain
(Lambadalsfjall) about 40 m higher in
elevation than Sjónfríð. They have not
during historical time been much bigger
than they are now.
Small glaciers are problematic to
map. They are usually covered by snow
and, therefore, not easy to distinguish
from fim fields, either in the field or on
aerial photographs and other types of
remote sensing. Their areal extent can
only be reliably traced in late summer in
an extended period of negative mass bal-
ance. Most maps of Iceland are of very
little value when estimating the areal
extent of small glaciers because of the
inability of cartographers to differentiate
glacier ice from fim fields.
A legal question has been brought
before the High Court of Iceland
(Icelandic: Hæstiréttur) about the possi-
bility of the existence of a glacier
(Icelandic: jökull) on the Fimmvörðuháls
mountain pass between the Eyjafjalla-
jökull and Mýrdalsjökull ice caps in
southem Iceland. Artifacts such as the
series of caims situated along the fre-
quently crossed mountain track and the
lack of geological evidence for glacier
action indicate that the two ice caps were
not contiguous (continuous glacier ice)
during historical time. On the other
hand, it may not be necessary to prove
the existence of a glacier that strictly
meets the glaciological definition,
because the Icelandic term jökull has
always denoted extensive fim fields and
large masses of snow as well as glaciers.
The following conclusions may be
drawn from the discussion above:
• There is a big difference between
the processes associated with a
glacier and a long-lived, persist-
ent fim field; they must be clearly
distinguished from each other in
any discussion. Of course, there
may be borderline cases not easy
to define, but they are expected to
be few and insignificant glacio-
logically.
• Glaciers tend to be quite stable in
time and space. Observations of
glaciers in Iceland during the cli-
mate variations from the cold 19th
century to the very mild 20th cen-
tury indicate that it would take a
glacier, even a small one, at least a
century to disappear. Extensive
fim fields, on the other hand, may
melt away in a few years.
• The preponderance of evidence
indicates that Glámujökull did
not exist in historical time, with
particular reference to the fact that
there was no glacier on Gláma in
the summer of 1893. This was at
the end of the coldest 30 years on
instmmental record in Iceland,
when most if not all other glaciers
in the country expanded and
reached their historical maximum
areal extent.
• The ice caps of Eyjafjallajökull
and Mýrdalsjökull, southern
Iceland, were not connected by
glacier ice during historical time.
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