Geoscience Reference
In-Depth Information
Epiglacial lakes can be seasonal or perennial, and in the course of years frequent changes
occur in the water storage and morphology on account of glacial movements and changing
meltwater inputs.
Example 6.1
. The characteristic dimensions are area A, thickness h, and renewal time-
scale T for a glacier or a lake. Clearly, for epiglacial lakes we have the approximate
relation
A
L
h
L
T
L
A
G
h
G
T
G
where the subscripts L and G refer
to glacier and lake,
respectively, Thus,
if
10 km
2
, h
G
*
10
3
a, the runoff from glacier becomes 2
10
6
×
A
G
*
200 m, and T
G
*
m
3
a
−
1
. This
2km
2
, h
L
*
10 m, and
T
L
*
10 a. Using the volume of glacier or lake, V ¼ Ah, we have V
G
:V
L
¼ T
G
:T
L
.
Epiglacial lakes are often perennially ice-covered, with occasional open water spots
forming as a result of advected heat on the landward sides melting the lake ice during
warm summers. The glacial meltwater can also occasionally
fl
flux of water is able to keep a lake with, e.g., A
L
*
fl
flood the surface and refreeze
restoring the
surface of the lake, as seen, e.g., at Edge Lake in Davis Valley.
In Antarctica, the exposed areas include coastal oases (e.g., Kaup et al. 1988; Priscu
1998; Sokratova 2011). The largest oasis is the McMurdo Dry Valleys situated near the
coast of the Ross Sea. Other large oases are found in the eastern Antarctica (Vestfold
Hills, Larsemann Hills, Bunger Hills, Schirmacher Oasis and Syowa Oasis), and at the
Ablation Point (Punta Ablaci
“
fl
at
”
n), on the east coast of Alexander Island at the Antarctic
Peninsula. In Schirmacher Oasis, epiglacial lakes are ice-free in summer (Kaup 1994;
Fedorova et al. 2010). Also in the Antarctic Peninsula and on the sub-antarctic islands the
lakes are often ice-free in summer. In the western Dronning Maud Land, East Antarctica
both ice-free and ice-covered epiglacial lakes are found at nunataks (Keskitalo et al. 2013;
Lepp
ó
ranta et al. 2013b). Lake Untersee in the central Dronning Maud Land is one of the
largest epiglacial lakes in Antarctica, with area of 11.4 km
2
and mean depth of 169 m
(Kaup et al. 1988; Wand et al. 1997). It is permanently covered by ice, which is 2
ä
6m
thick, and it is thought to have been such at least 100,000 years. Some of the largest
epiglacial lakes (Lake Fryxell and Lake Hoare) are found at glacier fronts in the McMurdo
Dry Valleys.
-
6.2.2 Physics of Epiglacial Lakes
The size of epiglacial lakes ranges from small ponds (Fig.
6.5
) to large lakes, and their
depth is up to more than 300 m. The time scale of the lakes may vary from seasonal to full
glacial cycles, and they may have seasonal or perennial ice cover. Epiglacial lakes can be
locally important fresh water resources. Example, this is true in northern Italy, where
glacial meltwater from the Alps is critically important for the agriculture. Outbursts of
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