Geoscience Reference
In-Depth Information
Table 3 Different concepts found in the literature to assess the importance of glaciers in total river runoff.
Q
g
is glacier runoff, P
l
is liquid precipitation, E is evaporation, M is melt, R is refreezing melt or rainwater,
and C is snow accumulation
Concept
Equation
Description
1
a
Q
g
= M
ice,firn,snow
-R ?P
l
-E
All runoff from glacierized area
2
Q
g
= M
ice,firn,snow
-R
Glacier meltwater runoff
3
Q
g
= M
ice/firn
Ice/firn melt (melt from snow-free surface of
the glacier)
4
Q
g
= C-M
ice,firn,snow
-R (for Q
g
[ 0)
Runoff from glacier net mass loss
5
Q
g
= C-M
ice,firn,snow
-R ? P
l
-E
As 4, but including other water balance components
(water balance approach)
6
Q
g
= C
Runoff assuming balanced glacier mass budget
if the budget is negative
All quantities are integrated over the glacierized area
a
Lateral or subglacial inflows/outflows are neglected here.
the water balance equation over the area of the glacier and corresponds to the quantity that
is directly measured by gauging the proglacial stream(s) at the glacier terminus. Thus,
glacier runoff includes the portion of all water inputs to the glacier through melt, rain, or
other inflow at the surface, laterally or subglacially that exit the glacier at the terminus.
Second, the term has also been used to describe only the component of runoff that
comes from the melting of the glacier itself, i.e., from glacier ice, snow, and firn (i.e., snow
that has survived at least one melt season but has not been transformed to glacier ice yet),
hence excluding any rainwater or other inflow to the glacier system (Concept 2). This
component is more accurately referred to as glacier meltwater runoff (Cogley et al.
2011
).
Fig. 2 a Schematic seasonal variation of total glacier runoff and its components following Concept 1
(Table
3
), E is evaporation. b cumulative glacier mass balance in specific units (m w.e. year
-1
) showing a
year with negative annual balance. According to Concept 4 (Table
3
), annual glacier runoff corresponds to
the annual mass loss
