Jökull - 01.01.2005, Síða 132

Sverrir Guðmundsson et al.
Figure 11. Six-day averages of air temperature (TG) and wind-speed (u) along a longitudinal central profile on
Brúarjökull (Profile 1 in Figure 1). Days displayed in (a-d) are the same as in Figure 5. – Hita- og vindstigull
milli veðurstöðva á Brúarjökli.
cation, 2005). This was measured by the AWSs at
Brúarjökull during the warm period from August 9-
14 (Figure 11c). At the ELA, the high solar radia-
tion during the period August 9-14 (Figure 3g) along
with abrupt lowering in the albedo on August 9 (Fig-
ure 10e) resulted in net radiation 135% above the Au-
gust average for 1996–2004 (Figure 3a). In all, the
high energy fluxes duringAugust 9-14 caused melting
124% above the August average at the 1200 m AWS
(Figure 3e).
Energy budget of Brúarjökull 2004
The net radiation over the outlet increased as the
snowline moved upglacier (R in Figure 5). The net
turbulent fluxes followed the temperature and wind-
speed changes (H in Figure 5 and Figure 11). The
high solar radiation and low albedo during the pe-
riod August 9–14 resulted in high net radiation over
the whole Brúarjökull, although much more occurred
below than above the snowline; ∼200 Wm−2 below
1100 m a.s.l. and ∼90 Wm−2 at the highest eleva-
tions (Figure 5). During that period, the high tur-
bulent heat fluxes were driven by exceptionally high
temperatures and strong, stable winds (Figures. 11c
and 10b). The variation with elevation of the turbu-
lent heat fluxes, from 110 Wm−2 at the lowest eleva-
tion down to 50Wm−2 around the ELA (1200m), and
again up to 80Wm−2 at the highest elevations (Figure
5), is consistent with the air temperature gradient seen
132 JÖKULL No. 55