Jökull - 01.01.2019, Page 19

Guðmundsson et al.
Figure 14. The development of terminus lakes by Hrútárjökull and Fjallsjökull. For explanations and credits
see Figures 3 and 12. – Þróun sporðlóna við Hrútárjökul og Fjallsjökul (sjá einnig 3. og 12. mynd).
than 1.0 km2 (Landsat 4–5, 1985–1994), (Figure 16).
Calving of the terminus intensified after 1994 and the
lake grew from < 1.5 km2 in 2000 to 3.7 km2 in 2018.
The growth rate was on average ∼0.02 km2 a−1 in
1936–1994 but ∼0.1 km2 a−1 in 1994–2018 (Landsat
5, 7–8; NLSI, aerial images; lidar DEM). Radio-echo
sounding measurements (Björnsson, 2009a; Magnús-
son and others, 2012) and recent soundings of water
depth show that the volume of the lake in 2018 was
∼170×106 m3 and the maximum depth near the mid-
dle of the calving front > 100 m. The subglacial to-
pography below Fjallsjökull features two large de-
pressions that reach below sea level where a > 200 m
deep lake with area ∼10 km2 will be formed if the
glacier eventually retreats out of these depressions.
The development of the lake, changes in the ice-
surface elevation and ice-flow velocity and the re-
sponse of the glacier dynamics to the calving into the
growing lake were studied by Dell and others (2019).
They found widespread thinning along the calving
front and marked increases in ice-flow velocity, espe-
cially along “fast-flow corridors” that were developed
in the northern part of the terminus around and after
2014.
Breiðárlón
The lake Breiðárlón by the western part of the ter-
minus of Breiðamerkurjökull started forming around
1930, a little earlier than Jökulsárlón (F. Björnsson,
1993) (Figures 15, 16 and 17). The lake first formed
east of the medial moraine in Breiðamerkurjökull
18 JÖKULL No. 69, 2019