Jökull - 01.01.2016, Page 52

Paweł Molewski and Leon Andrzejewski
Figure 1. Location of Tungnaárjökull (A) and close up (B) of study areas (1 and 2) on the glacier forefield. Bro-
ken lines indicated axes of volcanic ridges and dotted lines mark the boundary of area presented in a 3D model
(C) of the snout and forefield of Tungnaárjökull (Data from Loftmyndir ehf.). – Kort af rannsóknarsvæðinu við
jaðar Tungnaárjökuls. Þrívíddarkortið (C) er byggt á gögnum frá Loftmyndum ehf.
Since the end of the LIA, Tungnaárjökull’s dy-
namics have been dominated by long periods of re-
treat interrupted by glacier surges. The glacier has
been receding since the late 19th century, a pattern
interrupted by surges during the years of 1915–1920,
1945 and 1994–1995 (Thorarinsson, 1964; Frey-
steinsson, 1968; Andrzejewski, 2002). Geomorpho-
logical and sedimentological records of these surges
in the marginal zone of Tungnaárjökull are repre-
sented by a series of landforms associated with suc-
cessive advances and recessions of the glacier snout
(Andrzejewski, 2002; Andrzejewski et al., 2005;
Molewski et al., 2005; Evans et al., 2009). Periodic
contact of the Tungnaárjökull snout with the Jökul-
grindur ridge obstructed the outflow of its meltwa-
ters and caused the formation of ice-dammed lakes.
Such events took place when the glacier reached its
maximum extent at the end of the LIA and during the
surges of 1915–1920 and 1945. The changing hydro-
dynamic conditions at the contact of the lakes with
the glacier snout are expressed in a diverse complex
of landforms and deposits, including lake shorelines,
delta fans and kame terraces. A study aimed at recon-
structing the processes that shaped these landforms
52 JÖKULL No. 66, 2016