Jökull - 01.01.2020, Blaðsíða 27

Hannesdóttir et al.
Figure 12: The area change of the ice caps and glaciers in Iceland relative to their extent at the LIA maximum from ∼1890
until 2019, excluding the smallest glaciers (< 3 km2 in 2000). The LIA maximum for Drangajökull is dated to ∼1850 but
plotted starting in ∼1890 for simplicity. Glacier area derived from outlines not included in the GLIMS data set have been
added to increase the temporal resolution (open circles). They are based on Pálsson et al. (2012), Helgadóttir (2017), Belart
et al. (2020), and unpublished data from the IES-UI and IMO. – Hlutfallsleg flatarmálsbreyting jökla (að undanskildum
litlum jöklum minni en 3 km2). Þrátt fyrir að Drangajökull hafi náð hámarksútbreiðslu um 1850 miðast línuritið við 1890
til einföldunar. Flatarmál jökla skv. öðrum gögnum en gerð er grein fyrir hér og send hafa verið til GLIMS, er sýnt með
opnum hringjum. Þessi viðbótargögn eru frá Finni Pálssyni o.fl. (2012), Maríu Jónu Helgadóttir (2017), Joaquin Belart
o.fl. (2020) auk óbirtra gagna frá Jarðvísindastofnun háskólans og Veðurstofu Íslands.
shown on the glacier maps (see references in the fig-
ure caption). The smaller glaciers and ice caps with
steep outlets responded more rapidly to the cooler cli-
mate after 1960 than the larger glaciers, and gained
enough mass to advance 100–500 m, for example
Snæfellsjökull, Tindfjallajökull, Eyjafjallajökull and
Hrútfellsjökull, as can be seen from the more detailed
time series of those glaciers shown in Figure 12.
Glaciers with termini reaching down to low eleva-
tions experience larger relative area loss than glaciers
at high elevation. When the lower-lying glaciers/outlet
glaciers have lost a substantial proportion of their ab-
lation area, the rate of area loss tends to slow down.
Recently, dead ice lobes have been observed becom-
ing detached from some glacier tongues, for exam-
ple in 2018 when the snout of eastern Hagafellsjökull
was shortened by 700 m due to this process (Einars-
son, 2019, spordakost.jorfi.is), which may lead to an
abrupt change in glacier area for individual glaciers.
Some tens of small, named glaciers have essen-
tially disappeared since the year 2000. The first well-
known Icelandic glacier to be declared “dead” or non-
existing as a dynamically moving ice body, was Ok
glacier, which had a narrow elevation span (1100–
1200 m). Less than 1% of the maximum LIA area of
Ok glacier remain in the form of several thin, disinte-
grating ice patches in local depressions.
A comparison of area change and rates of area
change for the main ice caps and glaciers and for
groups of smaller glaciers for different time pe-
riods is presented in Table 3. The rate of total
area change, which is dominated by Vatnajökull,
24 JÖKULL No. 70, 2020