Jökull - 01.01.2020, Blaðsíða 30

Glacier extent in Iceland, 1890–2019
data set will be made openly available at GLIMS,
for distribution to various other global glacier and
open access mapping inventories and archives, it will
be available to other researchers and also for various
mapping purposes where this type of data is useful,
for example for science outreach projects.
CONCLUSION
Glacier-area variations in Iceland since ∼1890 show
a clear response to variations in climate. They have
been rather synchronous over the country, although
surges and subglacial volcanic activity influence the
position of some glacier margins.
Glaciers in Iceland have decreased by 18% in area
since ∼1890. The main ice caps have lost between
10% and 30% of their maximum LIA size, whereas
intermediate-size glaciers have been reduced by up to
80%.
The glacier area in 2019 was approximately
10,400 km2, and has decreased by more than
2200 km2 since the end of the 19th century and by
approximately 750 km2 since ∼2000. Some tens of
small glaciers have disappeared entirely during the
first two decades of 21st century. During that time
period, the rate of decrease in area has been approxi-
mately 40 km2 a−1.
The area decrease rates since the late 19thcentury
were highest during the most recent time peri-
ods (2000–2010, 2010–2014 and 2014–2019). The
glacier retreat rate may have been similar in the 1930s
and 1940s; the temporal resolution of the inventory is,
however, not sufficient to estimate this.
Glacier inventories are important for climate
change studies, for calibration of glacier models and
for studies of glacier surges and glacier dynamics and
for science outreach projects. It is now possible to ex-
tend the terminus variations database of the Iceland
Glaciological Society back to the end of the 19th by
comparison with the outlines of our inventory.
Acknowledgement
We thank everyone who has shared glacier outline
data and made it possible to complete this glacier in-
ventory, including Ágúst Þór Gunnlaugsson, Áslaug
Geirsdóttir, Bjarki Björgvinsson, Daði Björnsson at
Loftmyndir ehf., David Evans, David J. Harning, Ívar
Örn Benediktsson, María Jóna Helgadóttir and Skafti
Brynjólfsson. We also thank two anonymous review-
ers for a thorough review of the manuscript and Andri
Gunnarsson, Áslaug Geirsdóttir, Helgi Björnsson and
Skafti Brynjólfsson for useful comments. The collec-
tion of glacier outlines and preparation of the glacier
inventory was partly supported by the Nordic Centre
of Excellence SVALI. This paper was partly funded
by the Icelandic Ministry for the Environment and
Natural Resources through the cooperative project
Melting glaciers.
Ágrip
Gögnum um útbreiðslu íslenskra jökla hefur ver-
ið safnað saman frá nokkrum rannsóknarhópum og
stofnunum og nemendaverkefnum, þau samræmd og
yfirfarin og send til alþjóðlegs gagnasafn fyrir slík
gögn (GLIMS, sjá nsidc.org/glims). Jöklar á Íslandi
náðu ekki hámarksútbreiðslu á sama tíma en flestir
þeirra tóku að hörfa frá ystu jökulgörðum um 1890.
Heildarflatarmál jökla árið 2019 var um 10.400 km2
og hafa jöklarnir minnkað um meira en 2200 km2
frá lokum 19. aldar, sem samsvarar 18% flatarmáls-
ins um 1890. Jöklarnir hafa tapað um 750 km2 frá
aldamótunum 2000. Stærri jöklarnir hafa tapað 10–
30% af flatarmáli sínu en miðlungsstóru jöklarnir (3–
40 km2 árið 2000) hafa tapað allt að 80% flatarmáls-
ins. Á fyrstu tveimur árautugum 21. aldar hafa jökl-
arnir minnkað um u.þ.b. 40 km2 á ári. Á þessu tíma-
bili hafa margir litlir jöklar horfið með öllu. Gagna-
söfn um útbreiðslu jökla eru mikilvæg fyrir rannsókn-
ir á loftslagsbreytingum, til þess að stilla af jöklalíkön,
til rannsókna á framhlaupum og á eðli jökla. Þó að
framhlaup, eldgos undir jökli og jökulhlaup hafi áhrif
á stöðu einstakra jökulsporða hafa jöklabreytingar á
Íslandi verið fremur samstíga og fylgt að mestu leyti
veðurfarsbreytingum frá lokum 19. aldar.
REFERENCES
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and 21st century evolution of Hoffellsjökull glacier,
SE-Vatnajökull, Iceland. Cryosphere 5(4), 961–975.
http://doi.org/10.1029/2005JF000388
JÖKULL No. 70, 2020 27