AUTHOR=Aðalgeirsdóttir Guðfinna , Magnússon Eyjólfur , Pálsson Finnur , Thorsteinsson Thorsteinn , Belart Joaquín M. C. , Jóhannesson Tómas , Hannesdóttir Hrafnhildur , Sigurðsson Oddur , Gunnarsson Andri , Einarsson Bergur , Berthier Etienne , Schmidt Louise Steffensen , Haraldsson Hannes H. , Björnsson Helgi 

TITLE=Glacier Changes in Iceland From ∼1890 to 2019

JOURNAL=Frontiers in Earth Science

VOLUME=8

YEAR=2020

URL=https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2020.523646

DOI=10.3389/feart.2020.523646

ISSN=2296-6463

ABSTRACT=<p>The volume of glaciers in Iceland (∼3,400 <inline-formula id="inf1"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi mathvariant="normal">k</mml:mi><mml:msup><mml:mi mathvariant="normal">m</mml:mi><mml:mn>3</mml:mn></mml:msup></mml:mrow></mml:math></inline-formula> in 2019) corresponds to about 9 mm of potential global sea level rise. In this study, observations from 98.7% of glacier covered areas in Iceland (in 2019) are used to construct a record of mass change of Icelandic glaciers since the end of the 19th century i.e. the end of the Little Ice Age (LIA) in Iceland. Glaciological (<italic>in situ</italic>) mass-balance measurements have been conducted on Vatnajökull, Langjökull, and Hofsjökull since the glaciological years 1991/92, 1996/97, and 1987/88, respectively. Geodetic mass balance for multiple glaciers and many periods has been estimated from reconstructed surface maps, published maps, aerial photographs, declassified spy satellite images, modern satellite stereo imagery, and airborne lidar. To estimate the maximum glacier volume at the end of the LIA, a volume–area scaling method is used based on the observed area and volume from the three largest ice caps (over 90% of total ice mass) at 5–7 different times each, in total 19 points. The combined record shows a total mass change of −540 ± 130 Gt (−4.2 ± 1.0 Gt <inline-formula id="inf2"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mi mathvariant="normal">a</mml:mi><mml:mrow><mml:mo>−</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math></inline-formula> on average) during the study period (1890/91 to 2018/19). This mass loss corresponds to 1.50 ± 0.36 mm sea level equivalent or 16 ± 4% of mass stored in Icelandic glaciers around 1890. Almost half of the total mass change occurred in 1994/95 to 2018/19, or −240 ± 20 Gt (−9.6 ± 0.8 Gt <inline-formula id="inf3"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mi mathvariant="normal">a</mml:mi><mml:mrow><mml:mo>−</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math></inline-formula> on average), with most rapid loss in 1994/95 to 2009/10 (mass change rate −11.6 ± 0.8 Gt <inline-formula id="inf4"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mi mathvariant="normal">a</mml:mi><mml:mrow><mml:mo>−</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math></inline-formula>). During the relatively warm period 1930/31–1949/50, mass loss rates were probably close to those observed since 1994, and in the colder period 1980/81–1993/94, the glaciers gained mass at a rate of 1.5 ± 1.0 Gt <inline-formula id="inf5"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mi mathvariant="normal">a</mml:mi><mml:mrow><mml:mo>−</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math></inline-formula>. For other periods of this study, the glaciers were either close to equilibrium or experienced mild loss rates. For the periods of AR6 IPCC, the mass change rates are −3.1 ± 1.1 Gt <inline-formula id="inf6"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mi mathvariant="normal">a</mml:mi><mml:mrow><mml:mo>−</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math></inline-formula> for 1900/01–1989/90, −4.3 ± 1.0 Gt <inline-formula id="inf7"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mi mathvariant="normal">a</mml:mi><mml:mrow><mml:mo>−</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math></inline-formula> for 1970/71–2017/18, −8.3 ± 0.8 Gt <inline-formula id="inf8"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mi mathvariant="normal">a</mml:mi><mml:mrow><mml:mo>−</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math></inline-formula> for 1992/93–2017/18, and −7.6 ± 0.8 Gt <inline-formula id="inf9"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mi mathvariant="normal">a</mml:mi><mml:mrow><mml:mo>−</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math></inline-formula> for 2005/06–2017/18.</p>