Icelandic glacier loss

Guest post by Jenny Snell

Icelandic glaciers, like those in many regions around the world, are melting fast¹. Ice margins are retreating, and lakes are forming at these margins, called proglacial lakes¹. These lakes speed up the loss of ice, change the flow of sediment through rivers, cause coastal erosion and can create a risk to local people and infrastructure².

Satellite image of Iceland in August 2020, the larger ice masses including Vatnajökull to the East are visible (European Space Agency).

Iceland’s glaciers are particularly suffering because air temperatures are increasing faster there, with an average increase of 1°C since 2000; this is 3 to 4 times the rate in other areas in the northern hemisphere^3,4.

The rate of thinning, as seen in the work by Hugonnet et al. (2021)¹², is higher than in many regions; visible in the dark red elevation change bar in the figure below. If all of the ice in Iceland were to melt, this would rise the global sea level by 1cm¹.

Global scale glacier mass loss and shrinkage. Size of circle indicates amount of mass loss in gigatonnes (billions of tonnes), year 2000 to 2020. From Hugonnet et al., 2021.

Explore glacier thinning in Iceland

Visit Theia Cartographic to study the Hugonnet et al. (2021) dataset yourself. This dataset provides an unprecedented dataset of global glacier thinning, 2000-2019. All their data are freely available.

The About section (top left) in the webpage below gives more information on global glacier elevation change. Click on the image to be taken to Theia Cartographic.

Screenshot from Theia Cartographica showing glacier thinning over Iceland. *Hugonnet et al. 2021¹².*

You can also find out more about Icelandic glaciers through the Glacier Web Portal.

Glacier Web Portal for glaciers in Iceland

Proglacial lakes

Many of the glaciers in Iceland terminate in proglacial lakes. These lakes are important, because the lakes can influence glacier processes at the snout of the glacier. This can include increasing melt through encouraging calving of icebergs and melt into the lake, as well as encouraging floatation, thinning and faster velocities due to locally decreased friction. As global temperatures continue to rise, more of these lakes will form and existing ones will grow².

Skaftafellsjokull, South east Iceland. Credit: Bethan Davies

Breiðamerkurjökull and Jökulsárlón proglacial lake

In the southeast of Iceland is Europe’s largest icecap, Vatnajökull, which covers 8,100 km² (^5,6). Vatnajökull has been losing mass since 1995^6,7. The ice cap is drained by many outlet glaciers, including Breiðamerkurjökull, part of which terminates in the proglacial lake Jökulsárlón. Jökulsárlón proglacial lake is 24 km² in area and around 300 m deep⁸.

The Jökulsárlón proglacial lake is growing fast as the glacier shrinks, at approximately 0.5 km² per year since 1982^9,4. Breiðamerkurjökull is thinning and retreating rapidly (figure 5).

Jökulsárlón proglacial lake, Iceland from above. Glacier Breiðamerkurjökull is to the right of the image, The key road Route One is visible in the foreground. Photo: Areuland

At Breiðamerkurjökull, the areas of the glacier that end or terminate in the lake have retreated by 3.5 km between 1991 and 2015, which is equivalent to 1-3.5m a day^4,9. In comparison, the land terminating section has remained stable and moved very little⁴.

Glacier elevation loss at Breiðamerkurjökull between 2000 and 2019 (Hugonnet et al., 2021¹²)

The growth of the lake is clearly visible when viewed over sequential imagery, as shown below.

*Figure 7. Jökulsárlón (larger right lake) growth 1982-2018 (Baurely et al., 2020⁴)*

Impacts of glacial lake growth: Changes in sediment flow and coastal erosion

Icelandic proglacial lakes trap sediment that would previously have flown through rivers and down to the coast. At Breiðamerkurjökull, as the proglacial lake Jökulsárlón has grown, the sediment flux flowing down-river has decreased hugely. At the present day, very minimal amount of sediment flows out of the lake. However, at the end of the Little Ice Age (approximately 1850 CE), it was 14 million m³ a year¹¹.

This reduced sediment supply means that the rivers are eroding and incising, and that the coastline is consequently retreating¹⁰. Since 1904, the coastline downstream of the Jökulsárlón proglacial lake has eroded back 770m, approximately 8 m per year¹¹. This is an issue as the main road around Iceland, Route One, is getting ever closer to the coastline and is increasingly threatened by coastal storms. Other important infrastructure such as power lines are also threatened. You can see how close the road is to the coastline in the drone footage in Figure 4.

This glacier, proglacial lake and the beach, also known as the Diamond Beach (Figure 9), are major tourist destinations in southeast Iceland, therefore it is important to ensure the road and other infrastructure is safe, to ensure people can continue to visit, which benefits the Icelandic economy.

About the Author

Jenny Snell has a Masters by Research in Geoscience from Newcastle University. She studied the glaciers of Iceland for her MRes Dissertation.

References

1 – Jóhannesson, T., Björnsson, H., Magnússon, E., Guðmundsson, S., Pálsson, F., Sigurðsson, O., Thorsteinsson, T. & Berthier, E. (2013) ‘Ice-volume changes, bias estimation of mass-balance measurements and changes in subglacial lakes derived by lidar mapping of the surface of Icelandic glaciers’, Annals of Glaciology, 54(63), pp. 63–74.

2 – Carrivick, J.L. & Tweed, F.S. (2013) ‘Proglacial lakes: character, behaviour and geological importance’, Quaternary Science Reviews, 78pp. 34–52.

3 – Jones, P.D., Lister, D.H., Osborn, T.J., Harpham, C., Salmon, M. and Morice, C.P. (2012). Hemispheric and large-scale land-surface air temperature variations: An extensive revision and an update to 2010. Journal of Geophysical Research: Atmospheres, 117(D5). doi:https://doi.org/10.1029/2011jd017139.

4 – Baurley, N.R., Robson, B.A. & Hart, J.K. (2020) ‘Long-term impact of the proglacial lake Jökulsárlón on the flow velocity and stability of Breiðamerkurjökull glacier, Iceland’, Earth Surface Processes and Landforms, 45(11), pp. 2647–2663.

5 – Windnagel, A., Hock, R., Maussion, F., Paul, F., Rastner, P., Raup, B. & Zemp, M. (2023) ‘Which glaciers are the largest in the world?’, Journal of Glaciology, 69(274), pp. 301–310.

6 – Schomacker, A. (2010) ‘Expansion of ice-marginal lakes at the Vatnajökull ice cap, Iceland, from 1999 to 2009’, Geomorphology, 119(3-4), pp. 232–236.

7 – Guðmundsson, S., Björnsson, H., Pálsson, F., Magnússon, E., Sæmundsson, Þ. & Jóhannesson, T. (2019) ‘Terminus lakes on the south side of Vatnajökull ice cap, SE-Iceland’, JOKULL, 69pp. 1–34.

8 – Voytenko, D., Dixon, T.H., Howat, I.M., Gourmelen, N., Lembke, C., Werner, C.L., De La Peña, S. and Oddsson, B. (2015). Multi-year observations of Breiðamerkurjökull, a marine-terminating glacier in southeastern Iceland, using terrestrial radar interferometry. Journal of Glaciology, 61(225), pp.42–54. doi:https://doi.org/10.3189/2015jog14j099.

9 – Björnsson, H., Pálsson, F. & Guðmundsson, S. (2001) ‘Jökulsárlón at Breiðamerkursandur, Vatnajökull, Iceland: 20th century changes and future outlook’, JÖKULL, 50pp. 1–50.

10 – Kondolf, G.M., Gao, Y., Annandale, G.W., Morris, G.L., Jiang, E., Zhang, J., Cao, Y., Carling, P., Fu, K., Guo, Q., Hotchkiss, R., Peteuil, C., Sumi, T., Wang, H.-W., Wang, Z., Wei, Z., Wu, B., Wu, C. & Yang, C.T. (2014) ‘Sustainable sediment management in reservoirs and regulated rivers: Experiences from five continents’, Earth’s Future, 2(5), pp. 256–280.

11 – Jóhannesson, H. and Sigurðarson, S., (2005). Coastal erosion and coastal protection near the bridge across Jökulsá river, Breiðamerkursandur, Iceland. In 2nd international coastal symposium in Iceland. Höfn í Hornafirði.

12 – Hugonnet, R., McNabb, R., Berthier, E., Menounos, B., Nuth, C., Girod, L., Farinotti, D., Huss, M., Dussaillant, I., Brun, F. and Kääb, A. (2021). Accelerated global glacier mass loss in the early twenty-first century. Nature, 592, pp.726–731. doi:https://doi.org/10.1038/s41586-021-03436-z.