Changes of southeastern Vatnajökull

The Little Ice Age

When the first settlers came to Iceland, the glaciers were much smaller than today. Their advance during the Little Ice Age (ca. 1450–1900) and former size can be traced from glacial moraines of known age, data from lake sediments and descriptions in written historical accounts. The glaciers advanced far out onto the lowland, especially during the 17th and 18th centuries. In the first decades of the 19th century, they retreated slightly and then re-advanced and around 1890 nearly all of them had reached their maximum size in historical times. The local accounts and the writings of naturalists and travellers provide information about the extent of the outlet glaciers at their most advanced position. Descriptions of damaged pastures, hayfields and houses due to glacial rivers and advancing glaciers, along with difficult access to grazing areas, are prominent in the written records. A few historical mountain routes between farms and settlements also became impassable due to advancing glaciers during the Little Ice Age. One of those routes, the so-called Norðlingavegur from Fljótsdalur to Lón, was named after farmers who lived on the north side of the ice cap but travelled to the SE coast to fish.

 

Possible travel routes across Vatnajökull. Source: Based on a map in the book of Þórarinsson (1974).

Possible travel routes across Vatnajökull. Source: Based on a map in the book of Þórarinsson (1974).

 

Changes since the end of the 19th century

After 1890, most glaciers began to retreat. They receded fast in the 1930s and 1940s, and continued retreating, albeit more slowly, until the 1960s, after which the rate of retreat slowed further, and in the 1970s and 1980s some of the glaciers re-advanced or remained stationary. The outlet glaciers from Skaftafell to Höfn have retreated 1–8 km, depending on location, since the end of the 19th century until 2017. Altogether, they have lost an area of 340 km2 (equal to the Reykjavík capital region), and 140 km³ or 20% of their volume. The ice loss is equal to 14 billion truckloads of ice, and corresponds to a 0.3 mm rise in global sea level.

Since the year 2000, the outlet glaciers have retreated exceptionally fast, and their mass loss per unit area is among the highest recorded in the world. Individual outlet glaciers have lost 15–50% of their ice volume during this period. The loss depends on the size of their accumulation area, bed slope and whether they terminate in a glacial lake. The glaciers will continue to melt and retreat and could lose half of their volume by 2100. After 200 years, only small ice caps will remain on the highest mountains. The same fate awaits other glaciers in Iceland and elsewhere outside the polar regions.

 

Map showing the southern outlet glaciers of Vatnajökull ice cap and their extent from ca. 1890 to 2010. Source: Hannesdóttir et al. (2015a).

Map showing the southern outlet glaciers of Vatnajökull ice cap and their extent from ca. 1890 to 2010. Source: Hannesdóttir et al. (2015a).

 

The retreat of Breiðamerkurjökull and growth of Jökulsárlón glacial lake. Source: Glaciological Group of the Institute of Earth Sciences of University of Iceland.

The retreat of Breiðamerkurjökull and growth of Jökulsárlón glacial lake. Source: Glaciological Group of the Institute of Earth Sciences of University of Iceland.

 

Breiðamerkurjökull outlet glacier 1890, 1945, 2010. Source: Guðmundsson (2014).

Breiðamerkurjökull outlet glacier 1890, 1945, 2010. Source: Guðmundsson (2014).