Iceland


Glaciers

Types of Glaciers

Glacial Geomorphology

Proglacial Lakes

Glacial Retreat

References

Types of Glaciers

     A glacier is a mass of ice that is derived from snow and persists from year to year. Three types of glaciers that exist in Iceland are ice caps, valley/piedmont glaciers, and cirque glaciers. Ice caps are large glaciers that are unconstrained by topography such as the Vatnajökull ice cap in Iceland which is the largest glacial mass in Europe with an ice volume of 3300 km3. Outlet glaciers that spill out of ice sheets occupy valleys and sometimes move onto lowland areas forming piedmont glaciers such as Múlajökull in Iceland. Cirque glaciers form where snow accumulates in small depressions in mountainous areas and persists to form glacial ice such as Kambsjökull in Iceland. (3)

Glaciers in Iceland 1
Fig 1. Vatnajökull ice cap in Iceland (3)

Glaciers in Iceland 2
Fig 2. Múlajökull piedmont glacier in Iceland (3)

Glaciers in Iceland 3
Fig 3. Kambsjökull cirque glacier in Iceland (3)

Glacial Geomorphology

     When glaciers move, they grind up sediments and carry them through bed load at their base, internal load in their ice, and surface load on their surface. When the glaciers retreat, they leave behind moraines of unsorted sediments called glacial till. Moraines can form at the very end of a glacier (terminal moraine), along the sides of a glacier (lateral moraine), and at the confluence of two glaciers (medial moraine). (8) Icelandic moraines can be seen in the area surrounding the Skaftafellsjökull glacier.

Glacial Geomorphology 1
Fig 4. Graphic showing the formation of glacial moraines (8)

     Subglacial streams can carry sediments of several different sizes due to their high energy. When these sediments are deposited, they form long ridges of relatively poorly sorted sediments that trace the subglacial melt channels called eskers. Eskers in Iceland can be seen near the Brúarjökull glacier. (7)

Glacial Geomorphology 2
Fig 5. Photo showing eskers near the Brúarjökull glacier (4)

     When the ice at a glacial margin becomes weak and unsupported, it can break off in a process called calving. These chunks of ice then fall to the surface and are buried by glacial outwash sediments. Eventually, the climate warms to the point of melting the chunks of ice, leaving a depression in the landscape called a kettle hole. Kettle topography can be seen in the area surrounding the Skaftafellsjökull glacier in Iceland. (6)

Glacial Geomorphology 3
Fig 6. Graphic showing the formation of kettle holes (6)

Proglacial Lakes

     Proglacial lakes form when meltwater from a receding glacier is collected by the topography of a landscape. This water is typically rich in very fine-grained sediments, called rock flour, that formed when glaciers grind away at bedrock. When this rock flour enters a proglacial lake, it experiences the Tyndall effect which describes how light behaves in a liquid with suspended particles, giving the lakes a blue to turquoise color. (9) When the particles that make up rock flour settle out, they can form layers called varves. In the summer time when the water in a lake has more energy, larger sand and silt sized particles settle out. In the winter time when a lake is frozen over and has less energy, smaller clay sized particles settle out. The thickness of varves is determined by both the proximity to the glacial margin as well as the rate of glacial retreat and melting.
     One famous proglacial lake in Iceland is Jökulsárlón. Icebergs that have calved from the Vatnajökull glacier float in this proglacial lake and are left on the shore when the lake empties to the Atlantic Ocean. However, because of this exchange with the ocean and the resulting salinity of the lake, varves that would normally form in a proglacial lake, as seen in the nearby proglacial lakes of the glacier Breidamerkurjökull, are not able to form. (1)

Proglacial Lakes 1
Fig 7. Image of the proglacial lake Jökulsárlón in Iceland (5)

Glacial Retreat

    Global climate warming has led to the melting and retreat of glaciers in Iceland. This process can induce positive feedback loops that have significant consequences on the Earth System. For example, reduced ice cover will lead to a lower overall reflectivity, a property called albedo, of Earth’s surface and therefore more absorption of solar radiation causing further surface warming. Another example is freshwater glacial melt resulting in a rise in sea level as well as a decrease in the salinity of the North Atlantic Ocean which will impact thermohaline circulation patterns in Earth’s oceans. Methods to mitigate this glacial melt through carbon capture in Icelandic basalt have been researched as explained in the Carbon Capture and Storage section of this site.

Glacial Retreat 1
Fig 8. Sólheimajökull Glacier in Iceland photographed in 2009 (left) and 2011 (right) showing the extreme recent glacial retreat in Iceland (2)

References

(1) Harris, P. W. V. “The Seasonal Temperature-Salinity Structure of a Glacial Lake: Jökulsárlón, South-East Iceland.” Geografiska Annaler: Series A, Physical Geography, vol. 58, no. 4, 1976, pp. 329–336., doi:10.1080/04353676.1976.11879942.

(2) Ingber, Sasha. “Extreme Ice Survey chronicles melting glaciers.” ShareAmerica, 31 Mar. 2016, share.america.gov/extreme-ice-survey-chronicles-melting-glaciers/.

(3) Ingólfsson, Ólafur. “Icelandic Glaciers.” Ólafur Ingólfsson, notendur.hi.is/oi/icelandic_glaciers.htm.

(4) Ingólfsson, Ólafur. “Ólafur Ingólfsson.” Ólafur Ingólfsson, 11 May 2008, notendur.hi.is/oi/index.htm.

(5) Karsten, Matthew. “Iceland’s Amazing Jökulsárlón Glacier Lagoon.” Expert Vagabond, 27 Oct. 2017, expertvagabond.com/jokulsarlon-glacier-lagoon/.

(6) “Kettle Hole.” Landforms, www.landforms.eu/cairngorms/kettle%20hole.htm.

(7) Knudsen, Óskar. “Concertina eskers, Brúarjökull, Iceland: An indicator of surge-Type glacier behaviour.” Quaternary Science Reviews, vol. 14, no. 5, 1995, pp. 487–493., doi:10.1016/0277-3791(95)00018-k.

(8) Lukas, Sven. “Moraines – piles of dirt record glacier fluctuations.” Climatica, 11 Mar. 2014, climatica.org.uk/moraines-piles-dirt-record-glacier-fluctuations.

(9) Martha, Gale. “Why are Lakes and Rivers in the Canadian Rocky Mountains so Brilliantly Turquoise Blue?” Scientific Explorer, 26 Jan. 2016, sciexplorer.blogspot.com/2016/01/why-are-lakes-and-rivers-in-canadian.html.


By: Carter Boyd