Handbook for glacier guiding with special focus on Öræfajökull ice cap and its outlet glaciers by Þórður Bergsson
Index Fun facts about glaciers Glacier family Warm and Cold glacier The glacier ice Mass balance Flowing ice Accumulation layering Fold and foliation Basal ice layer Veins in the ice Ogives Crevasses Glacier surge Supraglacial debris Basal debris Englacial debris Melting process Glacial outburs floods Glacier lakes
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Glaciers in Iceland Vatnajökull History of Vatnajökull Öræfajökull History of Öræfajökull Early attempts to climb Öræfajökull Öræfasveit Svínafellsjökull Virkisjökull Kvíárjökull Fjallsjökull Breiðamerkurjökull Jökulsárlón and Breiðamerkusandur References Notes
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Fun facts about glaciers Glaciers occupy about 11% of the Earth’s land surface but hold roughly three-fourths of its fresh water. Antarctica ice sheet is about twice as big as Australia and contains about 91% of world fresh water ice. It is more than 4000 m thick. Greenland ice sheet is about the size of Mexico and contains about 8% of world fresh water ice. The inland ice is about 3000 m thick Among the largest ice caps are Austfonna and Vestfonna in Svalbard, North and South Patagonian ice caps and VatnajÜkull in Iceland. The smallest mountain glacier are only few hundred meters across, these glacier are called cirques.
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The earliest description of a glacier is from Icelandic 11th century literature. The fact that the glacier flows was not recorded until in the 16th century. The first serious scientific studies on glaciers were made in the late 18th century. In geological term we are living in a glacial era that began in Antarctica ca. 35 million years ago.
Cirques in North Iceland
Overview of world glaciers and ice caps
By far the largest area of glaciers and ice fields are found in Canada (about 201 000 km2), followed by Alaska (about 75 000 km2) with about 700 km2 in the rest of the USA. Glaciers and ice fields are concentrated in the High Arctic and western cordillera. The total area of glaciers and ice caps, without the ice sheets and surrounding glaciers and ice caps in Greenland and Antarctica, sums up to 540 000 km2.
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Glacier Family Ice sheets are the largest glaciers they extend in continuous sheets, moving outward in all directions. Ice sheets only existed on Antarctica and Greenland. Ice caps are similar to ice sheets but are smaller, they cover area of 50000 sq. km. or less. Glaciers confined within a path that directs the ice movement are called mountain glaciers. A complex of mountain glaciers burying much of a mountain range is called an ice field Valley glacier or outlet glacier are tongues of ice that flows downwards from ice field, ice cap or ice sheet. Where mountain valleys open into larger valleys or on to plains, valley glaciers spread out into wide lobes called piedmont glaciers.
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glaciers that spread on the ocean at the foot of glaciated regions are called ice shelves if they are coming from an ice sheet or tidewater glaciers it is coming from valley glacier. Nunatak is isolated mountain surrounded by glacier ice.
Aerial photograph of the piedmont outlet of Skeiรฐarรกrjรถkull, it is a surge-type outlet on the southern margin of Vatnajรถkull ice cap.
Family of mountain glaciers
This picture shows different forms of mountain and outlet glacier.
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Warm and cold glacier A polar glacier (cold glacier) is defined as one that is below the freezing temperature throughout its mass for the entire year A subpolar (polythermal) glacier contains ice below the freezing temperature, except for surface melting in the summer and a basal layer of temperate ice
Glaciers in Iceland are temperate and wet-based.
a temperate glacier (warm glacier) is at the melting temperature throughout its mass, but surface freezing occurs in winter A polar or subpolar glacier may be frozen to its bed (dry-based), or it may be at the melting temperature at the bed (wet-based).
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The temperature in temperate glacier is at melting point through out the ice.
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The glacier ice Glaciers ice can form where winter snow exceeds summer melting. After several years the snow has turn to ice due to it´s own weight. This process happens faster on temperate glacier than polar glacier. The snow turns to ice in several stages. 1. The snow crystals brake by settling or if they get wet. 2. Gradually the snowflakes change to grains that are rounded and sugar like. 3. As the snow becomes compressed it gets harder and denser. 4. Snow that has survived one melting season is called firn (or névé). The
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firn density is usually greater than 500 kg per cubic meter in tempered glacier. (Firn is german and means “old snow”) 5. The firn starts to recrystallize to larger crystals, air is now only present as bubbles inside crystals. In flowing glacier the crystals are in constant change. The glacier ice has 90% density of water. On sunny summer days the ice crystals in the ablation zone melts along their boundaries and the glacier surface acquires a knobby texture that is easy to walk on. The blueness color of the glacier ice is because water molecules preferentially absorb all colors of the light spectrum except blue.
The formation of glacier ice
The process from snowflakes to glacier ice can take decades in polar glaciers but only few years in tempered glaciers.
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Mass balance The glacier can be divided into two zones, accumulation zone (net gain) and ablation zone (net loss). Between the two zones there is the equilibrium line where the gain equals the loss. In tempered glaciers the equilibrium line is the same as the firn line. A healthy glacier is one that forms as much ice in the accumulation zone as is lost in the ablation zone.
Firn line
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a) shows movement of the ice, b) shows mass balance.
Mass balance zones and flow pattern of a glacier
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Flowing ice Glacier ice flows by three main reason. 1. by internal deformation (creep). 2. by basal sliding over a hard rocky bed. 3. by subglacial deformation. Internal deformation As the snow turns into ice, it´s crystals alter under the weight of material as it is buried and is subject to the influence of gravity. The stresses in the ice at depth, cause it to deform in plastic manner. Most of the deformation happens at the margins and just above the bed surface. The upper part of the glacier is brittle and create crevasses when it moves, his layer is about 30m in tempered glaciers and more in polar glacier.
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Basal sliding The glacier slides over hard rocky bed, melt water reduce friction between the bed and the glacier and make it moves. Tempered glaciers moves faster in the summer than in the winter. Basal sliding may accounts up for as much as 90% overall movement in tempered glacier Basal sliding produces fine sediment in melt-water (glacier milk), marks on bedrock (striations) and till, a distinctive type of sediment. Subglacial deformation Layer of unconsolidated sediment (till) underlies moving ice, it can be a mixture of fine clay to boulders. When saturated with water this sediment deforms
more easily than the basal ice. Glacier movement is assisted by shearing within the this soft sediment.
Internal deformation of the glacier ice, most of the deformation happens at the margins and the base.
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Accumulation layering Year-by-year accumulation of snow and it´s changing to ice develops a layered structure called sedimentary stratification. Each annual accumulation layer is represented as a thick layer of light blue bubbly ice. Between accumulation layers are dark blue clear ice, witch is snow that had become saturated with water during the melt season and refroze. When the glacier moves downhill the layers deform because of the plastic manner of the glacier ice. A period of excessive ablation may remove many of the layers and when new layer accumulate a marked discontinuity (unconformity) is visible.
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Accumulation layers of glacier ice
Firn stratification seen in the wall of a large crevasse on Weissmies, near Saas Grund, Switzerland.
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Fold and foliation As the glacier flows, the ice layers becomes more folded and makes new layered structure called foliation. Both fold and foliation develops in the plastic flow zone. Foliation develops mostly where the shearing is the greatest, such as close to the margins or where two streams of ice combines.
Layers of ice that have been deformed into a curved form by flow at depth in a glacier.
Most glaciers develop a prominent layered structure called foliation.
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Basal ice layer The base of the glacier consists of a zone of ice and debris. Ranges from couple of metes or less in temperate glacier to tens of meters in polythermal glaciers. It is a result from the freezing of subglacial water and debris from the glacier base, witch is then subject to strong shear. This ice appearance dark and clear.
Basal ice layer. The layer of ice at the bed of a glacier that is the product of melting and refreezing. It is strongly layered, sheared and incorporates a variable amount of debris.
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Veins in the ice Veins are result of fracturing and stretching of the ice without forming open crevasse. Thrust are low-angle faults that generate at glacier bed and extends upwards, usually where the ice is slowing down. Thrusts can carry basal debris into the body and to the surface of the glacier.
Thrust in the ice where it is under compression at the snout.
Crevasse traces are veins of clear blue ice that is often visible in crevasses. They are traces of old water-filled crevasses.
Crevasse traces, clear ice veins cutting foliated ice.
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Ogives Are sets of light and dark bands that curve across the glacier surface and are usually several meters wide. Ogives only develop within icefalls but not all icefalls generate ogives. Some ogives are annual features and represent years movement of the ice trough the icefall. One theory of the ogives is that the dark band represent the dirty ice that goes trough the icefall in the summer and the light band is the snow covered ice in the winter. Recent research show that basal debris associated with ogives indicate that the rapid slowing of the ice at the foot of the icefall generate folding and thrusting that may play big role in ogive formation.
Ogives are arcuate light and dark bands or waves, with their apices pointing down-glacier, that develop in an icefall. Each pair of bands, or one wave and trough, is believed to represent a year’s movement through the icefall. The photo shows ogives on SvinafellsjÜkull, southern Iceland.
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Crevasses Crevasses are V-shaped clefts that form where the ice is under tension. Only forms in the upper part of the glacier ice where the ice is brittle. In temperate glacier they are rarely open to depth of more than few tens of meters, but can go deeper in polar and polythermal glaciers. The reason why crevasses don´t go deeper is that bellow certain depth the weight of overlaying ice makes the ice plastic.
Crevasse
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Crevasse types of outlet glacier
Plan view of the principal types of crevasse in a valley glacier, together with the types of flow involved. Arrows indicate the direction which the ice is pulled apart.
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Glacier surge Glacier surge is when the glacier starts advance at much greater speed than it normally does trough a short period of time. Glacier surge almost everywhere on the globe, but Scandinavia and New Zealand are consider a surge free zones.
It is not know why glacier surge, but glacier size, shape orientation, gradient climate and bedrock has a lot to do with it. Especially it is believed that the melt-water at the bedrock is a great factor of a glacier surge.
Some glacier surge at fairly regular intervals, but predicting when a surge might occur is unreliable. The first indication of a surge is a sudden appearance of a thousands of crevasses. Surge front propagates down-glacier as a kinematic wave that moves faster than the ice itself.
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Photo from the glacier surge of SĂĂ°ujĂśkull outlet in 1994.
Known surging glaciers in Vatnajรถkull and the years when they have surge.
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supraglacial debris (surface debris)
the general surface of the ice. Big boulders can produce this effect as well in the form of glacier table.
Main source of supraglacial debris is frost shattering rock that falls from the mountainside above valley glaciers.
Streams on the surface can move much of the fine debris into hollows and depression where it collects, this debris will later, when the surrounding surface ablates, slow down the underlying ice and produce a dirt cone.
The lines of debris at the at the edge of the glacier is called lateral moraine. Where two streams of glaciers joins, the two lateral moraines combines and form single medial moraine. If the debris is dark and thin it melts the surrounding ice faster and creates depression in the ice called cryoconite. If the debris is thick and continuous, it slows down the ablation and the debris stand above
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Supraglacial debris, the rock that forms the supraglacial debris is usually angular.
Lateral and medial moraine on Skaftafellsjรถkull outlet in Iceland.
Dirt cone.
Perfect glacier table on the lower glacier tongue.
cryoconite hole.
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Basal debris (base debris) Is very different in character from supraglacial debris. It is more rounded and striated. Rocks and debris at the bed freeze onto the base of the glacier. Because the velocity of the glacier increase upwards the basal debris rock rotates an gets rounded. Most basal debris is picked up in the accumulation zone and is deposed in the ablation zone as a basal till. There are two main types of basal till. Where the ice is melting near its bed and sliding and deforming rapidly, the debris is plastered on to the bed making a lodgement till. The debris melts more directly out of the ice at the snout of the glacier and produces a meltout till.
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Partly rounded boulders in the basal debris layer of the advancing front of Solheimerjรถkull, Iceland.
Basal debris.
Longitudinal profile of glacier ice
A longitudinal profile through the lower reaches of a retreating land based glacier, illustrating how debris is transported and deposited.
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Englacial debris (debris inside a glacier) Supraglacial debris that gets on the glacier in the accumulation zone gets buried by the snow, and basal debris that goes along thrust, becomes incorporated in the interior of a glacier. Debris in glaciers can also be material that have been blown in the glacier by wind. In Iceland, Alaska and the Andes, volcanic eruptions have throw ash onto the glacier witch with time gets buried in the ice. Englacial debris layers, with complex folding and thrust structures.
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Volcanic ash layers in the Skeidararjokull, These ash layers were deposited centuries ago during major eruptions, primarily from the Grinsmvotn Caldera, during the 17th and 18th centuries.
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Melting process
Surface channel system develops only on crevasse free glacier.
The main factor of glacier melting is air temperature and solar radiation (albedo). Frictional heat that generates as the glacier slides over it´s bed can also produce meltwater.
Plane of weakness in the ice, such as former crevasse, are exploited of the meltwater to form a glacier mill or moulin.
Albedo melting depends on how well the snow reflect the solar radiation. 1.
2.
Heavy winter snowpack causes high-albedo snow to persist longer over the glacier in summer; thus, less meltwater is produced.
Small pools of standing water may develop on flatter parts of a glacier, they are known as a cryoconite holes and are formed by dark patches of debris that have melt down into the ice. The channels close up in the winter due to internal deformation of the ice.
Light winter snowfall causes older firn and ice of lower albedo to be exposed earlier in the summer, producing increased melt.
Meltwater discharge fluctuates both on a daly and seasonal basis. In temperate glaciers most water migrates through the glacier via network of channels and conduits.
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Moulin
Melting process of a glacier
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Glacial outburst floods (Jökulhlaup) These floods happen when drainage within a glacier is blocked by internal plastic flow and water is stored in or behind the glacier. The water finds a narrow path to trickle out. This movement will cause the path to be enlarged by melting, causing faster flow, more melting, a larger conduit, and so on until all the water is released quite suddenly. In Iceland this floods are common part of geothermal and volcanic activity under the glacier. The most resent catastrophic jökulhlaup in Iceland was in the year 1996, when a glacier meltwater from Grímsvötn volcano eruption bursted out from Skeiðarárjökull and on to
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the sand-plains of Skeiðarársandur. At the peak of the flood the flow rate was 50.000 cubic meters per second. Jökulhlaup from mt. Katla volcano under Myrdalsjökull glacier in Iceland, gan generate a flood with a flow rate of 300.000 cubic meters per second.
Jökulhlaup in Skeiðará, 5 November 1996. This photo shows how the flood has destroyed the bridge over Gýgja.
Glacier lakes Proglacial lakes forms in low relief areas in contact with the ice, or behind moraine ramparts during glacier retreats. Ice-damed lakes occur where a stream from a side valley meets the glacier, these lakes mostly form with polar glacier though some form with tempered glaciers. These lakes often causes floods. Moraine-dammed lakes form where debris-covered glaciers reduce from their terminal moraines. As the lakes grow and the moraine subside by slow melting of buried ice, the potential for flood increases.
Proglacial lake at the snout of Svinafellsjökull outlet.
Grænalón lagoon at the west end af Skeiðarárjökull outlet is Ice-damed lake.
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Glaciers in Iceland
rises from about 1100 m a.s.l. in the south to over 1700 m a.s.l. in the North.
Approximately 11% of Iceland landmass is covered with glaciers.
Since 1930 glaciers in Iceland have been unhealthy (more ablation than accumulation), with an exception between 1975-1995.
Glacier in Iceland has been forming in the last 2500 years, the remaining glacier from the last ice age was mostly gone 2500 y.a.
All glaciers in Iceland are temperate and wet-based.
Glaciers form where mean annual temperatures are below 0째C, and where winter precipitation in the form of snow surpasses summer melt. Mean annual temperatures are below 0째 C in areas above 600-700 m a.s.l. Precipitation is highest in the southeastern part of the country, where it surpasses 4000 mm water equivalents per year. Precipitation in the central and northern Iceland is at places less than 600 mm. The precipitation difference is reflected in the altitude of the glaciation limit (Equilibrium Line Altitude, ELA), which
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Estimated change in size of Icelandic ice caps, in km2,between 1958 and 2000.
Major ice caps in Iceland
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Vatnajökull Vatnajökull is the largest glacier in Iceland, covering an area of 3,200 sq. mi. (8,400 sq. km). It is the largest glacier in Europe in volume and the second largest (after Austfonna on Nordaustlandet, Svalbard) in area The glacier is classified as wetbased and temperate. It´s mean thickness is a little less than 500m and is 950-1000 m thick where it is thickest.
About 60% of the glacier surface is above the ELA. Vatnajökull covers a highland plateau, generally reaching 600-800 m altitude and a number of large volcanoes are covered by the ice cap.
The total ice volume of Vatnajökull is probably in the order of 3300 km3. The (ELA) lies at ca. 1100 m a.s.l. along its southern margins, at 1200 m along its western part, and at 1300 m in its northern part.
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Vatnajökull ice cap
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History of Vatnajökull Between 9000 y.a and 3000. y.a there was very mild climate in Iceland. Around 2500 y.a. the climate in Iceland started to cool and Vatnajökull glacier started to form. When Iceland was settled around 900 AD, was Vatnajökull glacier still much smaller than it is today. In that time the glacier was called Klofajökull glacier and it was probably two glacier at that time, there are evidence that suggest that it was possible to between them. (Klofajökull means “Split glacier”) In the 13th century the climate started to cool more and an era called the “little ice age” started. This era of cool temperature stayed
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almost undisturbed until the mid 19th century. Vatnajökull grew during the “Little Ice Age” and reached it peak in size around the year 1900. The glacier has been retreating since the year 1900 with the exception between the years 1975 - 1995.
The MWP and the Little Ice Age were temperature fluctuation in northern Europe.
Vatnajรถkull ice cap 2500 year ago.
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Öræfajökull Öræfajökull is the highest mountain in Iceland with Hvannadalshnúkur, Iceland´s highest point at 2110m a.s.l. Öræfajökull is the largest stratovolcano in Iceland, and has a volume of 370 km3, is considered Europe’s second-largest after mt. Etna (Italy), and Europe´s third tallest after mt. Beerenberger (Jan Mayen) and mt. Etna.
hyaloclastites. Rhyolite is also abundant. Hvannadalshnjukur is a rhyolitic peak rising 300m above the northwest rim of the summit caldera. Accumulation on the glacier is a little less than 10 m per year and the average annual precipitation is close to 5000 mm. Öræfajökull used to be called Knappafellsjökull.
The summit caldera is approx. 4-5 km in diameter and 12 km2. The caldera is ice-filled and is about 600-700 m deep. The diameter of the mountain at its foot is approx. 20 km. and it has a base area of almost 400 km². The volcano is made up of basaltic and andesitic lava and
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Öræfajökull
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History of Öræfajökull Öræfajökull has been created during the last 0.8 Ma by entwined interaction of volcanism and glacial erosion. Two historical eruptions in 1362 and 1727 are reported from the summit caldera of the volcano. 1362 Eruption 1. Approx. ten billion cubic meters of volcanic ash were emitted (or 10 km3). 2. About 30 cm of rhyolitic pumice were deposited along the southern plain, and carried northwestwards in such masses that ships sailing by the Western Fjords could hardly make their way through it. 3. The eruption was the largest plinian eruption in Europe
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4. 5.
6.
since Monte Somma on Vesuvius destroyed Pompeii and Herculaneum in 79 AD. The eruption was accompanied by catastrophic jökulhlaup. The 1362 tephra forms a 7-10 cm thick layer in the Hornafjörður region and has been diagnosed from peat bogs in Scandinavia. 30 farms, were laid waste so thoroughly that they remained abandoned for decades
1728 Eruption 1. Began in August 1727 and lasted for almost a year. 2. The tephra production was small compared with that of the 1362 eruption and probably did not exceed 0.2 km3.
3.
4.
5.
Tremendous jökulhlaup came from the Falljökull and Rótarfjallsjökull glaciers. The floods and tephra fall killed about 600 sheep and 150 horses some of which were found completely mangled by the bomb fall. Lava production was insignificant.
Hyaloclastite is a hydrated tuff-like breccia rich in black volcanic glass, formed during volcanic eruptions under water, under ice or where subaerial flows reach the sea or other bodies of water. It has the appearance of angular flat fragments sized between a millimeter to few centimeters. The fragmentation occurs by the force of the volcanic explosion, or by thermal shock during rapid cooling.
Öræfajökull and the farm of Svinafell.
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Early attempts to climb Öræfajökull Sveinn Pálsson - 1794 Sveinn Pálsson was the first person to make an attempt to walk on Öræfajökull. He walked up to a peak that is now called Sveinsgnípa about 1900 m a.s.l. Sveinn climbed the mountain on the 11th of August 1794 with two companions. He conducted glaciological research in Iceland, and his Glacier Account he put forth his theory that glaciers behaved as fluids. Hans Frisak - 1813 The first mountaineering to Hvannadalshnúkur in 1813 may have been a misinterpretation. The Norwegian Hans Frisak doesn't mention Hvannadalshnúkur but according to descriptions of the view he has probably walked on the Hnappur mountain peak.
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Frederick W.W. Howell - 1891 (First recorded attempt on Hvannadalshnjukur) The most part of the 19th century people believed that Hnappur was the highest mountaintop in Iceland. Frederick W.W. Howell walked to Hnappur and saw that the Hvannadalshnúkur peak is actually higher. He climbed Hvannadalshnúkur the same day along with Páll Jónsson and Þorlákur Þorláksson.
Hvannadalshnjukur seen from Skaftafell.
Öræfasveit The area from Breiðamerkursandur to the East to Skeiðarársandur in the West is called Öræfasveit or Öræfi. The area used to be called “littla hérað” (“little shire”) before the Öræfajökull volcanic eruption in 1362, after the eruption the area got the name “Öræfi” (“wilderness”)
During the settlement period of Iceland from AD 874 to AD 930 the outlet glaciers of southern Vatnajökull are thought to have been 20 km behind their present margins. Farms at Fjall and Breiðá were abandoned due to the advance of the glacier at the end of the 17th century.
Öræfasveit used to be very isolated due to big rivers and sand-planes both to the East and West. The old post-route to the area was over the Skeiðarárjökull glacier. The isolation ended in 1967 when the “Jökulsá á Breiðamerkursandi” river was bridged, and in 1975 the Skeiðará river was bridged and is still today the longest bridge in Iceland. Historical documentation provides valuable insights into the recent fluctuations of Breiðamerkurjökull and Fjallsjökull.
The old farmhouses in Skaftafell with skeiðarárjökull in background.
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Svínafellsjökull Svínafellsjökull is an icefall outlett from Öræfajökull internal ice cap. Named for the Svínafell farmstead. Svínafellsjökull outlet is approx. 12 km long and 24 km2. Batman begins movie was filmed at the outlet snout. Svínafellsjökull and Skaftafellsjökull outlet were merged until 1935.
Satellite photo of Öræfajökull internal ice cap and its outlet. Svinafellsjökull is second from left.
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Photo of Svinafellsjökull outlet and its icefall. The mountain on the left is Hrjútfjallstindar.
Svínfellsjökull icefall.
SOblique aerial photograph of the Skaftafellsjökull (left) and Svínafellsjökull (right) outlet glaciers on. View looking to the northeast toward the coalescence of the Vatnajökull ice cap and the Öræfajökull internal ice cap on the southern margin of Vatnajökull.
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Virkisjökull Virkisjökull glacier is an outlet glacier from Öræfajökull internal ice cap that merges with Falljökull under a debris cover. The origin of virki (Icelandic for a fortress or castle), for which it is named, is not known. Virkisjökull outlet is aprox. 8.5 km long and covers an area of 6 km2 (World Glacier Monitoring Service). Popular hiking route to Hvannadalshnjukur goes through Virkisjökull outlet.
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Retreat of Virkisjökull and Falljökull between 1996 and 2009.
Photo of Virkisjökull and Falljökull outlet glaciers. View looking to the North towards The summit of Öræfajökull. Virkisjökull (on the left) merges with Falljökull (on the right).
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Kvíárjökull Kvíárjökull is an outlet glacier on the southeastern margin of Öræfajökull internal ice cap. Named for the Kvíá river. Kvíárjökull outlet is approx. 13km long. Is the closest outlet glacier to the ocean in Iceland. Kvíárjökull has build up the highest terminal and lateral moraines in Iceland.
Glacial moraine build by Kvíárjökull outlet, these moraines goes up to 100m in hight.
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Kvíárjökull outlet glacier
Oblique aerial photograph of the Kvíárjökull outlet glacier. View looking to the northwest at the southeastern margin of the Öræfajökull internal ice cap. Kvíárjökull is distinguished by its prominent terminal moraine grading into its equally prominent lateral moraines and by the fact that it is the glacier closest to the ocean in Iceland.
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Fjallsjökull Fjallsjökull is a piedmont outlet glacier from Öræfajökull internal ice cap.
Fjallsárlon lagoon is a proglacial lake. Fjallsjökull glacier has been misspelled Fjallsárjökull glacier on some maps.
Named for the historic Fjall farmstead by Flosi Björnsson and Jón Eyþórsson. The two eastward-flowing outletglacier lobes, which are separated by the Ærfjall nunatak, were historically known as Hrútárjökull. As the terminus of Hrútárjökull receded and split up in two glaciers Fjallsjökull on the north, and Hrútárjökull on the south, now the smaller lobe of the two. Fjallsjökull outlet is approx. 15 km long and 3 km wide at it´s snout, it covers an area of 45 km2 (World Glacier Monitoring Service).
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Fjallsjökull outlet.
Oblique aerial photograph of the Fjallsjökull outlet glacier. View looking to the west toward the summit of the Öræfajökull internal ice cap, at the Hrútárjökull outlet glacier (on the left), which merges with Fjallsjökull (on the right) below the Ærfjall nunatak. Prominent ogives are evident on Fjallsjökull, which calves into Fjallsárlón, a proglacial lake. Icebergs are visible in Breiðárlón, on the right edge of the photograph.
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Breiðamerkurjökull Breiðamerkurjökull glacier is second largest outlet glacier of the southern margin of Vatnajökull, and is instantly visible from space mainly due to its well-developed medial moraines. In 1996 the glacier was 910 km2 in area, of which 410 km2 was ablation zone, and the ELA was at 1100 m a.s.l. The glacier bed extend below present sea level in two trenches. The Eastern trench goes as much as 300 m b.s.l. and is approx. 25 km long and forms the proglacial lake of Jökulsárlón. The subglacial drainage presently follows these two trenches, emptying into the proglacial lakes Breiðárlón and Jökulsárlón.
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In 1732 the Breiðamerkurjökull glacier snout lay about 9 km from the shore whereas in 1869 only 200 m separated the snout from the shore. Since 1894 the glacier has retreated 4 km and decreased in volume by 50-60 km3.
Satellite photo of Breiðamerkurjökull and other outlet glaciers from the eastern margin of Vatnajökull ice cap.
Oblique aerial photograph of Breiðamerkurjökull. View looking to the north toward the Esjufjöll nunataks on the southeastern margin of the Vatnajökull ice cap. The Breiðárlón and Jökulsárlón proglacial lakes are in front of the glacier. The Fjallsjökull outlet glacier is on the left.
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Breiรฐamerkurjรถkull
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Breiรฐamerkurjรถkull
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Jökulsárlón and Breiðamerkursandur Prior to 1930 the 1½ km long course of the glacial river Jökulsá was uninterrupted by any lagoon. Since then the glacier tongue has retreated and a lagoon, gradually increasing in area, was created.
built in 1967 across the outlet river, Jökulsá, which is currently located 300 m from the shoreline. The result will be a deep bay, which is going to grow longer the farther the glacier snout retreats.
The lagoon is very deep, at least 190 meters. Salmon, capelin and herring enter the lagoon and the harbour seals follow the food. Breiðamerkursandur is a collective name of the proglacial area of Hrútárjökull and Fjallsárjökull, outlet glaciers from Öræfajökull and Breiðamerkurjökull respectively. An average costal erosion of 5-10 m/year now threatens the bridge,
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Jökulsárlón lagoon
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References Hambrey M. and Alean J. Glacier, Second Edition. 2004. Cambridge Univ. Press. deBlij. H. J. and Muller P. O. Pysical Geography Of The Global Environment, Second Edition. 1996 John Wiley and Sons, Inc. Strahler. A. Physical Geography, Second Edition 2002. John Wiley and Sons, Inc. Sigurðsson. O and Williams, S. R. Jr. Geographic Names of Iceland's Glaciers: Historic and Modern FLUCTUATIONS OF GLACIERS 2000–2005 by World Glacier Monitoring Service (WGMS) Various documents from the Science Institute of University of Iceland
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