Grímsvötn 1919-2019: The legacy of Erik Ygberg and Hakon Wadell

The first recorded visit to Grímsvötn occurred on the 31st of August 1919. Two Swedish geology students, Hakon Wadell and Erik Ygberg, stood on the edge of a hitherto unknown large caldera. This discovery was the most significant finding in the first west-to-east transect across Vatnajökull, starting at Síðujökull on the 27th of August. This was an expedition into the unknown, but a principal aim was nevertheless to find the source of the large jökulhlaups on Skeiðarársandur. They named the ice-filled caldera “Svíagígur”. Studies of written sources in the 1930s revealed that this place was indeed Grímsvötn, well known in the 17th and 18th centuries but the name and location had been forgotten in the 19th century. From Svíagígur they continued eastwards, descending down the crevassed Heinabergsjökull, reaching civilization in the morning the 6th. They announced the news that a huge volcano existed under Vatnajökull and this was the source of the jökulhlaups emerging from Skeiðarárjökull. Upon their return to Stockholm, they received a hero’s welcome, but soon it all changed into no one believing them, as prominent figures in Sweden at this time insisted that a volcano can’t be active beneath a glacier! After they finished their studies, both left Sweden very disappointed. Hakon Wadell had a successful geological career in America presenting a doctoral thesis in 1932 from the University of Chicago. Erik Ygberg worked as an international prospector a few years before his bad health, a result of the hardships experienced at the end of the Vatnajökull expedition, forced him back to Sweden, where he had a career at the Swedish Geological Survey. The name Svíagígur has not been used but the two nunataks marking the highest points on Grímsfjall are named in the honour of the two Swedes, Svíahúkur eystri and Svíahnúkur vestri.

Channels of the glacial river Jökulsá á Breiðamerkursandi

The glacial river Jökulsá á Breiðamerkursandi drains the Jökulsárlón tidal lagoon (27 km2), in Southeast Iceland. Despite being the shortest glacial outlet (0.6 km), it is among the most voluminous rivers in Iceland, with an estimated average drainage of 250–300 m3/s and has doubled its volume at peak runoff. Until a bridge was established, this was one of Iceland’s most infamous river and for travellers, cruising on horseback, the greatest obstacle to cross on the main road. The river began shaping its present channel in the late 19th century but was not permanently settled until the mid-20th century. Before that it used to wander around the fan, occasionally in several branches, or as a single heavy moving water. In this paper we present a map of its known runoffs and channels that were formed in the 19th and 20th centuries. Few channels were digitized from old maps, but several of those were identified and recorded by the late Flosi Björnsson (1906–1993), a farmer from the Kvísker, who guided travellers across the river before the bridge was built. The Breiðamerkurjökull outlet glacier of Vatnajökull, Southeast Iceland, advanced 10–15 km during the Little Ice Age. During the LIA advance the wide fan shaped shore in front of Breiðamerkurjökull gradually extended outward by >1 km, mainly due to sediment deposition by the Jökulsá river and few other temporal glacial river branches. At the turn of the 20th century the outlet glacier started to retreat slowly and in the 1930s terminal lakes were formed. With the formation of the Jökulsárlón tidal lagoon river dumping at the shore terminated and was replaced by a progressive coastal erosion. Currently ca. 0.9 km has eroded off the coast since the 1930s. A 0.65 km wide strip now remains between the coast and Jökulsárlón tidal lagoon, where the Jökulsá river and the remains of its former runway channels are located.

Fostering glacier termini

The article presents an overview of the history of the monitoring programme of glacier termini fluctuations in Iceland. The programme was initiated by meteorologist Jón Eyþórsson in 1930, and the measurements were initially carried out by local farmers. In recent decades, the measurements have been conducted by volunteers of the Iceland Glaciological Society with a very diverse professional background. Every autumn, the distance to the glacier terminus has been measured from a reference post, usually marked with a cairn and/or a metal pole. Glacier terminus variations in Iceland since 1930 show a clear relationship with climate changes. The terminus variations data set also contains information about the surges of many glaciers.

The analog seismogram archives of Iceland: Scanning and preservation for future research

The history of seismography in Iceland began in 1909 with the installation of one horizontal Mainka seismograph in Reykjavík. Following a period of intermittent operation, regular operation was initiated in 1925 with the establishment of the Icelandic Meteorological Office. The number of stations increased gradually over the following decades, and in the sixties, four stations were in operation. The number of permanent stations proliferated following the Heimaey eruption in 1973 and during most of the eighties the number of stations was 40–50. The first digital seismograph stations were installed in 1990 and the analog seismic network was gradually replaced by digital stations over the next two decades. Between 1910 and 1920 the number of seismograms grew to an estimated 300,000. A four-year project to make this record collection accessible on the internet has been initiated and funded. So far around 175,000 seismograms have been scanned and the results are available and free for download on the open website seismis.hi.is. The seismograms are scanned with a resolution of 300 dpi and presented on the website as jpg-, and png-file. The high-resolution files are on the order of 4–8 Mb each. Digitization of the seismic traces has not been attempted since most of the seismograms are from short-period instruments and the waveforms are already lost. In addition to numerous teleseismic body-wave-phases, the record collection contains primary data from various tectonic and magmatic events in Iceland during the last century. This includes eruptions of Hekla in 1947, 1970, 1980–81, 1991 and 2000, Surtsey in 1963–1967, Heimaey in 1973, Askja in 1961, Grímsvötn in 1934, 1983, 1998, and 2004, Gjálp in 1996, rifting episode at Krafla in 1975–1984, persistent seismic activity of the Bárðarbunga and Katla volcanoes, numerous suspected subglacial magmatic events, earthquake swarms on the Reykjanes Peninsula Oblique Rift and within the Tjörnes Fracture Zone, and earthquake sequences in the transform zones of South and North Iceland and adjacent segments of the Mid-Atlantic Ridge.

Little Ice Age advance of Kvískerjajöklar, Öræfajökull, Iceland. A contribution to the assessment of glacier variations in Iceland since the late 18th century

We describe the changes of the Kvískerjajöklar outlet glaciers in SE Iceland (presently ranging 600–1600 m a.s.l.), from their Little Ice Age maximum (LIAmax) to the present. We assume that glacier extent of the late 19th century approximately describes LIAmax although the glaciers already reached their peak extent in the 18th century. The former glacier margins were delineated from moraines, historical descriptions, topographical maps, aerial and oblique photographs, Landsat images and a lidar DEM. Along the previous glacier margins, elevation differences with respect to the lidar DEM of 2011 were estimated and contour maps of the glacier drawn at selected dates, maintaining the shape of the glacier surface as available maps. During the period 1890 to 2011, the outlets lost -0.4 m a-1 water equivalent evenly distributed over their surface and their area was reduced by 37% (from 10 km2 to 6.4 km2, 0.03 km2 a-1, 0.43 km3 water equivalent in total, i.e. 0.003 km3 w.e. a-1).

Infinite Next: Grímsvötn caldera and planet Earth

In this article artists Anna Líndal and Bjarki Bragason discuss their work Two thousand nineteen hundred and Nineteen. The work was presented during the Iceland Glaciological Society’s (IGS) work trip to the Grímsvötn caldera in Vatnajökull glacier on 31. August 2019 in commemoration of the 100th anniversary of Hakon Wadell’s and Erik Ygberg’s 1919 expedition to the area and its subsequent mapping. Anna Líndal’s photographic work, Untouched expanse in the opening of the article addresses the importance of observing and recognizing the significance of minor events within the larger context of the environment. The Grímsvötn caldera is in the work observed as a self contained system which, although remote and harsh to its visitors, the artist proposes that it mirrors changes in the world at large. Even though footsteps trodden in the area vanish and blend into the environment, the bodily pressure of one person’s foot creates an imprint which acts as a reflector for sunbeams as ash is moved from the surface of the ice, making it more susceptible to exposure and melting. In this way the environment is continuously altered by human activity despite its constant appearance as untouched wilderness. Their two-part work presented and donated to the IGS cabin at Grímsfjall, Líndal and Bragason aimed to underscore the collision of human and geological time scales which may be discerned through the recognition of the anniversary of human eyes first laying sight on the caldera and its emergence from being an idea in the world (for example in Peter Raben’s 1720 map of Iceland) to becoming a mapped site. One component of the work is a set of cake plates which display two maps of Vatnajökull glacier, on the top side Wadell and Ygberg’s 1919 expedition path is dotted (the first recorded West-East crossing of the glacier). The underside of the plate reveals a recent map of Vatnajökull and the many, though not finite, survey lines established there in recent years and decades. Before the 22 participants in the trip to Grímsvötn drove together from the IGS cabin to the edge of the caldera, to stand in what is believed to be the spot where Wadell and Ygberg put down their tent a century ago, cake with a sugar printed map of the 1919 journey was served on the plates. The second component of the artistic gesture made during the 2019 trip was a wish from the artists to the participants in the trip to walk in silence from where the cars were parked towards the edge of the caldera. Silence in this context served as a means for individual critical and poetic reflection, offering participants for a short moment the opportunity to experience on their own terms the significance of seeing the caldera unfold in front of them at this momentous point in the site’s history.

Glacier variations 1930-1970, 1970-1995, 1995-2018 and 2018-2019

The Icelandic Glaciological Society received reports on approximately 50 measurements sites of glacier front variations in the autumn of 2019. Glacier retreat was observed at 80% of survey sites whereas advances where reported from 4 sites. The warm summer led to fewer snow-covered glacier margins, and more successful surveys. As in recent years the proglacial lakes make terminus measurements more difficult, although the laser rangefinder works well.

The 1845–46 and 1766–68 eruptions at Hekla volcano: new lava volume estimates, historical accounts and emplacement dynamics

We use new remote sensing data, historical reports, petrology and estimates of viscosity based on geochemical data to illuminate the lava emplacement flow-lines and vent structure changes of the summit ridge of Hekla during the large eruptions of 1845–46 and 1766–68. Based on the planimetric method we estimate the bulk volumes of these eruptions close to 0.4 km3 and 0.7 km3, respectively. However, comparison with volume estimates from the well-recorded 1947–48 eruption, indicates that the planimetric method appears to underestimate the lava bulk volumes by 40–60%. Hence, the true bulk volumes are more likely 0.5–0.6 km3 and 1.0–1.2 km3, respectively. Estimated melt viscosity averages for the 1766–68 eruption amount to 2.5 x10**2 Pa s (pre-eruptive) and 2.5x10**3 Pa s (degassed), and for the 1845–46 eruption 2.2x10**2 Pa s (pre-eruptive) and 1.9x10**3 Pa s (degassed). Pre-eruptive magmas are about one order of magnitude more fluid than degassed magmas. In the 1845–46 and 1947–48 eruptions, SiO2 decreased from 58–57 to 55–54 wt% agreeing with a conventional model that Hekla erupts from a large, layered magma chamber with the most evolved (silica-rich) magmas at the top. In contrast, the lava-flows from 1766–68 reveal a more complicated SiO2 trend. The lava fields emplaced in 1766 to the south have SiO2 values 54.9–56.5%, while the Hringlandahraun lava-flow that erupted from younger vents on the NE end of the Hekla ridge in March 1767 has higher SiO2 of 57.8%. This shows that the layered magma chamber model is not suitable for all lava-flows emplaced during Hekla eruptions.

A national glacier inventory and variations in glacier extent in Iceland from the Little Ice Age maximum to 2019

— A national glacier outline inventory for several different times since the end of the Little Ice Age (LIA) in Iceland has been created with input from several research groups and institutions, and submitted to the GLIMS (Global Land Ice Measurements from Space, nsidc.org/glims) database, where it is openly available. The glacier outlines have been revised and updated for consistency and the most representative outline chosen. The maximum glacier extent during the LIA was not reached simultaneously in Iceland, but many glaciers started retreating from their outermost LIA moraines around 1890. The total area of glaciers in Iceland in 2019 was approximately 10,400 km2, and has decreased by more than 2200 km2 since the end of the 19th century (corresponding to an 18% loss in area) and by approximately 750 km2 since ~2000. The larger ice caps have lost 10–30% of their maximum LIA area, whereas intermediate-size glaciers have been reduced by up to 80%. During the first two decades of the 21st century, the decrease rate has on average been approximately 40 km2 a-1. During this period, some tens of small glaciers have disappeared entirely. Temporal glacier inventories are important for climate change studies, for calibration of glacier models, for studies of glacier surges and glacier dynamics, and they are essential for better understanding of the state of glaciers. Although surges, volcanic eruptions and jökulhlaups influence the position of some glacier termini, glacier variations have been rather synchronous in Iceland, largely following climatic variations since the end of the 19th century.