Fieldwork in Iceland 2020
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Fieldwork in Iceland 2020

Written by Erik Sturkell

On the 4th of July I travelled to Iceland with multiple purposes: 1) to do field work, 2) to meet people, and 3) to attend our car and apartment. Upon arrival I took a Corona test that turned out to be negative, that’s positive! The first days I stayed mostly at home to be on the safe side. I used the time to write a popular science manuscript for the journal Jökull. This manuscript and future article addresses the 100-years’ anniversary of the expedition across Vatnajökull in 1919. This expedition was made by two young Stockholm students who discovered the volcano as the source of floods (jökulhlaup) coming out from Vatnajökull. The manuscript was completed and handed over to my co-author Magnús Tumi Guðmundsson.

On the 13th of July I organized a trip to the levelling line at Næfurholt 11 km direct west of the Hekla volcano. Measurements of changes in height in the east-west direction are sensitive to the detection of magma accumulation in the deep magma chamber underneath Hekla. The group that performed the measurements were Ásta Rut Hjartardóttir, Rikke Pedersen, Cécile Ducrocq and I. The measurements vent well and the results give a good indication of magma accumulation under the volcano (Figure 1) – see news on Icelandic MBL.

Figure 1. Rikke, Ásta Rut and Cécile performing the levelling at the Næfurholt tilt station. Photo: Erik Sturkell

On Monday the 20th Steini (Þorsteinn Jónsson) and I went to Langjökull to cut out a piece of glacier ice with ash. We travelled along Kaldudalur toward the western edge of the glacier. A road leads to the glacier edge (Figure 2), but all glacier ice was covered with a new snow layer of at least one meter’s thickness. Normally you would expect to find exposed glacier ice in the ablation zone. The ice sampling expedition thus failed completely due to the heavy snow layer. Despite the failure it was a fantastic day!

Figure 2. The road up on the Langjökull glacier and onto the manmade ice caves. The glacier is covered with new fallen snow making the ice in the ablation area inaccessible. Photo:Erik Sturkell

The next day, Revathy M. Parameswaran and I travelled north to Mývatn to join Chiara Lanzi, Siqi Li and Sveinbjörn Steinþórsson who had already been in the area for a week doing GPS fieldwork. When we joined them, the team had moved their measurements into the Krafla area. On Friday, the first receivers were moved into the Askja area. In Mývatn we met with Þorvaldur Þórðarson and Ármann Höskuldsson who were carrying out fieldwork in the north. I was fortunate to learn a new recipe from Ármann who is an excellent cook! He taught me how to make an extremely good sauce to be served with meat. First you chop a red onion, fry it with oil, and add broth (preferably of the meat you will serve). Into this you add cream and pepper cheese and bring it to boil under continues stirring. Season the sauce with oregano (or thyme), pepper, and parsley, and then add blueberry jam. After it has boiled, let it stand and cool while the meat is being prepared. Before serving, heat it up and perhaps add some red wine. This sauce was a huge success at the dinner we held with the rangers at Dreki. On Saturday the 25th Sveinbjörn, Chiara, and Revathy went into Askja with four instruments. Meanwhile Siqi and I went to Húsavík to resupply, but also to visit Marianne Rasmussen, who is a Danish whale researcher working in Iceland. On Sunday Siqi and I took down the last instruments in the Krafla area and picked up other instruments en route. The next day we installed instruments at the last three GPS sites. These were along the hiking sites in the caldera (Figure 3). We also managed to level about half of the levelling line in Askja, and this was finished on Tuesday. The same evening a dinner party was held with the rangers. The next day all the stations were taken down and we returned to Mývatn around 7 o’clock. On Thursday the fieldwork ended upon our return to Reykjavík. During the three weeks of fieldwork 95 GPS sites were measured and the 1.2 km long levelling line completed – well done all!

Figure 3. Siqi and Chiara on the way from the GPS site Olafsgigar to the centre (mið) Askja site, over the pumice field formed in 1875. Photo: Erik Sturkell

The result from the levelling

From what is known so far, a shallow magma chamber is located at 3 km’s depth under the centre of the large caldera of Askja. At approximately 16 km’s depth, a magma reservoir is situated at the base of the crust. Levelling is one of several geodetic methods used in the field to follow the crustal deformation caused by inflow, outflow, and solidification of magma. The results of the levelling carried out this summer show that the centre of the caldera has subsided from 1983 until now. The subsidence has decreased from a subsidence rate of 8.5 cm/yr in the early years to 3 cm/yr in 2020. This year’s subsidence is the lowest rate measured since subsidence began in 1983. In conclusion, subsidence rate is slowing down and no new magma has accumulated up to present. I left Iceland on the 2nd of August.