Glacial outburst flood probably in progress
Various observations signify that a glacial outburst flood (jökulhlaup) is in progress in Skaftá river; including the water level at Sveinstindur and electrical conductivity readings. Data from the GPS-station in the Eastern Skaftá cauldron in Vatnajökull is also being closely monitored (see plot 17 - 29 September), the last jökulhlaup from there having occurred in 2010.
29.9.2015 at 22:28: Floodwater is beginning to drain from the eastern Skaftá ice-cauldron, located beneath Vatnajökull. According to GPS measurements, the ice-surface above the lake began to subside late on 27 September. The rate of subsidence is increasing progressively, reflecting heightened discharge from the lake. The flood (jökulhlaup) will travel a distance of 40 km beneath western Vatnajökull, before entering the Skaftá river. The closest gauging station on Skaftá is at Sveinstindur, about 28 km downstream from the ice margin. The jökulhlaup will reach Sveinstindur at some point between Wednesday evening and the early hours of Thursday.
Floods in Skaftá are sourced from two ice cauldrons, formed due to persistent geothermal activity beneath Vatnajökull. On average, the cauldrons drain every two years, producing floods of up to 1,500 cubic metres per second. When the interval between floods is short the flood tends to be smaller. The eastern cauldron is responsible for the largest floods.