Including this just reported. As they say it's not usual but it may indicate some form of activity (or maybe not!)
"Glacial water is flowing into Múlakvísl river, south of Mýrdalsjökull. Increased conductivity has been measured in the river and gas measurements in the area show high concentrations of sulfur dioxide and hydrogen sulfide. People are advised not to travel near the river, due to gas pollution. It is not uncommon for glacial water to flow into Múlakvísl, causing increased conductivity and gas pollution.
According to local reports, the level of the Bláfjallakvísl glacial river is unusually high. Bláfjallakvísl originates from the northern side of Mýrdalsjökull and people are advised to show caution when crossing the river.
Written by a specialist at 29 Aug 19:33 GMT"