Seasonality of wildfires in Iceland

In the next volume of Náttúrufræðingsins, 84(1-2): 19-26, there is an article about the seasonality of wildfires in Iceland.

Summary. Data on wildfires was collected from news databases, and for the period 2003–2010 we had data from the Iceland Construction Authority, which contains the activity of all fire departments in Iceland. Most of the fires are small; however, there were ten wildfires larger than 1 hectare in the period 2007–2013, including six larger than 10
hectares. Most of the fires are due to ignition, deliberate or accidental. There is a clear seasonal signal in the occurrence of wildfires in Iceland using data from 1943–2012. Most often they occur in spring, with 29% of each year wildfires occurring in May, followed by 28% in April and 13% in March. There is also a clear New Year’s Eve signal in January (6% of the wildfires). The data is not detailed enough to allow estimation of changes in frequency or occurrence between months, since prior to 2002/3 there was no centralized registration of wildfires. However, one can infer that wildfire during the summer months is a relatively recent development. This fits well with increased biomass
due to global warming, denser summerhouse populations, and less grazing. This also exemplifies the need for action in developing risk assessments and including wildfires in
planning.

The distribution of wildfires each month for the period 1943–2000 (blue columns; 161 events) and 2001–2012 (red columns; 947 events), and standard deviation.

Eruption in Holuhraun and air quality considerations

The eruption in Holuhraun (Holu-lava field) has now been active for just over a week; since 31 Agust (if I remember correctly).

There is a fair bit of lava that has been extruded, as can be seen on this Landsat image from NASA. The lava flow is to the right on the figure, from a linear almost N-S fissure. There is a little red spot south of there, that is a new opening. There is a dike running from Bárðarbunga, underneath the glacier, to the eruption site (and even a bit further north). On of the things to look for is whether the fissure will open up underneath the glacier. Some flooding would follow and more explosions as magma and water interact.

Landsat 8 image from NASA on 6 September 2014.

The lava has reached the glacial river, Jökulsá á Fjöllum, which causes some steam explosions – making it still more difficult for the scientist working in the area.

But, one of the concerns, is the air pollution. Especially SO2 gas.

SO2 in 8 km of the atmospheric column (NASA).

Fortunately, this is a relatively small eruption.

Measurements in the eastern fjords, at Reyðarfjörður (large fjord middle of image), went up to 250 µg/m3 10-min value on 2 September. That is quite high, given that it is 125 km away from the eruption site, and this is a small eruption.

However, public health limits are 350 µg/m3 for 1-h average, and workers occupation limits are about 5 times higher than that. And real danger, requiring evacuation, seems to be at levels of 10 000 µg/m3.

Recent measurements in the eastern fjords indicate that the SO2 concentration is below 300 µg/m3, despite a distinctive blue haze being observed in the area. The haze can be seen quite clearly in the next figure.

MODIS image from NASA and IMO from 6 September 2014 at 13:30.

It will be interesting to follow the eruption and see whether: 1) the dike breaks to the surface underneath the glacier, 2) Bárðabunga will erupt, 3) Askja wakens, and erupts, or 4) the whole system simply slowly cools down.