''Dusty'' Glaciers

Hello again,

To continue the topic of last week, I am now presenting you with a case study that illustrates the influence of albedo change on melting.

First, I am pleased to introduce you to one of the most wonderful places on earth to find yourself for a day: the Langjökull Glacier in Iceland. Jökull in Icelandic means glacier and - on a different note - it is also the title of the national earth sciences journal, which is well worth reading.
Langjökull is the second largest glacier in the country and is located under the red dot on the map, or more specifically: 64°45′N 19°59′W.

Map of Iceland, red dot indicates Langjokull.

 Picture:http://www.hurstwic.org/photo/is2005/text/is052937.html

A picture I took on about 2/3rds from the glacier centre, in

July 2013. It is very clear that it is melting season.

WikiMiniAtlas

Second, the ones of you who wanted to fly between North America and Europe in April 2010 will remember very vividly: you could not. The eruption in Eyjafjallajökull caused large smoke plumes that obscured the sky for a while, but the lasting effect of this eruption is tephra fall. Tephra is the term for material produced in a volcanic eruption, regardless whether this material constitutes rocks or dust particles. In the context of glaciers, the most influential part of tephra is the dark grey dust, which is carried by wind and settles on the glacier's surface. It affects ablation, especially in the summer following an eruption, because it can reduce the glacier's albedo to values as low as 10%, or 0.1 (Bjornsson et al., 2008).

A picture I took from the massive car we drove

onto the glacier. I apologize for the awkward angle,

but this one shows best how gray the glacier

was.  July 2013



The mass balance of Langjokull is monitored at 23 locations on the glacier, since 1996. The specific mass balance for summer 2010 was -2.8 m/a. This is more than double the average negative mass balance that occured on the glacier in the warm years of 1996-2009, which was -1.3 m/a. (Gudmonsson et al., 2011) It is clear how serious the effects of the Eyjafjallajökull eruption are, also similar on the other major Icelandic glaciers.

Finally, my excursion onto Langjökull with a member of the glaciological society was fantastic, academically speaking, as well as painful. Actually being shown where the glacier ended a few summers ago and seeing where it ends now, was an interesting but mainly harsh confrontation with reality. The state of glaciers is precarious and we will not have them for much longer, at least not as the great ice masses they still are now.

Readings:

For anyone who is as interested in glaciers as I am (if so, please come talk to me!) or simply wants to know a bit more. The first paper I mention by Bjornsson et al. is a general overview of Icelandic glaciers. Very comprehensive, including meteorology, dynamics, geometry and a detailed future outlook.
The second mention links to a research abstract that discusses the 2010 volcanic eruption and the effect it has on the three major Icelandic glaciers. It gives some substantial numbers, and a more elaborate paper on the topic was published in Jokull.