Black carbon affects the local climate

Black carbon affects the local climate

Top image: Fans of coal dust can be clearly seen around the coal processing plant and open coal piles (left). The Svalbard airport is to the right. Photo: Marcus Eckerstorfer. 

For the first time the local climate impact of black carbon concentrations around Svalbard settlements has been investigated. Borgar Aamaas’ master thesis concludes that black carbon pollution by local sources increases snow melt in Longyearbyen and Svea. Aamaas will defend his master thesis June 15.

10 June 2009
Text: Eva Therese Jenssen

Svalbard is affected by both long-range and local pollution. In his master project, Borgar Aamaas investigated the black carbon (BC) concentrations in the snow pack and its effects upon the surface albedo (reflection) and its impact has been estimated.

The albedo factor is one of the important factors for the warming of the Arctic. The local BC emissions in Svalbard were estimated and compared to the long-range transported BC.

BC particles absorbs sunlight in a much more efficient manner that other dark particles. Snow and ice that contains BC particles will have accelerated melting compared to snow and ice without such particles.

Local sources of BC concentrations
In 2008 Aamaas measured BC concentrations in and around the three main settlements in Svalbard (Longyearbyen, Ny-Ålesund and Svea) to investigate the impacts of local settlements as sources for BC concentrations in the snow pack. Especially Longyearbyen and the mining community Svea are both affected by local BC producing factors, such as the mines, power plants and transportation vehicles. In contrast, the analysis of data Aamaas collected shows that there is no significant local pollution around Ny-Ålesund. This is explained by the small size of the settlement along with no coal mining activity.

Samples of coal dust

Filters with snow sample contaminants. A: sample taken close to Svalbard airport contaminated with BC. B: sample taken in Sassendalen. The filter is very clean indicating a low BC value. C: sample taken in Adventdalen. Sand and dust give the distinct brown color. Photos: Borgar Aamaas/UNIS.

Highly elevated BC concentrations were observed around Longyearbyen and Svea, and in those areas darkened snow was clearly visible from satellite images. The areas influenced by coal dust from open coal piles were the most affected.

The local pollution from Longeyearbyen was estimated to have an albedo effect of 2,2 % and from Svea an albedo effect of 5,4 % relative to the long-range pollution.

Earlier and increased snow melt
BC in snow has secondary climate effects, especially affecting snow metamorphism and snow grain growth, as these factors are accelerated by the presence of BC. The BC particles stay in the snow surface during melting.

Borgar Aamaas

Borgar Aamaas in the lab. Photo: Eva Therese Jenssen/UNIS.

As an example, on Longyearbreen an increase by a factor of 18 was measured in the surface snow from April to August, reducing the albedo by about 0,08 – thus less sunlight is reflected by the snow and instead more is absorbed by the snow and leading to increased melting.

The amount of BC particles was 200 times higher in the areas around Longyearbyen in the spring 2008 than the normal for the rest of the archipelago. This elevated particle concentration leads to not only an increase in snow melting in the area, but also an earlier snow melt season.

However, all in all, the pollution from settlements in Svalbard is actually insignificant compared to the vastness of the entire Arctic and its wilderness with few or no local BC sources.

Borgar Aamaas will defend his master thesis in geosciences at UNIS on June 15.

 

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