Hi-Speed Pollution of the Arctic | Polarjournal
This is how the Arctic sea ice likes to be seen: a vast white area that is connected. The white reflects the sun’s rays and thus protects the ice from high temperatures. But more and more often a dark layer of soot covers the white splendour. Picture: Michael Wenger

For most people, the Arctic sea ice or the large glacier areas on Svalbard and other Arctic regions are a white expanse. But more and more soot and other dark particles, also known as black carbon and black aerosols, are covering snow and ice. It has been known for a long time that this black carbon originates from industrialised and emerging nations and is transported to the far north by wind systems. An international group of researchers has now discovered that almost the entire Arctic is covered by just one geographic source and this in just a few days.

Within seven days, soot and other light-absorbing particles reach the areas of the Arctic and they spread there in almost all regions. This is the result of calculations made by John Backman of the Meteorological Institute in Finland together with Lauren Schmeisser of the University of Washington and Eija Asmi of the National Oceanographic and Atmospheric Adminstration NOAA. They cite data from six different monitoring stations throughout the Arctic region and from three years of records. Their calculations also include the corresponding meteorological data. The work was published in the journal Geophysical Research Letters.

The MODIS satellite image shows the northeastern part of India bordering Bangladesh and the Tibetan Plateau. The Indo-Gangetic plain is home to many of India’s industrial centers, which have long been among the largest emitters of air pollutants (the gray haze over the plain is a sign of air pollution). However, the current work shows that virtually the entire Arctic is affected from here. Image: MODIS Land Rapid Response Team, NASA GSFC

The team found above-average amounts of black carbon at five of six measuring stations (Alaska, Canada, Svalbard, Sweden, Russia) located in different regions of the Arctic. Through backtracking modeling incorporating meteorological data and calculated to a single day (but verified with three years of data), the researchers were able to determine the geographic location of the pollution source measured on day X at the five sites. The research team’s calculations clearly show that of two pollution centres in Asia, the Indus-Ganges Plain is responsible for polluting large parts of the Arctic and not eastern China, as is often assumed. While the latter region is also responsible for massive air pollution, it is not in the Arctic, the authors write in their paper. In addition, they were able to show that the particles can travel the several thousand kilometre distance between the source and the Arctic within seven days and are responsible for the deposits. They conclude that the path taken by “black carbon” particles is an important pollution route.

Dark ice does not always mean black carbon. Dust and dirt blown onto the ice with winds also has a darkening effect. The dark surface heats up faster and stronger and melts the underlying ice or snow. However, there has been a marked increase in the quantities of black carbon, mainly due to the emission of fossil fuels. Picture: Michael Wenger

The importance of “black carbon” for the melting of ice and snow in the Arctic and in high alpine regions has received increased attention in recent years. The amount of dark areas on glaciers, snow and sea ice has increased massively. By darkening, the heat radiation of the sun is not reflected but absorbed. This accelerates the melting of ice and snow. It has also been shown that more black carbon is deposited in winter than in summer, which has to do with meteorological conditions and correspondingly the transport of particles in the atmosphere. Backman and his team were able to show that the route from the Indus-Ganges plain via Central Asia to the Arctic is of enormous importance. Only Greenland is spared in the researchers’ model. Here, other sources of pollution are responsible for the deposits on the glaciers. With their work, however, the scientists show that the human impact on this important and sensitive region is also felt from a great distance, and that global cooperation is essential to find a solution to the problems.

Dr Michael Wenger, PolarJournal

Link to the study: Backman et al. (2021) Geophys Res Lett EPub Asian emissions explain much of the Arctic black carbon events; (Accepted article).; https://doi.org/10.1029/2020GL091913

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