Project aim

The energy budget on Earth is largely determined by the so-called greenhouse gases, which occur naturally in the atmosphere: mainly water vapor, carbon dioxide, methane, ozone and nitrous oxide. These gases block the Earth’s heat radiation, preventing it from escaping into space. Without this natural greenhouse effect the Earth would be a very cold place. Since the introduction of industrialism man has increased the amount of greenhouse gases in the atmosphere. Carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) as well as chlorofluorocarbons (CFC’s) show large increases over the past century due to human activity. The effect of this increase is forcing the climate towards a warmer atmosphere.

Whereas the greenhouse gases warm the Earth, particles in the atmosphere generally, but not always, have a cooling effect on the climate. When sunlight hits the particles in the atmosphere some of the light is scattered back from the Earth. This means that less of the sun’s radiation reaches the ground. Particles also cool the planet by modifying the droplet size distribution of clouds. Shifting the cloud droplet distribution to smaller sizes makes the cloud brighter, in other words it scatters more radiation back to space. Black particles such as soot tend to warm the atmosphere. Contrary to greenhouse gases, which stay in the atmosphere for a long time and are almost equally distributed over the world, the particle concentration is highly variable.

Our research aims at a better understanding of these atmospheric constituents and their roles in the climate system. We seek knowledge about their sources and sinks, transport and transformation processes and their interactions with clouds and climate. We do this through long-term measurements, currently at three locations (the Zeppelin station in Svalbard, Aspvreten in Sweden, and Pico Espejo in Venezuela), and by detailed spatial observations using aircraft platforms deployed from locations from pole to pole.

Research platforms

Aircraft measurements

The aircraft measurements are mainly conducted in collaboration with the German Alfred Wegener Institute (AWI), the Japanese National Institute of Polar Research and the German Aerospace Center. The antarctic campaign ANTSYO was performed towards the end of 2006, and will be reported upon in next years yearbook together with reports on the Arctic campaign ASTAR2007. Although the actual measurement flights were conducted at the very end of 2006 and beginning of 2007, preparations such as sea and ice survival training, high altitude and pressure chamber tests and instrument aircraft-certification, including test flights, took place in the summer of 2006 (picture 2). During ANTSYO the aircraft is based at the German station Neumayer and the Japanese station Syowa. The aircraft experiments are mainly funded by the Swedish Research Council (VR) with support from the Swedish Polar Research Secretariat.

Observations at the Zeppelin station

The Zeppelin station is located in Ny-Ålesund on the west coast of Svalbard (78°54’N, 11°53’E). The research station is an excellent platform for atmospheric studies, as its elevation of about 475 m a.s.l. on the Zeppelin mountain ridge minimizes influences from local sources. The station is owned by the Norwegian Polar Institute (NPI), but the two main users are Stockholm University and the Norwegian Institute for Air Research (NILU). The station was officially opened in 1990, but in 2000 the original building was replaced with a new and more user-friendly one. The activities at the Zeppelin station are mainly supported by the Swedish Environmental Protection Agency with support from the Swedish Polar Research Secretariat.

Measurements

Long-term measurements imply continuous or semi-continuous measurements that run throughout the year and from year to year. Despite this continuous operation many parameters are observed at a rate as high as one data point every minute. Such long-term, high frequency measurements are the only viable way to determine trends and to place campaign-like observations such as measurements from aircraft or ships into context.

Carbon dioxide

The air around us consists almost entirely of nitrogen (ca 78%) and oxygen (ca 21%). The remaining one percent is mainly argon, but also contains trace amounts of very important gases. One of the better known of these trace gases is carbon dioxide (CO₂). Because CO₂ absorbs thermal radiation emitted by the Earth, it functions like a blanket or greenhouse. The more CO₂ present in the atmosphere, the warmer the climate. The use of fossil fuel emits large amounts of CO₂ and as a result the carbon dioxide concentration in the atmosphere has increased quickly since the beginning of industrialization. When trees and other plants grow, they consume CO₂ from the atmosphere, which cause an annual cycle in the CO₂ concentration. Making measurements away from the direct sources and sinks provides a clearer signal in the data in order to monitor possible trends in trace gas concentrations.

Carbon dioxide is measured using a Non-dispersive Infrared Radiometer (NDIR), Li-COR model 7000. Figure 1 shows data from the Zeppelin station, which is actually the only long-term CO₂ monitoring operated by Sweden. The data series show not only the marked annual variation in CO₂ but also the very large increase in the baseline concentrations. The increase is currently between 2 and 3 ppmv (parts per million per volume) per year. Since the measurements started in the late 1980’s the CO₂ level has increased by almost 10%. Never before in any historical record, such as ice core data, has the magnitude of the concentration (in some years about 400 ppm) or the rate of increase been larger. It is truly unprecedented. On a global scale the polar regions present the largest increase. The reason for this is not clear, but changes in ocean temperature and altered thawing cycle are possible mechanisms to enhance the CO₂ level in the atmosphere. In addition to the real-time observations of CO₂, flask samples are taken weekly and analysed for CO₂, CH₄, CO, and ¹³CO₂, H₂, N₂O, SF⁶ and ¹⁸O in CO₂ by NOAA/CMDL, Boulder, Colorado, USA (Thomas J. Conway).

Particle measurements

Particles mixed with air are called aerosols. Aerosol particles are very small and in the atmosphere they are typically smaller than one micrometre (0.000001 m) in diameter. Despite their small size they are an important component of our environment in several aspects. In the atmosphere particles are an integral part of the energy budget of the Earth, in other words our climate. Particles scatter and absorb light from the sun that gives rise to many, often beautiful, optical phenomena. The fact that all cloud and rain drops began their life as small aerosol particles is of course of great interest to meteorologists. The source of particles may be natural, e.g. from the forests or oceans, or they may be anthropogenic, arising through human activities such as industry or traffic. By studying aerosols at different locations and over longer times we can better understand how aerosol particles affect our environment and us.

At the Zeppelin stations aerosols are characterized based on their number concentration, size distribution, light scattering and light absorbing properties, as well as their chemical compositions (inorganic chemistry analysis are performed by NILU). As aerosol particle’s properties range over a wide scale, an array of particle counters and instruments are needed to cover all relevant aspects.

Activities in 2006

Five visits were made to the station: (1.) at the end of January and beginning of February, (2.) at the end of April and beginning of May, (3.) at the end of July (4.) in October, and finally (5.) in December. Personnel from NPI perform daily supervision of the instruments but there is always room for maintenance and improvements. Each visit is typically between one and two weeks. Most of the year there are two flights per week to Ny-Ålesund from Longyearbyen. However the element of weather sometimes makes travelling difficult to plan in detail. Hence visits may sometimes be longer than anticipated.

During the visit in spring we experienced the most severe pollution event ever recorded in Ny-Ålesund. The photographs 2 and 3 illustrate the visual impression of this. Picture 1 was taken on 26 April 2006, the day prior to the first main plume of pollutants reaching Svalbard. The picture is taken from our laboratory room at the Zeppelin station, viewing due north towards Ny-Ålesund. The village can be seen by the waterfront. Photo 3 is taken on 2 May 2006 a few hours before the maximum values were observed.

The difference in visibility between the two days is striking and was caused by farmers in Eastern Europe who burned their fields before the start of the new growing season. Springtime agricultural burning in Eastern Europe appears to be a yearly event, so what caused it to make such impact in 2006? Two factors seem to be key players. Firstly, the fires were lit later in 2006 than previous years due to late melting of the snow in the area. Secondly, the European sector of the Arctic was very warm, as a matter of fact more than 10 degrees above average temperatures, which caused a reduced temperature contrast between the source region and the Arctic. These factors together pave the way for air from lower latitudes to quickly be transported into the Arctic.

With the warming of the Arctic it is possible that events such as this may be more frequent in the future. To emphasise the magnitude of the pollution, the estimated particle mass concentration for the day with the maximum concentrations during this event exceeded regulated values for urban environments. The fact that the impact of the pollution is visible, as in photo 3, implies that it has a large climate impact regionally. The plume contained a large amount of soot (black particles) that results in a so-called heating rate of almost half a degree per day. This means that in this case the particles in the atmosphere are driving the temperature to increase just as the greenhouse gases do.