Andreas Stohl Norwegian Institute for Air Research (NILU) and

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1 Andreas Stohl Norwegian Institute for Air Research (NILU) and E. Andrews, T. Berg, J. F. Burkhart, A. M. Fjæraa, C. Forster, A. Herber, S. Hoch, Ø. Hov, D. Kowal, C. Lunder, T. Mefford, W. W. McMillan, J. A. Ogren, S. Oltmans, S. Sharma, M. Shiobara, D. Simpson, S. Solberg, N. Spichtinger, K. Stebel, R. Stone, J. Ström, R. Treffeisen, K. Tørseth, K. Virkkunen, C. Wehrli, and K. E. Yttri

2 Some current science problems regarding Arctic air pollution Aerosol radiative forcing Aerosol direct radiative forcing is different from any other place large solar zenith angles pronounced haze layers high surface albedo (snow, ice, stratus cloud decks) lead to multiple scattering/reflection between haze layers and the surface and enhance the relevance of light absorption Aerosol indirect radiative forcing could be positive in the Arctic no solar radiation in winter Arctic clouds so thin that they are greybodies in the longwave, making them susceptible to aerosol effects in the longwave (thermal radiation) Thus, positive forcing, opposed to the shortwave effects

3 Some current science problems regarding Arctic air pollution Albedo effects Black carbon important light absorber in the atmosphere, but also when deposited on the ground, as it reduces the albedo of snow/ice surfaces. The efficacy of this effect is about twice as large as that of CO 2, thus leading to pronounced effects on the surface temperatures and sea ice melting.

4 Some current science problems regarding Arctic air pollution Uncertain sources of Arctic air pollution One study (Koch and Hansen, 2005) suggests South Asia as the main source of Black Carbon, another (Stohl, 2006) rejects this hypothesis quite heavily debated just recently in a workshop on Arctic climate forcing. Stohl (2006) suggests a new source of Black Carbon to be dominant in summer: biomass burning (esp. boreal forest fires) Pyro-convection can inject aerosols into the high-latitude stratosphere

5 Some current science problems regarding Arctic air pollution Ozone depletion events In springtime, ozone can disappear almost completely at surface stations Bromine clouds responsible, but unclear where the bromine originates

6 Satellites Satellites and models have problems in the Arctic No data from geostationary satellites No light in winter no observations in the shortwave Large solar zenith angles in summer still problems High albedo of snow and ice aerosol optical depth unreliable Models Highly stable atmosphere thin layers that cannot be resolved Many global models use a latitude/longitude grid singularity at the pole, which may lead to incorrect transport in large parts of the Arctic

7 IASOA observatories

8 Stohl (2006): J. Geophys. Res. 111, D11306, doi: /2005jd December, the darkest month Intercontinental transport - lowest 100 m of the atmosphere

9 Note the different scales!!! Time spent continuously north of 70 N - Lowest 100 m of the troposphere July January

10 Stohl (2006): Characteristics of atmospheric transport into the Arctic troposphere. J. Geophys. Res. 111, D11306, doi: /2005jd Average age of air north of 80 N

11 Continental BC contributions in dependence of time from a FLEXPART tracer model simulation no chemistry, no removal, only transport using BC emission inventory from T. Bond Lower troposphere Total column

12 Continental BC contributions in dependence of time BC inventories from T. Bond and D. Lavoue (boreal fires) Lower troposphere Total column

13 Pan-Arctic enhancements of light absorbing aerosol concentrations due to North American boreal forest fires during summer 2004 Stohl et al. (2006): JGR, 111, D22214, doi: /2006jd Pyro-Cb Damoah et al. (2006): Atmos. Chem. Phys. 6, was the most severe burning season in Alaska Strong fires also in western Canada > 5 million hectare burned

14 FLEXPART Tracer Simulation: Total CO column 90 N Alert Barrow 80 N

15 Comparison model / satellite image FLEXPART Total Column 5. July 2004 Alert MODIS satellite image Barrow

16 Barrow, Alaska Aerosol Optical Depth (AOD) measurements (symbols) and FLEXPART CO column (line) normal value EBC measurements (black line) and FLEXPART CO tracer at the surface (colors give the age since emission) Source analysis

17 Barrow, Alaska Source analysis using a FLEXPART backward calculation Emission sensitivity Barrow

18 Summit, Greenland Aerosol Optical Depth (AOD) measurements (symbols) and FLEXPART CO column (line) normal value EBC measurements (black line) and FLEXPART CO tracer at the surface (colors give the age since emission)

19 Zeppelin, Spitsbergen CO and EBC measurements from May til September CO Anomaly

20 Zeppelin, Spitsbergen Aerosol Optical Depth (AOD)- measurements (symbols) and FLEXPART CO column (line) normal value CO anomaly EBC measurements (black line) and FLEXPART CO tracer at the surface (colors give the age since emission) fog, rain

21 Effects on the albedo of snow Albedo at Summit, Greenland Snow drift Fresh snow

22 Arctic smoke record high air pollution levels in the European Arctic due to agricultural fires in Eastern Europe Stohl et al. (2006): Atmos. Chem. Phys. Discuss. 6, Fire detections in April/May 2006

23 Record warmth in the European Arctic Temperature at Ny Ålesund, Spitsbergen in April and May 2006 Warmth dismantles the polar dome and creates effective pathway into the Arctic!

24 Transport of fire emissions into the European Arctic

25 Extreme pollution Picture courtesy: Ann-Christine Engvall

26 Extreme pollution At Zeppelin, new records were set for practically all measured compounds Ozone, aerosol optical depth (both measured for about 15 years!) Carbon monoxide, particulate matter, etc. Ozone formation was highly efficient!

27 Extreme pollution At Iceland, a new ozone record was set, 15 ppb higher than any previously measured value

28 Polluted snow at Holtedahlfonna observed by John Burkhart Snowmobile track Polluted snow Ion chromatographic analysis of snow samples confirms BB source.

29 POLARCAT Polar Study using Aircraft, Remote Sensing, Surface Measurements and Models, of Climate, Chemistry, Aerosols, and Transport Contact me:

30 How? When? Where? Major Campaigns 1. March/April 2007: 2 aircraft based in Longyearbyen, Svalbard 2. February-May 2008: Approximately 5 aircraft, based at various locations throughout the Arctic, plus a ship cruise from North America to the Norwegian Sea 3. June-August 2008: Up to 10 aircraft based in Canada, Russia, Europe, Greenland, etc.; measurements with a railway carriage along the Transsiberian railroad Surface stations Zeppelin, Barrow, Summit, etc.: long-term monitoring, plus intensive campaigns Some of the POLARCAT Satellite data Retrievals will be made in platforms near-real... time for flight planning, and for post-mission analyses; algorithm validation and improvement Models A variety of chemistry-climate, chemistry-transport, and pure transport models will be used