Impacts of aerosols on climate in the Arctic

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1 Impacts of aerosols on climate in the Arctic Yutaka Kondo and Makoto Koike Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo, Tokyo, Japan Polar Climate, Ecosystem and Atmospheric Research Opportunities for Norway-Japan New Otani, Tokyo November 2, 2012

2 AMAP (2011): The impact of black carbon on arctic climate, Oslo Sources of BC: Incomplete combustion of fossil and bio fuels Light absorbing in visible range BC deposited to Arctic snow and ice exerts a greater warming than the within-arctic direct atmospheric radiative forcing OC species co-emitted with BC may exert a positive forcing over snow and ice covered surfaces. Both the sign and magnitude of aerosol indirect forcing in the Arctic are uncertain

3 Response of climate in the Arctic to changes in BC emissions (AMAP, 2011) Arctic climate is strongly coupled to the northern hemisphere climate and is thus sensitive also to extra-arctic radiative forcing There is no single appropriate environmental indicator to assess the Arctic climate response to changes in BC and OC emissions. An integrated evaluation using observations, reported emissions, and models is required.

4 Pathways of aerosol transport to the Arctic (AMAP 2011) Important findings: Transport of aerosols in the boundary layer from lower latitudes to the Arctic is most efficient (Polar Dome). Major sources of aerosols (BC + organic carbon) are estimated to be biomass burning in Canada and Eurasia based on studies of the data analysis and modeling.

5 Recommendations for improved characterization of distribution of BC and OC and deposition processes (AMAP, 2011) Improve the accuracy of measurements of BC and OC Continue efforts to resolve and standardize monitoring methods and protocols for BC and OC Implement routine measurements of BC and tracer species in snow in close proximity to long term monitoring sites to characterize BC deposition processes and sources of deposited BC Undertake process studies for characterizing aerosol removal during transport and dry and wet deposition for quantifying seasonally and spatially resolved deposition rates Studies of our group are closely related to these science needs

6 BC in the Arctic: Measurements vs models (AMAP, 2011) Obs. Model (DEHM) Long term measurements of BC have been used to understand spatial and temporal variations of BC Comparison of 3-D models are useful in understanding the transport and deposition of BC. However, the accuracy of the automated instruments of BC is not well quantified. More rigorous comparisons with models are needed.

7 Surface BC measurements by COSMOS 6 5 Slope=1.008, r 2 =0.97 1:1 SP2-BC ( g m -3 ) COSMOS-BC ( g m -3 ) Absorption coefficient (b abs ) at λ= 565nm with inlet heat at 400 o C Interference of non-refractory aerosols to COSMOS is small ( < 5%) Stable mass absorption cross section (MAC) Agree with SP2 and TOT (EC-OC instrument) to within 10% in Tokyo and Asia (fossil fuel and biomass) Further details are published in 11 papers [Kondo et al.]

8 New BC measurements at Ny-Alesund and Barrow COSMOS instruments were deployed at Ny-Alesund and Barrow in 2012 in cooperation with Polar research institutes of Norway and Japan, and NOAA (US)

9 Method for accurate measurements of BC in water We characterized size dependent extraction efficiency of BC (Ohata et al., 2011) We demonstrated accurate measurements of BC in rainwater, snow, and ice

10 Snow and rainwater sampling at Sverdrup Station 1) Use snow/rain collection system made of only glass 2) Sample snow accumulated near the station in spring 1) Estimate wet deposition flux of BC 2) Estimate total (wet + dry) deposition flux of BC

11 BC in rainwater in Okinawa, Japan 50 NC 3 Latitude ( N) SC KR Hedo JP 2 1 BC (Gg year -1 / grid) Longitude ( E) BC in rainwater is highest in spring. This is well reproduced by 3-D model (Koike and Matsui)

12 Tasks that should be done soon 1. Comparison of the COSMOS data with existing BC data. This enables estimates of the uncertainty of the long term BC data obtained at Ny-Alesund and Barrow. Data exchange is needed. 2. Installation of improved rain/snow sampling system to minimize BC loss 3. Collect snow deposited at Ny-Alesund and Barrow in spring 2013 We need close collaboration with scientists in Norway and US (NOAA and ARM site (DOE)) do conduct this work

13 Longer term collaboration with Norway Synthetic analysis of the data obtained at Ny-Alesund. This include other data sets (meteorological data, aerosol size distributions, tracers such as CO, chemical analysis of snow, etc.) Estimate deposition rate using model calculations. Update 3-D models of Norway including the observational results. Make updated estimate of the impact of BC on climate in the Arctic.

14 Acknowledgements We thank very much Dr. Max König and his colleagues at Norsk Polarinstitutt for their sincere cooperation and Svalbard Science Forum for letting us joining in the scientific activities at Ny- Alesund. This work was supported by the GRENE Program of the Ministry of Education, Culture, Sports, Science, and Technology (MEXT), and the global environment research fund of the Japanese Ministry of the Environment (A-1101).