DMS OXIDATION TO AEROSOL SULPHATE IN THE ARCTIC: AN ISOTOPE RECORD FROM 1993-2003

Sulfate aerosols, their sources and their formation mechanisms are critical components in understanding climate feedbacks to warming surface temperatures. The Arctic has experienced significant warming over the past two decades (1.8 °C). Increased air and ocean temperatures have resulted in significant changes to the presence and timing of open leads, ice pack breakup, and ice thickness. Biological response of the ocean phytoplankton and picoplankton species communities, an important parameter in assessing the effects of climate change, is difficult to identify on the basis of spatially and temporally diverse measurements of organisms themselves. Instead, gases released on decay of biogenic matter in the surface ocean, can act as a proxy that links large-scale changes in primary production and changes in radiative forcing due to aerosol formation. Biogenic sulfate, formed from the oxidation of dimethyl sulfide released to the atmosphere from open leads, is particularly relevant to the radiation budget as it can form cloud condensation nucleii. The proportion and amount of sulfate in arctic air from biogenic sulfate, either advected northward from more southerly ocean regions, or formed as a consequence of increased biological productivity in open leads is important to assess. Isotope apportionment techniques were used to separate the anthropogenic and biogenic components of aerosol sulfate collected at Alert, Nunavut, in northern Canada for the period 1993-2003. We report the trend in biogenic aerosol sulphate at Alert and examine its relevance at spatial scales by comparing these results to those from a second Arctic location in Europe.