BIOGENIC SULFUR AEROSOL IN THE ARCTIC TROPOSPHERE .2. TRENDS AND SEASONAL-VARIATIONS

An 11-year record of tropospheric aerosol methanesulfonate (MSA) in th e Canadian high Arctic at Alert, Northwest Territories, from 1980 to 1 991 shows marked seasonal and long-term variations. By using spectral- analysis techniques, the seasonal cycles and long-term variations have been quantified. There are two distinctly different seasonal peaks wi th levels of 12-23 ng m-3 in early May and 6-18 ng m-3 in July-August. Over the 11.3 years, the amplitudes of the MSA seasonal cycles and th erefore the annual means of MSA concentrations decreased significantly by 33% (3% annually). So far there is no evidence of experimental art ifact in this trend, but such a possibility will be further examined. Analysis of MSA monthly anomalies suggests that in spring they are wea kly but significantly related to sea surface temperature anomalies (SS TA) in the North Atlantic west of the coast of continental Europe. In summer, MSA monthly anomalies are significantly correlated with SSTA i n oceanic regions further north in the North Atlantic off the coast of Norway and in the northeast North Pacific.