Measurement of black carbon at Syowa station, Antarctica: seasonal variation, transport processes and pathways

Abstract

Measurement of black carbon (BC) was carried out at Syowa station Antarctica (69 • S, 39 • E) from February 2004 until January 2007. The BC concentration at Syowa ranged from below detection to 176 ng m −3 during the measurements. Higher BC concentra-tions were observed mostly under strong wind (blizzard) conditions due to the approach 5 of a cyclone and blocking event. The BC-rich air masses traveled from the lower tro-posphere of the Atlantic and Indian Oceans to Syowa (Antarctic coast). During the summer (November–February), the BC concentration showed a diurnal variation to-gether with surface wind speed and increased in the katabatic wind from the Antarctic continent. Considering the low BC source strength in the Antarctic continent, the higher 10 BC concentration in the continental air (katabatic wind) might be caused by long range transport of BC via the free troposphere from mid-and low-latitudes. The seasonal variation of BC at Syowa had a maximum in August, while at the other coastal sta-tions (Halley, Neumayer, and Ferraz) and the continental station (Amundsen-Scott), the maximum occurred in October. This difference may result from different transport 15 pathways and scavenging of BC by precipitation during the transport from the source regions. During the austral summer, long-range transport of BC via the free tropo-sphere is likely to make an important contribution to the ambient BC concentration. The BC transport flux indicated that BC injection into the Antarctic region strongly de-pended on the frequency of storm (blizzard) conditions. The seasonal variation of BC 20 transport flux increased by 290 mg m −2 month −1 in winter–spring when blizzards fre-quently occurred, whereas the flux decreased to lower than 50 mg m −2 month −1 in the summer with infrequent blizzards.