Abstract
Abstract. Vertical distributions of atmospheric dimethyl sulfide (DMS(g)) were sampled aboard the research aircraft Polar 6 near Lancaster Sound, Nunavut, Canada, in July 2014 and on pan-Arctic flights in April 2015 that started from Longyearbyen, Spitzbergen, and passed through Alert and Eureka, Nunavut, and Inuvik, Northwest Territories. Larger mean DMS(g) mixing ratios were present during April 2015 (campaign mean of 116 ± 8 pptv) compared to July 2014 (campaign mean of 20 ± 6 pptv). During July 2014, the largest mixing ratios were found near the surface over the ice edge and open water. DMS(g) mixing ratios decreased with altitude up to about 3 km. During April 2015, profiles of DMS(g) were more uniform with height and some profiles showed an increase with altitude. DMS reached as high as 100 pptv near 2500 m. Relative to the observation averages, GEOS-Chem (www.geos-chem.org) chemical transport model simulations were higher during July and lower during April. Based on the simulations, more than 90 % of the July DMS(g) below 2 km and more than 90 % of the April DMS(g) originated from Arctic seawater (north of 66° N). During April, 60 % of the DMS(g), between 500 and 3000 m originated from Arctic seawater. During July 2014, FLEXPART (FLEXible PARTicle dispersion model) simulations locate the sampled air mass over Baffin Bay and the Canadian Arctic Archipelago 4 days back from the observations. During April 2015, the locations of the air masses 4 days back from sampling were varied: Baffin Bay/Canadian Archipelago, the Arctic Ocean, Greenland and the Pacific Ocean. Our results highlight the role of open water below the flight as the source of DMS(g) during July 2014 and the influence of long-range transport (LRT) of DMS(g) from further afield in the Arctic above 2500 m during April 2015.
Highlights
The Arctic has experienced rapid climate change in recent decades (IPCC, 2013)
Assuming a DMS atmospheric lifetime of 1 to 4 days, these results suggest that the DMS(g) measured during July 2014 originated primarily from the local region over Baffin Bay and the Canadian Arctic Archipelago
Atmospheric samples for DMS(g) measurements were collected at different altitudes aboard the Polar 6 aircraft expeditions during July 2014 and April 2015, as part of the NETCARE project
Summary
The Arctic has experienced rapid climate change in recent decades (IPCC, 2013). Its high climate sensitivity distinguishes the Arctic from the rest of the world. They reported low DMS(g) mixing ratios (a few pptv) during spring and relatively high ones (a few tens pptv with some peaks around 100 to 300 pptv) during summer They concluded that the Arctic Ocean is the potential source of DMS(g), and DMS(g) ocean–atmosphere exchange is more important in early summer due to sea ice melt. Atmospheric DMS(g) samples were collected onto Tenax tubes during Polar 6 aircraft flights in the Arctic We compared these DMS(g) measurements to GEOSChem (www.geos-chem.org) chemical transport model simulations and conducted sensitivity simulations to examine the local vs long-range transport (LRT) DMS(g) sources for both the spring and summer.
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