Chemical Composition of Tropospheric Air Mass Encountered During High Altitude Flight (>11.5km) over Antarctica at Latitude 86S During the 2009 Fall Operation Ice Bridge Field Campaign

As part of the Operation Ice Bridge (OIB) campaign in 2009, the NASA DC-8 aircraft was used to fill the data-time gap in laser observation of the changes in ice sheets, glaciers and sea ice between the end of ICESat-I in 2009 and the launch of ICESat-II in 2015. In addition to the cryospheric instruments, four in situ atmospheric sampling instruments participated in this campaign, measuring CO2, CO, water vapor and various VOCs. During a high altitude research flight on October 25th 2009 (figure 1) strong enhancements of CO, CH4, N2O, CH3Cl, ethane, acetylene and methanol were observed in an air mass that was encountered at Latitude 86S. Other significant VOC enhancements observed included OCS, CFC-12, CFC-11, propane, ethanol, acetaldehyde, acetone and butanone. The presence of these hydrocarbons in the air mass and their correlation coefficients with CO suggests that the source of the plume is biomass burning. Hysplit forward and backward trajectories indicate that the possible origin of the plume could be the active fires burning in South America at the time. Due to the long lifetimes of both CFC-12 and CFC-11, their enhancements observed over Antarctica are consistent with transport from the Northern hemisphere. Unfortunately, the Southern hemisphere is heavily under-sampled during the austral spring, with few if any high-resolution airborne observations of atmospheric gases ever made over Antarctica. This leaves us without the basis for comparison with other data products. However, the data presented here shows evidence that tropospheric pollution (biomass burning emissions) is transported from lower latitudes toward the South pole, which may not have been observed in the past. Figure 1: October 25th, 2009: NASA DC-8 flight path from Punta Arenas, Chile, to Antarctica and return with the purpose of conducting a parallel survey from W 120° to E 10° along 86°S. Nearly the entire flight was flown at high altitude (>10.5 km) for a total duration of 11.5 hours.