Seasonal variations of atmospheric trace gases in the high Arctic at 79°N

Abstract

Abstract. Since March 1992 the total column abundances of several tropospheric and stratospheric trace gases have been monitored year-round from the Network for Detection of Stratospheric Change station in Ny/•desund, Spitsbergen (78.9øN, 11.9øE). A groundbased Fourier transform infrared (FTIR) spectrometer performed these measurements using the Sun as a light source during the summer, and the Moon during the winter. In situ measurements of C2H2, C2H6, and CC12F2, made from the top of a nearby mountain, were combined with the FTIR column data to infer additional information about the variation of the volume mixing ratio profiles with altitude and season. The short-lived tropospheric trace gases C2H2, C2H6, and CO exhibit large seasonal variations with a summer minimum, caused by reaction with OH. CH20 shows a second maximum during the summer, caused by its formation by methane oxidation. For the long-lived gases HF, N20 , and CH 4 the seasonal cycle is less pronounced and is forced mainly by wintertime stratospheric diabatic descent, which starts in early November and reaches a maximum in March. The total columns of the stratospheric trace gases indicate that the chemical repartitioning of HC1 into C1ONO2 starts in November, before the widespread production of polar stratospheric clouds. The total columns of the sum of HC1 plus C1ONO2 suggests that between December and March they are converted into their active counterparts. Photolysis of HNO 3 gives rise to its summer minimum, and its winter maximum, with no evidence for a strong winter denitrification.

Five years of CO, HCN, C<sub>2</sub>H<sub>6</sub>, C<sub>2</sub>H<sub>2</sub>, CH<sub>3</sub>OH, HCOOH and H<sub>2</sub>CO total columns measured in the Canadian high Arctic

“…Our retrieved CO total columns (based on the five-year average) are smaller by a factor of 1.3 compared to CO measured at Ny Ålesund (Norway; 79 • N, 12 • E) from 1992 to 1995 (Notholt et al, 1997b). This is consistent with the decrease of tropospheric CO of −0.61 ± 0.16 % yr −1 observed at high-latitude sites between 1996 and 2006 (Angelbratt et al, 2011).…”

“…Our HCN total columns are of the same order of magnitude, in term of absolute values and variabilities, as those reported by Notholt et al (1997b) in the Arctic from 1992 to 1995. They also agree well with HCN columns observed at mid-latitude regions, as in northern Japan at 44 • N in 1995 (Zhao et al, 2000) as well as at Jungfraujoch from 2001 to 2009 (Li et al, 2009).…”

“…Concerning C 2 H 6 , our total columns are smaller by a factor of 1.1 compared to measurements performed in the Arctic from 1992 to 1995 (Notholt et al, 1997b) as well as at Ny Ålesund from 1992 to 1999 (Albrecht et al, 2002). The similarity between high-latitude and mid-latitude C 2 H 2 concentrations has already been reported (Albrecht et al, 2002) and highlights the importance of transport for the C 2 H 2 budget in the Arctic.…”

Latitudinal variations of trace gas concentrations in the free troposphere measured by solar absorption spectroscopy during a ship cruise

“…This assumption is consistent with our measurements from the Arctic [Notholt et al, 1997a], where the seasonal cycle of C2H2 is found to be 3 times more pronounced than for CO and C2H6. The cruise data are 2-6 times lower than our observations in Spitsbergen during October-November , 1996], the formation via NMHCs can also be excluded.…”

“…Compared to our observations in Spitsbergen (79øN) all trace gases detected there [see Notholt et al, 1997a, Table 1] could be measured during the cruise, except NO. For this molecule, strong interference from nearby water lines prevented the analysis in the tropics, even at noon for solar zenith angles (SZAs) around 0 ø.…”