南极大气CO_2、CH_4和N_2O本底趋势特征分析

对南极大气温室气体CO_2(含δ~(13)C-CO_2和δ~(18)O-CO_2)、CH_4和N_2O长期测值进行比较分析。结果表明,南极是全球大气温室气体浓度(CO_2稳定同位素丰度值)随纬度分布变化中的最低(高)区域。南极大气温室气体浓度值变化趋势、年增长率与全球整体上一致,但在具体数值上存在差异。南极CO_2平均年增长率(1958—2014年)为(1.43±0.59)mg·L~(–1)·a~(–1),低于同期赤道(1.51±0.72)mg·L~(–1)·a~(–1),但1980—2014年和2000—2014年年增长率均高于南半球中纬度地区。δ~(13)C-CO_2和δ~(18)O-CO_2丰度趋势揭示了化石燃料排放和全球尺度过程对CO_2的影响,但南极是受影响最小的区域。1983—2014年南极CH_4平均增长率为(6.2±4.9)μg·L~(–1)·a~(–1),低于北半球中纬度(6.5±5.6)μg·L~(–1)·a~(–1)而高于赤道(5.6±5.3)μg·L~(–1)·a~(–1)和南半球中纬度(6.1±4.9)μg·L~(–1)·a~(–1),这与CH_4人为排放增强主要在北半球中纬度地区而显著被OH氧化在赤道和中纬度地区的事实是吻合的。南极N_2O平均年增长率为(0.87±0.15)μg·L~(–1)·a~(–1)(2005—2013年),与南半球中纬度地区接近但低于北半球而高于赤道地区。

Baseline trends of atmospheric CO2, CH4, and N2O concentrations in Antarctica

The long-term baseline trends of the atmospheric greenhouse gases (GHGs)CO₂ (including δ¹³C-CO₂and δ¹⁸O-CO₂ abundances),CH₄, andN₂O in Antarctica were compared with those from other latitudinal bands. The results suggest that global concentrations of GHGs increase with latitude from south to north, with the lowest (highest) abundance in Antarctica. The overall long-term trends and annual growth rates of GHGs in Antarctica are consistent with the global values, although the trends or growth rates of a concrete gas in Antarctica may quantitatively differentiate from the global values. During 1958–2014, the average growth rate ofCO₂ concentration in Antarctica (1.43 ± 0.59) mg·L^–1·a^–1 was lower than that in the tropics (1.51 ± 0.72) mg·L^–1·a^–1. Conversely, the average growth rate ofCO₂ concentration in Antarctica during the periods 1980–2014 and 2000–2014 were higher than that in the Southern Hemisphere Middle (SHM) latitudinal band but lower than that in the Northern Hemisphere (NH). The trends of δ¹³C-CO₂ and δ¹⁸O-CO₂ abundance reflect the effects of fossil fuel combustion and global-scale processes on globalCO₂ variations. During 1983–2014, the overall growth rate ofCH₄ concentration in Antarctica (1.43 ± 0.59) µg·L^–1·a^–1 was lower than that in the NH (6.5 ± 5.6) µg·L^–1·a^–1, but higher than that in the tropics (5.6 ± 5.3) µg·L^–1·a^–1 and the SHM (6.1 ± 4.9) µg·L^–1·a^–1. This confirmed the NH as the largest source ofCH₄, and the tropics and SHM as substantialCH₄ sinks via OH oxidation. The overall average growth rate of atmosphericN₂O in Antarctica was (0.87 ± 0.15) µg·L^–1·a^–1 during 2005–2013; lower (higher) than that in the NH (tropics) and very close to that in the SHM. The difference in the growth rate reflects anthropogenic emissions and the latitude-dependence of the vertical structure of the surface boundary layer, which has obvious influence on surface-level behavior of N₂O.