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The changing carbon cycle at Mauna Loa Observatory

机译：莫纳罗阿天文台的不断变化的碳循环

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The amplitude of the CO_2 seasonal cycle at the Mauna Loa Observatory (MLO) increased from the early 1970s to the early 1990s but decreased thereafter despite continued warming over northern continents. Because of its location relative to the large-scale atmospheric circulation, the MLO receives mainly Eurasian air masses in the northern hemisphere (NH) winter but relatively more North American air masses in NH summer. Consistent with this seasonal footprint, our findings indicate that the MLO amplitude registers North American net carbon uptake during the warm season and Eurasian net carbon release as well as anomalies in atmospheric circulation during the cold season. From the early 1970s to the early 1990s, our analysis was consistent with that of Keeling et al. [Keeling CD, Chin JFS, Whorf TP (1996) Nature 382:146-149], suggesting that the increase in the MLO CO_2 amplitude is dominated by enhanced photosynthetic drawdown in North America and enhanced respiration in Eurasia. In contrast, the recent decline in the CO_2 amplitude is attributed to reductions in carbon sequestration over North America associated with severe droughts from 1998 to 2003 and changes in atmospheric circulation leading to decreased influence of Eurasian air masses. With the return of rains to the U.S. in 2004, both the normalized difference vegetation index and the MLO amplitude sharply increased, suggesting a return of the North American carbon sink to more normal levels. These findings indicate that atmospheric CO_2 measurements at remote sites can continue to play an important role in documenting changes in land carbon flux, including those related to widespread drought, which may continue to worsen as a result of global warming.
机译：莫纳洛阿天文台（MLO）的CO_2季节性周期的振幅从1970年代初到1990年代初有所增加，但是尽管北部大陆持续变暖，但其后下降了。由于其相对于大规模大气环流的位置，MLO在北半球冬季主要接收欧亚气团，但在NH夏季则接收较多的北美气团。与这一季节性足迹一致，我们的发现表明，MLO幅度记录了在暖季和北美欧亚净碳释放以及在寒冷季节大气环流异常期间北美净碳吸收。从1970年代初到1990年代初，我们的分析与Keeling等人的分析一致。 [Keeling CD，Chin JFS，Whorf TP（1996）Nature 382：146-149]，表明MLO CO_2振幅的增加主要由北美的光合作用下降和欧亚大陆的呼吸增强所决定。相反，最近CO_2振幅的下降归因于北美地区1998年至2003年严重干旱造成的碳固存减少，以及大气环流变化导致欧亚空气质量影响降低。随着2004年降雨返回美国，归一化差异植被指数和MLO振幅均急剧增加，这表明北美碳汇已恢复到更正常的水平。这些发现表明，偏远地区的大气CO_2测量在记录土地碳通量的变化（包括那些与广泛干旱有关的变化）方面可以继续发挥重要作用，由于全球变暖，干旱可能继续恶化。

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