Does Terrestrial Drought Explain Global CO2 Flux Anomalies Induced by El Nino
Does Terrestrial Drought Explain Global CO2 Flux Anomalies Induced by El Nino
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DOI：
10.5194/bg-8-2493-2011
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发表时间：
2011-09
期刊：
影响因子：
4.9
通讯作者：
C. Schwalm;C. Williams;K. Schaefer;I. Baker;G. Collatz;C. Rödenbeck
中科院分区：
文献类型：
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作者：
C. Schwalm;C. Williams;K. Schaefer;I. Baker;G. Collatz;C. Rödenbeck
摘要。厄尔尼诺-南方涛动是全球气候年际变化的主要模式。厄尔尼诺现象对陆地碳循环的影响是由相关的气候异常介导的，主要是干旱，影响火灾排放和生物净生态系统交换（NEE）。在这里，我们评估厄尔尼诺是否从全球碳循环中产生一致的响应。我们采用一种新颖的自下而上的方法，基于FLUXNET数据，利用土地覆盖图和天气再分析来估计全球新东东距平。我们分析了13年（1997-2009）全球网格化观测的东北电距平数据，这些距平数据来自涡动相关通量数据、每月时间步长的遥感火排放，以及由大气输送反演估算的东北电距平数据。我们评估了生物圈对厄尔尼诺反应的总体一致性，以及更普遍的全球二氧化碳通量异常与厄尔尼诺引起的干旱之间的联系。我们的研究结果表明，在亚马逊、澳大利亚和南部非洲，每个事件都有不同的空间特征，只有有限的空间一致性。相对于方法和响应滞后的不确定性，我们的研究结果是稳健的。对于大多数地区来说，在厄尔尼诺事件期间，响应信号发生了变化。在5次厄尔尼诺事件中，生物东北东电异常的幅度在-1.34至+0.98 Pg C /年−1之间，而火排放异常的幅度通常较小（范围在-0.49至+0.53 Pg C /年−1之间）。在厄尔尼诺期间，总体干旱似乎不会造成一致的陆地二氧化碳通量异常，全球综合响应在-1.15至+0.49 Pg C /年−1之间变化很大。尽管CO2通量与厄尔尼诺指数之间存在显著的相关性，但我们发现，从全球综合来看，厄尔尼诺事件既增强了陆地汇强度，也减弱了陆地汇强度，但在不同事件之间没有一致的响应。
Abstract. The El Nino Southern Oscillation is the dominant year-to-year mode of global climate variability. El Nino effects on terrestrial carbon cycling are mediated by associated climate anomalies, primarily drought, influencing fire emissions and biotic net ecosystem exchange (NEE). Here we evaluate whether El Nino produces a consistent response from the global carbon cycle. We apply a novel bottom-up approach to estimating global NEE anomalies based on FLUXNET data using land cover maps and weather reanalysis. We analyze 13 years (1997–2009) of globally gridded observational NEE anomalies derived from eddy covariance flux data, remotely-sensed fire emissions at the monthly time step, and NEE estimated from an atmospheric transport inversion. We evaluate the overall consistency of biospheric response to El Nino and, more generally, the link between global CO2 flux anomalies and El Nino-induced drought. Our findings, which are robust relative to uncertainty in both methods and time-lags in response, indicate that each event has a different spatial signature with only limited spatial coherence in Amazonia, Australia and southern Africa. For most regions, the sign of response changed across El Nino events. Biotic NEE anomalies, across 5 El Nino events, ranged from –1.34 to +0.98 Pg C yr−1, whereas fire emissions anomalies were generally smaller in magnitude (ranging from –0.49 to +0.53 Pg C yr−1). Overall drought does not appear to impose consistent terrestrial CO2 flux anomalies during El Ninos, finding large variation in globally integrated responses from –1.15 to +0.49 Pg C yr−1. Despite the significant correlation between the CO2 flux and El Nino indices, we find that El Nino events have, when globally integrated, both enhanced and weakened terrestrial sink strength, with no consistent response across events.