Schlunegger Sarah, Rodgers Keith B, Sarmiento Jorge L, Ilyina Tatiana, Dunne John P, Takano Yohei, Christian James R, Long Matthew C, Frölicher Thomas L, Slater Richard, Lehner Flavio
Program in Atmospheric and Oceanic Sciences Princeton University Princeton NJ USA.
Center for Climate Physics Institute for Basic Science Busan South Korea.
Global Biogeochem Cycles. 2020 Aug;34(8):e2019GB006453. doi: 10.1029/2019GB006453. Epub 2020 Aug 23.
Anthropogenically forced changes in ocean biogeochemistry are underway and critical for the ocean carbon sink and marine habitat. Detecting such changes in ocean biogeochemistry will require quantification of the magnitude of the change (anthropogenic signal) and the natural variability inherent to the climate system (noise). Here we use Large Ensemble (LE) experiments from four Earth system models (ESMs) with multiple emissions scenarios to estimate Time of Emergence (ToE) and partition projection uncertainty for anthropogenic signals in five biogeochemically important upper-ocean variables. We find ToEs are robust across ESMs for sea surface temperature and the invasion of anthropogenic carbon; emergence time scales are 20-30 yr. For the biological carbon pump, and sea surface chlorophyll and salinity, emergence time scales are longer (50+ yr), less robust across the ESMs, and more sensitive to the forcing scenario considered. We find internal variability uncertainty, and model differences in the internal variability uncertainty, can be consequential sources of uncertainty for projecting regional changes in ocean biogeochemistry over the coming decades. In combining structural, scenario, and internal variability uncertainty, this study represents the most comprehensive characterization of biogeochemical emergence time scales and uncertainty to date. Our findings delineate critical spatial and duration requirements for marine observing systems to robustly detect anthropogenic change.
人为导致的海洋生物地球化学变化正在发生，这对海洋碳汇和海洋栖息地至关重要。检测海洋生物地球化学的此类变化将需要量化变化的幅度（人为信号）和气候系统固有的自然变率（噪声）。在此，我们使用来自四个地球系统模型（ESM）的大集合（LE）实验以及多种排放情景，来估计五个对生物地球化学重要的上层海洋变量中人为信号的出现时间（ToE）并划分预测不确定性。我们发现，对于海面温度和人为碳的侵入，ToE在各ESM之间是稳健的；出现时间尺度为20 - 30年。对于生物碳泵、海面叶绿素和盐度，出现时间尺度更长（50年以上），在各ESM之间不太稳健，并且对所考虑的强迫情景更敏感。我们发现内部变率不确定性以及内部变率不确定性中的模型差异，可能是未来几十年预测海洋生物地球化学区域变化时不确定性的重要来源。在综合结构、情景和内部变率不确定性方面，本研究是迄今为止对生物地球化学出现时间尺度和不确定性最全面的描述。我们的研究结果划定了海洋观测系统可靠检测人为变化所需的关键空间和持续时间要求。
