Robust Constraints on Past CO 2 Climate Forcing From the Boron Isotope Proxy
Robust Constraints on Past CO 2 Climate Forcing From the Boron Isotope Proxy
复制标题
硼同位素代理对过去 CO 2 气候强迫的严格约束
DOI：
10.1029/2018pa003362
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发表时间：
2018
影响因子：
3.5
通讯作者：
Hain M
中科院分区：
文献类型：
--
作者：
Hain M
温室气体二氧化碳（CO2）的大气浓度与海水的碳化学密切相关，因此，CO2的辐射气候强迫可以通过一系列物理，地球化学和生物海洋过程来改变。例如，生物固碳、海水冷却和碳酸钙净溶解通常被认为是二氧化碳变化的主要驱动力，这些变化放大了晚更新世轨道节奏的冰河时代周期。基于海洋化学的第一性原理论证，我们证明海水pH变化（ΔpH）是有效地将CO2辐射强迫（ΔF）设置在轨道时间尺度上的主要控制因素，这一点从独立的晚更新世pH和CO2重建中可以看出。简而言之，在轨道时间尺度上，所有与CO2相关的过程，包括温度变化，都会引起pH的变化，从而导致CO2的变化，从而产生ΔpH与CO2气候强迫的线性关系。此外，我们表明，即使海水硼同位素组成的约束不佳，没有第二个碳酸盐系统参数的信息，ΔpH和CO2气候强迫可以重建使用硼同位素pH代理比绝对pH或CO2更准确。因此，我们的形式主义放松，否则必要的假设，使准确确定轨道时间尺度的CO2辐射强迫硼同位素pH重建单独，从而消除了目前的方法来估计我们的地球的气候敏感性的地质记录的主要限制。
The atmospheric concentration of the greenhouse gas carbon dioxide, CO2, is intimately coupled to the carbon chemistry of seawater, such that the radiative climate forcing from CO2can be changed by an array of physical, geochemical, and biological ocean processes. For instance, biological carbon sequestration, seawater cooling, and net CaCO3dissolution are commonly invoked as the primary drivers of CO2change that amplify the orbitally paced ice age cycles of the late Pleistocene. Based on first‐principle arguments with regard to ocean chemistry, we demonstrate that seawater pH change (ΔpH) is the dominant control that effectively sets CO2radiative forcing (ΔF) on orbital timescales, as is evident from independent late Pleistocene reconstructions of pH and CO2. In short, all processes relevant for CO2on orbital timescales, including temperature change, cause pH to change to bring about fractional CO2change so as to yield a linear relationship of ΔpH to CO2climate forcing. Further, we show that ΔpH and CO2climate forcing can be reconstructed using the boron isotope pH proxy more accurately than absolute pH or CO2, even if seawater boron isotope composition is poorly constrained and without information on a second carbonate system parameter. Thus, our formalism relaxes otherwise necessary assumptions to allow the accurate determination of orbital timescale CO2radiative forcing from boron isotope pH reconstructions alone, thereby eliminating a major limitation of current methods to estimate our planet's climate sensitivity from the geologic record.