冰川旋回中的Ca循环与C循环初探

Circulation of Ca and C in Hydrosphere,Atmosphere and Biosphere during Glacial-Interglacial Cycle

钙同位素是近20a来才被人们关注的海洋中阳离子同位素,通过对东北印度洋近30万a来冰川旋回中浮游有孔虫Globigerinoides sacculifer壳体δ44Ca的研究,并与δ18O和δ13C的对比分析给出了冰川旋回中水圈、气圈、生物圈的Ca循环和C循环的一般模式:当大洋生产力升高时,由于海洋生物构建硬体的需要取走大量CaCO3,生物固定Ca2+和CO2的"泵"功能增强,海水中δ44Ca值升高,引起大气CO2浓度降低,促进了全球气候变冷;当大洋生产力降低、生物总量减少时,生物对Ca同位素分馏的弱化和对CO2需求的减少,必然导致大洋海水中δ44Ca值降低和CO2浓度的升高,大量CO2逸出海面,作为全球CO2的"源"促使大气中CO2浓度升高。

The calcium isotope, a kind of marine cation isotope, has attracted attentions in recent two decades. This essay shows the circulation of Ca and C in hydrosphere, atmosphere and biosphere during glacial-interglacial cycle, with researching and contrasting on δ^44Ca, δ^18O and δ^13C of foraminifera shell Globigerinoides sacculifer in Northeast Indian Ocean in recent 300 thousand years. The common pattern is that with the productivity increasing, the marine creatures absorb a large amount of CaCO3 from oceans to form their organism and skeleton, which enhances the ＂pump＂ function of fixing Ca^2＋ and CO2. Consequently, the value of δ^44Ca in oceans increases and the consistency of CO2 in the air reduces, which make the globe cooler. When the productivity of oceans decreases, the number of creatures reduces. Meanwhile, the fractionation of Ca isotope weakens and the demand of CO2 reduces, which brings about the drop of δ^44Ca value and the increase of CO2 consistency in oceans. Consequently, a large amount of CO2 escapes from the sea as the source of CO2 in the globe which promotes the rise of CO2 consistency in the air.