Opening the gateways for diatoms primes Earth for Antarctic glaciation
Opening the gateways for diatoms primes Earth for Antarctic glaciation
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DOI：
10.1016/j.epsl.2013.04.030
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发表时间：
2013-08-01
影响因子：
5.3
通讯作者：
Halliday, Alex N.
中科院分区：
文献类型：
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作者：
Egan, Katherine E.;Rickaby, Rosalind E. M.;Halliday, Alex N.
南极冰川在始新世-渐新世过渡期间的突然开始(类似于33.7 Ma，OI1)与大气中PCO(2)水平的下降有关，但迫使PCO(2)下降的机制仍然不清楚。生物硅循环与硅藻的长期和短期碳循环密不可分，硅藻是硅质壁状自养生物，如今占初级产量的40%。据推测，在始新世晚期，硅藻丰度的急剧上升可能通过增加埋藏在海洋沉积物中的有机碳比例而导致PCO(2)下降和全球变冷。本文首次将硅藻和海绵硅同位素比值(Si-30)结合起来，重建了始新世晚期-渐新世早期的大洋硅旋回，并对硅藻生产力在南极冰川中的作用提供了新的认识。在南大洋的ODP1090站位，硅藻增量Si-30在始新世晚期的千分之0.6的上升证明了硅藻硅酸利用率的增加，在最早的渐新世达到了接近现代的高价值。伴随而来的是莫德隆起689号ODP点海绵三角洲Si-30的千分之1.5的下降，这表明南部高纬度地区的中层硅酸浓度大约增加了一倍。中深度硅酸浓度达到峰值的时间约为31.5 Ma，与最终建立通过塔斯曼门和德雷克海峡的深水通道相吻合。这些结果表明，与环南极洋流自旋有关的上升流加强可能推动了始新世晚期硅藻的扩散。有机碳埋藏与较高的硅藻丰度和出口相关，提供了一种机制，不仅可以解释PCO(2)冰盖生长的PCO(2)“阈值”机制所要求的PCO(2)下降，而且还可以解释南极冰川之前的PCO(2)下降。(C)2013年提交人。爱思唯尔出版，版权所有。
The abrupt onset of Antarctic glaciation during the Eocene-Oligocene Transition (similar to 33.7 Ma, Oi1) is linked to declining atmospheric pCO(2) levels, yet the mechanisms that forced pCO(2) decline remain elusive. Biogenic silicon cycling is inextricably linked to both long and short term carbon cycling through the diatoms, siliceous walled autotrophs which today account for up to 40% of primary production. It is hypothesised that during the Late Eocene a sharp rise in diatom abundance could have contributed to pCO(2) drawdown and global cooling by increasing the proportion of organic carbon buried in marine sediment. Diatom and sponge silicon isotope ratios (delta Si-30) are here combined for the first time to reconstruct the late Eocene-early Oligocene ocean silicon cycle and provide new insight into the role of diatom productivity in Antarctic glaciation. At ODP site 1090 in the Southern Ocean, a 0.6 parts per thousand rise in diatom delta Si-30 through the late Eocene documents increasing diatom silicic acid utilisation with high, near modern values attained by the earliest Oligocene. A concomitant 1.5 parts per thousand decline in sponge delta Si-30 at ODP site 689 on the Maud Rise tracks an approximate doubling of intermediate depth silicic acid concentration in the high southern latitudes. Intermediate depth silicic acid concentration peaked at similar to 31.5 Ma, coincident with the final establishment of a deepwater pathway through the Tasman Gateway and Drake Passage. These results suggest that upwelling intensification related to the spin-up of a circum-Antarctic current may have driven late Eocene diatom proliferation. Organic carbon burial associated with higher diatom abundance and export provides a mechanism that can account for pCO(2) drawdown not only at, but also prior to, Antarctic glaciation as required by a pCO(2) 'threshold' mechanism for ice sheet growth. (c) 2013 The Authors. Published by Elsevier B.V. All rights reserved.