2022-08-17 カリフォルニア大学リバーサイド校(UCR)
この酸素と栄養素の循環が突然停止する可能性があることが、研究者らによって新たに明らかにされた。研究者たちは、複雑なコンピューターモデルを使って、大陸プレートの位置が海の酸素の移動に影響を与えるかどうかを調べた。その結果、大陸プレートの位置が酸素の移動に影響を及ぼしていることがわかった。
この研究では、海洋を3次元で表現し、海流を考慮したモデルを初めて使用した。地球規模の水循環の崩壊により、上層と下層で酸素濃度が大きく異なることが明らかになった。
＜関連情報＞
- https://news.ucr.edu/articles/2022/08/17/sleeping-giant-could-end-deep-ocean-life
- https://www.nature.com/articles/s41586-022-05018-z
大陸配置が支配する新生代海洋酸素供給量Continental configuration controls ocean oxygenation during the Phanerozoic
Alexandre Pohl,Andy Ridgwell,Richard G. Stockey,Christophe Thomazo,Andrew Keane,Emmanuelle Vennin & Christopher R. Scotes
Nature Published:17 August 2022
DOI:https://doi.org/10.1038/s41586-022-05018-z
Abstract
The early evolutionary and much of the extinction history of marine animals is thought to be driven by changes in dissolved oxygen concentrations ([O2]) in the ocean1,2,3. In turn, [O2] is widely assumed to be dominated by the geological history of atmospheric oxygen (pO2)4,5. Here, by contrast, we show by means of a series of Earth system model experiments how continental rearrangement during the Phanerozoic Eon drives profound variations in ocean oxygenation and induces a fundamental decoupling in time between upper-ocean and benthic [O2]. We further identify the presence of state transitions in the global ocean circulation, which lead to extensive deep-ocean anoxia developing in the early Phanerozoic even under modern pO2. Our finding that ocean oxygenation oscillates over stable thousand-year (kyr) periods also provides a causal mechanism that might explain elevated rates of metazoan radiation and extinction during the early Palaeozoic Era6. The absence, in our modelling, of any simple correlation between global climate and ocean ventilation, and the occurrence of profound variations in ocean oxygenation independent of atmospheric pO2, presents a challenge to the interpretation of marine redox proxies, but also points to a hitherto unrecognized role for continental configuration in the evolution of the biosphere.
