Expanded oxygen minimum zones during the late Paleocene-early Eocene: Hints from multiproxy comparison and ocean modeling

Xiaoli Zhou, Ellen Thomas, A. Winguth, A. Ridgwell, H. Scher, B. Hoogakker, R. Rickaby, Zunli Lu
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引用次数: 38

Abstract

Anthropogenic warming could well drive depletion of oceanic oxygen in the future. Important insight into the relationship between deoxygenation and warming can be gleaned from the geological record, but evidence is limited because few ocean oxygenation records are available for past greenhouse climate conditions. We use I/Ca in benthic foraminifera to reconstruct late Paleocene through early Eocene bottom and pore water redox conditions in the South Atlantic and Southern Indian Oceans and compare our results with those derived from Mn speciation and the Ce anomaly in fish teeth. We conclude that waters with lower oxygen concentrations were widespread at intermediate depths (1.5–2 km), whereas bottom waters were more oxygenated at the deepest site, in the Southeast Atlantic Ocean (>3 km). Epifaunal benthic foraminiferal I/Ca values were higher in the late Paleocene, especially at low-oxygen sites, than at well-oxygenated modern sites, indicating higher seawater total iodine concentrations in the late Paleocene than today. The proxy-based bottom water oxygenation pattern agrees with the site-to-site O2 gradient as simulated in a comprehensive climate model (Community Climate System Model Version 3), but the simulated absolute dissolved O2 values are low (< ~35 µmol/kg), while higher O2 values (~60–100 µmol/kg) were obtained in an Earth system model (Grid ENabled Integrated Earth system model). Multiproxy data together with improvements in boundary conditions and model parameterization are necessary if the details of past oceanographic oxygenation are to be resolved.
古新世晚期-始新世早期氧最小带扩展:来自多代理比较和海洋模拟的提示
未来,人为变暖很可能会导致海洋氧气的消耗。从地质记录中可以收集到关于脱氧和变暖之间关系的重要见解,但证据有限,因为很少有关于过去温室气候条件的海洋脱氧记录。我们利用底栖有孔虫的I/Ca重建了南大西洋和南印度洋晚古新世至早始新世的底部和孔隙水氧化还原条件,并将我们的结果与Mn物种形成和鱼齿中Ce异常的结果进行了比较。我们的结论是,氧浓度较低的水域在中深度(1.5-2 km)广泛存在,而在最深的地方,在东南大西洋(bbb30 km),底部水域的氧浓度较高。古新世晚期底栖有孔虫I/Ca值高于富氧地区,特别是低氧地区,表明古新世晚期海水总碘浓度高于今天。基于代理的底水氧合模式与综合气候模式(3版社区气候系统模式)模拟的站点间O2梯度一致,但模拟的绝对溶解O2值较低(< ~35µmol/kg),而地球系统模式(Grid ENabled Integrated Earth System model)模拟的O2值较高(~60 ~ 100µmol/kg)。如果要解决过去海洋氧合的细节问题,就需要多代理数据以及边界条件和模式参数化的改进。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Paleoceanography
Paleoceanography 地学-地球科学综合
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