Proxy‐Model Comparison for the Eocene‐Oligocene Transition in Southern High Latitudes

IF 3.2 2区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Paleoceanography and Paleoclimatology Pub Date : 2023-01-25 DOI:10.1029/2022PA004496

E. J. Tibbett, N. Burls, D. Hutchinson, S. Feakins

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引用次数: 1

Abstract

The Eocene‐Oligocene transition (EOT) marks the shift from greenhouse to icehouse conditions at 34 Ma, when a permanent ice sheet developed on Antarctica. Climate modeling studies have recently assessed the drivers of the transition globally. Here we revisit those experiments for a detailed study of the southern high latitudes in comparison to the growing number of mean annual sea surface temperature (SST) and mean air temperature (MAT) proxy reconstructions, allowing us to assess proxy‐model temperature agreement and refine estimates for the magnitude of the pCO2 forcing of the EOT. We compile and update published proxy temperature records on and around Antarctica for the late Eocene (38–34 Ma) and early Oligocene (34–30 Ma). Compiled SST proxies cool by up to 3°C and MAT by up to 4°C between the timeslices. Proxy data were compared to previous climate model simulations representing pre‐ and post‐EOT, typically forced with a halving of pCO2. We scaled the model outputs to identify the magnitude of pCO2 change needed to drive a commensurate change in temperature to best fit the temperature proxies. The multi‐model ensemble needs a 30 or 33% decrease in pCO2, to best fit MAT or SST proxies respectively. These proxy‐model intercomparisons identify declining pCO2 as the primary forcing of EOT cooling, with a magnitude (200 or 243 ppmv) approaching that of the pCO2 proxies (150 ppmv). However individual model estimates span a decrease of 66–375 ppmv, thus proxy‐model uncertainties are dominated by model divergence.

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南部高纬度始新世-渐新世过渡的代理模型比较

始新世-渐新世过渡（EOT）标志着34 Ma时从温室条件转变为冰库条件，当时南极洲形成了永久性冰盖。气候建模研究最近评估了全球转型的驱动因素。在这里，我们重新审视了这些实验，以对南部高纬度地区进行详细研究，并与越来越多的年平均海面温度（SST）和平均气温（MAT）替代重建进行了比较，使我们能够评估替代模型温度一致性，并完善EOT pCO2强迫幅度的估计。我们汇编并更新了已发表的始新世晚期（38-34 Ma）和渐新世早期（34-30 Ma）南极洲及其周围的代理温度记录。编译的SST代理在时间片之间冷却高达3°C，MAT冷却高达4°C。将代理数据与之前代表EOT前后的气候模型模拟进行了比较，通常会强制将pCO2减半。我们对模型输出进行了缩放，以确定驱动温度相应变化所需的pCO2变化幅度，从而最适合温度代理。多模型系综需要pCO2减少30%或33%，以分别最佳拟合MAT或SST代理。这些代理模型相互比较确定，pCO2下降是EOT冷却的主要原因，其幅度（200或243 ppmv）接近pCO2代理（150 ppmv）。然而，单个模型估计值的降幅为66–375 ppmv，因此代理模型的不确定性主要由模型偏差决定。

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来源期刊

Paleoceanography and Paleoclimatology Earth and Planetary Sciences-Atmospheric Science

CiteScore

6.20

自引率

11.40%

发文量

107

期刊介绍： Paleoceanography and Paleoclimatology (PALO) publishes papers dealing with records of past environments, biota and climate. Understanding of the Earth system as it was in the past requires the employment of a wide range of approaches including marine and lacustrine sedimentology and speleothems; ice sheet formation and flow; stable isotope, trace element, and organic geochemistry; paleontology and molecular paleontology; evolutionary processes; mineralization in organisms; understanding tree-ring formation; seismic stratigraphy; physical, chemical, and biological oceanography; geochemical, climate and earth system modeling, and many others. The scope of this journal is regional to global, rather than local, and includes studies of any geologic age (Precambrian to Quaternary, including modern analogs). Within this framework, papers on the following topics are to be included: chronology, stratigraphy (where relevant to correlation of paleoceanographic events), paleoreconstructions, paleoceanographic modeling, paleocirculation (deep, intermediate, and shallow), paleoclimatology (e.g., paleowinds and cryosphere history), global sediment and geochemical cycles, anoxia, sea level changes and effects, relations between biotic evolution and paleoceanography, biotic crises, paleobiology (e.g., ecology of “microfossils” used in paleoceanography), techniques and approaches in paleoceanographic inferences, and modern paleoceanographic analogs, and quantitative and integrative analysis of coupled ocean-atmosphere-biosphere processes. Paleoceanographic and Paleoclimate studies enable us to use the past in order to gain information on possible future climatic and biotic developments: the past is the key to the future, just as much and maybe more than the present is the key to the past.