26 research outputs found
Warming drove the Expansion of Marine Anoxia in the Equatorial Atlantic during the Cenomanian Leading up to Oceanic Anoxic Event 2
Oceanic Anoxic Event (OAE) 2 (~93.5 millions of years ago) is characterized by widespread marine anoxia and elevated burial rates of organic matter. However, the factors that led to this widespread marine deoxygenation and the possible link with climatic change remain debated. Here, we report long-term biomarker records of water column anoxia, water column and photic zone euxinia (PZE), and sea surface temperature (SST) from Demerara Rise in the equatorial Atlantic that span 3.8 million years of the late Cenomanian to Turonian, including OAE 2. We find that total organic carbon (TOC) contents are high but variable (0.41–17 wt. %) across the Cenomanian and increase with time. This long-term TOC increase coincides with a TEX86-derived SST increase from ~ 35 to 40 °C as well as the episodic occurrence of 28,30-dinorhopane (DNH) and lycopane, indicating warming and expansion of the oxygen minimum zone (OMZ) predating OAE 2. Water column euxinia persisted through much of the late Cenomanian, as indicated by the presence of C35 hopanoid thiophene, but only reached the photic zone during OAE 2, as indicated by the presence of isorenieratane. Using these biomarker records, we suggest that water column anoxia and euxinia in the equatorial Atlantic preceded OAE 2 and this deoxygenation was driven by global warming.</p
Cenozoic climate reconstructions associated with the formation of Tibet and the biodiversification of terrestrial ecosystems
Proxy evidence for state-dependence of climate sensitivity in the Eocene greenhouse
Despite recent advances, the link between the evolution of atmospheric CO2 and climate during the Eocene greenhouse remains uncertain. In particular, modelling studies suggest that in order to achieve the global warmth that characterised the early Eocene, warmer climates must be more sensitive to CO2 forcing than colder climates. Here, we test this assertion in the geological record by combining a new high-resolution boron isotope-based CO2 record with novel estimates of Global Mean Temperature. We find that Equilibrium Climate Sensitivity (ECS) was indeed higher during the warmest intervals of the Eocene, agreeing well with recent model simulations, and declined through the Eocene as global climate cooled. These observations indicate that the canonical IPCC range of ECS (1.5 to 4.5 °C per doubling) is unlikely to be appropriate for high-CO2 warm climates of the past, and the state dependency of ECS may play an increasingly important role in determining the state of future climate as the Earth continues to warm
The DeepMIP contribution to PMIP4: methodologies for selection, compilation and analysis of latest Paleocene and early Eocene climate proxy data, incorporating version 0.1 of the DeepMIP database
This is the final version of the article. Available from European Geosciences Union via the DOI in this record.Data availability.
The data referenced in this manuscript are provided as Supplement Data Files 1 to 8. In the final version, these files will form DeepMIP database version 0.1 and will be accessible online via a citable DOI reference.The early Eocene (56 to 48 million years ago) is inferred to have been the most recent time that Earth's atmospheric CO2 concentrations exceeded 1000âppm. Global mean temperatures were also substantially warmer than those of the present day. As such, the study of early Eocene climate provides insight into how a super-warm Earth system behaves and offers an opportunity to evaluate climate models under conditions of high greenhouse gas forcing. The Deep Time Model Intercomparison Project (DeepMIP) is a systematic modelâmodel and modelâdata intercomparison of three early Paleogene time slices: latest Paleocene, PaleoceneâEocene thermal maximum (PETM) and early Eocene climatic optimum (EECO). A previous article outlined the model experimental design for climate model simulations. In this article, we outline the methodologies to be used for the compilation and analysis of climate proxy data, primarily proxies for temperature and CO2. This paper establishes the protocols for a concerted and coordinated effort to compile the climate proxy records across a wide geographic range. The resulting climate âatlasâ will be used to constrain and evaluate climate models for the three selected time intervals and provide insights into the mechanisms that control these warm climate states. We provide version 0.1 of this database, in anticipation that this will be expanded in subsequent publications.Natural Environment Research Council (NERC)GNS Science Global Change through Time ProgrammeNational Science Foundation (NSF)KU Leuve
Coupled evolution of temperature and carbonate chemistry during the PaleoceneâEocene; new trace element records from the low latitude Indian Ocean
This is the final version. Available on open access from Elsevier via the DOI in this recordThe early Paleogene represents the most recent interval in Earthâs history characterized by global
greenhouse warmth on multi-million year timescales, yet our understanding of long-term climate and
carbon cycle evolution in the low latitudes, and in particular the Indian Ocean, remains very poorly
constrained. Here we present the first long-term sub-eccentricity-resolution stable isotope (ÎŽ13 30 C and
ÎŽ
18 O) and trace element (Mg/Ca and B/Ca) records spanning the late Paleoceneâearly Eocene (~58â
53 Ma) across a surfaceâdeep hydrographic reconstruction of the northern Indian Ocean, resolving
late Paleocene 405-kyr paced cyclicity and a portion of the PETM recovery. Our new records reveal a
long-term warming of ~4â5°C at all depths in the water column, with absolute surface ocean
temperatures and magnitudes of warming comparable to the low latitude Pacific. As a result of
warming, we observe a long-term increase in ÎŽ
18 Osw of the mixed layer, implying an increase in net
evaporation. We also observe a collapse in the temperature gradient between mixed layer- and
thermocline-dwelling species from ~57â54 Ma, potentially due to either the development of a more
homogeneous water column with a thicker mixed layer, or depth migration of the Morozovella in
response to warming. Synchronous warming at both low and high latitudes, along with decreasing
B/Ca ratios in planktic foraminifera indicating a decrease in ocean pH and/or increasing dissolved
inorganic carbon, suggest that global climate was forced by rising atmospheric CO2 concentrations
during this time.European Consortium for Ocean Research Drilling (ECORD)International Association of Sedimentologists (IAS)NSFNatural Environment Research Council (NERC
The DeepMIP contribution to PMIP4: methodologies for selection, compilation and analysis of latest Paleocene and early Eocene climate proxy data, incorporating version 0.1 of the DeepMIP database
The early Eocene (56 to 48 million years ago) is inferred to have been the most recent time that Earth's atmospheric COâ concentrations exceeded 1000âppm. Global mean temperatures were also substantially warmer than those of the present day. As such, the study of early Eocene climate provides insight into how a super-warm Earth system behaves and offers an opportunity to evaluate climate models under conditions of high greenhouse gas forcing. The Deep Time Model Intercomparison Project (DeepMIP) is a systematic modelâmodel and modelâdata intercomparison of three early Paleogene time slices: latest Paleocene, PaleoceneâEocene thermal maximum (PETM) and early Eocene climatic optimum (EECO). A previous article outlined the model experimental design for climate model simulations. In this article, we outline the methodologies to be used for the compilation and analysis of climate proxy data, primarily proxies for temperature and COâ. This paper establishes the protocols for a concerted and coordinated effort to compile the climate proxy records across a wide geographic range. The resulting climate âatlasâ will be used to constrain and evaluate climate models for the three selected time intervals and provide insights into the mechanisms that control these warm climate states. We provide version 0.1 of this database, in anticipation that this will be expanded in subsequent publications
Late Eoceneearly Oligocene paleoenvironmental changes recorded at Lhe Yunnan southwestern China
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Astronomically tuned age model for the early Eocene carbon isotope events: A new high-resolution delta C-13(benthic) record of ODP Site 1263 between similar to 49 and similar to 54 Ma
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