Fatima Abrantes, DivGM, Instituto Português do Mar e da Atmosfera, Portugal (fatima.abrantes@ipma... more Fatima Abrantes, DivGM, Instituto Português do Mar e da Atmosfera, Portugal ([email protected]) Fatima Abrantes, IPMA and CCMAR, Portugal; Teresa Rodrigues, IPMA and CCMAR, Portugal; Cristina Ventura, IPMA and CIMAR, Portugal; Célia Santos, IPMA and CCMAR, Portugal; Baohua Li, Nanjing Institute of Geology and Palaeontology Academia Sinica, China; Jin-Kyoung Kim, Korea Institute of Ocean Science and Technology, Korea; Ursula Röhl, MARUM – Center for Marine Environmental Sciences, University of Bremen, Germany; Antje Voelker, IPMA and CCMAR, Portugal; David Hodell, Cambridge University, UK.
The early Eocene (56 to 48 million years ago) is inferred to have been the most recent time that ... more 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 1000 ppm. Global mean temperatures were also substantially warmer than present day. As such, 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 model-model and model-data intercomparison of three early Paleogene time slices: latest Paleocene, Paleocene-Eocene thermal maximum and early Eocene climatic optimum. 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 "atlas" 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. predicting our future climate. Similarly, differences between models and data could indicate aspects of models and/or data that require further development. This is the rationale behind DeepMIP-the Deep-time Model Intercomparison Project (www.deepmip.org)-which brings together climate modellers and paleoclimate scientists from a wide range of disciplines in a coordinated, international effort to improve understanding of the climate of these time intervals, to improve the skill of climate models, and to improve the accuracy and precision of climate proxies. The term "Deep-time" as applied here refers to the history of the Earth prior to the Pliocene, i.e. prior to about 5 million years ago (Ma). DeepMIP is a working group in the wider Paleoclimate Modelling Intercomparison Project (PMIP4), which itself is a part of the sixth phase of the Coupled Model Intercomparison Project (CMIP6). In DeepMIP, we focus on three warm greenhouse time periods in the latest Paleocene and early Eocene (~57-48 Ma), and for the first time, carry out a formal coordinated model-model and model-proxy intercomparison. We have previously outlined the model experimental design of this project (Lunt et al., 2017). Here we outline the recommended methodologies for selection, compilation and analysis of climate proxy data sets for three selected time intervals: latest Paleocene (LP), Paleocene-Eocene thermal maximum (PETM) and early Eocene climatic optimum (EECO). Section 2 outlines previous compilations, and Section 3 formally defines the time periods of interest. Sections 4 and 5 describe the proxies for sea surface and land air temperature (SST and LAT), respectively. Section 6 describes the proxies for atmospheric carbon dioxide (CO2). For each proxy, we highlight their underlying mechanisms, their strengths and weaknesses, and recommendations for analytical methodologies. We focus on temperature in this article because it is the most commonly and readily reconstructed climatic variable and it is one of the best represented variables in climate models. When combined with CO2, it allows assessment of climate sensitivity, a key metric of climate models. However, the DeepMIP database will provide a structure for future compilations of other climate proxies, such as precipitation, evaporation, salinity, upwelling, bathymetry, circulation, currents and vegetation cover, but these are not discussed or compiled here. Section 7 outlines the structure of the planned DeepMIP database, which will accommodate the data presented in Supplementary Data Files 2-7 (which constitute Version 0.1 of the database) and additional datasets as they become available. Section 8 presents a preliminary synthesis of the paleotemperature data from these tables and includes a discussion of the geographic coverage and quality of existing paleotemperature data for the three selected time intervals. 2 Previous climate proxy compilations The first global climate proxy compilations for the Cenozoic were based on deep-sea records of stable isotopes from benthic
During the early Pliocene a dynamic marine-based ice sheet retreated from the Wilkes Land margin ... more During the early Pliocene a dynamic marine-based ice sheet retreated from the Wilkes Land margin with periodic ice advances beyond Last Glacial Maximum position. A change in sand provenance is indicative of a more stable Mertz Glacier system during the Late Pleistocene. East Antarctic Ice Sheet (EAIS) dynamics were evaluated through the analysis of marine diamictons from Integrated Ocean Drilling Program (IODP) site U1358 on the Adélie Land continental shelf. The warmer than present conditions of the early Pliocene coupled with the site's proximity to the landward sloping Wilkes Subglacial Basin provided the rationale for the investigations at this site. Based on visual core descriptions, particle size distributions, and major and trace element ratios, we interpret the origin of lower Pliocene strata by intermittent glaciomarine sedimentation with open-marine conditions and extensive glacial advances to the outer shelf. Heavy mineral analyses show that sand-sized detritus in the...
Our study addresses fundamental questions of the mode and timing of orbital and millennial-scale ... more Our study addresses fundamental questions of the mode and timing of orbital and millennial-scale changes in the meridional overturning circulation (MOC) of the subarctic North Pacific. Particular concerns are the vertical mixing, the present and past abundance of nutrients in surface waters despite strong stratification, and the North Pacific-North Atlantic seesaw of oscillations in sea surface temperature (SST). We do this by generating and interpreting multiple records for glacial terminations I-V down two long piston cores, one each from the western and eastern subarctic Pacific. Chlorins and biogenic opal are proxies for surface water productivity; d 13 C of epibenthic foraminifera is a record of deepwater ventilation; and the d 13 C of N. pachyderma sin. is a tracer of nutrients in subsurface waters that extend up to the sea surface during times of vertical mixing. The degree of mixing is traced by pairing SST and d 18 O records of planktic surface and subsurface (pycnocline) dwellers. Tight age control is deduced from a suite of age-calibrated 14 C plateau boundaries for Termination I and benthic d 18 O and geomagnetic events for the last 800 ka. Carbon 14 paleoreservoir ages record the ages of surface and deep waters to uncover short-term changes in MOC over Termination I. We have defined a standard sequence of short-term productivity events for Termination I, also evident during terminations II to V and subsequent interglacials over the last 450 ka. The peak glacial regime of stable stratification and low productivity terminated, together with the end of ice rafting and melting, near 17 ka, $2000 years after the onset of Termination I. Pulses of vertical mixing and incursion of warm surface waters from the subtropics followed. Convected young water masses finally penetrated down to 3600-m water depth at 17.0 to less than 14.5 ka, significantly improving bottom water ventilation through the late deglacial and earliest interglacial. Mixing with upwelled nutrients from the pycnocline induced short-term maxima in algal production of chlorins and biogenic opal near 17-15 and 15-12 ka, respectively. Deglacial meltwater incursions in the Aleutian Current and silica input from North American rivers also promoted East Pacific productivity after 15.5 ka. Productivity decreased during the late deglacial and early interglacial, coeval with an exceptional peak in CaCO 3 preservation caused by both low organic flux and well-ventilated deepwater. Subsequently, low salinity and cool surface waters and in turn, stratification were gradually restored. A second, opaldominated productivity maximum marked the ends of interglacials. The deglacial pulses of vertical mixing around 17-11 ka imply an important contribution of the North Pacific to the coeval release of oceanic CO 2 into the atmosphere and support the east-west seesaw model of climate change.
Fatima Abrantes, DivGM, Instituto Português do Mar e da Atmosfera, Portugal (fatima.abrantes@ipma... more Fatima Abrantes, DivGM, Instituto Português do Mar e da Atmosfera, Portugal ([email protected]) Fatima Abrantes, IPMA and CCMAR, Portugal; Teresa Rodrigues, IPMA and CCMAR, Portugal; Cristina Ventura, IPMA and CIMAR, Portugal; Célia Santos, IPMA and CCMAR, Portugal; Baohua Li, Nanjing Institute of Geology and Palaeontology Academia Sinica, China; Jin-Kyoung Kim, Korea Institute of Ocean Science and Technology, Korea; Ursula Röhl, MARUM – Center for Marine Environmental Sciences, University of Bremen, Germany; Antje Voelker, IPMA and CCMAR, Portugal; David Hodell, Cambridge University, UK.
The early Eocene (56 to 48 million years ago) is inferred to have been the most recent time that ... more 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 1000 ppm. Global mean temperatures were also substantially warmer than present day. As such, 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 model-model and model-data intercomparison of three early Paleogene time slices: latest Paleocene, Paleocene-Eocene thermal maximum and early Eocene climatic optimum. 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 "atlas" 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. predicting our future climate. Similarly, differences between models and data could indicate aspects of models and/or data that require further development. This is the rationale behind DeepMIP-the Deep-time Model Intercomparison Project (www.deepmip.org)-which brings together climate modellers and paleoclimate scientists from a wide range of disciplines in a coordinated, international effort to improve understanding of the climate of these time intervals, to improve the skill of climate models, and to improve the accuracy and precision of climate proxies. The term "Deep-time" as applied here refers to the history of the Earth prior to the Pliocene, i.e. prior to about 5 million years ago (Ma). DeepMIP is a working group in the wider Paleoclimate Modelling Intercomparison Project (PMIP4), which itself is a part of the sixth phase of the Coupled Model Intercomparison Project (CMIP6). In DeepMIP, we focus on three warm greenhouse time periods in the latest Paleocene and early Eocene (~57-48 Ma), and for the first time, carry out a formal coordinated model-model and model-proxy intercomparison. We have previously outlined the model experimental design of this project (Lunt et al., 2017). Here we outline the recommended methodologies for selection, compilation and analysis of climate proxy data sets for three selected time intervals: latest Paleocene (LP), Paleocene-Eocene thermal maximum (PETM) and early Eocene climatic optimum (EECO). Section 2 outlines previous compilations, and Section 3 formally defines the time periods of interest. Sections 4 and 5 describe the proxies for sea surface and land air temperature (SST and LAT), respectively. Section 6 describes the proxies for atmospheric carbon dioxide (CO2). For each proxy, we highlight their underlying mechanisms, their strengths and weaknesses, and recommendations for analytical methodologies. We focus on temperature in this article because it is the most commonly and readily reconstructed climatic variable and it is one of the best represented variables in climate models. When combined with CO2, it allows assessment of climate sensitivity, a key metric of climate models. However, the DeepMIP database will provide a structure for future compilations of other climate proxies, such as precipitation, evaporation, salinity, upwelling, bathymetry, circulation, currents and vegetation cover, but these are not discussed or compiled here. Section 7 outlines the structure of the planned DeepMIP database, which will accommodate the data presented in Supplementary Data Files 2-7 (which constitute Version 0.1 of the database) and additional datasets as they become available. Section 8 presents a preliminary synthesis of the paleotemperature data from these tables and includes a discussion of the geographic coverage and quality of existing paleotemperature data for the three selected time intervals. 2 Previous climate proxy compilations The first global climate proxy compilations for the Cenozoic were based on deep-sea records of stable isotopes from benthic
During the early Pliocene a dynamic marine-based ice sheet retreated from the Wilkes Land margin ... more During the early Pliocene a dynamic marine-based ice sheet retreated from the Wilkes Land margin with periodic ice advances beyond Last Glacial Maximum position. A change in sand provenance is indicative of a more stable Mertz Glacier system during the Late Pleistocene. East Antarctic Ice Sheet (EAIS) dynamics were evaluated through the analysis of marine diamictons from Integrated Ocean Drilling Program (IODP) site U1358 on the Adélie Land continental shelf. The warmer than present conditions of the early Pliocene coupled with the site's proximity to the landward sloping Wilkes Subglacial Basin provided the rationale for the investigations at this site. Based on visual core descriptions, particle size distributions, and major and trace element ratios, we interpret the origin of lower Pliocene strata by intermittent glaciomarine sedimentation with open-marine conditions and extensive glacial advances to the outer shelf. Heavy mineral analyses show that sand-sized detritus in the...
Our study addresses fundamental questions of the mode and timing of orbital and millennial-scale ... more Our study addresses fundamental questions of the mode and timing of orbital and millennial-scale changes in the meridional overturning circulation (MOC) of the subarctic North Pacific. Particular concerns are the vertical mixing, the present and past abundance of nutrients in surface waters despite strong stratification, and the North Pacific-North Atlantic seesaw of oscillations in sea surface temperature (SST). We do this by generating and interpreting multiple records for glacial terminations I-V down two long piston cores, one each from the western and eastern subarctic Pacific. Chlorins and biogenic opal are proxies for surface water productivity; d 13 C of epibenthic foraminifera is a record of deepwater ventilation; and the d 13 C of N. pachyderma sin. is a tracer of nutrients in subsurface waters that extend up to the sea surface during times of vertical mixing. The degree of mixing is traced by pairing SST and d 18 O records of planktic surface and subsurface (pycnocline) dwellers. Tight age control is deduced from a suite of age-calibrated 14 C plateau boundaries for Termination I and benthic d 18 O and geomagnetic events for the last 800 ka. Carbon 14 paleoreservoir ages record the ages of surface and deep waters to uncover short-term changes in MOC over Termination I. We have defined a standard sequence of short-term productivity events for Termination I, also evident during terminations II to V and subsequent interglacials over the last 450 ka. The peak glacial regime of stable stratification and low productivity terminated, together with the end of ice rafting and melting, near 17 ka, $2000 years after the onset of Termination I. Pulses of vertical mixing and incursion of warm surface waters from the subtropics followed. Convected young water masses finally penetrated down to 3600-m water depth at 17.0 to less than 14.5 ka, significantly improving bottom water ventilation through the late deglacial and earliest interglacial. Mixing with upwelled nutrients from the pycnocline induced short-term maxima in algal production of chlorins and biogenic opal near 17-15 and 15-12 ka, respectively. Deglacial meltwater incursions in the Aleutian Current and silica input from North American rivers also promoted East Pacific productivity after 15.5 ka. Productivity decreased during the late deglacial and early interglacial, coeval with an exceptional peak in CaCO 3 preservation caused by both low organic flux and well-ventilated deepwater. Subsequently, low salinity and cool surface waters and in turn, stratification were gradually restored. A second, opaldominated productivity maximum marked the ends of interglacials. The deglacial pulses of vertical mixing around 17-11 ka imply an important contribution of the North Pacific to the coeval release of oceanic CO 2 into the atmosphere and support the east-west seesaw model of climate change.
Uploads
Papers by Ursula Roehl