scholarly journals Marine20—The Marine Radiocarbon Age Calibration Curve (0–55,000 cal BP)

Radiocarbon ◽  
2020 ◽  
Vol 62 (4) ◽  
pp. 779-820 ◽  
Author(s):  
Timothy J Heaton ◽  
Peter Köhler ◽  
Martin Butzin ◽  
Edouard Bard ◽  
Ron W Reimer ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Calibration Curve ◽  
General Circulation ◽  
Circulation Model ◽  
Box Model ◽  
Polar Regions ◽  
Total Uncertainty ◽  
Radiocarbon Age ◽  
Global Average ◽  
Reservoir Age

ABSTRACTThe concentration of radiocarbon (14C) differs between ocean and atmosphere. Radiocarbon determinations from samples which obtained their 14C in the marine environment therefore need a marine-specific calibration curve and cannot be calibrated directly against the atmospheric-based IntCal20 curve. This paper presents Marine20, an update to the internationally agreed marine radiocarbon age calibration curve that provides a non-polar global-average marine record of radiocarbon from 0–55 cal kBP and serves as a baseline for regional oceanic variation. Marine20 is intended for calibration of marine radiocarbon samples from non-polar regions; it is not suitable for calibration in polar regions where variability in sea ice extent, ocean upwelling and air-sea gas exchange may have caused larger changes to concentrations of marine radiocarbon. The Marine20 curve is based upon 500 simulations with an ocean/atmosphere/biosphere box-model of the global carbon cycle that has been forced by posterior realizations of our Northern Hemispheric atmospheric IntCal20 14C curve and reconstructed changes in CO2 obtained from ice core data. These forcings enable us to incorporate carbon cycle dynamics and temporal changes in the atmospheric 14C level. The box-model simulations of the global-average marine radiocarbon reservoir age are similar to those of a more complex three-dimensional ocean general circulation model. However, simplicity and speed of the box model allow us to use a Monte Carlo approach to rigorously propagate the uncertainty in both the historic concentration of atmospheric 14C and other key parameters of the carbon cycle through to our final Marine20 calibration curve. This robust propagation of uncertainty is fundamental to providing reliable precision for the radiocarbon age calibration of marine based samples. We make a first step towards deconvolving the contributions of different processes to the total uncertainty; discuss the main differences of Marine20 from the previous age calibration curve Marine13; and identify the limitations of our approach together with key areas for further work. The updated values for ΔR, the regional marine radiocarbon reservoir age corrections required to calibrate against Marine20, can be found at the data base http://calib.org/marine/.

scholarly journals The IntCal20 Northern Hemisphere Radiocarbon Age Calibration Curve (0–55 cal kBP)

Radiocarbon ◽  
2020 ◽  
Vol 62 (4) ◽  
pp. 725-757 ◽  
Author(s):  
Paula J Reimer ◽  
William E N Austin ◽  
Edouard Bard ◽  
Alex Bayliss ◽  
Paul G Blackwell ◽  
...  
Keyword(s):  
Tree Ring ◽  
Ocean Circulation ◽  
Calibration Curve ◽  
Three Dimensional ◽  
Circulation Model ◽  
Radiocarbon Age ◽  
Calibration Curves ◽  
Tree Ring Data ◽  
Ocean Surface Layer ◽  
Reservoir Age

ABSTRACTRadiocarbon (14C) ages cannot provide absolutely dated chronologies for archaeological or paleoenvironmental studies directly but must be converted to calendar age equivalents using a calibration curve compensating for fluctuations in atmospheric 14C concentration. Although calibration curves are constructed from independently dated archives, they invariably require revision as new data become available and our understanding of the Earth system improves. In this volume the international 14C calibration curves for both the Northern and Southern Hemispheres, as well as for the ocean surface layer, have been updated to include a wealth of new data and extended to 55,000 cal BP. Based on tree rings, IntCal20 now extends as a fully atmospheric record to ca. 13,900 cal BP. For the older part of the timescale, IntCal20 comprises statistically integrated evidence from floating tree-ring chronologies, lacustrine and marine sediments, speleothems, and corals. We utilized improved evaluation of the timescales and location variable 14C offsets from the atmosphere (reservoir age, dead carbon fraction) for each dataset. New statistical methods have refined the structure of the calibration curves while maintaining a robust treatment of uncertainties in the 14C ages, the calendar ages and other corrections. The inclusion of modeled marine reservoir ages derived from a three-dimensional ocean circulation model has allowed us to apply more appropriate reservoir corrections to the marine 14C data rather than the previous use of constant regional offsets from the atmosphere. Here we provide an overview of the new and revised datasets and the associated methods used for the construction of the IntCal20 curve and explore potential regional offsets for tree-ring data. We discuss the main differences with respect to the previous calibration curve, IntCal13, and some of the implications for archaeology and geosciences ranging from the recent past to the time of the extinction of the Neanderthals.

scholarly journals Palaeogeographic controls on climate and proxy interpretation

2016 ◽  
Vol 12 (5) ◽  
pp. 1181-1198 ◽  
Author(s):  
Daniel J. Lunt ◽  
Alex Farnsworth ◽  
Claire Loptson ◽  
Gavin L. Foster ◽  
Paul Markwick ◽  
...  
Keyword(s):  
Global Change ◽  
Carbon Cycle ◽  
Ocean Circulation ◽  
General Circulation ◽  
Regional Scale ◽  
Circulation Model ◽  
Adjustment Factor ◽  
Climate Signal ◽  
Proxy Records ◽  
Global Mean

Abstract. During the period from approximately 150 to 35 million years ago, the Cretaceous–Paleocene–Eocene (CPE), the Earth was in a “greenhouse” state with little or no ice at either pole. It was also a period of considerable global change, from the warmest periods of the mid-Cretaceous, to the threshold of icehouse conditions at the end of the Eocene. However, the relative contribution of palaeogeographic change, solar change, and carbon cycle change to these climatic variations is unknown. Here, making use of recent advances in computing power, and a set of unique palaeogeographic maps, we carry out an ensemble of 19 General Circulation Model simulations covering this period, one simulation per stratigraphic stage. By maintaining atmospheric CO2 concentration constant across the simulations, we are able to identify the contribution from palaeogeographic and solar forcing to global change across the CPE, and explore the underlying mechanisms. We find that global mean surface temperature is remarkably constant across the simulations, resulting from a cancellation of opposing trends from solar and palaeogeographic change. However, there are significant modelled variations on a regional scale. The stratigraphic stage–stage transitions which exhibit greatest climatic change are associated with transitions in the mode of ocean circulation, themselves often associated with changes in ocean gateways, and amplified by feedbacks related to emissivity and planetary albedo. We also find some control on global mean temperature from continental area and global mean orography. Our results have important implications for the interpretation of single-site palaeo proxy records. In particular, our results allow the non-CO2 (i.e. palaeogeographic and solar constant) components of proxy records to be removed, leaving a more global component associated with carbon cycle change. This “adjustment factor” is used to adjust sea surface temperatures, as the deep ocean is not fully equilibrated in the model. The adjustment factor is illustrated for seven key sites in the CPE, and applied to proxy data from Falkland Plateau, and we provide data so that similar adjustments can be made to any site and for any time period within the CPE. Ultimately, this will enable isolation of the CO2-forced climate signal to be extracted from multiple proxy records from around the globe, allowing an evaluation of the regional signals and extent of polar amplification in response to CO2 changes during the CPE. Finally, regions where the adjustment factor is constant throughout the CPE could indicate places where future proxies could be targeted in order to reconstruct the purest CO2-induced temperature change, where the complicating contributions of other processes are minimised. Therefore, combined with other considerations, this work could provide useful information for supporting targets for drilling localities and outcrop studies.

scholarly journals Lower-Tropospheric Mixing as a Constraint on Cloud Feedback in a Multiparameter Multiphysics Ensemble

2016 ◽  
Vol 29 (17) ◽  
pp. 6259-6275 ◽  
Author(s):  
Youichi Kamae ◽  
Hideo Shiogama ◽  
Masahiro Watanabe ◽  
Tomoo Ogura ◽  
Tokuta Yokohata ◽  
...  
Keyword(s):  
General Circulation ◽  
Circulation Model ◽  
Cloud Feedback ◽  
Total Uncertainty ◽  
Large Member ◽  
Large Spread ◽  
Low Cloud ◽  
Equatorial Ocean ◽  
Structural Uncertainties ◽  
Emergent Constraint

Abstract Factors and possible constraints to extremely large spread of effective climate sensitivity (ECS) ranging about 2.1–10.4 K are examined by using a large-member ensemble of quadrupling CO2 experiments with an atmospheric general circulation model (AGCM). The ensemble, called the multiparameter multiphysics ensemble (MPMPE), consists of both parametric and structural uncertainties in parameterizations of cloud, cumulus convection, and turbulence based on two different versions of AGCM. The sum of the low- and middle-cloud shortwave feedback explains most of the ECS spread among the MPMPE members. For about half of the perturbed physics ensembles (PPEs) in the MPMPE, variation in lower-tropospheric mixing intensity (LTMI) corresponds well with the ECS variation, whereas it does not for the other half. In the latter PPEs, large spread in optically thick middle-cloud feedback over the equatorial ocean substantially affects the ECS, disrupting the LTMI–ECS relationship. Although observed LTMI can constrain uncertainty in the low-cloud feedback, total uncertainty of the ECS among the MPMPE cannot solely be explained by the LTMI, suggesting a limitation of single emergent constraint for the ECS.

scholarly journals Modeling cosmogenic radionuclides <sup>10</sup>Be and <sup>7</sup>Be during the Maunder Minimum using the ECHAM5-HAM General Circulation Model

2008 ◽  
Vol 8 (10) ◽  
pp. 2797-2809 ◽  
Author(s):  
U. Heikkilä ◽  
J. Beer ◽  
J. Feichter
Keyword(s):  
Solar Activity ◽  
General Circulation Model ◽  
General Circulation ◽  
Circulation Model ◽  
Maunder Minimum ◽  
Ice Age ◽  
Deposition Flux ◽  
Polar Regions ◽  
Cosmogenic Radionuclides ◽  
Deposition Fluxes

Abstract. All existing 10Be records from Greenland and Antarctica show increasing concentrations during the Maunder Minimum period (MM), 1645–1715, when solar activity was very low and the climate was colder (little ice age). In detail, however, the 10Be records deviate from each other. We investigate to what extent climatic changes influence the 10Be measured in ice by modeling this period using the ECHAM5-HAM general circulation model. Production calculations show that during the MM the mean global 10Be production was higher by 32% than at present due to lower solar activity. Our modeling shows that the zonally averaged modeled 10Be deposition flux deviates by only ~8% from the average increase of 32%, indicating that climatic effects are much smaller than the production change. Due to increased stratospheric production, the 10Be content in the downward fluxes is larger during MM, leading to larger 10Be deposition fluxes in the subtropics, where stratosphere-troposphere exchange (STE) is strongest. In polar regions the effect is small. In Greenland the deposition change depends on latitude and altitude. In Antarctica the change is larger in the east than in the west. We use the 10Be/7Be ratio to study changes in STE. We find larger change between 20° N–40° N during spring, pointing to a stronger STE in the Northern Hemisphere during MM. In the Southern Hemisphere the change is small. These findings indicate that climate changes do influence the 10Be deposition fluxes, but not enough to significantly disturb the production signal. Climate-induced changes remain small, especially in polar regions.

scholarly journals Impacto da duplicação de CO2 no clima global simulado por um modelo de circulação geral da atmosfera

2004 ◽  
Vol 27 ◽  
pp. 27-52
Author(s):  
Felipe Das Neves Roque da Silva ◽  
José Ricardo Almeida França
Keyword(s):  
General Circulation ◽  
Climate Changes ◽  
Hydrological Cycle ◽  
Circulation Model ◽  
Co2 Concentration ◽  
Polar Regions ◽  
Control Case ◽  
Model Resolution ◽  
Low Latitudes ◽  
Atmosphere General Circulation Model

The objective of this work is to evaluate climate changes caused by atmospheric CO2 concentration duplication. The LMD-Z atmosphere general circulation model (AGCM) was used (Laboratoire de Météorologie Dynamique - France). The model was integrated for a fifty years period and only the last forty years were used for analyses. This experiment have made two simulations: the first using the current CO2 concentration (control case) and the second using this concentration doubled (duplication case). Both were made with a variable spatial resolution with maximum of it centered in Rio de Janeiro. This way, there is a significant increase of model resolution in this region. To verify climate changes, anomaly fields generated by the model (duplication case minus control) were studied. It was possible to observe some characteristic effects of this type of experiment, such as great temperature increasing at surface in polar regions and in upper levels at low latitudes, cooling in stratosphere and intensification of hydrological cycle.

scholarly journals Modeling cosmogenic radionuclides <sup>10</sup>Be and <sup>7</sup>Be during the Maunder Minimum using the ECHAM5-HAM General Circulation Model

2007 ◽  
Vol 7 (6) ◽  
pp. 15341-15372 ◽  
Author(s):  
U. Heikkilä ◽  
J. Beer ◽  
J. Feichter
Keyword(s):  
Solar Activity ◽  
General Circulation Model ◽  
General Circulation ◽  
Circulation Model ◽  
Maunder Minimum ◽  
Ice Age ◽  
Deposition Flux ◽  
Polar Regions ◽  
Cosmogenic Radionuclides ◽  
Deposition Fluxes

Abstract. All existing 10Be records from Greenland and Antarctica show increasing concentrations during the Maunder Minimum period (MM), 1645–1715, when solar activity was very low and the climate was colder (little ice age). In detail, however, the 10Be records deviate from each other. We investigate to what extent climatic changes influence the 10Be measured in ice by modeling this period using the ECHAM5-HAM general circulation model. Production calculations show that during the MM the mean global 10Be production was higher by 32% than at present due to lower solar activity. Our modeling shows that the zonally averaged modeled 10Be deposition flux deviates by only ~8% from the average increase of 32%, indicating that climatic effects are much smaller than the production change. Due to increased stratospheric production, the 10Be content in the downward fluxes is larger during MM, leading to larger 10Be deposition fluxes in the subtropics, where stratosphere-troposphere exchange (STE) is strongest. In polar regions the effect is small. In Greenland the deposition change depends on latitude and altitude. In Antarctica the change is larger in the east than in the west. We use the 10Be/7Be ratio to study changes in STE. We find larger change between 20° N–40° N during spring, pointing to a stronger STE in the Northern Hemisphere during MM. In the Southern Hemisphere the change is small. These findings indicate that climate changes do influence the 10Be deposition fluxes, but not enough to significantly disturb the production signal. Climate-induced changes remain small, especially in polar regions.

scholarly journals Oceanic dominance of interannual subtropical North Atlantic heat content variability

2013 ◽  
Vol 10 (1) ◽  
pp. 27-53 ◽  
Author(s):  
M. Sonnewald ◽  
J. J.-M. Hirschi ◽  
R. Marsh
Keyword(s):  
Heat Transport ◽  
North Atlantic ◽  
General Circulation ◽  
Low Frequency ◽  
Heat Content ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Heat Fluxes ◽  
Ocean Heat Content ◽  
Box Model

Abstract. Ocean heat content varies on a range of timescales. Traditionally the atmosphere is seen to dominate the oceanic heat content variability. However, this variability can be driven either by oceanic or atmospheric heat fluxes. To diagnose the relative contributions and respective timescales, this study uses a box model forced with output from an ocean general circulation model (OGCM) to investigate the heat content variability of the upper 800 m of the subtropical North Atlantic from 26° N to 36° N. The ocean and air-sea heat flux data needed to force the box model is taken from a 19 yr (1988 to 2006) simulation performed with the 1/12° version of the OCCAM OGCM. The box model heat content is compared to the corresponding heat content in OCCAM for verification. The main goal of the study is to identify to what extent the seasonal to interannual ocean heat content variability is of atmospheric or oceanic origin. To this end, the box model is subjected to a range of scenarios forced either with the full (detrended) ocean and air-sea fluxes, or their deseasoned counterparts. Results show that in all cases, the seasonal variability is dominated by the seasonal component of the air-sea fluxes, which produce a seasonal range in mean temperature of the upper 800 m of ~ 0.42 °C. However, on longer timescales oceanic heat transport dominates, with changes of up to ~ 0.30 °C over 4 yr. The technique is subsequently applied to observational data. For the ocean heat fluxes, we use data from the RAPID program at 26° N from April 2004 to January 2011. At 36° N heat transport is inferred using a linear regression model based on the oceanic low-frequency transport in OCCAM. The air-sea flux from OCCAM is used for the period 2004 to 2006 when the RAPID timeseries and the OCCAM simulation overlap, and a climatology is used for the air-sea flux from 2006 onwards. The results confirm that on longer (> 2 yr) timescales the ocean dominates the ocean heat content variability, which is further verified using data from the ARGO project. This work illustrates that oceanic divergence significantly impacts the ocean heat content variability on timescales relevant for applications such as seasonal hurricane forecasts.

scholarly journals Ocean carbon cycling during the past 130,000 years – a pilot study on inverse paleoclimate record modelling

2016 ◽  
Author(s):  
Christoph Heinze ◽  
Babette Hoogakker ◽  
Arne Winguth
Keyword(s):  
Carbon Cycle ◽  
Sediment Core ◽  
Ocean Circulation ◽  
General Circulation ◽  
General Pattern ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Last Glacial ◽  
Modelling Studies ◽  
The Last Glacial

Abstract. What role did changes in marine carbon cycle processes and calcareous organisms play for glacial-interglacial variation in atmospheric pCO2? In order to answer this question, we explore results from an ocean biogeochemical ocean general circulation model. We make an attempt to systematically reconcile model results with time dependent sediment core data from the observations. For this purpose, simulated sensitivities of oceanic tracer concentrations to changes in governing carbon cycle parameters are fitted to measured sediment core data.We assume that the time variation of the governing carbon cycle parameters follows the general pattern of the glacial-interglacial deuterium anomaly. Our analysis provides an independent estimate of a maximum mean sea surface temperature drawdown of about 5 °C and a maximum outgassing of the land biosphere by about 430 PgC at the last glacial maximum as compared to preindustrial times. The overall fit of modelled paleoclimate tracers to observations, however, remains quite weak indicating the potential of more detailed modelling studies for full exploitation of the information as stored in the paleo-climatic archive. It can be confirmed, however, that a decline in ocean temperature and a more efficient biological carbon pump in combination with changes in ocean circulation are the key factors for explaining the glacial CO2 drawdown. The analysis suggests that potential changes in the export rain ratio POC:CaCO3 may not have a substantial imprint on the paleo-climatic archive. The use of the last glacial as an inverted analogue to potential ocean acidification impacts thus may be quite limited. A potential strong decrease in CaCO3 export production could contribute to the glacial CO2 decline in the atmosphere but remains hypothetical.

scholarly journals Impact of changes in river nutrient fluxes on the global marine silicon cycle: a model comparison

2009 ◽  
Vol 6 (2) ◽  
pp. 4463-4492
Author(s):  
C. Y. Bernard ◽  
G. G. Laruelle ◽  
C. P. Slomp ◽  
C. Heinze
Keyword(s):  
General Circulation Model ◽  
Time Scales ◽  
General Circulation ◽  
Circulation Model ◽  
Box Model ◽  
Global Ocean ◽  
Export Production ◽  
River Input ◽  
Silicon Cycle ◽  
Ocean Response

Abstract. The availability of dissolved silica in the ocean provides a major control on the growth of siliceous phytoplankton. Diatoms in particular account for a large proportion of oceanic primary production. The original source of the silica is rock weathering, followed by transport of dissolved and biogenic silica to the coastal zone. This model study aims at assessing the sensitivity of the global marine silicon cycle to variations in the river input of silica and other nutrients on timescales ranging from several centuries to millennia. We compare the performance of a box model for the marine Si cycle to that of a global biogeochemical ocean general circulation model (HAMOCC2 and 5). Results indicate that the average global ocean response to changes in river input of Si is surprisingly similar in the models on time scales up to 150 kyrs. While the trends in export production and opal burial are the same, the box model shows a delayed response to the imposed perturbations compared to the general circulation model. Results of both models confirm the important role of the continental margins as a sink for silica at the global scale. While general circulation models are indispensable when assessing the spatial variation in opal export production and biogenic Si burial in the ocean, this study demonstrates that box models provide a good alternative when studying the average global ocean response to perturbations of the oceanic silica cycle (especially on longer time scales).

scholarly journals Mid-Pliocene global climate simulation with MRI-CGCM2.3: set-up and initial results of PlioMIP Experiments 1 and 2

2012 ◽  
Vol 5 (3) ◽  
pp. 793-808 ◽  
Author(s):  
Y. Kamae ◽  
H. Ueda
Keyword(s):  
General Circulation ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Climate Simulation ◽  
Polar Regions ◽  
The North ◽  
Set Up

Abstract. The mid-Pliocene (3.3 to 3.0 million yr ago), a globally warm period before the Quaternary, is recently attracting attention as a new target for paleoclimate modelling and data-model synthesis. This paper reports set-ups and results of experiments proposed in Pliocene Model Intercomparison Project (PlioMIP) using a global climate model, MRI-CGCM2.3. We conducted pre-industrial and mid-Pliocene runs by using the coupled atmosphere-ocean general circulation model (AOGCM) and its atmospheric component (AGCM) for the PlioMIP Experiments 2 and 1, respectively. In addition, we conducted two types of integrations in AOGCM simulation, with and without flux adjustments on sea surface. General characteristics of differences in the simulated mid-Pliocene climate relative to the pre-industrial in the three integrations are compared. In addition, patterns of predicted mid-Pliocene biomes resulting from the three climate simulations are compared in this study. Generally, difference of simulated surface climate between AGCM and AOGCM is larger than that between the two AOGCM runs, with and without flux adjustments. The simulated climate shows different pattern between AGCM and AOGCM particularly over low latitude oceans, subtropical land regions and high latitude oceans. The AOGCM simulations do not reproduce wetter environment in the subtropics relative to the present-day, which is suggested by terrestrial proxy data. The differences between the two types of AOGCM runs are small over the land, but evident over the ocean particularly in the North Atlantic and polar regions.

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