Radiocarbon in modern carbon cycle research

2021 ◽  
Author(s):  
Ingeborg Levin
Keyword(s):  
Carbon Cycle ◽  
Fossil Fuel ◽  
Regional Scale ◽  
Anthropogenic Input ◽  
Isotope Tracer ◽  
Continental Scale ◽  
Nuclear Weapon Testing ◽  
Bomb Radiocarbon ◽  
Weapon Testing ◽  
Transient Tracer

<p>Atmospheric nuclear weapon testing in the 1950s and 1960s has been worrying, however, in many aspects it was extremely beneficial for environmental sciences. The artificial production of more than 6 x 10<sup>28</sup> atoms or about 0.6 tons of radiocarbon (<sup>14</sup>C), leading to a doubling of the <sup>14</sup>C/C ratio in tropospheric CO<sub>2</sub> of the Northern Hemisphere, has generated a prominent spike in 1963. This “bomb-spike” has been used as transient tracer in all compartments of the carbon cycle, but also to study atmospheric dynamics, such as inter-hemispheric and stratosphere-troposphere air mass exchange. Moreover, our attempt to accurately determine total bomb produced <sup>14</sup>C led to improved estimates of the atmosphere-ocean gas exchange rate and to a new constraint of the residence time of carbon in the terrestrial biosphere. Today, the transient bomb-radiocarbon signal has levelled off, and the anthropogenic input of radiocarbon-free fossil fuel CO<sub>2</sub> into the atmosphere has become the dominant driver of the <sup>14</sup>C/C ratio in global atmospheric CO<sub>2</sub>. The observed decreasing <sup>14</sup>C/C trend in atmospheric CO<sub>2</sub> may thus help scrutinising the total global release of fossil fuel CO<sub>2</sub> into the atmosphere. On the local and regional scale, atmospheric <sup>14</sup>C/C measurements are already routinely conducted to separate fossil fuel from biogenic CO<sub>2</sub> signals and to estimate trends of regional fossil fuel CO<sub>2</sub> emissions. Some prominent examples where the bomb <sup>14</sup>CO<sub>2</sub> disturbance has been successfully used to study dynamic processes in the carbon cycle are discussed as well as our current activities applying this unique isotope tracer for continental scale carbon cycle budgeting.</p>

Radiocarbon in modern Carbon Cycle research

2020 ◽  
Author(s):  
Ingeborg Levin
Keyword(s):  
Carbon Cycle ◽  
Fossil Fuel ◽  
Environmental Sciences ◽  
Anthropogenic Input ◽  
Isotope Tracer ◽  
Continental Scale ◽  
Nuclear Weapon Testing ◽  
Bomb Radiocarbon ◽  
Weapon Testing ◽  
Transient Tracer

<p>Atmospheric nuclear weapon testing in the 1950s and 1960s has been worrying, however, in many aspects it was extremely beneficial for environmental sciences. The artificial production of more than 6 x 10<sup>28</sup> atoms or about 0.6 tons of <sup>14</sup>C, leading to a doubling of the <sup>14</sup>C/C ratio in tropospheric CO<sub>2</sub> of the Northern Hemisphere has generated a prominent <sup>14</sup>C spike in 1963. This “bomb-spike” has been used as transient tracer in all compartments of the carbon cycle, but also to study atmospheric dynamics, such as inter-hemispheric and stratosphere-troposphere air mass exchange. Moreover, our attempt to accurately determine total bomb produced <sup>14</sup>C led to improved estimates of the atmosphere-ocean gas exchange rate and to a new constraint of the residence time of carbon in the terrestrial biosphere. Today, the transient bomb-radiocarbon signal has levelled off, and the anthropogenic input of radiocarbon-free fossil fuel CO<sub>2</sub> into the atmosphere has become the dominant driver of the decreasing <sup>14</sup>C/C ratio in atmospheric CO<sub>2</sub>; the observed trend may thus help scrutinising the total global release of fossil fuel CO<sub>2</sub> into the atmosphere. Prominent examples where the bomb <sup>14</sup>C disturbance has been successfully used to study dynamic processes in the carbon cycle are discussed as well as our current activities applying this unique isotope tracer for continental scale carbon cycle budgeting.</p>

scholarly journals Biogeochemical contrast between different latitudes and the effect of human activity on spatio-temporal carbon cycle change in Asian river systems

2017 ◽  
Author(s):  
Tadanobu Nakayama
Keyword(s):  
Carbon Cycle ◽  
Hot Spots ◽  
Carbon Flux ◽  
Yangtze River ◽  
Regional Scale ◽  
River Network ◽  
Network Data ◽  
River Systems ◽  
Continental Scale ◽  
Vertical Fluxes

Abstract. Recent research has shown inland water may play some role in carbon cycling, although the extent of its contribution has remained uncertain due to limited amount of reliable data available. In this study, the author applied an advanced model coupling eco-hydrology and biogeochemical cycle (NICE-BGC) to regional-continental scales, which incorporates complex coupling of hydrologic-carbon cycle and interplay between inorganic and organic carbon. The author evaluates latitudinal effect and human impact on hydrologic and carbon cycles between boreal Ob River, temperate Yangtze River, and subtropical Mekong River basins in Asia by using different resolutions of river network data. The model simulated more heterogenous distributions of water and carbon flux in the finer river network data in these regions, and helped to identify some hot spots on a regional scale. Then, the model was extended to continental scale at 1° × 1° resolution with a time step of Δt = 1 day to evaluate seasonal and diurnal variations in carbon flux parameters. The model result showed there is a seasonal variability of horizontal transport and vertical fluxes among boreal, temperate, and tropical regions and among each continent, which reflects seasonal variations of biologic and hydrologic processes there. The result showed CO2 evasion increases and sediment storage decreases in nighttime, particularly clearly seen temporarily in summer in Yangtze River, which implied some hot spots and hot moments in the day-night difference of vertical fluxes in regional scale. These results emphasize the important role of Asian river systems on global carbon cycle, and the further need to improve the resolution of simulation, to implement carbon observation network, and to apply satellite data in the higher-resolution.

scholarly journals Global atmospheric CO<sub>2</sub> inverse models converging on neutral tropical land exchange but diverging on fossil fuel and atmospheric growth rate

2018 ◽  
Author(s):  
Benjamin Gaubert ◽  
Britton B. Stephens ◽  
Sourish Basu ◽  
Frédéric Chevallier ◽  
Feng Deng ◽  
...  
Keyword(s):  
Growth Rate ◽  
Carbon Cycle ◽  
Northern Hemisphere ◽  
High Performance ◽  
Fossil Fuel ◽  
Regional Scale ◽  
Vertical Mixing ◽  
Co2 Concentration ◽  
Environmental Research ◽  
Inverse Models

Abstract. We have compared a suite of recent global CO2 atmospheric inversion results to independent airborne observations and to each other, to assess their dependence on differences in northern extratropical vertical transport and to identify some of the drivers of model spread. We evaluate posterior CO2 concentration profiles against observations from the High-Performance Instrumented Airborne Platform for Environmental Research (HIAPER) Pole-to-Pole Observations (HIPPO) aircraft campaigns over the mid Pacific in 2009–2011. Although the models differ in inverse approaches, assimilated observations, prior fluxes, and transport models, their latitudinal distributions of land fluxes have converged significantly since the Atmospheric Carbon Cycle Inversion Intercomparison (TransCom3) and the REgional Carbon Cycle Assessment and Processes (RECCAP) projects, with model spread reduced by 80 % since TransCom3 and 70 % since RECCAP. Most modelled CO2 fields agree reasonably well with the HIPPO observations, in particular for annual mean vertical gradients in the northern hemisphere. Northern hemisphere vertical mixing no longer appears to be a dominant driver of northern versus tropical annual flux differences. Our newer suite of models still gives modest northern extratropical land uptake and near neutral tropical land uptake for 2009–2011, thus implying a continued strong uptake in intact tropical forests given estimates of emissions from deforestation. The results from these models for other time periods (2004–2014, 2001–2004, 1992–1996), and re-evaluation of the TransCom3 Level 2 and RECCAP results confirms that tropical land carbon fluxes including deforestation have been near neutral for several decades. However, models still have large disagreements on ocean-land partitioning, and this is influenced by differences in prescribed fossil fuel emissions and is associated with differences in retrieved atmospheric growth rate. The fossil fuel and the atmospheric growth rate terms have been thought to be the best-known terms in the global carbon budget, but we show that they dominate the model spread at the largest scales and currently limit our ability to assess regional scale terrestrial fluxes and ocean-land partitioning from the model ensemble.

scholarly journals Global atmospheric CO<sub>2</sub> inverse models converging on neutral tropical land exchange, but disagreeing on fossil fuel and atmospheric growth rate

2019 ◽  
Vol 16 (1) ◽  
pp. 117-134 ◽  
Author(s):  
Benjamin Gaubert ◽  
Britton B. Stephens ◽  
Sourish Basu ◽  
Frédéric Chevallier ◽  
Feng Deng ◽  
...  
Keyword(s):  
Growth Rate ◽  
Carbon Cycle ◽  
Northern Hemisphere ◽  
High Performance ◽  
Fossil Fuel ◽  
Regional Scale ◽  
Vertical Mixing ◽  
Co2 Concentration ◽  
Environmental Research ◽  
Inverse Models

Abstract. We have compared a suite of recent global CO2 atmospheric inversion results to independent airborne observations and to each other, to assess their dependence on differences in northern extratropical (NET) vertical transport and to identify some of the drivers of model spread. We evaluate posterior CO2 concentration profiles against observations from the High-Performance Instrumented Airborne Platform for Environmental Research (HIAPER) Pole-to-Pole Observations (HIPPO) aircraft campaigns over the mid-Pacific in 2009–2011. Although the models differ in inverse approaches, assimilated observations, prior fluxes, and transport models, their broad latitudinal separation of land fluxes has converged significantly since the Atmospheric Carbon Cycle Inversion Intercomparison (TransCom 3) and the REgional Carbon Cycle Assessment and Processes (RECCAP) projects, with model spread reduced by 80 % since TransCom 3 and 70 % since RECCAP. Most modeled CO2 fields agree reasonably well with the HIPPO observations, specifically for the annual mean vertical gradients in the Northern Hemisphere. Northern Hemisphere vertical mixing no longer appears to be a dominant driver of northern versus tropical (T) annual flux differences. Our newer suite of models still gives northern extratropical land uptake that is modest relative to previous estimates (Gurney et al., 2002; Peylin et al., 2013) and near-neutral tropical land uptake for 2009–2011. Given estimates of emissions from deforestation, this implies a continued uptake in intact tropical forests that is strong relative to historical estimates (Gurney et al., 2002; Peylin et al., 2013). The results from these models for other time periods (2004–2014, 2001–2004, 1992–1996) and re-evaluation of the TransCom 3 Level 2 and RECCAP results confirm that tropical land carbon fluxes including deforestation have been near neutral for several decades. However, models still have large disagreements on ocean–land partitioning. The fossil fuel (FF) and the atmospheric growth rate terms have been thought to be the best-known terms in the global carbon budget, but we show that they currently limit our ability to assess regional-scale terrestrial fluxes and ocean–land partitioning from the model ensemble.

scholarly journals A multiresolution spatial parameterization for the estimation of fossil-fuel carbon dioxide emissions via atmospheric inversions

2014 ◽  
Vol 7 (5) ◽  
pp. 1901-1918 ◽  
Author(s):  
J. Ray ◽  
V. Yadav ◽  
A. M. Michalak ◽  
B. van Bloemen Waanders ◽  
S. A. McKenna
Keyword(s):  
Spatial Variability ◽  
Carbon Dioxide Emissions ◽  
Fossil Fuel ◽  
Matching Pursuit ◽  
Regional Scale ◽  
Reconstruction Algorithm ◽  
Spatiotemporal Variability ◽  
Realistic Representation ◽  
Non Gaussian ◽  
Low Dimensional

Abstract. The characterization of fossil-fuel CO2 (ffCO2) emissions is paramount to carbon cycle studies, but the use of atmospheric inverse modeling approaches for this purpose has been limited by the highly heterogeneous and non-Gaussian spatiotemporal variability of emissions. Here we explore the feasibility of capturing this variability using a low-dimensional parameterization that can be implemented within the context of atmospheric CO2 inverse problems aimed at constraining regional-scale emissions. We construct a multiresolution (i.e., wavelet-based) spatial parameterization for ffCO2 emissions using the Vulcan inventory, and examine whether such a~parameterization can capture a realistic representation of the expected spatial variability of actual emissions. We then explore whether sub-selecting wavelets using two easily available proxies of human activity (images of lights at night and maps of built-up areas) yields a low-dimensional alternative. We finally implement this low-dimensional parameterization within an idealized inversion, where a sparse reconstruction algorithm, an extension of stagewise orthogonal matching pursuit (StOMP), is used to identify the wavelet coefficients. We find that (i) the spatial variability of fossil-fuel emission can indeed be represented using a low-dimensional wavelet-based parameterization, (ii) that images of lights at night can be used as a proxy for sub-selecting wavelets for such analysis, and (iii) that implementing this parameterization within the described inversion framework makes it possible to quantify fossil-fuel emissions at regional scales if fossil-fuel-only CO2 observations are available.

Climate as the great equalizer of continental-scale erosion

2021 ◽  
Author(s):  
Gilby Jepson ◽  
Barbara Carrapa ◽  
Jack Gillespie ◽  
Ran Feng ◽  
Peter DeCelles ◽  
...  
Keyword(s):  
Central Asia ◽  
Regional Scale ◽  
Continental Scale ◽  
Active Tectonic ◽  
Tectonically Active ◽  
High Precipitation ◽  
Tectonic Boundaries ◽  
Great Equalizer ◽  
Tian Shan

&lt;p&gt;Central Asia is one of the most tectonically active and orographically diverse regions in the world and is the location of the highest topography on Earth resulting from major plate tectonic collisional events. Yet the role of tectonics versus climate on erosion remains one of the greatest debates of our time. We present the first regional scale analysis of 2526 published low-temperature thermochronometric dates from Central Asia spanning the Altai-Sayan, Tian Shan, Tibet, Pamir, and Himalaya. We compare these dates to tectonic processes (proximity to tectonic boundaries, crustal thickness, seismicity) and state-of-the-art paleoclimate simulations in order to constrain the relative influences of climate and tectonics on the topographic architecture and erosion of Central Asia. Predominance of pre-Cenozoic ages in much of the interior of central Asia suggests that significant topography was created prior to the India-Eurasia collision and implies limited subsequent erosion. Increasingly young cooling ages are associated with increasing proximity to active tectonic boundaries, suggesting a first-order control of tectonics on erosion. However, areas that have been sheltered from significant precipitation for extensive periods of time retain old cooling ages. This suggests that ultimately climate is the great equalizer of erosion. Climate plays a key role by enhancing erosion in areas with developed topography and high precipitation such as the Tian Shan and Altai-Sayan during the Mesozoic and the Himalaya during the Cenozoic. Older thermochronometric dates are associated with sustained aridity following more humid periods.&lt;/p&gt;

scholarly journals Cambridge University Natural Radiocarbon Measurements IV: Nuclear-Weapon Testing and the Atmospheric Radiocarbon Concentration

Radiocarbon ◽  
1961 ◽  
Vol 3 ◽  
pp. 77-80 ◽  
Author(s):  
H. Godwin ◽  
E. H. Willis
Keyword(s):  
Rapid Growth ◽  
Nuclear Weapon ◽  
Annual Ring ◽  
Populus Nigra ◽  
Annual Rings ◽  
Cambridge University ◽  
Annual Crops ◽  
Nuclear Weapon Testing ◽  
Weapon Testing

In continuance of investigations upon successive annual crops of oats reported in Radiocarbon Supplement, Volume 2, we undertook the analysis of successive annual rings of a tree that had been growing throughout the period covered by the oat-crop assays, namely 1953 to 1959. The selected tree was a straight-boled specimen of Populus nigra from the Forestry Commission's plantations at Santon Downham, near Thetford, Norfolk. It had been planted in 1929 and was felled on 21 October, 1959. Shortly afterwards, it was brought into the laboratory and sawn into slices just over 1 in. thick. The surfaces having been smoothed, the annual-ring contacts were marked, and within each annual ring the inner (spring) wood was marked off from the outer (autumn) wood. The tree had been chosen as one exhibiting rapid growth and it proved fairly easy to dissect off with a chisel all the separate half-rings between spring 1953 and the end of 1959. In the event, activities were determined only upon four of the half or whole rings.

scholarly journals The Orbiting Carbon Observatory-2: first 18 months of science data products

2017 ◽  
Vol 10 (2) ◽  
pp. 549-563 ◽  
Author(s):  
Annmarie Eldering ◽  
Chris W. O'Dell ◽  
Paul O. Wennberg ◽  
David Crisp ◽  
Michael R. Gunson ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Atmospheric Carbon Dioxide ◽  
Eastern China ◽  
Regional Scale ◽  
Central Africa ◽  
Retrieval Algorithm ◽  
Science Data ◽  
The North ◽  
Data Products ◽  
Atmospheric Carbon

Abstract. The Orbiting Carbon Observatory-2 (OCO-2) is the first National Aeronautics and Space Administration (NASA) satellite designed to measure atmospheric carbon dioxide (CO2) with the accuracy, resolution, and coverage needed to quantify CO2 fluxes (sources and sinks) on regional scales. OCO-2 was successfully launched on 2 July 2014 and has gathered more than 2 years of observations. The v7/v7r operational data products from September 2014 to January 2016 are discussed here. On monthly timescales, 7 to 12 % of these measurements are sufficiently cloud and aerosol free to yield estimates of the column-averaged atmospheric CO2 dry air mole fraction, XCO2, that pass all quality tests. During the first year of operations, the observing strategy, instrument calibration, and retrieval algorithm were optimized to improve both the data yield and the accuracy of the products. With these changes, global maps of XCO2 derived from the OCO-2 data are revealing some of the most robust features of the atmospheric carbon cycle. This includes XCO2 enhancements co-located with intense fossil fuel emissions in eastern US and eastern China, which are most obvious between October and December, when the north–south XCO2 gradient is small. Enhanced XCO2 coincident with biomass burning in the Amazon, central Africa, and Indonesia is also evident in this season. In May and June, when the north–south XCO2 gradient is largest, these sources are less apparent in global maps. During this part of the year, OCO-2 maps show a more than 10 ppm reduction in XCO2 across the Northern Hemisphere, as photosynthesis by the land biosphere rapidly absorbs CO2. As the carbon cycle science community continues to analyze these OCO-2 data, information on regional-scale sources (emitters) and sinks (absorbers) which impart XCO2 changes on the order of 1 ppm, as well as far more subtle features, will emerge from this high-resolution global dataset.

scholarly journals Multicentury Changes to the Global Climate and Carbon Cycle: Results from a Coupled Climate and Carbon Cycle Model

2005 ◽  
Vol 18 (21) ◽  
pp. 4531-4544 ◽  
Author(s):  
G. Bala ◽  
K. Caldeira ◽  
A. Mirin ◽  
M. Wickett ◽  
C. Delire
Keyword(s):  
Carbon Cycle ◽  
Radiative Forcing ◽  
Fossil Fuel ◽  
Global Climate ◽  
Second Century ◽  
Cycle Model ◽  
Carbon Cycle Model ◽  
Living Biomass ◽  
Long Term Consequences

Abstract A coupled climate and carbon (CO2) cycle model is used to investigate the global climate and carbon cycle changes out to the year 2300 that would occur if CO2 emissions from all the currently estimated fossil fuel resources were released to the atmosphere. By the year 2300, the global climate warms by about 8 K and atmospheric CO2 reaches 1423 ppmv. The warming is higher than anticipated because the sensitivity to radiative forcing increases as the simulation progresses. In this simulation, the rate of emissions peaks at over 30 Pg C yr−1 early in the twenty-second century. Even at the year 2300, nearly 50% of cumulative emissions remain in the atmosphere. Both soils and living biomass are net carbon sinks throughout the simulation. Despite having relatively low climate sensitivity and strong carbon uptake by the land biosphere, these model projections suggest severe long-term consequences for global climate if all the fossil fuel carbon is ultimately released into the atmosphere.

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.

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