Earth system transition during the Tonian–Cambrian interval of biological innovation: nutrients, climate, oxygen and the marine organic carbon capacitor

Abstract. A new, low-order Earth System Model is described, calibrated and tested against Earth system data. The model features modules for the atmosphere, ocean, ocean sediment, land biosphere and lithosphere and has been designed to simulate global change on time scales of years to millions of years. The atmosphere module considers radiation balance, meridional transport of heat and water vapor between low-mid latitude and high latitude zones, heat and gas exchange with the ocean and sea ice and snow cover. Gases considered are carbon dioxide and methane for all three carbon isotopes, nitrous oxide and oxygen. The ocean module has 100 m vertical resolution, carbonate chemistry and prescribed circulation and mixing. Ocean biogeochemical tracers are phosphate, dissolved oxygen, dissolved inorganic carbon for all three carbon isotopes and alkalinity. Biogenic production of particulate organic matter in the ocean surface layer depends on phosphate availability but with lower efficiency in the high latitude zone, as determined by model fit to ocean data. The calcite to organic carbon rain ratio depends on surface layer temperature. The semi-analytical, ocean sediment module considers calcium carbonate dissolution and oxic and anoxic organic matter remineralisation. The sediment is composed of calcite, non-calcite mineral and reactive organic matter. Sediment porosity profiles are related to sediment composition and a bioturbated layer of 0.1 m thickness is assumed. A sediment segment is ascribed to each ocean layer and segment area stems from observed ocean depth distributions. Sediment burial is calculated from sedimentation velocities at the base of the bioturbated layer. Bioturbation rates and oxic and anoxic remineralisation rates depend on organic carbon rain rates and dissolved oxygen concentrations. The land biosphere module considers leaves, wood, litter and soil. Net primary production depends on atmospheric carbon dioxide concentration and remineralization rates in the litter and soil are related to mean atmospheric temperatures. Methane production is a small fraction of the soil remineralization. The lithosphere module considers outgassing, weathering of carbonate and silicate rocks and weathering of rocks containing old organic carbon and phosphorus. Weathering rates are related to mean atmospheric temperatures. A pre-industrial, steady state calibration to Earth system data is carried out. Ocean observations of temperature, carbon 14, phosphate, dissolved oxygen, dissolved inorganic carbon and alkalinity constrain air-sea exchange and ocean circulation, mixing and biogeochemical parameters. Observed calcite and organic carbon distributions and inventories in the ocean sediment help constrain sediment module parameters. Carbon isotopic data and carbonate vs. silicate weathering fractions are used to estimate initial lithosphere outgassing and rock weathering rates. Model performance is tested by simulating atmospheric greenhouse gas increases, global warming and model tracer evolution for the period 1765 to 2000, as forced by prescribed anthropogenic greenhouse gas inputs and other anthropogenic and natural forcing. Long term, transient model behavior is studied with a set of 100 000 year simulations, forced by a slow, 5000 Gt C input of CO2 to the atmosphere, and with a 1.5 million year simulation, forced by a doubling of lithosphere CO2 outgassing.

Download Full-text

Anomalous 13C enrichment in modern marine organic carbon

Nature ◽

10.1038/315216a0 ◽

1985 ◽

Vol 315 (6016) ◽

pp. 216-218 ◽

Cited By ~ 149

Author(s):

Michael A. Arthur ◽

Walter E. Dean ◽

George E. Claypool

Keyword(s):

Organic Carbon ◽

Marine Organic Carbon

Download Full-text

Bromine counts from XRF scanning as an estimate of the marine organic carbon content of sediment cores

Geochemistry Geophysics Geosystems ◽

10.1029/2007gc001932 ◽

2008 ◽

Vol 9 (5) ◽

pp. n/a-n/a ◽

Cited By ~ 119

Author(s):

Martin Ziegler ◽

Tom Jilbert ◽

Gert J. de Lange ◽

Lucas J. Lourens ◽

Gert-Jan Reichart

Keyword(s):

Organic Carbon ◽

Carbon Content ◽

Sediment Cores ◽

Organic Carbon Content ◽

Xrf Scanning ◽

Marine Organic Carbon

Download Full-text

Field-warmed soil carbon changes imply high 21st century modeled uncertainty

10.5194/bg-2018-72 ◽

2018 ◽

Cited By ~ 1

Author(s):

Katherine Todd-Brown ◽

Bin Zheng ◽

Thomas Crowther

Keyword(s):

Organic Carbon ◽

Soil Carbon ◽

21St Century ◽

Temperature Sensitivity ◽

Carbon Stock ◽

Earth System Model ◽

System Model ◽

Earth System ◽

Soil Carbon Stock ◽

Q10 Values

Abstract. The feedback between planetary warming and soil carbon loss has been the focus of considerable scientific attention in recent decades, due to its potential to accelerate anthropogenic climate change. The soil carbon temperature sensitivity is traditionally estimated from short-term respiration measurements – either from laboratory incubations that are artificially manipulated, or field measurements that cannot distinguish between plant and microbial respiration. To address these limitations of previous approaches, we developed a new method to estimate temperature sensitivity (Q10) of soil carbon directly from warming-induced changes in soil carbon stocks measured in 36 field experiments across the world. Variations in warming magnitude and control organic carbon percentage explained much of field-warmed organic carbon percentage (R2 = 0.96), revealing Q10 across sites of 2.2, [1.6, 2.7] 95 % Confidence Interval (CI). When these field-derived Q10 values were extrapolated over the 21st century using a post-hoc correction of 20 CMIP5 Earth system model outputs, the multi-model mean soil carbon stock changes shifted from the previous value of 83 ± 156 Pg-carbon (weighted mean ± 1 SD), to 16 ± 156 Pg-carbon with a Q10 driven 95 % CI of 245 ± 194 to −99 ± 208 Pg-carbon. On average, incorporating the field-derived Q10 values into Earth system model simulations led to reductions in the projected amount of carbon sequestered in the soil over the 21st century. However, the considerable parameter uncertainty led to extremely high variability in soil carbon stock projections within each model; intra-model uncertainty driven by the measured Q10 was as great as that between model variation. This study demonstrates that data integration may not improve model certainty, but instead should strive to capture the variation of the system as well as mean trends.

Download Full-text

Changes in soil organic carbon storage predicted by Earth system models during the 21st century

Biogeosciences Discussions ◽

10.5194/bgd-10-18969-2013 ◽

2013 ◽

Vol 10 (12) ◽

pp. 18969-19004 ◽

Cited By ~ 7

Author(s):

K. E. O. Todd-Brown ◽

J. T. Randerson ◽

F. Hopkins ◽

V. Arora ◽

T. Hajima ◽

...

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

21St Century ◽

Decomposition Rate ◽

Radiative Forcing ◽

Atmospheric Carbon Dioxide ◽

Earth System ◽

System Models ◽

Organic Carbon Storage ◽

Earth System Models

Abstract. Soil is currently thought to be a sink for carbon; however, the response of this sink to increasing levels of atmospheric carbon dioxide and climate change is uncertain. In this study, we analyzed soil organic carbon (SOC) changes from 11 Earth system models (ESMs) under the historical and high radiative forcing (RCP 8.5) scenarios between 1850 and 2100. We used a reduced complexity model based on temperature and moisture sensitivities to analyze the drivers of SOC losses. ESM estimates of SOC change over the 21st century (2090–2099 minus 1997–2006) ranged from a loss of 72 Pg C to a gain 253 Pg C with a multi-model mean gain of 63 Pg C. All ESMs showed cumulative increases in both NPP (15% to 59%) and decreases in SOC turnover times (15% to 28%) over the 21st century. Most of the model-to-model variation in SOC change was explained by initial SOC stocks combined with the relative changes in soil inputs and decomposition rates (R2 = 0.88, p<0.01). Between models, increases in decomposition rate were well explained by a combination of initial decomposition rate, ESM-specific Q10-factors, and changes in soil temperature (R2 = 0.80, p<0.01). All SOC changes depended on sustained increases in NPP with global change (primarily driven by increasing CO2) and conversion of additional plant inputs into SOC. Most ESMs omit potential constraints on SOC storage, such as priming effects, nutrient availability, mineral surface stabilization and aggregate formation. Future models that represent these constraints are likely to estimate smaller increases in SOC storage during the 21st century.

Download Full-text

ORCHIDEE MICT-LEAK (r5459), a global model for the production, transport, and transformation of dissolved organic carbon from Arctic permafrost regions – Part 1: Rationale, model description, and simulation protocol

Geoscientific Model Development ◽

10.5194/gmd-12-3503-2019 ◽

2019 ◽

Vol 12 (8) ◽

pp. 3503-3521 ◽

Cited By ~ 4

Author(s):

Simon P. K. Bowring ◽

Ronny Lauerwald ◽

Bertrand Guenet ◽

Dan Zhu ◽

Matthieu Guimberteau ◽

...

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

High Latitude ◽

Land Surface ◽

River Network ◽

Model Description ◽

Surface Model ◽

System Modelling ◽

Earth System ◽

Simulation Protocol

Abstract. Few Earth system models adequately represent the unique permafrost soil biogeochemistry and its respective processes; this significantly contributes to uncertainty in estimating their responses, and that of the planet at large, to warming. Likewise, the riverine component of what is known as the “boundless carbon cycle” is seldom recognised in Earth system modelling. The hydrological mobilisation of organic material from a ∼1330–1580 PgC carbon stock to the river network results in either sedimentary settling or atmospheric “evasion”, processes widely expected to increase with amplified Arctic climate warming. Here, the production, transport, and atmospheric release of dissolved organic carbon (DOC) from high-latitude permafrost soils into inland waters and the ocean are explicitly represented for the first time in the land surface component (ORCHIDEE) of a CMIP6 global climate model (Institut Pierre Simon Laplace – IPSL). The model, ORCHIDEE MICT-LEAK, which represents the merger of previously described ORCHIDEE versions MICT and LEAK, mechanistically represents (a) vegetation and soil physical processes for high-latitude snow, ice, and soil phenomena and (b) the cycling of DOC and CO2, including atmospheric evasion, along the terrestrial–aquatic continuum from soils through the river network to the coast at 0.5 to 2∘ resolution. This paper, the first in a two-part study, presents the rationale for including these processes in a high-latitude-specific land surface model, then describes the model with a focus on novel process implementations, followed by a summary of the model configuration and simulation protocol. The results of these simulation runs, conducted for the Lena River basin, are evaluated against observational data in the second part of this study.

Download Full-text

Abiotic synthesis of graphite in hydrothermal vents

Nature Communications ◽

10.1038/s41467-019-13216-z ◽

2019 ◽

Vol 10 (1) ◽

Author(s):

Emily R. Estes ◽

Debora Berti ◽

Nicole R. Coffey ◽

Michael F. Hochella ◽

Andrew S. Wozniak ◽

...

Keyword(s):

Organic Carbon ◽

Hydrothermal Vents ◽

Direct Evidence ◽

Settling Velocity ◽

East Pacific Rise ◽

Deep Ocean ◽

Analytical Techniques ◽

Filtration Method ◽

East Pacific ◽

Marine Organic Carbon

AbstractDeciphering the origin, age, and composition of deep marine organic carbon remains a challenge in understanding the dynamics of the marine carbon cycle. In particular, the composition of aged organic carbon and what allows its persistence in the deep ocean and in sediment is unresolved. Here, we observe that both high and low temperature hydrothermal vents at the 9° 50′ N; 104° 17.5 W East Pacific Rise (EPR) vent field are a source for (sub)micron-sized graphite particles. We demonstrate that commonly applied analytical techniques for quantification of organic carbon detect graphite. These analyses thereby classify graphite as either dissolved or particulate organic carbon, depending on the particle size and filtration method, and overlook its relevance as a carbon source to the deep ocean. Settling velocity calculations indicate the potential for these (sub)micron particles to become entrained in the buoyant plume and distributed far from the vent fields. Thus, our observations provide direct evidence for hydrothermal vents acting as a source of old carbon to the deep ocean.

Download Full-text