Erratum to: Global and regional ocean carbon uptake and climate change: sensitivity to a substantial mitigation scenario

Abstract Climate change over the last several decades is suggested to cause a decrease in the magnitude of the uptake of CO2 by the Southern Ocean (Le Quere et al.). In this study, the atmospheric fields from NCEP R1 for the years 1948–2003 are used to drive an ocean biogeochemical model to probe how changes in the heat and freshwater fluxes and in the winds affect the Southern Ocean’s uptake of carbon. Over this period, the model simulations herein show that the increases in heat and freshwater fluxes drive a net increase in Southern Ocean uptake (south of 40°S) while the increases in wind stresses drive a net decrease in uptake. The total Southern Ocean response is nearly identical with the simulation without climate change because the heat and freshwater flux response is approximately both equal and opposite to the wind stress response. It is also shown that any change in the Southern Ocean anthropogenic carbon uptake is always opposed by a much larger change in the natural carbon air–sea exchange. For the 1948–2003 period, the changes in the natural carbon cycle dominate the Southern Ocean carbon uptake response to climate change. However, it is shown with a simple box model that when atmospheric CO2 levels exceed the partial pressure of carbon dioxide (pCO2) of the upwelled Circumpolar Deep Water (≈450 μatm) the Southern Ocean uptake response will be dominated by the changes in anthropogenic carbon uptake. Therefore, the suggestion that the Southern Ocean carbon uptake is a positive feedback to global warming is only a transient response that will change to a negative feedback in the near future if the present climate trend continues. Associated with the increased outgassing of carbon from the natural carbon cycle was a reduction in the aragonite saturation state of the high-latitude Southern Ocean (south of 60°S). In the simulation with just wind stress changes, the reduction in the high-latitude Southern Ocean aragonite saturation state (≈0.2) was comparable to the magnitude of the decline in the aragonite saturation state over the last 4 decades because of rising atmospheric CO2 levels (≈0.2). The simulation showed that climate change could significantly impact aragonite saturation state in the Southern Ocean.

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Nonlinearity of Carbon Cycle Feedbacks

Journal of Climate ◽

10.1175/2011jcli3898.1 ◽

2011 ◽

Vol 24 (16) ◽

pp. 4255-4275 ◽

Cited By ~ 32

Author(s):

Kirsten Zickfeld ◽

Michael Eby ◽

H. Damon Matthews ◽

Andreas Schmittner ◽

Andrew J. Weaver

Keyword(s):

Climate Change ◽

Carbon Cycle ◽

Climate Model ◽

Co2 Concentration ◽

Carbon Uptake ◽

Earth System ◽

Carbon Sinks ◽

Ocean Carbon ◽

Different Response ◽

Atmospheric Co2 Concentrations

Abstract Coupled climate–carbon models have shown the potential for large feedbacks between climate change, atmospheric CO2 concentrations, and global carbon sinks. Standard metrics of this feedback assume that the response of land and ocean carbon uptake to CO2 (concentration–carbon cycle feedback) and climate change (climate–carbon cycle feedback) combine linearly. This study explores the linearity in the carbon cycle response by analyzing simulations with an earth system model of intermediate complexity [the University of Victoria Earth System Climate Model (UVic ESCM)]. The results indicate that the concentration–carbon and climate–carbon cycle feedbacks do not combine linearly to the overall carbon cycle feedback. In this model, the carbon sinks on land and in the ocean are less efficient when exposed to the combined effect of elevated CO2 and climate change than to the linear combination of the two. The land accounts for about 80% of the nonlinearity, with the ocean accounting for the remaining 20%. On land, this nonlinearity is associated with the different response of vegetation and soil carbon uptake to climate in the presence or absence of the CO2 fertilization effect. In the ocean, the nonlinear response is caused by the interaction of changes in physical properties and anthropogenic CO2. These findings suggest that metrics of carbon cycle feedback that postulate linearity in the system’s response may not be adequate.

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Nonlinearity of Ocean Carbon Cycle Feedbacks in CMIP5 Earth System Models

Journal of Climate ◽

10.1175/jcli-d-13-00452.1 ◽

2014 ◽

Vol 27 (11) ◽

pp. 3869-3888 ◽

Cited By ~ 36

Author(s):

Jörg Schwinger ◽

Jerry F. Tjiputra ◽

Christoph Heinze ◽

Laurent Bopp ◽

James R. Christian ◽

...

Keyword(s):

Climate Change ◽

Carbon Cycle ◽

Ocean Circulation ◽

Coupled Model ◽

Co2 Concentration ◽

Atmospheric Co2 ◽

Climate Feedback ◽

Carbon Uptake ◽

Near Surface ◽

Ocean Carbon

Abstract Carbon cycle feedbacks are usually categorized into carbon–concentration and carbon–climate feedbacks, which arise owing to increasing atmospheric CO2 concentration and changing physical climate. Both feedbacks are often assumed to operate independently: that is, the total feedback can be expressed as the sum of two independent carbon fluxes that are functions of atmospheric CO2 and climate change, respectively. For phase 5 of the Coupled Model Intercomparison Project (CMIP5), radiatively and biogeochemically coupled simulations have been undertaken to better understand carbon cycle feedback processes. Results show that the sum of total ocean carbon uptake in the radiatively and biogeochemically coupled experiments is consistently larger by 19–58 petagrams of carbon (Pg C) than the uptake found in the fully coupled model runs. This nonlinearity is small compared to the total ocean carbon uptake (533–676 Pg C), but it is of the same order as the carbon–climate feedback. The weakening of ocean circulation and mixing with climate change makes the largest contribution to the nonlinear carbon cycle response since carbon transport to depth is suppressed in the fully relative to the biogeochemically coupled simulations, while the radiatively coupled experiment mainly measures the loss of near-surface carbon owing to warming of the ocean. Sea ice retreat and seawater carbon chemistry contribute less to the simulated nonlinearity. The authors’ results indicate that estimates of the ocean carbon–climate feedback derived from “warming only” (radiatively coupled) simulations may underestimate the reduction of ocean carbon uptake in a warm climate high CO2 world.

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Detecting Climate Fingerprints in Southern Ocean Carbon using a Biogeochemical Ocean Model

10.5194/egusphere-egu21-11116 ◽

2021 ◽

Author(s):

Rebecca Wright ◽

Corinne Le Quéré ◽

Erik Buitenhuis ◽

Dorothee Bakker

Keyword(s):

Climate Change ◽

Climate Variability ◽

Southern Ocean ◽

Observational Data ◽

Ecosystem Dynamics ◽

Global Ocean ◽

Subsurface Waters ◽

Climatic Drivers ◽

Ocean Carbon ◽

And Storage

The Southern Ocean plays an important role in the uptake, transport and storage of carbon by the global oceans. These properties are dominated by the response to the rise in anthropogenic CO2 in the atmosphere, but they are modulated by climate variability and climate change. Here we explore the effect of climate variability and climate change on ocean carbon uptake and storage in the Southern Ocean. We assess the extent to which climate change may be distinguishable from the anthropogenic CO2 signal and from the natural background variability. We use a combination of biogeochemical ocean modelling and observations from the GLODAPv2020 database to detect climate fingerprints in dissolved inorganic carbon (DIC).We conduct an ensemble of hindcast model simulations of the period 1920-2019, using a global ocean biogeochemical model which incorporates plankton ecosystem dynamics based on twelve plankton functional types. We use the model ensemble to isolate the changes in DIC due to rising anthropogenic CO2 alone and the changes due to climatic drivers (both climate variability and climate change), to determine their relative roles in the emerging total DIC trends and patterns. We analyse these DIC trends for a climate fingerprint over the past four decades, across spatial scales from the Southern Ocean, to basin level and down to regional ship transects. Highly sampled ship transects were extracted from GLODAPv2020 to obtain locations with the maximum spatiotemporal coverage, to reduce the inherent biases in patchy observational data. Model results were sampled to the ship transects to compare the climate fingerprints directly to the observational data.Model results show a substantial change in DIC over a 35-year period, with a range of more than +/- 30 &#181;mol/L. In the surface ocean, both anthropogenic CO2 and climatic drivers act to increase DIC concentration, with the influence of anthropogenic CO2 dominating at lower latitudes and the influence of climatic drivers dominating at higher latitudes. In the deep ocean, the anthropogenic CO2 generally acts to increase DIC except in the subsurface waters at lower latitudes, while climatic drivers act to decrease DIC concentration. The combined fingerprint of anthropogenic CO2 and climatic drivers on DIC concentration is for an increasing trend at the surface and decreasing trends in low latitude subsurface waters. Preliminary comparison of the model fingerprints to observational ship transects will also be presented.

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Linkage between multi-model uncertainties and the role of ocean heat content in ocean carbon uptake

Ocean Dynamics ◽

10.1007/s10236-018-1199-8 ◽

2018 ◽

Vol 68 (10) ◽

pp. 1311-1319

Author(s):

Weiwei Fu

Keyword(s):

Heat Content ◽

Ocean Heat Content ◽

Carbon Uptake ◽

Model Uncertainties ◽

Ocean Carbon

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Feedback mechanisms and sensitivities of ocean carbon uptake under global warming

Tellus B ◽

10.3402/tellusb.v53i5.16637 ◽

2001 ◽

Vol 53 (5) ◽

pp. 564-592 ◽

Cited By ~ 2

Author(s):

G.-K. Plattner ◽

F. Joos ◽

T. F. Stocker ◽

O. Marchal

Keyword(s):

Global Warming ◽

Carbon Uptake ◽

Feedback Mechanisms ◽

Ocean Carbon

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Carbon Uptake and Climate Change

Managing Boreal Forests in the Context of Climate Change ◽

10.1201/9781315166063-10 ◽

2016 ◽

pp. 63-88

Keyword(s):

Climate Change ◽

Carbon Uptake

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Diagnosing CO2 emission-induced feedbacks between the Southern Ocean carbon cycle and the climate system: A multiple Earth System Model analysis using a water mass tracking approach

Journal of Climate ◽

10.1175/jcli-d-20-0889.1 ◽

2021 ◽

pp. 1-62

Author(s):

Tilla Roy ◽

Jean Baptiste Sallée ◽

Laurent Bopp ◽

Nicolas Metzl

Keyword(s):

Climate Change ◽

Southern Ocean ◽

Water Mass ◽

Buffering Capacity ◽

Climate Impacts ◽

System Model ◽

Earth System ◽

Local Climate ◽

Mode Waters ◽

Ocean Carbon

AbstractAnthropogenic CO2 emission-induced feedbacks between the carbon cycle and the climate system perturb the efficiency of atmospheric CO2 uptake by land and ocean carbon reservoirs. The Southern Ocean is a region where these feedbacks can be largest and differ most among Earth System Model projections of 21st century climate change. To improve our mechanistic understanding of these feedbacks, we develop an automated procedure that tracks changes in the positions of Southern Ocean water masses and their carbon uptake. In an idealised ensemble of climate change projections, we diagnose two carbon–concentration feedbacks driven by atmospheric CO2 (due to increasing air-sea CO2 partial pressure difference, dpCO2, and reducing carbonate buffering capacity) and two carbon–climate feedbacks driven by climate change (due to changes in the water mass surface outcrop areas and local climate impacts). Collectively these feedbacks increase the CO2 uptake by the Southern Ocean and account for one-fifth of the global uptake of CO2 emissions. The increase in CO2 uptake is primarily dpCO2-driven, with Antarctic intermediate waters making the largest contribution; the remaining three feedbacks partially offset this increase (by ~25%), with maximum reductions in Subantarctic mode waters. The process dominating the decrease in CO2 uptake is water mass-dependent: reduction in carbonate buffering capacity in Subtropical and Subantarctic mode waters, local climate impacts in Antarctic intermediate waters, and reduction in outcrop areas in circumpolar deep waters and Antarctic bottom waters. Intermodel variability in the feedbacks is predominately dpCO2–driven and should be a focus of efforts to constrain projection uncertainty.

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Resolving ecological feedbacks on the ocean carbon sink in Earth system models

10.5194/esd-2020-41 ◽

2020 ◽

Author(s):

David I. Armstrong McKay ◽

Sarah E. Cornell ◽

Katherine Richardson ◽

Johan Rockström

Keyword(s):

Climate Change ◽

Carbon Sink ◽

Biological Pump ◽

Earth System ◽

Temperature Dependent ◽

System Models ◽

Plankton Ecology ◽

Ocean Carbon ◽

The Impact ◽

Earth System Models

Abstract. The Earth’s oceans are one of the largest sinks in the Earth system for anthropogenic CO2 emissions, acting as a negative feedback on climate change. Earth system models predict, though, that climate change will lead to a weakening ocean carbon uptake rate as warm water holds less dissolved CO2 and biological productivity declines. However, most Earth system models do not incorporate the impact of warming on bacterial remineralisation and rely on simplified representations of plankton ecology that do not resolve the potential impact of climate change on ecosystem structure or elemental stoichiometry. Here we use a recently-developed extension of the cGEnIE Earth system model (ecoGEnIE) featuring a trait-based scheme for plankton ecology (ECOGEM), and also incorporate cGEnIE's temperature-dependent remineralisation (TDR) scheme. This enables evaluation of the impact of both ecological dynamics and temperature-dependent remineralisation on the soft-tissue biological pump in response to climate change. We find that including TDR strengthens the biological pump relative to default runs due to increased nutrient recycling, while ECOGEM weakens the biological pump by enabling a shift to smaller plankton classes. However, interactions with concurrent ocean acidification cause opposite sign responses for the carbon sink in both cases: TDR leads to a smaller sink relative to default runs whereas ECOGEM leads to a larger sink. Combining TDR and ECOGEM results in a net strengthening of the biological pump and a small net reduction in carbon sink relative to default. These results clearly illustrate the substantial degree to which ecological dynamics and biodiversity modulate the strength of climate-biosphere feedbacks, and demonstrate that Earth system models need to incorporate more ecological complexity in order to resolve carbon sink weakening.

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