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

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

<p>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 CO<sub>2</sub> 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 CO<sub>2</sub> 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).</p><p>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 CO<sub>2</sub> 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.</p><p>Model results show a substantial change in DIC over a 35-year period, with a range of more than +/- 30 µmol/L. In the surface ocean, both anthropogenic CO<sub>2</sub> and climatic drivers act to increase DIC concentration, with the influence of anthropogenic CO<sub>2</sub> dominating at lower latitudes and the influence of climatic drivers dominating at higher latitudes. In the deep ocean, the anthropogenic CO<sub>2</sub> 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 CO<sub>2</sub> 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.</p>

scholarly journals 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

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.

The Southern Ocean carbon sink 1985-2018: first results of the RECCAP2 project

2021 ◽  
Author(s):  
Judith Hauck ◽  
Luke Gregor ◽  
Cara Nissen ◽  
Eric Mortenson ◽  
Seth Bushinsky ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Seasonal Cycle ◽  
Carbon Sink ◽  
Global Ocean ◽  
Biogeochemical Models ◽  
Wide Range ◽  
Data Products ◽  
First Results ◽  
Ocean Carbon ◽  
Indian Sector

<p>The Southern Ocean is the main gateway for anthropogenic CO<sub>2</sub> into the ocean owing to the upwelling of old water masses with low anthropogenic CO<sub>2</sub> concentration, and the transport of the newly equilibrated surface waters into the ocean interior through intermediate, deep and bottom water formation. Here we present first results of the Southern Ocean chapter of RECCAP2, which is the Global Carbon Project’s second systematic study on Regional Carbon Cycle Assessment and Processes. In the Southern Ocean chapter, we aim to assess the Southern Ocean carbon sink 1985-2018 from a wide range of available models and data sets, and to identify patterns of regional and temporal variability, model limitations and future challenges.</p><p>We gathered global and regional estimates of the air-sea CO<sub>2</sub> flux over the period 1985-2018 from global ocean biogeochemical models, surface pCO<sub>2</sub>-based data products, and data-assimilated models. The analysis on the Southern Ocean quantified geographical patterns in the annual mean and seasonal amplitude of air-sea CO<sub>2</sub> flux, with results presented here aggregated to the level of large-scale ocean biomes.</p><p>Considering the suite of observed and modelled estimates, we found that the subtropical seasonally stratified (STSS) biome stands out with the largest air-sea CO<sub>2</sub> flux per area and a seasonal cycle with largest ocean uptake of CO<sub>2</sub> in winter, whereas the ice (ICE) biome is characterized by a large ensemble spread and a pronounced seasonal cycle with the largest ocean uptake of CO<sub>2</sub> in summer. Connecting these two, the subpolar seasonally stratified (SPSS) biome has intermediate flux densities (flux per area), and most models have difficulties simulating the seasonal cycle with strongest uptake during the summer months.</p><p>Our analysis also reveals distinct differences between the Atlantic, Pacific and Indian sectors of the aforementioned biomes. In the STSS, the Indian sector contributes most to the ocean carbon sink, followed by the Atlantic and then Pacific sectors. This hierarchy is less pronounced in the models than in the data-products. In the SPSS, only the Atlantic sector exhibits net CO<sub>2</sub> uptake in all years, likely linked to strong biological production. In the ICE biome, the Atlantic and Pacific sectors take up more CO<sub>2</sub> than the Indian sector, suggesting a potential role of the Weddell and Ross Gyres.</p><p>These first results confirm the global relevance of the Southern Ocean carbon sink and highlight the strong regional and interannual variability of the Southern Ocean carbon uptake in connection to physical and biogeochemical processes.</p>

Influences of climate change on the uptake and storage of anthropogenic CO2 in the global ocean

2012 ◽  
Vol 26 (3) ◽  
pp. 304-317 ◽  
Author(s):  
Yangchun Li ◽  
Yongfu Xu ◽  
Min Chu ◽  
Yongqiang Yu
Keyword(s):  
Climate Change ◽  
Global Ocean ◽  
Anthropogenic Co2 ◽  
And Storage

scholarly journals Environmental forcing and Southern Ocean marine predator populations: effects of climate change and variability

2007 ◽  
Vol 362 (1488) ◽  
pp. 2351-2365 ◽  
Author(s):  
P.N Trathan ◽  
J Forcada ◽  
E.J Murphy
Keyword(s):  
Climate Change ◽  
Southern Ocean ◽  
Food Webs ◽  
Time Scales ◽  
Trophic Level ◽  
Global Ocean ◽  
Ecosystem Structure ◽  
Marine Predator ◽  
Enso Events ◽  
Biological Responses

The Southern Ocean is a major component within the global ocean and climate system and potentially the location where the most rapid climate change is most likely to happen, particularly in the high-latitude polar regions. In these regions, even small temperature changes can potentially lead to major environmental perturbations. Climate change is likely to be regional and may be expressed in various ways, including alterations to climate and weather patterns across a variety of time-scales that include changes to the long interdecadal background signals such as the development of the El Niño–Southern Oscillation (ENSO). Oscillating climate signals such as ENSO potentially provide a unique opportunity to explore how biological communities respond to change. This approach is based on the premise that biological responses to shorter-term sub-decadal climate variability signals are potentially the best predictor of biological responses over longer time-scales. Around the Southern Ocean, marine predator populations show periodicity in breeding performance and productivity, with relationships with the environment driven by physical forcing from the ENSO region in the Pacific. Wherever examined, these relationships are congruent with mid-trophic-level processes that are also correlated with environmental variability. The short-term changes to ecosystem structure and function observed during ENSO events herald potential long-term changes that may ensue following regional climate change. For example, in the South Atlantic, failure of Antarctic krill recruitment will inevitably foreshadow recruitment failures in a range of higher trophic-level marine predators. Where predator species are not able to accommodate by switching to other prey species, population-level changes will follow. The Southern Ocean, though oceanographically interconnected, is not a single ecosystem and different areas are dominated by different food webs. Where species occupy different positions in different regional food webs, there is the potential to make predictions about future change scenarios.

scholarly journals Controls of ocean carbon cycle feedbacks from different ocean basins and meridional overturning in CMIP6

2021 ◽  
Author(s):  
Anna Katavouta ◽  
Richard G. Williams
Keyword(s):  
Climate Change ◽  
Atlantic Ocean ◽  
Carbon Cycle ◽  
Southern Ocean ◽  
Carbon Storage ◽  
Carbon Concentration ◽  
Climate Feedback ◽  
Meridional Overturning ◽  
Ocean Carbon ◽  
Southern Oceans

Abstract. The ocean response to carbon emissions involves a competition between the increase in atmospheric CO2 acting to enhance the ocean carbon storage, characterised by the carbon-concentration feedback, and climate change acting to decrease the ocean carbon storage, characterised by the carbon-climate feedback. The contribution from different ocean basins to the carbon cycle feedbacks and its control by the ocean carbonate chemistry, physical ventilation and biological processes is explored in diagnostics of 10 CMIP6 Earth system models. To gain mechanist insight, the dependence of these feedbacks to the Atlantic Meridional Overturning Circulation (AMOC) is also investigated in an idealised climate model and the CMIP6 models. The Atlantic, Pacific and Southern Oceans contribute equally to the carbon-concentration feedback, despite their different size. This large contribution from the Atlantic Ocean relative to its size is associated with an enhanced carbon storage in the ocean interior due to a strong local physical ventilation and an influx of carbon transported from the Southern Ocean. The Atlantic Ocean provides the largest contribution to the carbon-climate feedback relative to its size, which is primarily due to climate change acting to reduce the physical ventilation. The Southern Ocean provides a relatively small contribution to the carbon-climate feedback, due to a compensation between the climate effects of the combined decrease in solubility and physical ventilation, and the increase in accumulation of regenerated carbon in the ocean interior. In the Atlantic Ocean, the AMOC strength and its weakening with warming has a strong control on the carbon cycle feedbacks that leads to a moderate dependence of these feedbacks to AMOC on global scale. In the Pacific, Indian and Southern Oceans there is no clear correlation between AMOC and the carbon cycle feedbacks, suggesting that other processes control the ocean ventilation and carbon storage there.

scholarly journals Twentieth-Century Oceanic Carbon Uptake and Storage in CESM1(BGC)*

2013 ◽  
Vol 26 (18) ◽  
pp. 6775-6800 ◽  
Author(s):  
Matthew C. Long ◽  
Keith Lindsay ◽  
Synte Peacock ◽  
J. Keith Moore ◽  
Scott C. Doney
Keyword(s):  
Climate Variability ◽  
Carbon Cycle ◽  
North Atlantic ◽  
Carbon Uptake ◽  
Dissolution Profile ◽  
Co2 Fluxes ◽  
Zone Formation ◽  
The North ◽  
Ocean Carbon ◽  
And Storage

Abstract Ocean carbon uptake and storage simulated by the Community Earth System Model, version 1–Biogeochemistry [CESM1(BGC)], is described and compared to observations. Fully coupled and ocean-ice configurations are examined; both capture many aspects of the spatial structure and seasonality of surface carbon fields. Nearly ubiquitous negative biases in surface alkalinity result from the prescribed carbonate dissolution profile. The modeled sea–air CO2 fluxes match observationally based estimates over much of the ocean; significant deviations appear in the Southern Ocean. Surface ocean pCO2 is biased high in the subantarctic and low in the sea ice zone. Formation of the water masses dominating anthropogenic CO2 (Cant) uptake in the Southern Hemisphere is weak in the model, leading to significant negative biases in Cant and chlorofluorocarbon (CFC) storage at intermediate depths. Column inventories of Cant appear too high, by contrast, in the North Atlantic. In spite of the positive bias, this marks an improvement over prior versions of the model, which underestimated North Atlantic uptake. The change in behavior is attributable to a new parameterization of density-driven overflows. CESM1(BGC) provides a relatively robust representation of the ocean–carbon cycle response to climate variability. Statistical metrics of modeled interannual variability in sea–air CO2 fluxes compare reasonably well to observationally based estimates. The carbon cycle response to key modes of climate variability is basically similar in the coupled and forced ocean-ice models; however, the two differ in regional detail and in the strength of teleconnections.

scholarly journals Relationship between Ocean Carbon and Heat Multidecadal Variability

2018 ◽  
Vol 31 (4) ◽  
pp. 1467-1482 ◽  
Author(s):  
Jordan Thomas ◽  
Darryn Waugh ◽  
Anand Gnanadesikan
Keyword(s):  
Southern Ocean ◽  
Carbon Content ◽  
Climate Model ◽  
Deep Convection ◽  
Heat Content ◽  
Weddell Sea ◽  
Global Ocean ◽  
Multidecadal Variability ◽  
Model Simulations ◽  
Ocean Carbon

The global ocean serves as a critical sink for anthropogenic carbon and heat. While significant effort has been dedicated to quantifying the oceanic uptake of these quantities, less research has been conducted on the mechanisms underlying decadal-to-centennial variability in oceanic heat and carbon. Therefore, little is understood about how much such variability may have obscured or reinforced anthropogenic change. Here the relationship between oceanic heat and carbon content is examined in a suite of coupled climate model simulations that use different parameterization settings for mesoscale mixing. The differences in mesoscale mixing result in very different multidecadal variability, especially in the Weddell Sea where the characteristics of deep convection are drastically changed. Although the magnitude and frequency of variability in global heat and carbon content is different across the model simulations, there is a robust anticorrelation between global heat and carbon content in all simulations. Global carbon content variability is primarily driven by Southern Ocean carbon variability. This contrasts with global heat content variability. Global heat content is primarily driven by variability in the southern midlatitudes and tropics, which opposes the Southern Ocean variability.

Changes in the Antarctic sea ice ecosystem: potential effects on krill and baleen whales

2008 ◽  
Vol 59 (5) ◽  
pp. 361 ◽  
Author(s):  
Stephen Nicol ◽  
Anthony Worby ◽  
Rebecca Leaper
Keyword(s):  
Climate Change ◽  
Southern Ocean ◽  
Sea Ice ◽  
Ocean Circulation ◽  
Trophic Levels ◽  
Global Ocean ◽  
Ecological Change ◽  
Cetacean Species ◽  
Baleen Whales ◽  
The Antarctic

The annual formation and loss of some 15 million km2 of sea ice around the Antarctic significantly affects global ocean circulation, particularly through the formation of dense bottom water. As one of the most profound seasonal changes on Earth, the formation and decay of sea ice plays a major role in climate processes. It is also likely to be impacted by climate change, potentially changing the productivity of the Antarctic region. The sea ice zone supports much wildlife, particularly large vertebrates such as seals, seabirds and whales, some exploited to near extinction. Cetacean species in the Southern Ocean will be directly impacted by changes in sea ice patterns as well as indirectly by changes in their principal prey, Antarctic krill, affected by modifications to their own environment through climate change. Understanding how climate change will affect species at all trophic levels in the Southern Ocean requires new approaches and integrated research programs. This review focuses on the current state of knowledge of the sea ice zone and examines the potential for climatic and ecological change in the region. In the context of changes already documented for seals and seabirds, it discusses potential effects on the most conspicuous vertebrate of the region, baleen whales.

scholarly journals Coupling of Surface Ocean Heat and Carbon Perturbations over the Subtropical Cells under Twenty-First Century Climate Change

2020 ◽  
Vol 33 (23) ◽  
pp. 10321-10338
Author(s):  
K. B. Rodgers ◽  
M. Ishii ◽  
T. L. Frölicher ◽  
S. Schlunegger ◽  
O. Aumont ◽  
...  
Keyword(s):  
Climate Change ◽  
Feedback Mechanism ◽  
Earth System Model ◽  
System Model ◽  
Climate Feedback ◽  
Global Ocean ◽  
Earth System ◽  
Driving Mechanisms ◽  
Ocean Carbon ◽  
Additional Perturbation

AbstractIt is well established that the ocean plays an important role in absorbing anthropogenic carbon Cant from the atmosphere. Under global warming, Earth system model simulations and theoretical arguments indicate that the capacity of the ocean to absorb Cant will be reduced, with this constituting a positive carbon–climate feedback. Here we apply a suite of sensitivity simulations with a comprehensive Earth system model to demonstrate that the surface waters of the shallow overturning structures (spanning 45°S–45°N) sustain nearly half of the global ocean carbon–climate feedback. The main results reveal a feedback that is initially triggered by warming but that amplifies over time as Cant invasion enhances the sensitivity of surface pCO2 to further warming, particularly in the warmer season. Importantly, this “heat–carbon feedback” mechanism is distinct from (and significantly weaker than) what one would expect from temperature-controlled solubility perturbations to pCO2 alone. It finds independent confirmation in an additional perturbation experiment with the same Earth system model. There mechanism denial is applied by disallowing the secular trend in the physical state of the ocean under climate change, while simultaneously allowing the effects of heating to impact sea surface pCO2 and thereby CO2 uptake. Reemergence of Cant along the equator within the shallow overturning circulation plays an important role in the heat–carbon feedback, with the decadal renewal time scale for thermocline waters modulating the feedback response. The results here for 45°S–45°N stand in contrast to what is found in the high latitudes, where a clear signature of a broader range of driving mechanisms is present.

The Variable Southern Ocean Carbon Sink

2019 ◽  
Vol 11 (1) ◽  
pp. 159-186 ◽  
Author(s):  
Nicolas Gruber ◽  
Peter Landschützer ◽  
Nicole S. Lovenduski
Keyword(s):  
Southern Ocean ◽  
Carbon Sink ◽  
Global Ocean ◽  
The Pacific ◽  
Southward Shift ◽  
Storage Rate ◽  
The Pacific Ocean ◽  
Ocean Models ◽  
Ocean Carbon ◽  
Decadal Predictions

The CO2uptake by the Southern Ocean (<35°S) varies substantially on all timescales and is a major determinant of the variations of the global ocean carbon sink. Particularly strong are the decadal changes characterized by a weakening period of the Southern Ocean carbon sink in the 1990s and a rebound after 2000. The weakening in the 1990s resulted primarily from a southward shift of the westerlies that enhanced the upwelling and outgassing of respired (i.e., natural) CO2. The concurrent reduction in the storage rate of anthropogenic CO2in the mode and intermediate waters south of 35°S suggests that this shift also decreased the uptake of anthropogenic CO2. The rebound and the subsequent strong, decade-long reinvigoration of the carbon sink appear to have been driven by cooling in the Pacific Ocean, enhanced stratification in the Atlantic and Indian Ocean sectors, and a reduced overturning. Current-generation ocean models generally do not reproduce these variations and are poorly skilled at making decadal predictions in this region.

Sign in / Sign up

Export Citation Format

Share Document