scholarly journals Climate-induced interannual variability of marine primary and export production in three global coupled climate carbon cycle models

2008 ◽  
Vol 5 (2) ◽  
pp. 597-614 ◽  
Author(s):  
B. Schneider ◽  
L. Bopp ◽  
M. Gehlen ◽  
J. Segschneider ◽  
T. L. Frölicher ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Temporal Variability ◽  
Future Climate Change ◽  
Spatial And Temporal Variability ◽  
Ocean Colour ◽  
Coupled Models ◽  
Low Latitude ◽  
Tropical Ocean ◽  
Export Production ◽  
Ocean Carbon

Abstract. Fully coupled climate carbon cycle models are sophisticated tools that are used to predict future climate change and its impact on the land and ocean carbon cycles. These models should be able to adequately represent natural variability, requiring model validation by observations. The present study focuses on the ocean carbon cycle component, in particular the spatial and temporal variability in net primary productivity (PP) and export production (EP) of particulate organic carbon (POC). Results from three coupled climate carbon cycle models (IPSL, MPIM, NCAR) are compared with observation-based estimates derived from satellite measurements of ocean colour and results from inverse modelling (data assimilation). Satellite observations of ocean colour have shown that temporal variability of PP on the global scale is largely dominated by the permanently stratified, low-latitude ocean (Behrenfeld et al., 2006) with stronger stratification (higher sea surface temperature; SST) being associated with negative PP anomalies. Results from all three coupled models confirm the role of the low-latitude, permanently stratified ocean for anomalies in globally integrated PP, but only one model (IPSL) also reproduces the inverse relationship between stratification (SST) and PP. An adequate representation of iron and macronutrient co-limitation of phytoplankton growth in the tropical ocean has shown to be the crucial mechanism determining the capability of the models to reproduce observed interactions between climate and PP.

scholarly journals Spatio-temporal variability of marine primary and export production in three global coupled climate carbon cycle models

2007 ◽  
Vol 4 (3) ◽  
pp. 1877-1921 ◽  
Author(s):  
B. Schneider ◽  
L. Bopp ◽  
M. Gehlen ◽  
J. Segschneider ◽  
T. L. Frölicher ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Temporal Variability ◽  
Satellite Observations ◽  
Future Climate Change ◽  
Nutrient Concentrations ◽  
Ocean Colour ◽  
Coupled Models ◽  
Low Latitude ◽  
Export Production ◽  
The Impact

Abstract. This study compares spatial and temporal variability in net primary productivity (PP) and particulate organic carbon (POC) export production (EP) from three different coupled climate carbon cycle models (IPSL, MPIM, NCAR) with observation-based estimates derived from satellite measurements of ocean colour and inverse modelling. Satellite observations of ocean colour have shown that temporal variability of PP on the global scale is largely dominated by the permanently stratified, low-latitude ocean (Behrenfeld et al., 2006)\\nocite{Behrenfeld06} with stronger stratification (higher SSTs) leading to negative PP anomalies and vice versa. Results from all three coupled models confirm the role of the low-latitude, permanently stratified ocean for global PP anomalies. Two of the models also reproduce the inverse relationship between stratification (SST) and PP, especially in the equatorial Pacific. With the help of the model results we are able to explain the chain of cause and effect leading from stratification (SST) through nutrient concentrations to PP and finally to EP. There are significant uncertainties in observational PP and especially EP. Our finding of a good agreement between independent estimates from coupled models and satellite observations provides increased confidence that such models can be used as a first basis to estimate the impact of future climate change on marine productivity and carbon export.

scholarly journals Climate–Carbon Cycle Feedback Analysis: Results from the C4MIP Model Intercomparison

2006 ◽  
Vol 19 (14) ◽  
pp. 3337-3353 ◽  
Author(s):  
P. Friedlingstein ◽  
P. Cox ◽  
R. Betts ◽  
L. Bopp ◽  
W. von Bloh ◽  
...  
Keyword(s):  
Climate Change ◽  
Carbon Cycle ◽  
Net Primary Productivity ◽  
Future Climate ◽  
Climate Feedback ◽  
Future Climate Change ◽  
Ocean Carbon Cycle ◽  
Intergovernmental Panel ◽  
Ocean Carbon ◽  
The Impact

Abstract Eleven coupled climate–carbon cycle models used a common protocol to study the coupling between climate change and the carbon cycle. The models were forced by historical emissions and the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) A2 anthropogenic emissions of CO2 for the 1850–2100 time period. For each model, two simulations were performed in order to isolate the impact of climate change on the land and ocean carbon cycle, and therefore the climate feedback on the atmospheric CO2 concentration growth rate. There was unanimous agreement among the models that future climate change will reduce the efficiency of the earth system to absorb the anthropogenic carbon perturbation. A larger fraction of anthropogenic CO2 will stay airborne if climate change is accounted for. By the end of the twenty-first century, this additional CO2 varied between 20 and 200 ppm for the two extreme models, the majority of the models lying between 50 and 100 ppm. The higher CO2 levels led to an additional climate warming ranging between 0.1° and 1.5°C. All models simulated a negative sensitivity for both the land and the ocean carbon cycle to future climate. However, there was still a large uncertainty on the magnitude of these sensitivities. Eight models attributed most of the changes to the land, while three attributed it to the ocean. Also, a majority of the models located the reduction of land carbon uptake in the Tropics. However, the attribution of the land sensitivity to changes in net primary productivity versus changes in respiration is still subject to debate; no consensus emerged among the models.

scholarly journals High and low latitude controls on Mid-Brunhes coccolithophore bloom and its implications on ocean carbon cycle

2021 ◽  
Author(s):  
Hongrui Zhang ◽  
Chuanlian Liu ◽  
Iván Hernández‐Almeida ◽  
Luz Maria Mejia ◽  
Heather Stoll
Keyword(s):  
Carbon Cycle ◽  
Southern Ocean ◽  
High Latitude ◽  
Polar Front ◽  
Low Latitude ◽  
Ocean Carbon Cycle ◽  
High Productivity ◽  
Driving Mechanisms ◽  
Light Duration ◽  
Ocean Carbon

Abstract Periodic ~400 kyr orbital scale variations in the ocean carbon cycle, manifest in indicators of deep sea dissolution and benthic 13C, have been observed throughout the Cenozoic but the driving mechanisms remain under debate. Changes in coccolithophore productivity may change the global rain ratio (Corganic: Cinorganic fluxes from ocean into sediment) and the balance of ocean carbonate system and thereby, potentially contributing to the ~400 kyr oscillation of the marine carbon cycle. Some evidence suggests that Pleistocene coccolithophore productivity was characterized by “bloom” events of high productivity coincident with the orbital benthic 13C signal. However, there is no consensus on the mechanism responsible for bloom events nor whether they were regional or global phenomena. In this study, we investigate the timing and spatial pattern of the most recent purported coccolithophore bloom event, which occurred during the Mid-Brunhes period. We find that maximum coccolithophore productivity is diachronous, peaking in the Southern Ocean sub-Antarctic zone with eccentricity minimum (~430 ka), peaking in upwelling zones some ~28 kyr later, and finally peaking in the western tropical Pacific occurred some ~80 kyr later. Simple globally homogeneous mechanisms of driving productivity such as temperature or light duration are not consistent with this pattern. Rather, we propose a dual high and low latitude control on blooms. Coincident with eccentricity minimum, increased high-latitude diatom silica consumption lowers the Si/P, leading to coccolithophorid blooms in the Southern Ocean north of the polar front. Coincident with increasing eccentricity, stronger tropical monsoons deliver higher fluvial nutrients to surface waters, increasing total (diatom and coccolithophore) productivity. Most of the tropical and subtropical locations are influenced by both processes with varying degrees, through the effect of silicic acid leakage on tropical thermocline waters and monsoon-related nutrient supply. Moreover, we propose that the high latitude processes have intensified over the Pleistocene, extending the 405 kyr carbon cycle to about 500 kyr.

Climate Change and Carbon Cycle Feedbacks

2016 ◽  
Author(s):  
Pierre Friedlingstein
Keyword(s):  
Climate Change ◽  
Carbon Cycle ◽  
Time Scales ◽  
Positive Feedback ◽  
Future Climate Change ◽  
Tightly Coupled ◽  
Centennial Time Scale ◽  
Ocean Carbon ◽  
Earth System Models ◽  
Global Carbon

Climate and carbon cycle are tightly coupled on many time scales, from the interannual to the multimillennial. Observation always shows a positive feedback between climate and the carbon cycle: elevated atmospheric CO2 leads to warming, but warming is expected to further release of carbon to the atmosphere, enhancing the atmospheric CO2 increase. Earth system models do represent these climate–carbon cycle feedbacks, always simulating a positive feedback over the 21st century; that is, climate change will lead to loss of carbon from the land and ocean reservoirs. These processes partially offset the increases in land and ocean carbon sinks caused by rising atmospheric CO2. As a result, more of the emitted anthropogenic CO2 will remain in the atmosphere. There is, however, a large uncertainty on the magnitude of this feedback. Recent studies now help to reduce this uncertainty. On short, interannual, time scales, El Niño years record larger-than-average atmospheric CO2 growth rate, with tropical land ecosystems being the main drivers. These climate–carbon cycle anomalies can be used as emerging constraint on the tropical land carbon response to future climate change. On a longer, centennial, time scale, the variability of atmospheric CO2 found in records of the last millennium can be used to constrain the overall global carbon cycle response to climate. These independent methods confirm that the climate–carbon cycle feedback is positive, but probably more consistent with the lower end of the comprehensive models range, excluding very large climate–carbon cycle feedbacks.

scholarly journals The "Ocean Carbon States" Database: a proof-of-concept application of cluster analysis in the ocean carbon cycle

2017 ◽  
Author(s):  
Rebecca Latto ◽  
Anastasia Romanou
Keyword(s):  
Data Mining ◽  
Cluster Analysis ◽  
Carbon Cycle ◽  
Observational Data ◽  
Numerical Models ◽  
Future Climate Change ◽  
Model Assessment ◽  
Proof Of Concept ◽  
Ocean Carbon Cycle ◽  
Ocean Carbon

Abstract. In this paper, we present a database of the basic regimes of carbon cycle in the ocean as obtained using data mining and patter recognition techniques in observational as well as model data. Advanced data mining techniques are becoming widely used in Climate and Earth Sciences with the purpose of extracting new meaningful information from large and complex datasets. Such techniques need to be rigorously tested, however, in simple, well-understood cases to better assess their utility. This is particularly important for studies of the global carbon cycle, where the interaction of physical and biogeochemical drivers confounds our ability to accurately describe, understand, and predict CO2 concentrations and their changes in the major planetary carbon reservoirs. In addition to observational data of the carbon cycle, numerical simulations of the Earth System are becoming increasingly more complex and harder to evaluate. Without reliable numerical models, however, our predictions of future climate change are haphazard. Here we describe the use of a specific data-mining technique, cluster analysis, as a means of identifying and comparing spatial and temporal patterns extracted from observational and model datasets. As the observational data is organized into various regimes, which we will call "ocean carbon states", we gain insight into the physical and/or biogeochemical processes controlling the ocean carbon cycle in nature as well as how well these processes are simulated by the model. Assessment of cluster analysis results demonstrates that this technique effectively produces realistic, dynamic regimes that can be associated with specific processes at different temporal scales for both observations and the model. Furthermore, these regimes can be used to illustrate and characterize the model biases in the model air-sea flux of CO2 which are then attributed to model misrepresentations of salinity, sea surface temperature, wind speed, and nitrate. The goal of this proof-of-concept study is to establish a methodology for implementing and interpreting k-means cluster analysis on observations and model output which will enable us to subsequently apply the analysis to larger, higher frequency datasets of the ocean carbon cycle. To enable further testing and extending the method discussed, all data and analysis scripts are freely available at data.giss.nasa.gov/oceans/carbonstates/ (DOI: https://doi.org/doi:10.5281/zenodo.996891).

scholarly journals Reframing the carbon cycle of the subpolar Southern Ocean

2019 ◽  
Vol 5 (8) ◽  
pp. eaav6410 ◽  
Author(s):  
Graeme A. MacGilchrist ◽  
Alberto C. Naveira Garabato ◽  
Peter J. Brown ◽  
Loïc Jullion ◽  
Sheldon Bacon ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Southern Ocean ◽  
Global Climate ◽  
Dominant Role ◽  
World Ocean ◽  
Future Climate Change ◽  
Carbon Uptake ◽  
Shelf Sea ◽  
Horizontal Circulation ◽  
Ocean Carbon

Global climate is critically sensitive to physical and biogeochemical dynamics in the subpolar Southern Ocean, since it is here that deep, carbon-rich layers of the world ocean outcrop and exchange carbon with the atmosphere. Here, we present evidence that the conventional framework for the subpolar Southern Ocean carbon cycle, which attributes a dominant role to the vertical overturning circulation and shelf-sea processes, fundamentally misrepresents the drivers of regional carbon uptake. Observations in the Weddell Gyre—a key representative region of the subpolar Southern Ocean—show that the rate of carbon uptake is set by an interplay between the Gyre’s horizontal circulation and the remineralization at mid-depths of organic carbon sourced from biological production in the central gyre. These results demonstrate that reframing the carbon cycle of the subpolar Southern Ocean is an essential step to better define its role in past and future climate change.

scholarly journals An isopycnic ocean carbon cycle model

2009 ◽  
Vol 2 (2) ◽  
pp. 1023-1079 ◽  
Author(s):  
K. M. Assmann ◽  
M. Bentsen ◽  
J. Segschneider ◽  
C. Heinze
Keyword(s):  
Carbon Cycle ◽  
Global Ocean ◽  
System Modelling ◽  
Surface Boundary ◽  
Cycle Model ◽  
Biological Production ◽  
Carbon Cycle Model ◽  
Export Production ◽  
Sensitivity Studies ◽  
Ocean Carbon

Abstract. The carbon cycle is a major forcing component in the global climate system. Modelling studies aiming to explain recent and past climatic changes and to project future ones thus increasingly include the interaction between the physical and biogeochemical systems. Their ocean components are generally z-coordinate models that are conceptually easy to use but that employ a vertical coordinate that is alien to the real ocean structure. Here we present first results from a newly developed isopycnic carbon cycle model and demonstrate the viability of using an isopycnic physical component for this purpose. As expected, the model represents interior ocean transport of biogeochemical tracers well and produces realistic tracer distributions. Difficulties in employing a purely isopycnic coordinate lie mainly in the treatment of the surface boundary layer which is often represented by a bulk mixed layer. The most significant adjustments of the biogeochemical code for use with an isopycnic coordinate are in the representation of upper ocean biological production. We present a series of sensitivity studies exploring the effect of changes in biogeochemical and physical processes on export production and nutrient distribution. Apart from giving us pointers for further model development, they highlight the importance of preformed nutrient distributions in the Southern Ocean for global nutrient distributions. Use of a prognostic slab atmosphere allows us to assess the effect of the changes in export production on global ocean carbon uptake and atmospheric CO2 levels. Sensitivity studies show that iron limitation for biological particle production, the treatment of light penetration for biological production, and the role of diapycnal mixing result in significant changes of modelled air-sea fluxes and nutrient distributions.

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