Bopp Laurent

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Correction to “Using altimetry to help explain patchy changes in hydrographic carbon measurements”

(American Geophysical Union, 2009-12-09) Rodgers, Keith B. ; Key, Robert M. ; Gnanadesikan, Anand ; Sarmiento, Jorge L. ; Aumont, Olivier ; Bopp, Laurent ; Doney, Scott C. ; Dunne, John P. ; Glover, David M. ; Ishida, Akio ; Ishii, Masao ; Jacobson, Andrew R. ; Monaco, Claire Lo ; Maier-Reimer, Ernst ; Mercier, Herlé ; Metzl, Nicolas ; Perez, Fiz F. ; Rios, Aida F. ; Wanninkhof, Rik ; Wetzel, Patrick ; Winn, Christopher D. ; Yamanaka, Yasuhiro
Comparing food web structures and dynamics across a suite of global marine ecosystem models

(Elsevier, 2013-05-16) Sailley, Sevrine F. ; Vogt, Meike ; Doney, Scott C. ; Aita, M. N. ; Bopp, Laurent ; Buitenhuis, Erik T. ; Hashioka, Taketo ; Lima, Ivan D. ; Le Quere, Corinne ; Yamanaka, Yasuhiro

Dynamic Green Ocean Models (DGOMs) include different sets of Plankton Functional Types (PFTs) and equations, thus different interactions and food webs. Using four DGOMs (CCSM-BEC, PISCES, NEMURO and PlankTOM5) we explore how predator–prey interactions influence food web dynamics. Using each model's equations and biomass output, interaction strengths (direct and specific) were calculated and the role of zooplankton in modeled food webs examined. In CCSM-BEC the single size-class adaptive zooplankton preys on different phytoplankton groups according to prey availability and food preferences, resulting in a strong top-down control. In PISCES the micro- and meso-zooplankton groups compete for food resources, grazing phytoplankton depending on their availability in a mixture of bottom-up and top-down control. In NEMURO macrozooplankton controls the biomass of other zooplankton PFTs and defines the structure of the food web with a strong top-down control within the zooplankton. In PlankTOM5, competition and predation between micro- and meso-zooplankton along with strong preferences for nanophytoplankton and diatoms, respectively, leads to their mutual exclusion with a mixture of bottom-up and top-down control of the plankton community composition. In each model, the grazing pressure of the zooplankton PFTs and the way it is exerted on their preys may result in the food web dynamics and structure of the model to diverge from the one that was intended when designing the model. Our approach shows that the food web dynamics, in particular the strength of the predator–prey interactions, are driven by the choice of parameters and more specifically the food preferences. Consequently, our findings stress the importance of equation and parameter choice as they define interactions between PFTs and overall food web dynamics (competition, bottom-up or top-down effects). Also, the differences in the simulated food-webs between different models highlight the gap of knowledge for zooplankton rates and predator–prey interactions. In particular, concerted effort is needed to identify the key growth and loss parameters and interactions and quantify them with targeted laboratory experiments in order to bring our understanding of zooplankton at a similar level to phytoplankton.
Recent trends and drivers of regional sources and sinks of carbon dioxide

(Copernicus Publications on behalf of the European Geosciences Union, 2015-02-02) Sitch, Stephen ; Friedlingstein, Pierre ; Gruber, Nicolas ; Jones, S. D. ; Murray-Tortarolo, G. ; Ahlstrom, Andreas P. ; Doney, Scott C. ; Graven, Heather ; Heinze, Christoph ; Huntingford, Chris ; Levis, Samuel ; Levy, Peter E. ; Lomas, Mark ; Poulter, Benjamin ; Viovy, Nicolas ; Zaehle, Sonke ; Zeng, Ning ; Arneth, Almut ; Bonan, Gordon B. ; Bopp, Laurent ; Canadell, Josep G. ; Chevallier, Frédéric ; Ciais, Philippe ; Ellis, Richard ; Gloor, Emanuel ; Peylin, Philippe ; Piao, S. L. ; Le Quere, Corinne ; Smith, Benjamin ; Zhu, Zaichun ; Myneni, Ranga

The land and ocean absorb on average just over half of the anthropogenic emissions of carbon dioxide (CO2) every year. These CO2 "sinks" are modulated by climate change and variability. Here we use a suite of nine dynamic global vegetation models (DGVMs) and four ocean biogeochemical general circulation models (OBGCMs) to estimate trends driven by global and regional climate and atmospheric CO2 in land and oceanic CO2 exchanges with the atmosphere over the period 1990–2009, to attribute these trends to underlying processes in the models, and to quantify the uncertainty and level of inter-model agreement. The models were forced with reconstructed climate fields and observed global atmospheric CO2; land use and land cover changes are not included for the DGVMs. Over the period 1990–2009, the DGVMs simulate a mean global land carbon sink of −2.4 ± 0.7 Pg C yr−1 with a small significant trend of −0.06 ± 0.03 Pg C yr−2 (increasing sink). Over the more limited period 1990–2004, the ocean models simulate a mean ocean sink of −2.2 ± 0.2 Pg C yr−1 with a trend in the net C uptake that is indistinguishable from zero (−0.01 ± 0.02 Pg C yr−2). The two ocean models that extended the simulations until 2009 suggest a slightly stronger, but still small, trend of −0.02 ± 0.01 Pg C yr−2. Trends from land and ocean models compare favourably to the land greenness trends from remote sensing, atmospheric inversion results, and the residual land sink required to close the global carbon budget. Trends in the land sink are driven by increasing net primary production (NPP), whose statistically significant trend of 0.22 ± 0.08 Pg C yr−2 exceeds a significant trend in heterotrophic respiration of 0.16 ± 0.05 Pg C yr−2 – primarily as a consequence of widespread CO2 fertilisation of plant production. Most of the land-based trend in simulated net carbon uptake originates from natural ecosystems in the tropics (−0.04 ± 0.01 Pg C yr−2), with almost no trend over the northern land region, where recent warming and reduced rainfall offsets the positive impact of elevated atmospheric CO2 and changes in growing season length on carbon storage. The small uptake trend in the ocean models emerges because climate variability and change, and in particular increasing sea surface temperatures, tend to counter\-act the trend in ocean uptake driven by the increase in atmospheric CO2. Large uncertainty remains in the magnitude and sign of modelled carbon trends in several regions, as well as regarding the influence of land use and land cover changes on regional trends.
Response of ocean ecosystems to climate warming

(American Geophysical Union, 2004-07-14) Sarmiento, Jorge L. ; Slater, Richard D. ; Barber, Richard T. ; Bopp, Laurent ; Doney, Scott C. ; Hirst, A. C. ; Kleypas, Joan A. ; Matear, Richard J. ; Mikolajewicz, U. ; Monfray, Patrick ; Soldatov, V. ; Spall, S. A. ; Stouffer, R.

We examine six different coupled climate model simulations to determine the ocean biological response to climate warming between the beginning of the industrial revolution and 2050. We use vertical velocity, maximum winter mixed layer depth, and sea ice cover to define six biomes. Climate warming leads to a contraction of the highly productive marginal sea ice biome by 42% in the Northern Hemisphere and 17% in the Southern Hemisphere, and leads to an expansion of the low productivity permanently stratified subtropical gyre biome by 4.0% in the Northern Hemisphere and 9.4% in the Southern Hemisphere. In between these, the subpolar gyre biome expands by 16% in the Northern Hemisphere and 7% in the Southern Hemisphere, and the seasonally stratified subtropical gyre contracts by 11% in both hemispheres. The low-latitude (mostly coastal) upwelling biome area changes only modestly. Vertical stratification increases, which would be expected to decrease nutrient supply everywhere, but increase the growing season length in high latitudes. We use satellite ocean color and climatological observations to develop an empirical model for predicting chlorophyll from the physical properties of the global warming simulations. Four features stand out in the response to global warming: (1) a drop in chlorophyll in the North Pacific due primarily to retreat of the marginal sea ice biome, (2) a tendency toward an increase in chlorophyll in the North Atlantic due to a complex combination of factors, (3) an increase in chlorophyll in the Southern Ocean due primarily to the retreat of and changes at the northern boundary of the marginal sea ice zone, and (4) a tendency toward a decrease in chlorophyll adjacent to the Antarctic continent due primarily to freshening within the marginal sea ice zone. We use three different primary production algorithms to estimate the response of primary production to climate warming based on our estimated chlorophyll concentrations. The three algorithms give a global increase in primary production of 0.7% at the low end to 8.1% at the high end, with very large regional differences. The main cause of both the response to warming and the variation between algorithms is the temperature sensitivity of the primary production algorithms. We also show results for the period between the industrial revolution and 2050 and 2090.
Detection of anthropogenic climate change in satellite records of ocean chlorophyll and productivity

(Copernicus Publications on behalf of the European Geosciences Union, 2010-02-15) Henson, Stephanie A. ; Sarmiento, Jorge L. ; Dunne, John P. ; Bopp, Laurent ; Lima, Ivan D. ; Doney, Scott C. ; John, Jasmin G. ; Beaulieu, C.

Global climate change is predicted to alter the ocean's biological productivity. But how will we recognise the impacts of climate change on ocean productivity? The most comprehensive information available on its global distribution comes from satellite ocean colour data. Now that over ten years of satellite-derived chlorophyll and productivity data have accumulated, can we begin to detect and attribute climate change-driven trends in productivity? Here we compare recent trends in satellite ocean colour data to longer-term time series from three biogeochemical models (GFDL, IPSL and NCAR). We find that detection of climate change-driven trends in the satellite data is confounded by the relatively short time series and large interannual and decadal variability in productivity. Thus, recent observed changes in chlorophyll, primary production and the size of the oligotrophic gyres cannot be unequivocally attributed to the impact of global climate change. Instead, our analyses suggest that a time series of ~40 years length is needed to distinguish a global warming trend from natural variability. In some regions, notably equatorial regions, detection times are predicted to be shorter (~20–30 years). Analysis of modelled chlorophyll and primary production from 2001–2100 suggests that, on average, the climate change-driven trend will not be unambiguously separable from decadal variability until ~2055. Because the magnitude of natural variability in chlorophyll and primary production is larger than, or similar to, the global warming trend, a consistent, decades-long data record must be established if the impact of climate change on ocean productivity is to be definitively detected.
Phytoplankton competition during the spring bloom in four plankton functional type models

(Copernicus Publications on behalf of the European Geosciences Union, 2013-11-02) Hashioka, Taketo ; Vogt, Meike ; Yamanaka, Yasuhiro ; Le Quere, Corinne ; Buitenhuis, Erik T. ; Aita, M. N. ; Alvain, S. ; Bopp, Laurent ; Hirata, T. ; Lima, Ivan D. ; Sailley, Sevrine F. ; Doney, Scott C.

We investigated the mechanisms of phytoplankton competition during the spring bloom, one of the most dramatic seasonal events in lower-trophic-level ecosystems, in four state-of-the-art plankton functional type (PFT) models: PISCES, NEMURO, PlankTOM5 and CCSM-BEC. In particular, we investigated the relative importance of different ecophysiological processes on the determination of the community structure, focusing both on the bottom-up and the top-down controls. The models reasonably reproduced the observed global distribution and seasonal variation of phytoplankton biomass. The fraction of diatoms with respect to the total phytoplankton biomass increases with the magnitude of the spring bloom in all models. However, the governing mechanisms differ between models, despite the fact that current PFT models represent ecophysiological processes using the same types of parameterizations. The increasing trend in the percentage of diatoms with increasing bloom magnitude is mainly caused by a stronger nutrient dependence of diatom growth compared to nanophytoplankton (bottom-up control). The difference in the maximum growth rate plays an important role in NEMURO and PlankTOM5 and determines the absolute values of the percentage of diatoms during the bloom. In CCSM-BEC, the light dependency of growth plays an important role in the North Atlantic and the Southern Ocean. The grazing pressure by zooplankton (top-down control), however, strongly contributes to the dominance of diatoms in PISCES and CCSM-BEC. The regional differences in the percentage of diatoms in PlankTOM5 are mainly determined by top-down control. These differences in the mechanisms suggest that the response of marine ecosystems to climate change could significantly differ among models, even if the present-day ecosystem is reproduced to a similar degree of confidence. For further understanding of plankton competition and for the prediction of future change in marine ecosystems, it is important to understand the relative differences in each physiological rate and life history rate in the bottom-up and the top-down controls between PFTs.
Challenges of modeling depth-integrated marine primary productivity over multiple decades : a case study at BATS and HOT

(American Geophysical Union, 2010-09-15) Saba, Vincent S. ; Friedrichs, Marjorie A. M. ; Carr, Mary-Elena ; Antoine, David ; Armstrong, Robert A. ; Asanuma, Ichio ; Aumont, Olivier ; Bates, Nicholas R. ; Behrenfeld, Michael J. ; Bennington, Val ; Bopp, Laurent ; Bruggeman, Jorn ; Buitenhuis, Erik T. ; Church, Matthew J. ; Ciotti, Aurea M. ; Doney, Scott C. ; Dowell, Mark ; Dunne, John P. ; Dutkiewicz, Stephanie ; Gregg, Watson ; Hoepffner, Nicolas ; Hyde, Kimberly J. W. ; Ishizaka, Joji ; Kameda, Takahiko ; Karl, David M. ; Lima, Ivan D. ; Lomas, Michael W. ; Marra, John F. ; McKinley, Galen A. ; Melin, Frederic ; Moore, J. Keith ; Morel, Andre ; O'Reilly, John ; Salihoglu, Baris ; Scardi, Michele ; Smyth, Tim J. ; Tang, Shilin ; Tjiputra, Jerry ; Uitz, Julia ; Vichi, Marcello ; Waters, Kirk ; Westberry, Toby K. ; Yool, Andrew

The performance of 36 models (22 ocean color models and 14 biogeochemical ocean circulation models (BOGCMs)) that estimate depth-integrated marine net primary productivity (NPP) was assessed by comparing their output to in situ 14C data at the Bermuda Atlantic Time series Study (BATS) and the Hawaii Ocean Time series (HOT) over nearly two decades. Specifically, skill was assessed based on the models' ability to estimate the observed mean, variability, and trends of NPP. At both sites, more than 90% of the models underestimated mean NPP, with the average bias of the BOGCMs being nearly twice that of the ocean color models. However, the difference in overall skill between the best BOGCM and the best ocean color model at each site was not significant. Between 1989 and 2007, in situ NPP at BATS and HOT increased by an average of nearly 2% per year and was positively correlated to the North Pacific Gyre Oscillation index. The majority of ocean color models produced in situ NPP trends that were closer to the observed trends when chlorophyll-a was derived from high-performance liquid chromatography (HPLC), rather than fluorometric or SeaWiFS data. However, this was a function of time such that average trend magnitude was more accurately estimated over longer time periods. Among BOGCMs, only two individual models successfully produced an increasing NPP trend (one model at each site). We caution against the use of models to assess multiannual changes in NPP over short time periods. Ocean color model estimates of NPP trends could improve if more high quality HPLC chlorophyll-a time series were available.
Global carbon budget 2017

(Copernicus Publications on behalf of the European Geosciences Union, 2018-03-12) Le Quere, Corinne ; Andrew, Robbie M. ; Friedlingstein, Pierre ; Sitch, Stephen ; Pongratz, Julia ; Manning, Andrew C. ; Korsbakken, Jan Ivar ; Peters, Glen P. ; Canadell, Josep G. ; Jackson, Robert B. ; Boden, Thomas A. ; Tans, Pieter P. ; Andrews, Oliver D. ; Arora, Vivek K. ; Bakker, Dorothee ; Barbero, Leticia ; Becker, Meike ; Betts, Richard A. ; Bopp, Laurent ; Chevallier, Frédéric ; Chini, Louise Parsons ; Ciais, Philippe ; Cosca, Catherine E. ; Cross, Jessica N. ; Currie, Kim I. ; Gasser, Thomas ; Harris, Ian ; Hauck, Judith ; Haverd, Vanessa ; Houghton, Richard A. ; Hunt, Christopher W. ; Hurtt, George ; Ilyina, Tatiana ; Jain, Atul K. ; Kato, Etsushi ; Kautz, Markus ; Keeling, Ralph F. ; Klein Goldewijk, Kees ; Körtzinger, Arne ; Landschützer, Peter ; Lefèvre, Nathalie ; Lenton, Andrew ; Lienert, Sebastian ; Lima, Ivan D. ; Lombardozzi, Danica ; Metzl, Nicolas ; Millero, Frank J. ; Monteiro, Pedro M. S. ; Munro, David R. ; Nabel, Julia E. M. S. ; Nakaoka, Shin-ichiro ; Nojiri, Yukihiro ; Padin, X. Antonio ; Peregon, Anna ; Pfeil, Benjamin ; Pierrot, Denis ; Poulter, Benjamin ; Rehder, Gregor ; Reimer, Janet ; Rödenbeck, Christian ; Schwinger, Jorg ; Séférian, Roland ; Skjelvan, Ingunn ; Stocker, Benjamin D. ; Tian, Hanqin ; Tilbrook, Bronte ; Tubiello, Francesco N. ; van der Laan-Luijkx, Ingrid T. ; van der Werf, Guido R. ; van Heuven, Steven ; Viovy, Nicolas ; Vuichard, Nicolas ; Walker, Anthony P. ; Watson, Andrew J. ; Wiltshire, Andrew J. ; Zaehle, Sonke ; Zhu, Dan

Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere – the "global carbon budget" – is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. CO2 emissions from fossil fuels and industry (EFF) are based on energy statistics and cement production data, respectively, while emissions from land-use change (ELUC), mainly deforestation, are based on land-cover change data and bookkeeping models. The global atmospheric CO2 concentration is measured directly and its rate of growth (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) and terrestrial CO2 sink (SLAND) are estimated with global process models constrained by observations. The resulting carbon budget imbalance (BIM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the last decade available (2007–2016), EFF was 9.4 ± 0.5 GtC yr−1, ELUC 1.3 ± 0.7 GtC yr−1, GATM 4.7 ± 0.1 GtC yr−1, SOCEAN 2.4 ± 0.5 GtC yr−1, and SLAND 3.0 ± 0.8 GtC yr−1, with a budget imbalance BIM of 0.6 GtC yr−1 indicating overestimated emissions and/or underestimated sinks. For year 2016 alone, the growth in EFF was approximately zero and emissions remained at 9.9 ± 0.5 GtC yr−1. Also for 2016, ELUC was 1.3 ± 0.7 GtC yr−1, GATM was 6.1 ± 0.2 GtC yr−1, SOCEAN was 2.6 ± 0.5 GtC yr−1, and SLAND was 2.7 ± 1.0 GtC yr−1, with a small BIM of −0.3 GtC. GATM continued to be higher in 2016 compared to the past decade (2007–2016), reflecting in part the high fossil emissions and the small SLAND consistent with El Niño conditions. The global atmospheric CO2 concentration reached 402.8 ± 0.1 ppm averaged over 2016. For 2017, preliminary data for the first 6–9 months indicate a renewed growth in EFF of +2.0 % (range of 0.8 to 3.0 %) based on national emissions projections for China, USA, and India, and projections of gross domestic product (GDP) corrected for recent changes in the carbon intensity of the economy for the rest of the world. This living data update documents changes in the methods and data sets used in this new global carbon budget compared with previous publications of this data set (Le Quéré et al., 2016, 2015b, a, 2014, 2013). All results presented here can be downloaded from https://doi.org/10.18160/GCP-2017 (GCP, 2017).
Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms

( 2005-07-29) Orr, James C. ; Fabry, Victoria J. ; Aumont, Olivier ; Bopp, Laurent ; Doney, Scott C. ; Feely, Richard A. ; Gnanadesikan, Anand ; Gruber, Nicolas ; Ishida, Akio ; Joos, Fortunat ; Key, Robert M. ; Lindsay, Keith ; Maier-Reimer, Ernst ; Matear, Richard J. ; Monfray, Patrick ; Mouchet, Anne ; Najjar, Raymond G. ; Plattner, Gian-Kasper ; Rodgers, Keith B. ; Sabine, Christopher L. ; Sarmiento, Jorge L. ; Schlitzer, Reiner ; Slater, Richard D. ; Totterdell, Ian J. ; Weirig, Marie-France ; Yamanaka, Yasuhiro ; Yool, Andrew

The surface ocean is everywhere saturated with respect to calcium carbonate (CaCO3). Yet increasing atmospheric CO2 reduces ocean pH and carbonate ion concentrations [CO32−] and thus the level of saturation. Reduced saturation states are expected to affect marine calcifiers even though it has been estimated that all surface waters will remain saturated for centuries. Here we show, however, that some surface waters will become undersaturated within decades. When atmospheric CO2 reaches 550 ppmv, in year 2050 under the IS92a business-as-usual scenario, Southern Ocean surface waters begin to become undersaturated with respect to aragonite, a metastable form of CaCO3. By 2100 as atmospheric CO2 reaches 788 ppmv, undersaturation extends throughout the entire Southern Ocean (< 60°S) and into the subarctic Pacific. These changes will threaten high-latitude aragonite secreting organisms including cold-water corals, which provide essential fish habitat, and shelled pteropods, an abundant food source for marine predators.
Factors challenging our ability to detect long-term trends in ocean chlorophyll

(Copernicus Publications on behalf of the European Geosciences Union, 2013-04-23) Beaulieu, C. ; Henson, Stephanie A. ; Sarmiento, Jorge L. ; Dunne, John P. ; Doney, Scott C. ; Rykaczewski, Ryan R. ; Bopp, Laurent

Global climate change is expected to affect the ocean's biological productivity. The most comprehensive information available about the global distribution of contemporary ocean primary productivity is derived from satellite data. Large spatial patchiness and interannual to multidecadal variability in chlorophyll a concentration challenges efforts to distinguish a global, secular trend given satellite records which are limited in duration and continuity. The longest ocean color satellite record comes from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), which failed in December 2010. The Moderate Resolution Imaging Spectroradiometer (MODIS) ocean color sensors are beyond their originally planned operational lifetime. Successful retrieval of a quality signal from the current Visible Infrared Imager Radiometer Suite (VIIRS) instrument, or successful launch of the Ocean and Land Colour Instrument (OLCI) expected in 2014 will hopefully extend the ocean color time series and increase the potential for detecting trends in ocean productivity in the future. Alternatively, a potential discontinuity in the time series of ocean chlorophyll a, introduced by a change of instrument without overlap and opportunity for cross-calibration, would make trend detection even more challenging. In this paper, we demonstrate that there are a few regions with statistically significant trends over the ten years of SeaWiFS data, but at a global scale the trend is not large enough to be distinguished from noise. We quantify the degree to which red noise (autocorrelation) especially challenges trend detection in these observational time series. We further demonstrate how discontinuities in the time series at various points would affect our ability to detect trends in ocean chlorophyll a. We highlight the importance of maintaining continuous, climate-quality satellite data records for climate-change detection and attribution studies.
Projected 21st century decrease in marine productivity : a multi-model analysis

(Copernicus Publications on behalf of the European Geosciences Union, 2010-03-11) Steinacher, M. ; Joos, Fortunat ; Frolicher, T. L. ; Bopp, Laurent ; Cadule, P. ; Cocco, V. ; Doney, Scott C. ; Gehlen, M. ; Lindsay, Keith ; Moore, J. Keith ; Schneider, B. ; Segschneider, J.

Changes in marine net primary productivity (PP) and export of particulate organic carbon (EP) are projected over the 21st century with four global coupled carbon cycle-climate models. These include representations of marine ecosystems and the carbon cycle of different structure and complexity. All four models show a decrease in global mean PP and EP between 2 and 20% by 2100 relative to preindustrial conditions, for the SRES A2 emission scenario. Two different regimes for productivity changes are consistently identified in all models. The first chain of mechanisms is dominant in the low- and mid-latitude ocean and in the North Atlantic: reduced input of macro-nutrients into the euphotic zone related to enhanced stratification, reduced mixed layer depth, and slowed circulation causes a decrease in macro-nutrient concentrations and in PP and EP. The second regime is projected for parts of the Southern Ocean: an alleviation of light and/or temperature limitation leads to an increase in PP and EP as productivity is fueled by a sustained nutrient input. A region of disagreement among the models is the Arctic, where three models project an increase in PP while one model projects a decrease. Projected changes in seasonal and interannual variability are modest in most regions. Regional model skill metrics are proposed to generate multi-model mean fields that show an improved skill in representing observation-based estimates compared to a simple multi-model average. Model results are compared to recent productivity projections with three different algorithms, usually applied to infer net primary production from satellite observations.
Biogeochemical protocols and diagnostics for the CMIP6 Ocean Model Intercomparison Project (OMIP)

(Copernicus Publications on behalf of the European Geosciences Union, 2017-06-09) Orr, James C. ; Najjar, Raymond G. ; Aumont, Olivier ; Bopp, Laurent ; Bullister, John L. ; Danabasoglu, Gokhan ; Doney, Scott C. ; Dunne, John P. ; Dutay, Jean-Claude ; Graven, Heather ; Griffies, Stephen M. ; John, Jasmin G. ; Joos, Fortunat ; Levin, Ingeborg ; Lindsay, Keith ; Matear, Richard J. ; McKinley, Galen A. ; Mouchet, Anne ; Oschlies, Andreas ; Romanou, Anastasia ; Schlitzer, Reiner ; Tagliabue, Alessandro ; Tanhua, Toste ; Yool, Andrew

The Ocean Model Intercomparison Project (OMIP) focuses on the physics and biogeochemistry of the ocean component of Earth system models participating in the sixth phase of the Coupled Model Intercomparison Project (CMIP6). OMIP aims to provide standard protocols and diagnostics for ocean models, while offering a forum to promote their common assessment and improvement. It also offers to compare solutions of the same ocean models when forced with reanalysis data (OMIP simulations) vs. when integrated within fully coupled Earth system models (CMIP6). Here we detail simulation protocols and diagnostics for OMIP's biogeochemical and inert chemical tracers. These passive-tracer simulations will be coupled to ocean circulation models, initialized with observational data or output from a model spin-up, and forced by repeating the 1948–2009 surface fluxes of heat, fresh water, and momentum. These so-called OMIP-BGC simulations include three inert chemical tracers (CFC-11, CFC-12, SF6) and biogeochemical tracers (e.g., dissolved inorganic carbon, carbon isotopes, alkalinity, nutrients, and oxygen). Modelers will use their preferred prognostic BGC model but should follow common guidelines for gas exchange and carbonate chemistry. Simulations include both natural and total carbon tracers. The required forced simulation (omip1) will be initialized with gridded observational climatologies. An optional forced simulation (omip1-spunup) will be initialized instead with BGC fields from a long model spin-up, preferably for 2000 years or more, and forced by repeating the same 62-year meteorological forcing. That optional run will also include abiotic tracers of total dissolved inorganic carbon and radiocarbon, CTabio and 14CTabio, to assess deep-ocean ventilation and distinguish the role of physics vs. biology. These simulations will be forced by observed atmospheric histories of the three inert gases and CO2 as well as carbon isotope ratios of CO2. OMIP-BGC simulation protocols are founded on those from previous phases of the Ocean Carbon-Cycle Model Intercomparison Project. They have been merged and updated to reflect improvements concerning gas exchange, carbonate chemistry, and new data for initial conditions and atmospheric gas histories. Code is provided to facilitate their implementation.
Historical and future trends in ocean climate and biogeochemistry

(The Oceanography Society, 2014-03) Doney, Scott C. ; Bopp, Laurent ; Long, Matthew C.

Changing atmospheric composition due to human activities, primarily carbon dioxide (CO2) emissions from fossil fuel burning, is already impacting ocean circulation, biogeochemistry, and ecology, and model projections indicate that observed trends will continue or even accelerate over this century. Elevated atmospheric CO2 alters Earth's radiative balance, leading to global-scale warming and climate change. The ocean stores the majority of resulting anomalous heat, which in turn drives other physical, chemical, and biological impacts. Sea surface warming and increased ocean vertical stratification are projected to reduce global-integrated primary production and export flux as well as to lower subsurface dissolved oxygen concentrations. Upper trophic levels will be affected both directly by warming and indirectly from changes in productivity and expanding low oxygen zones. The ocean also absorbs roughly one-quarter of present-day anthropogenic CO2 emissions. The resulting changes in seawater chemistry, termed ocean acidification, include declining pH and saturation state for calcium carbon minerals that may have widespread impacts on many marine organisms. Climate warming will likely slow ocean CO2 uptake but is not expected to significantly reduce upper ocean acidification. Improving the accuracy of future model projections requires better observational constraints on current rates of ocean change and a better understanding of the mechanisms controlling key physical and biogeochemical processes.
Climate-induced interannual variability of marine primary and export production in three global coupled climate carbon cycle models

(Copernicus Publications on behalf of the European Geosciences Union, 2008-04-23) Schneider, B. ; Bopp, Laurent ; Gehlen, M. ; Segschneider, J. ; Frolicher, T. L. ; Cadule, P. ; Friedlingstein, Pierre ; Doney, Scott C. ; Behrenfeld, Michael J. ; Joos, Fortunat

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.
Climate-carbon cycle feedback analysis : results from the C4MIP model intercomparison

(American Meteorological Society, 2006-07-15) Friedlingstein, Pierre ; Cox, P. ; Betts, Richard A. ; Bopp, Laurent ; von Bloh, W. ; Brovkin, V. ; Cadule, P. ; Doney, Scott C. ; Eby, Michael ; Fung, Inez Y. ; Bala, G. ; John, Jasmin G. ; Jones, C. D. ; Joos, Fortunat ; Kato, T. ; Kawamiya, M. ; Knorr, W. ; Lindsay, Keith ; Matthews, H. D. ; Raddatz, T. ; Rayner, Peter ; Reick, C. ; Roeckner, E. ; Schnitzler, K.-G. ; Schnur, R. ; Strassmann, K. ; Weaver, Andrew J. ; Yoshikawa, C. ; Zeng, Ning

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.
Using altimetry to help explain patchy changes in hydrographic carbon measurements

(American Geophysical Union, 2009-09-18) Rodgers, Keith B. ; Key, Robert M. ; Gnanadesikan, Anand ; Sarmiento, Jorge L. ; Aumont, Olivier ; Bopp, Laurent ; Doney, Scott C. ; Dunne, John P. ; Glover, David M. ; Ishida, Akio ; Ishii, Masao ; Jacobson, Andrew R. ; Monaco, Claire Lo ; Maier-Reimer, Ernst ; Mercier, Herlé ; Metzl, Nicolas ; Perez, Fiz F. ; Rios, Aida F. ; Wanninkhof, Rik ; Wetzel, Patrick ; Winn, Christopher D. ; Yamanaka, Yasuhiro

Here we use observations and ocean models to identify mechanisms driving large seasonal to interannual variations in dissolved inorganic carbon (DIC) and dissolved oxygen (O2) in the upper ocean. We begin with observations linking variations in upper ocean DIC and O2 inventories with changes in the physical state of the ocean. Models are subsequently used to address the extent to which the relationships derived from short-timescale (6 months to 2 years) repeat measurements are representative of variations over larger spatial and temporal scales. The main new result is that convergence and divergence (column stretching) attributed to baroclinic Rossby waves can make a first-order contribution to DIC and O2 variability in the upper ocean. This results in a close correspondence between natural variations in DIC and O2 column inventory variations and sea surface height (SSH) variations over much of the ocean. Oceanic Rossby wave activity is an intrinsic part of the natural variability in the climate system and is elevated even in the absence of significant interannual variability in climate mode indices. The close correspondence between SSH and both DIC and O2 column inventories for many regions suggests that SSH changes (inferred from satellite altimetry) may prove useful in reducing uncertainty in separating natural and anthropogenic DIC signals (using measurements from Climate Variability and Predictability's CO2/Repeat Hydrography program).
Global Carbon Budget 2016

(Copernicus Publications, 2016-11-14) Le Quere, Corinne ; Andrew, Robbie M. ; Canadell, Josep G. ; Sitch, Stephen ; Korsbakken, Jan Ivar ; Peters, Glen P. ; Manning, Andrew C. ; Boden, Thomas A. ; Tans, Pieter P. ; Houghton, Richard A. ; Keeling, Ralph F. ; Alin, Simone R. ; Andrews, Oliver D. ; Anthoni, Peter ; Barbero, Leticia ; Bopp, Laurent ; Chevallier, Frédéric ; Chini, Louise Parsons ; Ciais, Philippe ; Currie, Kim I. ; Delire, Christine ; Doney, Scott C. ; Friedlingstein, Pierre ; Gkritzalis, Thanos ; Harris, Ian ; Hauck, Judith ; Haverd, Vanessa ; Hoppema, Mario ; Klein Goldewijk, Kees ; Jain, Atul K. ; Kato, Etsushi ; Körtzinger, Arne ; Landschützer, Peter ; Lefèvre, Nathalie ; Lenton, Andrew ; Lienert, Sebastian ; Lombardozzi, Danica ; Melton, Joe R. ; Metzl, Nicolas ; Millero, Frank J. ; Monteiro, Pedro M. S. ; Munro, David R. ; Nabel, Julia E. M. S. ; Nakaoka, Shin-ichiro ; O'Brien, Kevin ; Olsen, Are ; Omar, Abdirahman M. ; Ono, Tsuneo ; Pierrot, Denis ; Poulter, Benjamin ; Rödenbeck, Christian ; Salisbury, Joseph E. ; Schuster, Ute ; Schwinger, Jorg ; Séférian, Roland ; Skjelvan, Ingunn ; Stocker, Benjamin D. ; Sutton, Adrienne J. ; Takahashi, Taro ; Tian, Hanqin ; Tilbrook, Bronte ; van der Laan-Luijkx, Ingrid ; van der Werf, Guido R. ; Viovy, Nicolas ; Walker, Anthony P. ; Wiltshire, Andrew J. ; Zaehle, Sonke

Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere – the “global carbon budget” – is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and methodology to quantify all major components of the global carbon budget, including their uncertainties, based on the combination of a range of data, algorithms, statistics, and model estimates and their interpretation by a broad scientific community. We discuss changes compared to previous estimates and consistency within and among components, alongside methodology and data limitations. CO2 emissions from fossil fuels and industry (EFF) are based on energy statistics and cement production data, respectively, while emissions from land-use change (ELUC), mainly deforestation, are based on combined evidence from land-cover change data, fire activity associated with deforestation, and models. The global atmospheric CO2 concentration is measured directly and its rate of growth (GATM) is computed from the annual changes in concentration. The mean ocean CO2 sink (SOCEAN) is based on observations from the 1990s, while the annual anomalies and trends are estimated with ocean models. The variability in SOCEAN is evaluated with data products based on surveys of ocean CO2 measurements. The global residual terrestrial CO2 sink (SLAND) is estimated by the difference of the other terms of the global carbon budget and compared to results of independent dynamic global vegetation models. We compare the mean land and ocean fluxes and their variability to estimates from three atmospheric inverse methods for three broad latitude bands. All uncertainties are reported as ±1σ, reflecting the current capacity to characterise the annual estimates of each component of the global carbon budget. For the last decade available (2006–2015), EFF was 9.3 ± 0.5 GtC yr−1, ELUC 1.0 ± 0.5 GtC yr−1, GATM 4.5 ± 0.1 GtC yr−1, SOCEAN 2.6 ± 0.5 GtC yr−1, and SLAND 3.1 ± 0.9 GtC yr−1. For year 2015 alone, the growth in EFF was approximately zero and emissions remained at 9.9 ± 0.5 GtC yr−1, showing a slowdown in growth of these emissions compared to the average growth of 1.8 % yr−1 that took place during 2006–2015. Also, for 2015, ELUC was 1.3 ± 0.5 GtC yr−1, GATM was 6.3 ± 0.2 GtC yr−1, SOCEAN was 3.0 ± 0.5 GtC yr−1, and SLAND was 1.9 ± 0.9 GtC yr−1. GATM was higher in 2015 compared to the past decade (2006–2015), reflecting a smaller SLAND for that year. The global atmospheric CO2 concentration reached 399.4 ± 0.1 ppm averaged over 2015. For 2016, preliminary data indicate the continuation of low growth in EFF with +0.2 % (range of −1.0 to +1.8 %) based on national emissions projections for China and USA, and projections of gross domestic product corrected for recent changes in the carbon intensity of the economy for the rest of the world. In spite of the low growth of EFF in 2016, the growth rate in atmospheric CO2 concentration is expected to be relatively high because of the persistence of the smaller residual terrestrial sink (SLAND) in response to El Niño conditions of 2015–2016. From this projection of EFF and assumed constant ELUC for 2016, cumulative emissions of CO2 will reach 565 ± 55 GtC (2075 ± 205 GtCO2) for 1870–2016, about 75 % from EFF and 25 % from ELUC. This living data update documents changes in the methods and data sets used in this new carbon budget compared with previous publications of this data set (Le Quéré et al., 2015b, a, 2014, 2013). All observations presented here can be downloaded from the Carbon Dioxide Information Analysis Center (doi:10.3334/CDIAC/GCP_2016).
Inconsistent strategies to spin up models in CMIP5 : implications for ocean biogeochemical model performance assessment

(Copernicus Publications on behalf of the European Geosciences Union, 2016-05-12) Seferian, Roland ; Gehlen, Marion ; Bopp, Laurent ; Resplandy, Laure ; Orr, James ; Marti, Olivier ; Dunne, John P. ; Christian, James R. ; Doney, Scott C. ; Ilyina, Tatiana ; Lindsay, Keith ; Halloran, Paul R. ; Heinze, Christoph ; Segschneider, Joachim ; Tjiputra, Jerry ; Aumont, Olivier ; Romanou, Anastasia

During the fifth phase of the Coupled Model Intercomparison Project (CMIP5) substantial efforts were made to systematically assess the skill of Earth system models. One goal was to check how realistically representative marine biogeochemical tracer distributions could be reproduced by models. In routine assessments model historical hindcasts were compared with available modern biogeochemical observations. However, these assessments considered neither how close modeled biogeochemical reservoirs were to equilibrium nor the sensitivity of model performance to initial conditions or to the spin-up protocols. Here, we explore how the large diversity in spin-up protocols used for marine biogeochemistry in CMIP5 Earth system models (ESMs) contributes to model-to-model differences in the simulated fields. We take advantage of a 500-year spin-up simulation of IPSL-CM5A-LR to quantify the influence of the spin-up protocol on model ability to reproduce relevant data fields. Amplification of biases in selected biogeochemical fields (O2, NO3, Alk-DIC) is assessed as a function of spin-up duration. We demonstrate that a relationship between spin-up duration and assessment metrics emerges from our model results and holds when confronted with a larger ensemble of CMIP5 models. This shows that drift has implications for performance assessment in addition to possibly aliasing estimates of climate change impact. Our study suggests that differences in spin-up protocols could explain a substantial part of model disparities, constituting a source of model-to-model uncertainty. This requires more attention in future model intercomparison exercises in order to provide quantitatively more correct ESM results on marine biogeochemistry and carbon cycle feedbacks.
Projected decreases in future marine export production : the role of the carbon flux through the upper ocean ecosystem

(Copernicus Publications on behalf of the European Geosciences Union, 2016-07-14) Laufkötter, Charlotte ; Vogt, Meike ; Gruber, Nicolas ; Aumont, Olivier ; Bopp, Laurent ; Doney, Scott C. ; Dunne, John P. ; Hauck, Judith ; John, Jasmin G. ; Lima, Ivan D. ; Seferian, Roland ; Völker, Christoph

Accurate projections of marine particle export production (EP) are crucial for predicting the response of the marine carbon cycle to climate change, yet models show a wide range in both global EP and their responses to climate change. This is, in part, due to EP being the net result of a series of processes, starting with net primary production (NPP) in the sunlit upper ocean, followed by the formation of particulate organic matter and the subsequent sinking and remineralisation of these particles, with each of these processes responding differently to changes in environmental conditions. Here, we compare future projections in EP over the 21st century, generated by four marine ecosystem models under the high emission scenario Representative Concentration Pathways (RCP) 8.5 of the Intergovernmental Panel on Climate Change (IPCC), and determine the processes driving these changes. The models simulate small to modest decreases in global EP between −1 and −12 %. Models differ greatly with regard to the drivers causing these changes. Among them, the formation of particles is the most uncertain process with models not agreeing on either magnitude or the direction of change. The removal of the sinking particles by remineralisation is simulated to increase in the low and intermediate latitudes in three models, driven by either warming-induced increases in remineralisation or slower particle sinking, and show insignificant changes in the remaining model. Changes in ecosystem structure, particularly the relative role of diatoms matters as well, as diatoms produce larger and denser particles that sink faster and are partly protected from remineralisation. Also this controlling factor is afflicted with high uncertainties, particularly since the models differ already substantially with regard to both the initial (present-day) distribution of diatoms (between 11–94 % in the Southern Ocean) and the diatom contribution to particle formation (0.6–3.8 times higher than their contribution to biomass). As a consequence, changes in diatom concentration are a strong driver for EP changes in some models but of low significance in others. Observational and experimental constraints on ecosystem structure and how the fixed carbon is routed through the ecosystem to produce export production are urgently needed in order to improve current generation ecosystem models and their ability to project future changes.
Magnitude, trends, and variability of the global ocean carbon sink from 1985‐2018

(American Geophysical Union, 2023-09-11) DeVries, Tim ; Yamamoto, Kana ; Wanninkhof, Rik ; Gruber, Nicolas ; Hauck, Judith ; Muller, Jens Daniel ; Bopp, Laurent ; Carroll, Dustin ; Carter, Brendan ; Chau, Thi-Tuyet-Trang ; Doney, Scott C. ; Gehlen, Marion ; Gloege, Lucas ; Gregor, Luke ; Henson, Stephanie A. ; Kim, Ji-Hyun ; Iida, Yosuke ; Ilyina, Tatiana ; Landschutzer, Peter ; Le Quere, Corinne ; Munro, David R. ; Nissen, Cara ; Patara, Lavinia ; Perez, Fiz F. ; Resplandy, Laure ; Rodgers, Keith B. ; Schwinger, Jorg ; Seferian, Roland ; Sicardi, Valentina ; Terhaar, Jens ; Trinanes, Joaquin ; Tsujino, Hiroyuki ; Watson, Andrew J. ; Yasunaka, Sayaka ; Zeng, Jiye

This contribution to the RECCAP2 (REgional Carbon Cycle Assessment and Processes) assessment analyzes the processes that determine the global ocean carbon sink, and its trends and variability over the period 1985–2018, using a combination of models and observation-based products. The mean sea-air CO2 flux from 1985 to 2018 is −1.6 ± 0.2 PgC yr−1 based on an ensemble of reconstructions of the history of sea surface pCO2 (pCO2 products). Models indicate that the dominant component of this flux is the net oceanic uptake of anthropogenic CO2, which is estimated at −2.1 ± 0.3 PgC yr−1 by an ensemble of ocean biogeochemical models, and −2.4 ± 0.1 PgC yr−1 by two ocean circulation inverse models. The ocean also degasses about 0.65 ± 0.3 PgC yr−1 of terrestrially derived CO2, but this process is not fully resolved by any of the models used here. From 2001 to 2018, the pCO2 products reconstruct a trend in the ocean carbon sink of −0.61 ± 0.12 PgC yr−1 decade−1, while biogeochemical models and inverse models diagnose an anthropogenic CO2-driven trend of −0.34 ± 0.06 and −0.41 ± 0.03 PgC yr−1 decade−1, respectively. This implies a climate-forced acceleration of the ocean carbon sink in recent decades, but there are still large uncertainties on the magnitude and cause of this trend. The interannual to decadal variability of the global carbon sink is mainly driven by climate variability, with the climate-driven variability exceeding the CO2-forced variability by 2–3 times. These results suggest that anthropogenic CO2 dominates the ocean CO2 sink, while climate-driven variability is potentially large but highly uncertain and not consistently captured across different methods.

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