Efforts to control climate change require the stabilization of atmospheric CO2 concentrations. This can only be achieved through a drastic reduction of global CO2 emissions. Yet fossil fuel emissions increased by 29% between 2000 and 2008, in conjunction with increased contributions from emerging economies, from the production and international trade of goods and services, and from the use of coal as a fuel source. In contrast, emissions from land-use changes were nearly constant. Between 1959 and 2008, 43% of each year's CO2 emissions remained in the atmosphere on average; the rest was absorbed by carbon sinks on land and in the oceans. In the past 50 years, the fraction of CO2 emissions that remains in the atmosphere each year has likely increased, from about 40% to 45%, and models suggest that this trend was caused by a decrease in the uptake of CO2 by the carbon sinks in response to climate change and variability. Changes in the CO2 sinks are highly uncertain, but they could have a significant influence on future atmospheric CO2 levels. It is therefore crucial to reduce the uncertainties.

/pdf/trends-in-the-sources-and-sinks-of-carbon-dioxide-46ucyvejv1.pdf

Trends in the sources and sinks of carbon dioxide

. Accurate assessments of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere is important to better understand the global carbon cycle, support the climate policy process, and project future climate change. Present-day analysis requires the combination of a range of data, algorithms, statistics and model estimates and their interpretation by a broad scientific community. Here we describe datasets and a methodology developed by the global carbon cycle science community to quantify all major components of the global carbon budget, including their uncertainties. We discuss changes compared to previous estimates, consistency within and among components, and methodology and data limitations. CO2 emissions from fossil fuel combustion and cement production (EFF) are based on energy statistics, while emissions from Land-Use Change (ELUC), including deforestation, are based on combined evidence from land cover change data, fire activity in regions undergoing deforestation, and models. The global atmospheric CO2 concentration is measured directly and its rate of growth (GATM) is computed from the 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. Finally, the global residual terrestrial CO2 sink (SLAND) is estimated by the difference of the other terms. For the last decade available (2002–2011), EFF was 8.3 p 0.4 PgC yr−1, ELUC 1.0 p 0.5 PgC yr−1, GATM 4.3 p 0.1 PgC yr−1, SOCEAN 2.5 p 0.5 PgC yr−1, and SLAND 2.6 p 0.8 PgC yr−1. For year 2011 alone, EFF was 9.5 p 0.5 PgC yr−1, 3.0 percent above 2010, reflecting a continued trend in these emissions; ELUC was 0.9 p 0.5 PgC yr−1, approximately constant throughout the decade; GATM was 3.6 p 0.2 PgC yr−1, SOCEAN was 2.7 p 0.5 PgC yr−1, and SLAND was 4.1 p 0.9 PgC yr−1. GATM was low in 2011 compared to the 2002–2011 average because of a high uptake by the land probably in response to natural climate variability associated to La Nina conditions in the Pacific Ocean. The global atmospheric CO2 concentration reached 391.31 p 0.13 ppm at the end of year 2011. We estimate that EFF will have increased by 2.6% (1.9–3.5%) in 2012 based on projections of gross world product and recent changes in the carbon intensity of the economy. All uncertainties are reported as p1 sigma (68% confidence assuming Gaussian error distributions that the real value lies within the given interval), reflecting the current capacity to characterise the annual estimates of each component of the global carbon budget. This paper is intended to provide a baseline to keep track of annual carbon budgets in the future. All data presented here can be downloaded from the Carbon Dioxide Information Analysis Center ( doi:10.3334/CDIAC/GCP_V2013 ). Global carbon budget 2013

https://essd.copernicus.org/articles/5/165/2013/essd-5-165-2013.pdf

The global carbon budget 1959-2011

A new marine ecosystem model designed for the global domain is presented, and model output is compared with field data from nine different locations. Field data were collected as part of the international Joint Global Ocean Flux Study (JGOFS) program, and from historical time series stations. The field data include a wide variety of marine ecosystem types, including nitrogen- and iron-limited systems, and different physical environments from high latitudes to the mid-ocean gyres. Model output is generally in good agreement with field data from these diverse ecosystems. These results imply that the ecosystem model presented here can be reliably applied over the global domain. The model includes multiple potentially limiting nutrients that regulate phytoplankton growth rates. There are three phytoplankton classes, diatoms, diazotrophs, and a generic small phytoplankton class. Growth rates can be limited by available nitrogen, phosphorus, iron, and/or light levels. The diatoms can also be limited by silicon. The diazotrophs are capable of nitrogen fixation of N2 gas and cannot be nitrogen-limited. Calcification by phytoplankton is parameterized as a variable fraction of primary production by the small phytoplankton group. There is one zooplankton class that grazes the three phytoplankton groups and a large detrital pool. The large detrital pool sinks out of the mixed layer, while a smaller detrital pool, representing dissolved organic matter and very small particulates, does not sink. Remineralization of the detrital pools is parameterized with a temperature-dependent function. We explicitly model the dissolved iron cycle in marine surface waters including inputs of iron from subsurface sources and from atmospheric dust deposition. © 2001 Elsevier Science Ltd. All rights reserved.

/pdf/an-intermediate-complexity-marine-ecosystem-model-for-the-1x1x16wey8.pdf

An intermediate complexity marine ecosystem model for the global domain

Mesoscale phenomena are ubiquitous and highly energetic features of ocean circulation. Their influence on biological and biogeochemical processes varies widely, stemming not only from advective transport but also from the generation of variations in the environment that affect biological and chemical rates. The ephemeral nature of mesoscale features in the ocean makes it difficult to elucidate the attendant mechanisms of physical-biological-biogeochemical interaction, necessitating the use of multidisciplinary approaches involving in situ observations, remote sensing, and modeling. All three aspects are woven through this review in an attempt to synthesize current understanding of the topic, with particular emphasis on novel developments in recent years.

/pdf/mechanisms-of-physical-biological-biogeochemical-interaction-gha72btqwx.pdf

Mechanisms of Physical-Biological-Biogeochemical Interaction at the Oceanic Mesoscale

The motivation to study the vertical exchanges of tracers associated with mesoscale eddies is that the mean concentration of most oceanic tracers changes rapidly with depth. Because mesoscale processes may transport these tracers vertically, biogeochemists hypothesized that these vertical exchanges may strongly affect global tracer budgets. This hypothesis has motivated a large number of biogeochemical studies that we review here by focusing on the significant advances that have been achieved and the remaining issues and uncertainties. The main question that emerges concerns the importance of the submesoscales (10 km in the horizontal) in these vertical exchanges. Independently, in the past decade, fluid dynamicists examined the three-dimensional properties of submesoscales generated by a mesoscale (100 km in the horizontal) turbulent eddy field. We review their results and discuss how the vertical exchanges associated with these submesoscales may answer the issues raised by biogeochemical studies and inspire future directions.

/pdf/the-oceanic-vertical-pump-induced-by-mesoscale-and-5g8qlcgkow.pdf

The oceanic vertical pump induced by mesoscale and submesoscale turbulence.

Although pelagic ecosystem models, coupled with ocean circulation models, are being widely used to quantify fluxes of nutrients and carbon in the ocean at regional and basin scales, relatively little work has been done on understanding their intrinsic dynamics independently of physical forcing. In this study, the dynamics of three common formulations for the NPZD class of models (nutrient, phytoplankton, zooplankton and detritus) using two different types of predation functional response are analysed and compared. Our goal is to characterize the stability properties of this class of models with respect to variations in light and total nutrient concentrations. Despite important structural differences, the different model formulations all show asymptotic stable equilibria at low total nutrient concentrations and high to moderate light intensities, and limit cycle oscillations at low light intensities and high total nitrogen concentrations. Limit cycles are formed through a Hopf bifurcation as a phase lag develops between predator (Z i ) and prey (P i or Z i-1 ) due to a relatively sharp increase in the growth rate of the prey in relation to that of the predator. The use of variable preferences in the functional response provides a density-dependent mechanism that allows the system to self-regulate, increasing system stability considerably, but does not eliminate the instabilities completely. Instabilities occur at light and nutrient levels that correspond to those observed on the bottom of the euphotic zone near the nutricline, where the deep chlorophyll maximum is usually located. This suggests that the deep chlorophyll maximum might be dynamically unstable. This dynamic disequilibrium in species composition and the characteristically long transient times would allow species persistence in the presence of seasonal and mesoscale variations and provide a mechanism for species coexistence in the relatively homogeneous open ocean environment, thereby providing a potential solution for the 'paradox of plankton'. In the multi-species models, the higher diversity of species (wider range of values for the biological parameters) allows biological activity (photosynthesis, grazing and predation) to occur under a wider range of light and nutrient conditions, resulting in higher primary and secondary production and lower nutrient concentrations at light intensities equivalent to those in the upper part of the euphotic zone, than in the single-species model.

/pdf/intrinsic-dynamics-and-stability-properties-of-size-tprspw2za2.pdf

Intrinsic dynamics and stability properties of size-structured pelagic ecosystem models

https://iopscience.iop.org/article/10.1088/1748-9326/ab5abc/pdf

Attributing ocean acidification to major carbon producers

Observational studies report a rapid decline of ocean CO2 uptake in the temperate North Atlantic during the last decade. We analyze these findings using ocean physical‐biological numerical simulations forced with interannually varying atmospheric conditions for the period 1979–2004. In the simulations, surface ocean water mass properties and CO2 system variables exhibit substantial multiannual variability on sub‐basin scales in response to wind‐driven reorganization in ocean circulation and surface warming/cooling. The simulated temporal evolution of the ocean CO2 system is broadly consistent with reported observational trends and is influenced substantially by the phase of the North Atlantic Oscillation (NAO). Many of the observational estimates cover a period after 1995 of mostly negative or weakly positive NAO conditions, which are characterized in the simulations by reduced North Atlantic Current transport of subtropical waters into the eastern basin and by a decline in CO2 uptake. We suggest therefore that air‐sea CO2 uptake may rebound in the eastern temperate North Atlantic during future periods of more positive NAO, similar to the patterns found in our model for the sustained positive NAO period in the early 1990s. Thus, our analysis indicates that the recent rapid shifts in CO2 flux reflect decadal perturbations superimposed on more gradual secular trends. The simulations highlight the need for long‐term ocean carbon observations and modeling to fully resolve multiannual variability, which can obscure detection of the long‐term changes associated with anthropogenic CO2 uptake and climate change.

Changes in the North Atlantic Oscillation influence CO2 uptake in the North Atlantic over the past 2 decades

Recent research has quantified the contributions of CO2 andCH4 emissions traced to the products of major fossil fuel companies and cementmanufacturers to global atmospheric CO2, surface temperature, and sea level rise. This work has informed societal considerations of the climate responsibilities of thesemajor industrial carbon producers. Here, we extend this work to historical (1880–2015) and recent (1965–2015) acidification of theworld’s ocean. Using an energy balance carbon-cyclemodel, wefind that emissions traced to the 88 largest industrial carbon producers from 1880–2015 and 1965–2015 have contributed∼55%and∼51%, respectively, of the historical 1880–2015 decline in surface ocean pH. As ocean acidification is not spatially uniform, we employ a three-dimensional oceanmodel and identify fivemarine regions with large declines in surfacewater pH and aragonite saturation state over similar historical (average 1850–1859 to average 2000–2009) and recent (average 1960–1969 to average of 2000–2009) time periods.We characterize the biological and socioeconomic systems in these regions facing loss and damage fromocean acidification in the context of climate change and other stressors. Such analysis can inform societal consideration of carbon producer responsibility for current and near-term risks of further loss and damage to human communities dependent onmarine ecosystems andfisheries vulnerable to ocean acidification.

/pdf/marine-biogeochemical-modeling-recent-advances-and-future-1hr494wr80.pdf

Marine Biogeochemical Modeling: Recent Advances and Future Challenges SPECIAL ISSUE - JGOFS

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Intrinsic dynamics and stability properties of size-structured pelagic ecosystem models

Attributing ocean acidification to major carbon producers

Changes in the North Atlantic Oscillation influence CO2 uptake in the North Atlantic over the past 2 decades

Attributing ocean acidification to major carbon producers

Marine Biogeochemical Modeling: Recent Advances and Future Challenges SPECIAL ISSUE - JGOFS