Posts Tagged 'globalmodeling'

Upper-ocean variability of the marine carbonate system in the Northeast Pacific

Published 2 June 2026 Science Leave a Comment
Tags: , , , , ,

In the Northeast Pacific, the marine carbonate system’s variability across timescales is not well constrained. Here, we quantify observed seasonal and non-seasonal variability in Dissolved Inorganic Carbon (DIC), partial pressure of carbon dioxide () and aragonite saturation state  and discuss potential drivers. We used three decades of observations from four Line P time series stations, the longest marine carbonate system time series in the Northeast Pacific (1990–2019). To gauge the spatial extent of the variability patterns, we used output from a global ocean model representing the observed period. In the Northeast Pacific, seasonal and non-seasonal  variability at 10 m was minimal, mostly damped by the opposing influence of DIC and temperature changes at both seasonal and interannual timescales. For DIC and , the seasonal cycle dominated total variability in the top 60–70 m, with mean-transect 10 m seasonal amplitudes of 35  3 μmol  and 0.31  0.04, respectively. In the upper 60–70 m, the magnitude of non-seasonal variability was at least half that of the seasonal variability for most variables. From five climate indices examined, we focused on the basin-scale Pacific Decadal Oscillation index (PDO) to investigate potential drivers of non-seasonal variability, with 20%–40% of the non-seasonal variability in DIC and  associated to this index. In the Northeast Pacific, positive PDO periods were linked to a mean reduction in 10 m DIC of 5 μmol  and an increase in 10 m  of 0.04 for each PDO unit increase, which could potentially reduce the occurrence and severity of ocean acidification events. The opposite could be expected during negative PDO periods.

Plain Language Summary

Using 30 years of observations from the Northeast Pacific, we characterized sources of variability for three marine carbonate system variables: , dissolved inorganic carbon (DIC) and the saturation state of aragonite (an common indicator of ocean acidification). The  seasonal and non-seasonal variability was minimal in the top 10 m. The seasonal cycle of DIC and aragonite saturation state was the major contributor to total variability in the top 60–70 m, and not detectable below. Also, in the top 70 m of the water column, up to 20%–40% of the DIC and aragonite saturation state non-seasonal variability was associated to the Pacific Decadal Oscillation index (PDO). The PDO is a statistics-derived index that captures variability patterns influencing the whole Pacific basin and has a positive and negative phase. We found that a warmer than usual upper water column in the Northeast Pacific during a positive PDO phase, potentially driven by reduced mixing, was linked to a lower DIC and higher values of aragonite saturation state. The opposite could be expected during negative PDO periods. Knowing the magnitude of natural variability in the marine carbonate system is important to identify the emergence of ocean acidification and other human-driven changes in the ocean.

Continue reading ‘Upper-ocean variability of the marine carbonate system in the Northeast Pacific’

Acidification in the Earthʼs oceans: trends and persistence

Published 13 April 2026 Newsletters and reports Closed
Tags: , ,

This paper applies fractional integration methods to obtain evidence on ocean acidification, namely the decrease in the pH level in the Earth’s oceans, using the annual Hawaii Ocean Time-series Station ALOHA series as well as the logged one for the period 1985-2024. The chosen modelling framework is more general than standard ones based on the I(0) versus I(1) dichotomy and sheds light on the long memory and persistence properties, as well as on the possible presence of trends, in the pH Level in the Earth’s oceans. The results indicate that the series exhibit a negative and significant time trend; however, whether or not the null hypothesis of a unit root is rejected depends on the assumption made about the errors. The key finding (when the errors are not incorrectly specified as I(0) processes) is the presence of long memory, which implies that the effects of shocks are long-lived, regardless of whether or not mean reversion occurs. Moreover, the recursive analysis indicates that both the degree of persistence and the downward trend in the pH level have increased over time. This evidence points to the urgent need for decisive policies to address the issue of ocean acidification and protect marine life and biodiversity.

Continue reading ‘Acidification in the Earthʼs oceans: trends and persistence’

Acidification and deoxygenation matter in assessing redistribution of global cold-water coral biodiversity induced by climate change

Published 24 March 2026 Science Closed
Tags: , , , , , ,

The ocean is undergoing significant changes, including warming, acidification, and deoxygenation, which pose great challenges to marine biodiversity. However, most models projecting the impacts of climate change on marine species overlook predictor variables critically meaningful for species’ ecologies such as pH and dissolved oxygen. The recent release of high-resolution projections of different future climate-change scenarios offers the opportunity to explore species redistribution under multiple threats beyond ocean warming. Accordingly, we conducted a global comparative analysis to study the impact of incorporating predictor variables describing pH and dissolved oxygen into marine species distribution models. We used models trained for 268 cold-water coral species to project potential future distributions for different climate and dispersal scenarios over different time periods. We found that, irrespective of scenario or period, models using pH and dissolved oxygen projected 11.5–21.4% higher impacts of climate change than those without them. For instance, by the end of the century under a high emission scenario, models including pH and oxygen projected an average range contraction of 48.2% for cold-water corals under a no-dispersal scenario, compared with a 26.8% contraction projected by models excluding these two predictors. Given the substantial differences in the predicted distribution patterns and the biological importance of these variables, we highlight that researchers should consider more diverse sets of predictor variables when predicting future range shifts for marine biodiversity assessments under climate change.

Continue reading ‘Acidification and deoxygenation matter in assessing redistribution of global cold-water coral biodiversity induced by climate change’

Synthesis of data products for ocean carbonate chemistry

Published 5 March 2026 Science Closed
Tags: , , , ,

As the largest active carbon reservoir on Earth, the ocean is a cornerstone of the global carbon cycle, playing a pivotal role in modulating ocean health and the Earth’s climate system. Understanding these crucial roles requires access to a broad array of data products documenting the changing chemistry of the global ocean as a vast and interconnected system. This review article provides an overview of 68 existing ocean carbonate chemistry data products and data product sets, encompassing compilations of cruise datasets, derived gap-filled data products, model simulations, and compilations thereof. It is intended to help researchers identify and access data products that best align with their research objectives, thereby advancing our understanding of the ocean’s evolving carbonate chemistry. The list will be updated periodically to incorporate new data products. The most up-to-date list is available at https://oceanco2.github.io/co2-products/ (Gregor and Jiang, 2026).

Continue reading ‘Synthesis of data products for ocean carbonate chemistry’

A global perspective on river alkalinity: drivers and implications for coastal ocean carbonate chemistry

Published 4 December 2025 Science Closed
Tags: , , ,

Abstract

The chemical nature of river water significantly influences the coastal carbonate system, contributing to coastal acidification and creating suboptimal conditions for marine calcifiers. While several regional efforts have assessed observationally based riverine concentrations and fluxes of total alkalinity (TA) and dissolved inorganic carbon (DIC), these values in global ocean biogeochemical models have generally been simplified, often set to zero or balanced against global sediment calcium carbonate burial. To enhance our understanding of rivers’ role in the coastal carbonate system, we applied multiple linear regression (MLR) to develop global empirical relationships for estimating river TA and DIC from watershed properties. We find that river TA values are primarily controlled by forest, carbonate rock coverage, and annual mean precipitation, explaining 74% of the spatial variability in TA. The variability explained improves to 77% with the inclusion of permafrost and glacial coverage, especially in high latitude and altitude regions. Additionally, nearly 30% of the spatial variability in the river DIC-to-TA ratio can be explained by terrestrial gross primary production and carbonate rock coverage. Applying these MLR-derived TA and DIC concentrations to a 1/4° resolution global ocean model reduces the high bias in model estimates of global coastal CO2 uptake by 69% (equivalent to 0.11 Pg C yr−1 less CO2 uptake) compared to the case with zero river TA and DIC. This study elucidates key drivers of the river carbonate system and underscores the importance of accurately representing riverine inputs to improve predictions of global coastal carbon dynamics and ecosystem responses to environmental changes.

Plain Language Summary

Rivers play a critical role in shaping the chemistry of coastal waters, influencing how much carbon dioxide (CO2) the ocean absorbs and creating conditions that affect marine life, such as shellfish and corals. Global models are essential for predicting carbon dynamics at large scales, offering insights into the interactions between rivers, coastal systems, and the global ocean. However, global models often simplify or partially overlook key chemical contributions from rivers, leading to biases in predictions. In this study, we analyzed how river chemistry, particularly river carbon inputs, is influenced by factors such as forest cover, carbonate rocks, rainfall, permafrost, and glaciers on land. We developed statistical models to estimate two key properties: total alkalinity and dissolved inorganic carbon. Incorporating these improved river chemistry estimates into a global ocean model markedly reduced the overestimation of coastal CO2 absorption. This research underscores the importance of accurately including riverine inputs in global models to enhance predictions of coastal carbon dynamics and ecosystem responses to climate change.

Key Points

  • Global empirical relationships are developed using multiple linear regression (MLR) to estimate river TA and DIC concentrations from watershed properties
  • Forest and carbonate rock coverage, and annual mean precipitation explain 74% of the spatial variability in global river TA values
  • Applying MLR-derived river TA and DIC concentrations to a global ocean model substantially reduces biases in coastal CO2 uptake estimates
Continue reading ‘A global perspective on river alkalinity: drivers and implications for coastal ocean carbonate chemistry’

Spaces of anthropogenic CO2 emissions compatible with climate boundaries

Published 14 November 2025 Science Closed
Tags: , , ,

Climate boundaries are planetary boundaries for the climate system: limits within which humanity can sustainably prosper. Here we introduce a modelling framework to analyse global warming, ocean acidification, sea-level rise and Arctic sea-ice melt. Using a reduced-form model, we map out anthropogenic CO2 emissions, carbon dioxide removal and solar radiation management pathways compatible with these boundaries. We define safety levels as the probability to stay within one or several boundaries considering physical uncertainty. If CO2 emissions peak in 2030, net-zero CO2 is reached in 2050, and carbon dioxide removal capacity is 10 PgC yr−1, without solar radiation management, remaining within the global warming boundary of 2 °C exhibits a safety level of 80%. When all four boundaries are considered together, the safety level drops to 35%. Our results highlight key trade-offs in mitigation options and suggest a need to assess climate boundaries holistically to develop sustainable future strategies.

Continue reading ‘Spaces of anthropogenic CO2 emissions compatible with climate boundaries’

From global emissions to local impacts: spatially explicit modeling of ocean acidification in life cycle assessment

Published 22 October 2025 Science Closed
Tags: , , , ,

Ocean acidification poses a critical threat to marine ecosystems. While life cycle assessment frameworks provide a method for assessing and combatting many anthropogenic impacts, marine impact models remain underdeveloped compared to their terrestrial counterparts. This study presents the first spatially explicit characterization model for quantifying the impacts of ocean acidification that includes both midpoint and endpoint characterization factors (CFs). Midpoint CFs were spatially delineated by using marine ecoregions and Food and Agriculture Organization fishing areas, leveraging spatially explicit fate and fate sensitivity factors. Endpoint CFs were calculated using species sensitivity distributions that include species across a range of calcification levels, climate zones, and trophic levels. Results demonstrate significant geographic variability in ocean acidification impacts, with polar regions showing heightened vulnerability. Our findings emphasize the need for spatially explicit modeling to account for the diverse biogeochemical and ecological responses to ocean acidification. This work advances marine impact assessment by integrating spatial and biological complexity, providing critical tools for quantifying ocean acidification’s global ecological and economic consequences.

Continue reading ‘From global emissions to local impacts: spatially explicit modeling of ocean acidification in life cycle assessment’

Mapping the safe operating space of marine ecosystems under contrasting emission pathways

Published 17 October 2025 Science Closed
Tags: , ,

Anthropogenic greenhouse gas emissions cause multiple changes in the ocean and its ecosystems through climate change and ocean acidification. These changes can occur progressively with rising atmospheric carbon dioxide concentrations, but there is also the possibility of large-scale abrupt, and/or potentially irreversible changes, which would leave limited opportunity for marine ecosystems to adapt. Such changes, either progressive or abrupt, pose a threat to biodiversity, food security, and human societies. However, it remains notoriously difficult to determine exact limits of a “safe operating space” for humanity. Here, we map, for a variety of ocean impact metrics, the crossing of limits, which we define using the available literature and to represent a wide range of deviations from the unperturbed state. We assess the crossing of these limits in three future emission pathways: two climate mitigation scenarios, including an overshoot scenario, and one high-emission no-mitigation scenario. These scenarios are simulated by the latest generation of Earth system models and large perturbed-parameter ensembles with two Earth system models of intermediate complexity. Using this comprehensive model database, we estimate the timing and warming level at which 15 different impact metrics exceed 4 limits, along with an assessment of the associated uncertainties. We find that under the high-emissions scenario, the strongest severity of impacts is expected with high probability for marine heatwaves’ duration, loss of Arctic summer sea ice extent, expansion of ocean areas that are undersaturated with respect to aragonite, and decrease in plankton biomass. The probability of exceeding a given limit generally decreases clearly under low-emissions scenario. Yet, exceedance of ambitious limits related to steric sea level rise, Arctic summer sea ice extent, Arctic aragonite undersaturation, and plankton biomass are projected to be difficult to avoid (high probability) even under the low-emissions scenario. Compared to the high-emissions scenario, the scenario including a temporary overshoot reduces with high probability the risk of exceeding limits by year 2100 related to marine heatwave duration, Arctic summer sea ice extent, strength of the Atlantic meridional overturning circulation, aragonite undersaturation, global deoxygenation, plankton biomass, and metabolic index. Our study highlights the urgent need for ambitious mitigation efforts to drastically minimize extensive impacts and potentially irreversible changes to the world’s ocean ecosystems.

Continue reading ‘Mapping the safe operating space of marine ecosystems under contrasting emission pathways’

Relative enrichment of ammonium and its impacts on open-ocean phytoplankton community composition under a high-emissions scenario

Published 7 October 2025 Science Closed
Tags: , , , , , , ,

Ammonium (NH4+) is an important component of the ocean’s dissolved inorganic nitrogen (DIN) pool, especially in stratified marine environments where intense recycling of organic matter elevates its supply over other forms. Using a global-ocean biogeochemical model with good fidelity to the sparse NH4+ data that are available, we project increases in the NH4+: DIN ratio in over 98 % of the ocean by the end of the 21st century under a high-emission scenario. This relative enrichment of NH4+ is driven largely by circulation changes and secondarily by warming-induced increases in microbial metabolism, as well as reduced nitrification rates due to pH decreases. Supplementing our model projections with geochemical measurements and phytoplankton abundance data from Tara Oceans, we demonstrate that shifts in the form of DIN to NH4+ may impact phytoplankton communities by disadvantaging nitrate-dependent taxa like diatoms while promoting taxa better adapted to NH4+. This could have cascading effects on marine food webs, carbon cycling and fishery productivity. Overall, the form of bioavailable nitrogen emerges as a potentially underappreciated driver of ecosystem structure and function in the changing ocean.

Continue reading ‘Relative enrichment of ammonium and its impacts on open-ocean phytoplankton community composition under a high-emissions scenario’

The evolution of ocean carbon cycle feedbacks in observations and models

Published 7 October 2025 Science Closed
Tags: , , , , ,

Since the Industrial Revolution, the ocean has absorbed a cumulative ~40% of the anthropogenic carbon (Cant) released into the atmosphere by fossil fuel emissions. Cant accumulation in the upper ocean has driven an increase in the partial pressure of carbon dioxide gas (pCO2) and associated declines in pH and carbonate ion concentration. These chemical changes, collectively referred to as ocean acidification (OA), progressively weaken the ocean’s buffer capacity and reflect the evolution of a positive marine carbon cycle feedback that reduces the efficiency of future Cant uptake and amplifies the influence of natural variability on the carbonate system. This dissertation investigates the spatial and temporal changes in the ocean carbon cycle caused by Cant using a combination of in situ observations, data synthesis products, and output from regional and global ocean models to improve our understanding of the processes governing the ocean carbon sink and its evolving feedbacks. Chapter 1 evaluates the impact of Cant accumulation on multiple OA metrics throughout the water column in the North Pacific Ocean and California Current Large Marine Ecosystem using ship-based observations. Results indicate that the greatest increases in pCO2 occur subsurface, where Cant content is moderate and pCO2 change can exceed overlying surface change by ≥100%. Amplified pCO2 responses in the interior ocean are related to background ocean carbonate chemistry, with the greatest subsurface changes associated with poorly buffered waters that have experienced substantial organic matter remineralization. Chapter 2 evaluates the impact of Cant on the seasonal variability of pCO2 in the surface ocean using output from global ocean biogeochemical models (GOBMs) used by global carbon budgeting efforts to estimate the historical ocean carbon sink strength. Results indicate that dissimilar model representations of surface ocean pCO2 seasonality, particularly during winter, lead to increasing disagreement in annual ocean carbon sink strength estimates over time. Chapter 3 examines how differences in representations of interior ocean Cant and natural carbon influence patterns of amplified subsurface pCO2 change using the same set of GOBMs, in addition to observation-based data products. Results indicate that GOBMs dissimilarly simulate subsurface Cant-induced pCO2 changes, particularly at the depth of maximum winter mixing, when these signals can re-emerge at the surface and bias estimates of the annual ocean carbon sink strength. This research contributes to ongoing international efforts to better constrain the global ocean carbon sink. Discrepancies between observation- and model-based estimates of the modern ocean carbon sink have grown over time, with across-model disagreements compounding in future climate projections. This points to an outstanding need to constrain sources of model discrepancies. This work helps to address this by clarifying: (1) a model’s projected end-of-century ocean carbon sink magnitude is highly dependent on its post-spin-up seasonal and annual mean-state; (2) a more realistic representation of interior ocean carbon distributions and ecosystem processes is needed to achieve a more realistic representation of ocean carbon cycle change and the evolution of its feedbacks.

Continue reading ‘The evolution of ocean carbon cycle feedbacks in observations and models’

Cumulative impacts to global marine ecosystems projected to more than double by midcentury

Published 12 September 2025 Science Closed
Tags: , , ,

Pressures from human activities are expected to increase significantly, impacting marine ecosystems globally. To plan for a sustainable future, we need to forecast distributions of cumulative impacts from multiple pressures. Here we mapped (10km resolution) future cumulative impacts of ten climate, land-based, fishing and other pressures on twenty marine habitats under two climate scenarios at midcentury (~2050). We found cumulative impacts are projected to increase 2.2 to 2.6 times globally, with coastal habitats facing higher impacts but offshore regions facing faster increases, especially in equatorial regions. Furthermore, many countries dependent on marine resources will have large increases in impacts. Incorporating these results into strategic policy and management will support more sustainable use and protection of marine ecosystems and the services provided to people.

Continue reading ‘Cumulative impacts to global marine ecosystems projected to more than double by midcentury’

Potential for regional resilience to ocean warming and acidification extremes: projected vulnerability under contrasting pathways and thresholds

Published 30 July 2025 Science Closed
Tags: , , , , , ,

We analyze the frequency and amplitude of projected warming and ocean acidification extremes under high CO2 and strongly mitigating scenarios. We find interpretational differences in projections arising from methodological choices associated with specification of stressor thresholds. Use of absolute versus distribution-based thresholds, and, in the distribution-based case, the inclusion or exclusion of seasonal variability, can lead to very different regional patterns in projected stress. The choice of fixed versus adaptive baseline, for example, determines whether future stress frequency in the low-CO2 scenario most closely resembles that in the high-emissions scenario or historical period. We find that mitigation through emissions reductions, in combination with representation of rates of adaptation that are realistic for some marine organisms, has the potential to dampen end of century threshold exceedance to frequencies of occurrence closer to the recent historical period than to the high-emissions scenario.

Continue reading ‘Potential for regional resilience to ocean warming and acidification extremes: projected vulnerability under contrasting pathways and thresholds’

Pulses of ocean acidification at the Triassic–Jurassic boundary

Published 23 July 2025 Science Closed
Tags: , , , ,

Mass extinctions have repeatedly perturbed the history of life, but their causes are often elusive. Ocean acidification has been implicated during Triassic–Jurassic environmental perturbations, but this interval lacks direct reconstructions of ocean pH. Here, we present boron isotope data from well-preserved fossil oysters, which provide evidence for acidification of ≥ 0.29 pH units coincident with a 2 ‰ negative carbon isotope excursion (the “main” CIE) following the end–Triassic extinction. These results suggest a prolonged interval of CO2-driven environmental perturbation that may have delayed ecosystem recovery. Earth system modelling with cGENIE paired with our pH constraints demonstrates this was driven by predominantly mantle-derived carbon. Ocean acidification therefore appears to be associated with three of the five largest extinction events in Earth history, highlighting the catastrophic ecological impact of major perturbations to the carbon cycle in Earth’s past, and possibly Earth’s anthropogenically perturbed future.

Continue reading ‘Pulses of ocean acidification at the Triassic–Jurassic boundary’

Synthesis of data products for ocean carbonate chemistry

Published 11 June 2025 Science Closed
Tags: , , , ,

As the largest active carbon reservoir on Earth, the ocean is a cornerstone of the global carbon cycle, playing a pivotal role in modulating ocean health and regulating climate. Understanding these crucial roles requires access to a broad array of data products documenting the changing chemistry of the global ocean as a vast and interconnected system. This review article provides a comprehensive overview of 60 existing ocean carbonate chemistry data products, encompassing compilations of cruise datasets, derived gap-filled data products, model simulations, and compilations thereof. It is intended to help researchers identify and access data products that best align with their research objectives, thereby advancing our understanding of the ocean’s evolving carbonate chemistry.

Continue reading ‘Synthesis of data products for ocean carbonate chemistry’

Surface and subsurface compound marine heatwave and biogeochemical extremes under climate change

Published 6 May 2025 Science Closed
Tags: , , ,

Marine species are increasingly threatened by extreme and compound events, as warming, deoxygenation, and acidification unfold. Yet, the surface and especially the subsurface distribution and evolution of such compound events remain poorly understood. We present the current and projected distributions of compound marine heatwave (MHW), low oxygen (LOX), and high acidity (OAX) events throughout the water column, using observation‐based data from 2004 to 2019 and large ensemble Earth system model simulations from 1890 to 2100. Our findings reveal that compound MHW‐OAX and OAX‐LOX events are prevalent in the low to mid latitudes at the ocean surface. At 200 and 600 m, MHW‐OAX and MHW‐LOX events are frequent in the high latitudes and parts of the tropics, while OAX‐LOX events occur globally. Subsurface compound events are often associated with vertical displacements of water masses, with the climatological vertical gradients of ecosystem stressors typically explaining their occurrence patterns. Projections show a strong rise in compound event frequency over the historical period and under continued global warming, primarily driven by shifts in mean oceanic conditions. The portion of the top 2,000 m affected by extreme or compound events rises from 20% % to 98% % under 2°C of global warming in a high emissions scenario using a preindustrial baseline, and to 30% % using a shifting‐mean baseline. However, physical and biogeochemical changes may also lead to regional decreases in subsurface events, highlighting complexities in how warming, deoxygenation, and acidification unfold in the ocean interior. Increasing compound event frequency poses a major threat to marine ecosystems, potentially disrupting food webs and biodiversity.

Continue reading ‘Surface and subsurface compound marine heatwave and biogeochemical extremes under climate change’

A global monthly 3D field of seawater pH over 3 decades: a machine learning approach

Published 14 April 2025 Science Closed
Tags: , ,

The continuous uptake of anthropogenic CO2 by the ocean leads to ocean acidification, which is an ongoing threat to marine ecosystem. The ocean acidification rate has been globally documented in the surface ocean, but this information is limited below the surface. Here, we present a monthly 4D 1°×1° gridded product of global seawater pH on the total scale and at in situ temperature (without standardization to 25 °C), derived from a machine learning algorithm trained on pH observations from the Global Ocean Data Analysis Project (GLODAP). The proposed pH product covers the years from 1992 to 2020 and depths from the surface to 2 km on 41 levels. A three-step machine-learning-based algorithm was used to construct the pH product, incorporating region division via a self-organizing map neural network, predictor selection via the stepwise regression algorithm that adds and removes variables from network inputs based on their contribution to reducing reconstruction errors, and nonlinear relationship regression by feedforward neural networks (FFNNs). The performance of the machine learning algorithm was validated using real observations with a cross-validation method, in which four repeating iterations were carried out with each iteration utilizing a different 25 % subset of observations for validation and the complementary 75 % subset for training. The proposed pH product is evaluated using comparisons to time-series observations and the GLODAP pH climatology. The overall root-mean-square error between the FFNN-reconstructed pH and the GLODAP measurements is 0.028, ranging from 0.044 at the surface to 0.013 at 2000 m. The pH product is distributed via the Marine Science Data Center of the Chinese Academy of Sciences: https://doi.org/10.12157/IOCAS.20230720.001 (Zhong et al., 2023).

Continue reading ‘A global monthly 3D field of seawater pH over 3 decades: a machine learning approach’

Research on Atlantic surface pCO2 reconstruction based on machine learning

Published 11 March 2025 Science Closed
Tags: , ,

Highlights

  • The XGBoost machine learning model has been refined, leading to a superior prediction of atmospheric carbon dioxide partial pressure over the Atlantic Ocean.
  • We introduced the GeoDetector, a spatial statistical analysis method, to quantitatively assess the influence of various factors on the atmospheric carbon dioxide partial pressure over the ocean surface.
  • Comprehensive validation ensures the robustness and reliability of the XGBoost model in this region.
  • Investigations into the atmospheric carbon dioxide partial pressure over the Atlantic Ocean offer valuable insights into global marine ecosystems.

Abstract

Ocean acidification is transforming marine ecosystems at an unprecedented rate, which in turn requires the estimation of sea surface carbon dioxide partial pressure (pCO2) as a crucial metric to gauge acidification. This has substantial implications for marine resource assessment and management, marine ecosystems, and global climate change research. This study utilizes SOCAT cruise survey data to assess the accuracy of global sea surface pCO2 products offered by Copernicus Marine Service and the Chinese Academy of Sciences Ocean Science Research Center. Through the application of a geographic information analysis method—geographical detector—the study quantitatively reveals the significance of environmental influencing factors, such as longitude, latitude, sea surface 10 m wind speed (U10), total precipitation (TP), evaporation (E), and significant height of combined wind waves and swell (SHWW), in the reconstruction of sea surface pCO2. Subsequently, various machine learning models, which include convolutional neural network (CNN), back propagation neural network (BP), long short-term memory network (LSTM), extreme learning machine (ELM), support vector regression (SVR), and extreme gradient boosting tree (XGBoost), are used to reconstruct the monthly sea surface pCO2 data for the Atlantic Ocean from 2001 to 2020 to investigate the potential and suitability of high-precision reconstruction of the sea surface pCO2 dataset for this sea area. The findings indicate that: (1) The geographical detector effectively quantifies the contribution of various environmental factors used in sea surface pCO2 reconstruction. Notably, the Copernicus pCO2 and CODC-GOSD pCO2 contribute the most, with both contributing ∼0.72. These are followed by TP, latitude, longitude, SHWW, U10, and E. (2) After comprehensive data testing, the six machine learning models select the optimal hyperparameters for reconstruction. Among these, the XGBoost model notably improved the quality of the original dataset when using Copernicus pCO2 and CODC-GOSD pCO2 products in conjunction with SHWW, U10, and TP environmental variable data. Compared with SOCAT data, the overall reconstruction accuracy in the Atlantic Ocean reached an impressive 94 %, outperforming the standalone use of either Copernicus pCO2 or CODC-GOSD pCO2 products. Furthermore, the XGBoost model demonstrated strong applicability in regions with numerous outliers, maintaining a reconstruction accuracy of ≥95 %. (3) Stability test results reveal that the XGBoost model exhibits low sensitivity to uncertainties in all input variables. This indicates that the model can accommodate environmental data errors induced by abrupt changes in marine environments. Such robustness enhances its reliability in sea surface pCO2 reconstruction. The reconstruction of the Atlantic sea surface pCO2 is conducive to the assessment of global ocean acidification and provides a theoretical basis for the sustainable development of the marine environment.

    Continue reading ‘Research on Atlantic surface pCO2 reconstruction based on machine learning’

    Global surface ocean calcite saturation (Ωcal) estimation using satellite and in-situ observations

    Published 10 March 2025 Science Closed
    Tags: , , ,

    Highlights

    • Developed an MLR model using in-situ and satellite data to estimate Ocean Ωcal.
    • Spatiotemporal Ωcal variability driven by physical, chemical, and biological factors.
    • Showed strong agreement with low errors between satellite-derived and in-situ Ωcal.
    • Emphasized a declining Ωcal trend (2012–2022), indicating accelerating ocean acidification.

    Abstract

    Calcite saturation (Ωcal) in global surface ocean waters is a crucial parameter for assessing marine ecosystem health. This study presents a multiparametric linear regression (MLR) model integrating satellite and in-situ observations to estimate global surface ocean Ωcal. The model was developed using in-situ measurements of sea surface temperature (SST), sea surface salinity (SSS), total alkalinity (TA), dissolved inorganic carbon (DIC) and Ωcal obtained from the National Center for Environmental Information (NCEI), combined with satellite derived chlorophyll concentrations (Chla). Model validation demonstrated strong agreement with in-situ data, indicating high accuracy of estimation. Satellite derived Ωcal estimates also showed robust correlations with in-situ measurements, confirming the MLR model reliability. Sensitivity analysis highlighted the model resilience to variations in input parameters. This study reveals significant spatiotemporal variability in Ωcal, driven by physical, chemical, and biological processes, including seasonal patterns and climate phenomena like the El Nino Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO). Analysis of interannual trends and the rate of change in Ωcal emphasize the impacts of ocean acidification, revealing a declining trend that poses challenges to marine ecosystems. The proposed approach offers a valuable tool for monitoring global ocean carbonate chemistry, providing insights into the long term impacts of environmental changes on marine health and enabling informed decision making for ecosystem management.

    Continue reading ‘Global surface ocean calcite saturation (Ωcal) estimation using satellite and in-situ observations’

    A global upward trend in ocean-atmosphere carbon dioxide fugacity

    Published 28 February 2025 Science Closed
    Tags: , , , ,

    The carbon dioxide fugacity in the global oceans has shown a slow upward trend, over the past 20 years, the carbon dioxide fugacity in global oceans has increased by 6.7%.This conclusion is based on over 160,000 quality-controlled measurements of surface ocean carbon dioxide fugacity from 2000 to 2020, and employing machine learning methods, a satellite-based assessment model for sea-air carbon dioxide fugacity (fCO2) has been developed, aiming to reveal global changes in fCO2 over the past 20 years. This study investigates the factors influencing sea-air carbon dioxide fugacity (fCO₂) by integrating a comprehensive dataset, including satellite data coordinates, fundamental seawater parameters (e.g., salinity and temperature), wind speed, seawater acidity and alkalinity, seawater velocity, geostrophic seawater velocity, surface partial pressure of carbon dioxide in seawater, downward mass flux of carbon dioxide expressed as carbon, concentrations of dissolved inorganic carbon, phosphate, nitrate, silicate, chlorophyll, and dissolved oxygen. A comparative analysis was conducted among various machine learning methods, such as XGBoost, Random Forest, Light Gradient Booster, Feedforward Neural Network, Convolutional Neural Network, and Backpropagation Neural Network. Based on the best performance, the XGBoost algorithm was selected for model construction. The results of independent field validation demonstrate that the model has a low root mean square error (RMSE = 18.08 μatm), mean absolute percentage error (MAPE = 1.1%), and a high coefficient of determination (R² = 0.91). Ultimately, the global distribution of sea-air carbon dioxide fugacity at a resolution of 0.25° × 0.25° from 2000 to 2020 was reconstructed.

    Continue reading ‘A global upward trend in ocean-atmosphere carbon dioxide fugacity’

    What controls planktic foraminiferal calcification?

    Published 17 February 2025 Science Closed
    Tags: , , , , , , ,

    Planktic foraminifera are key producers of pelagic carbonate, and their shell weight is suggested to have been influenced by the environment in which they calcify. However, there is debate about the use of size-normalised weight (SNW) as a proxy, as some authors invoke a carbonate system control on calcification (and by extension SNW as a pCO2 proxy), while others suggest that species optimum conditions, nutrient concentration, or temperature drive shell weight. To better understand this proxy, we investigate what drives SNW and whether discrepancies in the proposed control on weight are due to differing data collection methodologies and/or regionally different drivers. We integrate new and published SNW data with environmental hindcast data from the CMIP6 modelling suite. Using Bayesian regression modelling, we find that the environment alone does not explain the variability in SNW across species. Although physiology likely modulates the response to the environment, we find little evidence of a unifying driver at the ecogroup level. Instead, we identify species-specific responses associated with drivers including (but not limited to) the carbonate system, which are likely different between ocean basins. We hypothesise that this is partly influenced by cryptic species and regional phenotypic plasticity in changes to shell weight that are not well understood, such as the thickness of calcite deposited during some species’ reproductive phases. Consequently, which species to use as a pCO2 proxy or whether multiple species should be used in parallel to reduce uncertainty should be carefully considered. We strongly encourage the regional testing and calibration of pCO2–SNW relationships.

    Continue reading ‘What controls planktic foraminiferal calcification?’

    Subscribe

    Search

    • Reset

    OA-ICC Highlights

    Resources