Magnitude, Trends, and Variability of the Global Ocean Carbon Sink From 1985 to 2018

Global Biogeochemical Cycles, Journal Year: 2023, Volume and Issue: 37(10)

Published: Sept. 11, 2023

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

Language: Английский

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Assessment of Global Ocean Biogeochemistry Models for Ocean Carbon Sink Estimates in RECCAP2 and Recommendations for Future Studies

Journal of Advances in Modeling Earth Systems, Journal Year: 2024, Volume and Issue: 16(3)

Published: March 1, 2024

Abstract The ocean is a major carbon sink and takes up 25%–30% of the anthropogenically emitted CO 2 . A state‐of‐the‐art method to quantify this are global biogeochemistry models (GOBMs), but their simulated uptake differs between systematically lower than estimates based on statistical methods using surface p interior measurements. Here, we provide an in‐depth evaluation from 1980 2018 GOBM ensemble. As sources inter‐model differences ensemble‐mean biases our study identifies (a) model setup, such as length spin‐up, starting date simulation, fluxes rivers into sediments, (b) circulation, Atlantic Meridional Overturning Circulation Southern Ocean mode intermediate water formation, (c) oceanic buffer capacity. Our analysis suggests that late in circulation cause too low anthropogenic across Surface might also be low, current setup prevents robust assessment. For simulations sink, recommend short‐term start at common before industrialization associated atmospheric increase, conduct sufficiently long spin‐up GOBMs reach steady‐state, key metrics for biogeochemistry, land‐ocean interface. In long‐term, improving representation these GOBMs.

Language: Английский

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An Assessment of CO₂ Storage and Sea‐Air Fluxes for the Atlantic Ocean and Mediterranean Sea Between 1985 and 2018

Global Biogeochemical Cycles, Journal Year: 2024, Volume and Issue: 38(4)

Published: April 1, 2024

Abstract As part of the second phase Regional Carbon Cycle Assessment and Processes project (RECCAP2), we present an assessment carbon cycle Atlantic Ocean, including Mediterranean Sea, between 1985 2018 using global ocean biogeochemical models (GOBMs) estimates based on surface dioxide (CO 2 ) partial pressure (pCO products) interior dissolved inorganic observations. Estimates basin‐wide long‐term mean net annual CO uptake GOBMs pCO products are in reasonable agreement (−0.47 ± 0.15 PgC yr −1 −0.36 0.06 , respectively), with higher GOBM‐based likely being a consequence deficit representation natural outgassing land derived carbon. In GOBMs, increases time at rates close to what one would expect from atmospheric increase, but estimate rate twice as fast. The largest disagreement flux is found north 50°N, coinciding seasonal interannual variability. accumulation anthropogenic (C ant over 1994–2007 Ocean 0.52 0.11 according 28% 20% lower than that Around 70% this C taken up atmosphere, while remainder imported Southern through lateral transport.

Language: Английский

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Improved atmospheric constraints on Southern Ocean CO ₂ exchange

Proceedings of the National Academy of Sciences, Journal Year: 2024, Volume and Issue: 121(6)

Published: Jan. 30, 2024

We present improved estimates of air–sea CO 2 exchange over three latitude bands the Southern Ocean using atmospheric measurements from global airborne campaigns and an 4-box inverse model based on a mass-indexed isentropic coordinate (M θe ). These flux show two features not clearly resolved in previous inverting surface measurements: weak winter-time outgassing polar region sharp phase transition seasonal cycles between polar/subpolar subtropical regions. The suggest much stronger summer-time uptake regions than derived through neural-network interpolation pCO data obtained with profiling floats but somewhat weaker recent study by Long et al. [ Science 374 , 1275–1280 (2021)], who used same multiple transport models (ATMs) to constrain fluxes. Our also uses moist static energy (MSE) budgets reanalyses that most ATMs tend have excessive diabatic mixing (transport across isentrope, θ e or M surfaces) at high southern latitudes austral summer, which leads biases exchange. Furthermore, we MSE-based constraint is consistent independent combining observations.

Language: Английский

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An Assessment of CO₂ Uptake in the Arctic Ocean From 1985 to 2018

Global Biogeochemical Cycles, Journal Year: 2023, Volume and Issue: 37(11)

Published: Nov. 1, 2023

Abstract As a contribution to the Regional Carbon Cycle Assessment and Processes phase 2 (RECCAP2) project, we present synthesized estimates of Arctic Ocean sea‐air CO fluxes their uncertainties from surface ocean p ‐observation products, biogeochemical hindcast data assimilation models, atmospheric inversions. For period 1985–2018, was net sink 116 ± 4 TgC yr −1 in 92 30 91 21 The uptake peaks late summer early autumn, is low winter when sea ice inhibits fluxes. long‐term mean primarily caused by steady‐state natural carbon (70% 15%), enhanced increase (19% 5%) climate change (11% 18%). annual increased 1985 2018 at rate 31 13 dec 10 32 16 Moreover, 77% 38% trend over time change, due rapid loss recent years. Furthermore, true may be larger than given ensemble standard deviations common structural biases across all individual estimates.

Language: Английский

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Machine learning reveals regime shifts in future ocean carbon dioxide fluxes inter-annual variability

Communications Earth & Environment, Journal Year: 2024, Volume and Issue: 5(1)

Published: Feb. 24, 2024

Abstract The inter-annual variability of global ocean air-sea CO 2 fluxes are non-negligible, modulates the warming signal, and yet it is poorly represented in Earth System Models (ESMs). ESMs highly sophisticated computationally demanding, making challenging to perform dedicated experiments investigate key drivers flux across spatial temporal scales. Machine learning methods can objectively systematically explore large datasets, ensuring physically meaningful results. Here, we show that a kernel ridge regression reconstruct present future five ESMs. Surface concentration dissolved inorganic carbon (DIC) alkalinity emerge as critical drivers, but former projected play lesser role due decreasing vertical gradient. Our results demonstrate new approach efficiently interpret massive datasets produced by ESMs, offer guidance into model development better constrain flux.

Language: Английский

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High‐Resolution Variability of the Ocean Carbon Sink

Global Biogeochemical Cycles, Journal Year: 2024, Volume and Issue: 38(8)

Published: Aug. 1, 2024

Abstract Measurements of the surface ocean fugacity carbon dioxide ( f CO 2 ) provide an important constraint on global sink, yet gap‐filling products developed so far to cope with sparse observations are relatively coarse (1° × 1° by 1 month). Here, we overcome this limitation using a novel combination machine learning‐based methods and target transformations estimate associated sea‐air fluxes F globally at resolution 8‐day 0.25° (8D) over period 1982 through 2022. Globally, method reconstructs accuracy similar that low‐resolution (∼19 μatm), but improves it in coastal ocean. Although uptake differs little, 8D product captures 15% more variance . Most increase comes from better‐represented subseasonal scale variability, which is largely driven better‐resolved variability winds, also contributed The high‐resolution capable capturing signal short‐lived regional events such as hurricanes. For example, reveals was least 25 μatm lower wake Hurricane Maria (2017), result complex interplay between decrease temperature, entrainment carbon‐rich waters, primary production. By providing new insights into role higher frequency variations sink underlying processes, fills gap.

Language: Английский

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Accuracy of Ocean CO₂ Uptake Estimates at a Risk by a Reduction in the Data Collection

Geophysical Research Letters, Journal Year: 2024, Volume and Issue: 51(9)

Published: April 30, 2024

Abstract Observation‐based quantification of ocean carbon dioxide (CO 2 ) uptake relies on synthesis data sets such as the Surface Ocean CO ATlas (SOCAT). However, collection effort has dramatically declined and number annual in SOCATv2023 decreased by ∼35% from 2017 to 2021. This decline led a 65% increase (from 0.15 0.25 Pg C yr −1 standard deviation seven SOCAT‐based air‐sea flux estimates. Reducing availability that year 2000 creates substantial bias (50%) long‐term trend. The mean is insensitive seasonal skew SOCAT addition lower accuracy set available SOCAT. Our study highlights need for sustained synthesis, inform Global Carbon Budget assessment, UN‐led climate negotiations, measurement, reporting, verification ocean‐based removal projects.

Language: Английский

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Drivers of decadal trends in the ocean carbon sink in the past, present, and future in Earth system models

Biogeosciences, Journal Year: 2024, Volume and Issue: 21(17), P. 3903 - 3926

Published: Sept. 4, 2024

Abstract. The ocean and the land biosphere are two major sinks of anthropogenic carbon at present. When emissions become zero temperatures stabilize, is projected to dominant only global natural sink carbon. Despite ocean's importance for cycle hence climate, uncertainties about decadal variability in this underlying drivers remain large because observing detecting changes over time challenging. main tools that used provide annually resolved estimates last decades observation-based pCO2 products extrapolate sparse observations space biogeochemical models forced with atmospheric reanalysis data. However, these (i) limited 3 7 decades, which hinders statistical analyses trends; (ii) all based on same internal climate state, makes it impossible separate externally internally contributions (iii) cannot assess robustness future, especially when decline or cease entirely. Here, I use an ensemble 12 Earth system (ESMs) from phase 6 Coupled Model Intercomparison Project (CMIP6) understand trends past, present, future sink. simulations by ESMs span period 1850 2100 include four different Shared Socioeconomic Pathways (SSPs), low high mitigation mitigation. Using ensemble, show 80 % can be explained CO2 as long remains smaller than 4.5 Pg C yr−1. remaining 20 due heat uptake, result a loss ocean. exceeds yr−1, occurs high-emission SSP3-7.0 SSP5-8.5, rises faster, change accelerates, overturning chemical capacity take up atmosphere reduce, so substantially estimated trends. breakdown relationship both pathways also implies increase effectively ∼1 yr−1 dec−1 pathways, even if trend continues increase. Previously proposed drivers, such growth rate CO2, explain specific periods, example, during exponential growth, but fail start decrease again. robust suggests very positive negative some highly unlikely around 2000 likely products.

Language: Английский

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Global air-sea CO2 flux inversion based on multi-source data fusion and machine learning

Chaos Solitons & Fractals, Journal Year: 2025, Volume and Issue: 192, P. 115963 - 115963

Published: Jan. 8, 2025

Language: Английский

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