Hazards of decreasing marine oxygen: the near-term and
millennial-scale benefits of meeting the Paris climate targets

Battaglia, Gianna; Joos, Fortunat

doi:10.5194/esd-2017-90

Cited by 9 publications

(15 citation statements)

References 43 publications

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“…Deoxygenation peaks at year A.D. 4000 when deep water had sufficient time to age, to accumulate remineralized nutrients, and to integrate losses by oxygen consumption. In addition, warming causes O 2 loss due to changes in solubility (see also Battaglia & Joos, 2017 for process attribution).…”

Section: Transient Circulation Changes Export Production and Deoxygmentioning

confidence: 99%

Marine N₂O Emissions From Nitrification and Denitrification Constrained by Modern Observations and Projected in Multimillennial Global Warming Simulations

Battaglia

Joos

2018

Global Biogeochemical Cycles

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Nitrous oxide (N2O) is a potent greenhouse gas (GHG) and ozone destructing agent; yet global estimates of N2O emissions are uncertain. Marine N2O stems from nitrification and denitrification processes which depend on organic matter cycling and dissolved oxygen (O2). We introduce N2O as an obligate intermediate product of denitrification and as an O2‐dependent by‐product from nitrification in the Bern3D ocean model. A large model ensemble is used to probabilistically constrain modern and to project marine N2O production for a low (Representative Concentration Pathway (RCP)2.6) and high GHG (RCP8.5) scenario extended to A.D. 10,000. Water column N2O and surface ocean partial pressure N2O data serve as constraints in this Bayesian framework. The constrained median for modern N2O production is 4.5 (±1σ range: 3.0 to 6.1) Tg N yr−1, where 4.5% stems from denitrification. Modeled denitrification is 65.1 (40.9 to 91.6) Tg N yr−1, well within current estimates. For high GHG forcing, N2O production decreases by 7.7% over this century due to decreasing organic matter export and remineralization. Thereafter, production increases slowly by 21% due to widespread deoxygenation and high remineralization. Deoxygenation peaks in two millennia, and the global O2 inventory is reduced by a factor of 2 compared to today. Net denitrification is responsible for 7.8% of the long‐term increase in N2O production. On millennial timescales, marine N2O emissions constitute a small, positive feedback to climate change. Our simulations reveal tight coupling between the marine carbon cycle, O2, N2O, and climate.

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Section: Transient Circulation Changes Export Production and Deoxygmentioning

confidence: 99%

Marine N₂O Emissions From Nitrification and Denitrification Constrained by Modern Observations and Projected in Multimillennial Global Warming Simulations

Battaglia

Joos

2018

Global Biogeochemical Cycles

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“…They attributed this potential reoxygenation of the tropical ocean thermocline to intensified ventilation that kicked in their simulation after 2150 and to a decline in tropical export production leading to reduced biological O 2 consumption in the underlying thermocline. In the deep ocean, several studies suggested a recovery of deep ocean O 2 levels under multimillennial global warming scenarios (Battaglia & Joos, 2018; Ridgwell & Schmidt, 2010; Schmittner et al, 2008; Yamamoto et al, 2015). In all of these models, the recovery was caused by a millennial‐scale emergence of a more vigorous deep ocean ventilation under protracted global warming.…”

Section: Introductionmentioning

confidence: 99%

Contrasting Upper and Deep Ocean Oxygen Response to Protracted Global Warming

Frölicher

Aschwanden

Gruber

et al. 2020

Global Biogeochemical Cycles

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It is well established that the ocean is currently losing dissolved oxygen (O2) in response to ocean warming, but the long‐term, equilibrium response of O2 to a warmer climate is neither well quantified nor understood. Here we use idealized multimillennial global warming simulations with a comprehensive Earth system model to show that the equilibrium response in ocean O2 differs fundamentally from the ongoing transient response. After physical equilibration of the model (>4,000 years) under a two times preindustrial CO2 scenario, the deep ocean is better ventilated and oxygenated compared to preindustrial conditions, even though the deep ocean is substantially warmer. The recovery and overshoot of deep convection in the Weddell Sea and especially the Ross Sea after ~720 years causes a strong increase in deep ocean O2 that overcompensates the solubility‐driven decrease in O2. In contrast, O2 in most of the upper tropical ocean is substantially depleted owing to the warming‐induced O2 decrease dominating over changes in ventilation and biology. Our results emphasize the millennial‐scale impact of global warming on marine life, with some impacts emerging many centuries or even millennia after atmospheric CO2 has stabilized.

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“…Dynamics of the dissolved oxygen in the ocean has been attracting considerable attention over the last decade [8,9,[22][23][24]. The existing observations point out at a gradual decrease of the average oxygen level across the globe, with the areas of extreme conditions (a severe lack of oxygen resulting in anoxia and mass mortality of the marine fauna) being fast growing in size.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

Pattern Formation in a Model Oxygen-Plankton System

Sekerci

Petrovskii

2018

Computation

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Decreasing level of dissolved oxygen has recently been reported as a growing ecological problem in seas and oceans around the world. Concentration of oxygen is an important indicator of the marine ecosystem’s health as lack of oxygen (anoxia) can lead to mass mortality of marine fauna. The oxygen decrease is thought to be a result of global warming as warmer water can contain less oxygen. Actual reasons for the observed oxygen decay remain controversial though. Recently, it has been shown that it may as well result from a disruption of phytoplankton photosynthesis. In this paper, we further explore this idea by considering the model of coupled plankton-oxygen dynamics in two spatial dimensions. By means of extensive numerical simulations performed for different initial conditions and in a broad range of parameter values, we show that the system’s dynamics normally lead to the formation of a rich variety of patterns. We reveal how these patterns evolve when the system approaches the tipping point, i.e., the boundary of the safe parameter range beyond which the depletion of oxygen is the only possibility. In particular, we show that close to the tipping point the spatial distribution of the dissolved oxygen tends to become more regular; arguably, this can be considered as an early warning of the approaching catastrophe.

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Hazards of decreasing marine oxygen: the near-term and millennial-scale benefits of meeting the Paris climate targets

Cited by 9 publications

References 43 publications

Marine N₂O Emissions From Nitrification and Denitrification Constrained by Modern Observations and Projected in Multimillennial Global Warming Simulations

Marine N₂O Emissions From Nitrification and Denitrification Constrained by Modern Observations and Projected in Multimillennial Global Warming Simulations

Contrasting Upper and Deep Ocean Oxygen Response to Protracted Global Warming

Pattern Formation in a Model Oxygen-Plankton System

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Hazards of decreasing marine oxygen: the near-term and millennial-scale benefits of meeting the Paris climate targets

Cited by 9 publications

References 43 publications

Marine N2O Emissions From Nitrification and Denitrification Constrained by Modern Observations and Projected in Multimillennial Global Warming Simulations

Marine N2O Emissions From Nitrification and Denitrification Constrained by Modern Observations and Projected in Multimillennial Global Warming Simulations

Contrasting Upper and Deep Ocean Oxygen Response to Protracted Global Warming

Pattern Formation in a Model Oxygen-Plankton System

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Resources

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Marine N₂O Emissions From Nitrification and Denitrification Constrained by Modern Observations and Projected in Multimillennial Global Warming Simulations

Marine N₂O Emissions From Nitrification and Denitrification Constrained by Modern Observations and Projected in Multimillennial Global Warming Simulations