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Open accessJournal ArticleDOI: 10.1073/PNAS.2008478118

The quiet crossing of ocean tipping points

02 Mar 2021-Proceedings of the National Academy of Sciences of the United States of America (National Academy of Sciences)-Vol. 118, Iss: 9
Abstract: Anthropogenic climate change profoundly alters the ocean’s environmental conditions, which, in turn, impact marine ecosystems. Some of these changes are happening fast and may be difficult to reverse. The identification and monitoring of such changes, which also includes tipping points, is an ongoing and emerging research effort. Prevention of negative impacts requires mitigation efforts based on feasible research-based pathways. Climate-induced tipping points are traditionally associated with singular catastrophic events (relative to natural variations) of dramatic negative impact. High-probability high-impact ocean tipping points due to warming, ocean acidification, and deoxygenation may be more fragmented both regionally and in time but add up to global dimensions. These tipping points in combination with gradual changes need to be addressed as seriously as singular catastrophic events in order to prevent the cumulative and often compounding negative societal and Earth system impacts.

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Topics: Global warming (50%)
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Open access
01 Jan 1993-

2,271 Citations


Open access
01 Dec 2016-
Abstract: The reasons for concern framework communicates scientific understanding about risks in relation to varying levels of climate change. The framework, now a cornerstone of the IPCC assessments, aggregates global risks into five categories as a function of global mean temperature change. We review the framework's conceptual basis and the risk judgments made in the most recent IPCC report, confirming those judgments in most cases in the light of more recent literature and identifying their limitations. We point to extensions of the framework that offer complementary climate change metrics to global mean temperature change and better account for possible changes in social and ecological system vulnerability. Further research should systematically evaluate risks under alternative scenarios of future climatic and societal conditions.

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Topics: Climate change (57%)

155 Citations


Open accessJournal Article
Abstract: The decline in oxygen supply to the ocean associated with global warming of sea-surface temperatures is expected to expand the oxygen minimum zones (OMZs). This global trend can be attenuated or amplified by regional processes. In the Arabian Sea, the World's thickest OMZ is highly vulnerable to changes in the Indian monsoon wind. Evidence from paleo records and future climate projections indicate strong variations of the Indian monsoon wind intensity over climatic timescales. Yet, the response of the OMZ to these wind changes remains poorly understood and its amplitude and timescale unexplored. Here, we investigate the impacts of perturbations in Indian monsoon wind intensity (from -50% to +50%) on the size and intensity of the Arabian Sea OMZ, and examine the biogeochemical and ecological implications of these changes. To this end, we conducted a series of eddy-resolving simulations of the Arabian Sea using the Regional Oceanic Modeling System (ROMS) coupled to a nitrogen based Nutrient-Phytoplankton-Zooplankton-Detritus (NPZD) ecosystem model that includes a representation of the O2 cycle. We show that the Arabian Sea productivity increases and its OMZ expands and deepens in response to monsoon wind intensification. These responses are dominated by the perturbation of the summer monsoon wind, whereas the changes in the winter monsoon wind play a secondary role. While the productivity responds quickly and nearly linearly to wind increase (i.e., on a timescale of years), the OMZ response is much slower (i.e., a timescale of decades). Our analysis reveals that the OMZ expansion at depth is driven by increased oxygen biological consumption, whereas its surface weakening is induced by increased lateral ventilation. The enhanced lateral ventilation favors episodic intrusions of oxic waters in the lower epipelagic zone (100-200m) of the western and central Arabian Sea, leading to intermittent expansions of habitats and a more frequent alternation of hypoxic and oxic conditions there. The increased productivity and deepening of the OMZ also lead to a strong intensification of denitrification at depth, resulting in a substantial amplification of fixed nitrogen depletion in the Arabian Sea. We conclude that changes in the Indian monsoon can affect, on longer timescales, the large-scale biogeochemical cycles of nitrogen and carbon, with a positive feedback on climate change in the case of stronger winds.

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Topics: Monsoon (60%), Monsoon of South Asia (57%), Oxygen minimum zone (53%)

6 Citations


Open accessJournal ArticleDOI: 10.1017/SUS.2021.2
Erik Pihl, Eva Alfredsson1, Magnus Bengtsson, Kathryn Bowen2  +57 moreInstitutions (44)
18 Oct 2021-
Abstract: Non-technical summary We summarize some of the past year's most important findings within climate change-related research. New research has improved our understanding of Earth's sensitivity to carbon dioxide, finds that permafrost thaw could release more carbon emissions than expected and that the uptake of carbon in tropical ecosystems is weakening. Adverse impacts on human society include increasing water shortages and impacts on mental health. Options for solutions emerge from rethinking economic models, rights-based litigation, strengthened governance systems and a new social contract. The disruption caused by COVID-19 could be seized as an opportunity for positive change, directing economic stimulus towards sustainable investments. Technical summary A synthesis is made of ten fields within climate science where there have been significant advances since mid-2019, through an expert elicitation process with broad disciplinary scope. Findings include: (1) a better understanding of equilibrium climate sensitivity; (2) abrupt thaw as an accelerator of carbon release from permafrost; (3) changes to global and regional land carbon sinks; (4) impacts of climate change on water crises, including equity perspectives; (5) adverse effects on mental health from climate change; (6) immediate effects on climate of the COVID-19 pandemic and requirements for recovery packages to deliver on the Paris Agreement; (7) suggested long-term changes to governance and a social contract to address climate change, learning from the current pandemic, (8) updated positive cost-benefit ratio and new perspectives on the potential for green growth in the short- A nd long-term perspective; (9) urban electrification as a strategy to move towards low-carbon energy systems and (10) rights-based litigation as an increasingly important method to address climate change, with recent clarifications on the legal standing and representation of future generations. Social media summary Stronger permafrost thaw, COVID-19 effects and growing mental health impacts among highlights of latest climate science. Copyright © The Author(s), 2021. Published by Cambridge University Press. (Less)

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Topics: Climate governance (66%), Climate model (56%), Climate change (56%) ... read more

6 Citations


Journal ArticleDOI: 10.2139/SSRN.3860950
Abstract: Marine plants and animals should be thriving in ocean waters because of the current high concentrations of carbon dioxide and nutrients along with slightly elevated temperatures - but they are not. We have lost 50% of all marine life over the last 70 years; this decline is continuing today at a rate of 1% year on year. The GOES team has used its collective professional and academic experience to undertake analysis of peer- reviewed and published data to explore the reasons for this decline and its implications for climate and humanity. In our view, this loss of marine life is directly related to the presence of toxic chemicals and plastic which started to appear with the ‘chemical revolution’ in the1950’s. There is no doubt that tiny ocean planktonic plants and animals are key to regulating our climate, but this keystone of the planet’s largest ecosystem seems to be ignored as one of the tools to address climate change. Every second breath we take comes from marine photosynthesis, a process which also uses 60-90% of our carbon dioxide. Now that we have lost 50% of a key climate regulator, surely it is time to stop, take a fresh look at ocean chemistry and biodiversity and ask ourselves some fundamental questions: Why have we lost this level of marine life? Why is the decline continuing? What does this mean for our climate and humanity? Of particular concern from a climate change perspective is the level of carbonic acid in the oceans. This carbonic acid is created when atmospheric carbon dioxide dissolves into the oceans. In the 1940’s, ocean pH was 8.2, but in 2020, pH had dropped to 8.04, indicating that the oceans are becoming more acidic. If there are not enough plants to use up carbon, the unused carbonic acid moves the pH downwards. Reports from respected institutes around the globe flag an acceleration of the ocean acidification process. This decline will result in the loss of more marine plants and animals, especially those that have carbonate shells and body structures (aragonite) based. These same reports forecast that in 25 years (by 2045), pH will drop to 7.95, and estimate that with this, 80% to 90% of all remaining marine life will be lost. The GOES team’s opinion is that this is a tipping point: a planetary boundary which must not be exceeded if humanity is to survive. No ecosystem can survive a 90% loss; the result is a trophic cascade collapse. We will lose all the corals, whales, seals, birds, fish and food supply for 2 billion people – an outcome worse than climate change. Let’s be clear: If by some miracle the world achieves net zero by 2045, evidence from the Intergovernmental Panel on Climate Change (IPCC) BIOACID report [1] demonstrates that this reduction will not be enough to stop a drop in ocean pH to 7.95. If the level of marine life (both plant and animal) is reduced, then the oceans’ ability to lockout carbon into the abyss is depleted. It is clear to the GOES team that if we only pursue carbon mitigation strategies and don’t do more to regenerate plant and animal life in oceans, we will reach a tipping point: a planetary boundary from which there will be no return, because all life on Earth depends upon the largest ecosystem on the planet. Humanity will suffer terribly from global warming, but it must be understood that the oceans are already showing signs of instability today at pH 8.04, (the start of the tipping point) and in 25 years when the pH has dropped to pH 7.95 represents the end point, the point of no return.

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Topics: Ocean acidification (58%), Global warming (56%), Tipping point (climatology) (53%) ... read more

3 Citations


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140 results found



Journal ArticleDOI: 10.1038/35098000
Marten Scheffer1, S. R. Carpenter2, Jonathan A. Foley2, Carl Folke3  +1 moreInstitutions (4)
11 Oct 2001-Nature
Abstract: All ecosystems are exposed to gradual changes in climate, nutrient loading, habitat fragmentation or biotic exploitation. Nature is usually assumed to respond to gradual change in a smooth way. However, studies on lakes, coral reefs, oceans, forests and arid lands have shown that smooth change can be interrupted by sudden drastic switches to a contrasting state. Although diverse events can trigger such shifts, recent studies show that a loss of resilience usually paves the way for a switch to an alternative state. This suggests that strategies for sustainable management of such ecosystems should focus on maintaining resilience.

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5,705 Citations


Open accessJournal ArticleDOI: 10.1126/SCIENCE.1259855
Will Steffen1, Will Steffen2, Katherine Richardson3, Johan Rockström2  +21 moreInstitutions (17)
13 Feb 2015-Science
Abstract: The planetary boundaries framework defines a safe operating space for humanity based on the intrinsic biophysical processes that regulate the stability of the Earth system. Here, we revise and update the planetary boundary framework, with a focus on the underpinning biophysical science, based on targeted input from expert research communities and on more general scientific advances over the past 5 years. Several of the boundaries now have a two-tier approach, reflecting the importance of cross-scale interactions and the regional-level heterogeneity of the processes that underpin the boundaries. Two core boundaries—climate change and biosphere integrity—have been identified, each of which has the potential on its own to drive the Earth system into a new state should they be substantially and persistently transgressed.

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5,367 Citations


Open access
01 Jan 2008-
Abstract: Dead zones in the coastal oceans have spread exponentially since the 1960s and have serious consequences for ecosystem functioning. The formation of dead zones has been exacerbated by the increase in primary production and consequent worldwide coastal eutrophication fueled by riverine runoff of fertilizers and the burning of fossil fuels. Enhanced primary production results in an accumulation of particulate organic matter, which encourages microbial activity and the consumption of dissolved oxygen in bottom waters. Dead zones have now been reported from more than 400 systems, affecting a total area of more than 245,000 square kilometers, and are probably a key stressor on marine ecosystems.

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Topics: Marine ecosystem (55%)

4,230 Citations


Journal ArticleDOI: 10.1126/SCIENCE.1156401
Robert J. Diaz1, Rutger Rosenberg2Institutions (2)
15 Aug 2008-Science
Abstract: Dead zones in the coastal oceans have spread exponentially since the 1960s and have serious consequences for ecosystem functioning. The formation of dead zones has been exacerbated by the increase in primary production and consequent worldwide coastal eutrophication fueled by riverine runoff of fertilizers and the burning of fossil fuels. Enhanced primary production results in an accumulation of particulate organic matter, which encourages microbial activity and the consumption of dissolved oxygen in bottom waters. Dead zones have now been reported from more than 400 systems, affecting a total area of more than 245,000 square kilometers, and are probably a key stressor on marine ecosystems.

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Topics: Marine ecosystem (56%), Eutrophication (53%), Hypoxia (environmental) (52%) ... read more

4,093 Citations


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