There is a threat of imminent abrupt and irreversible transitions in the Earth system, both on land and in the ocean. A reduction in greenhouse gas (GHG) emissions and in land-use change must be implemented urgently to mitigate these changes through political, economic, and societal measures. Yet, considerable knowledge gaps remain concerning the processes underlying the dynamics of tipping elements,
Three EU funded Horizon2020 projects have been investigating tipping behaviour in the Earth system: Tipping Points in the Earth System (TiPES), Our Common Future Ocean in the Earth System (COMFORT), and Tipping Points in Antarctic Climate Components (TiPACCs). In the joint policy brief, you can find key findings of the three projects, persisting knowledge gaps as well as policy recommendations.
The policy brief is available for free download here and here.
We are pleased to share that COMFORT has been a top-ranking contributor to the latest IPCC report (Working Group II: Impacts, Adaptation and Vulnerability) among the European Climate, Infrastructure and Environment Executive Agency (CINEA)
In a joint seminar and discussion series organised by AIMES, WCRP, and the Earth commission on ‘Tipping Elements, Irreversibility, and Abrupt Change’ an event on the ocean as a potential tipping element took place on 11 February 2022 with speakers Christoph Heinze (“Ocean tipping points – an overview”) and Stefan Rahmstorf (PIK, Germany) (“Recent insights on AMOC”, AMOC = Atlantic Meridional Overturning Circulation) as well as moderators Didier Swingedouw (Univ. Bordeaux, France) and Helene Hewitt (UK MetOffice). Up to 363 participants followed the talks and subsequent discussions online. A number of important potential regime shifts such as the Arctic sea ice retreat, coral reef decline, and changes in biogeochemical regimes under further progressing deoxygenation were presented and discussed. A recording of the event can be watched below:
Bourgeois, T., Goris, N., Schwinger, J., & Tjiputra, J. F. (2022). Stratification constrains future heat and carbon uptake in the Southern Ocean between 30°S and 55°S. Nature Communications, 13(1), 340. https://doi.org/10.1038/s41467-022-27979-5
The Southern Ocean between 30°S and 55°S is a major sink of excess heat and anthropogenic carbon, but model projections of these sinks remain highly uncertain. Reducing such uncertainties is required to effectively guide the development of climate mitigation policies for meeting the ambitious climate targets of the Paris Agreement. This study shows that the large spread in the projections of future excess heat uptake efficiency and cumulative anthropogenic carbon uptake in this region are strongly linked to the models’ contemporary stratification. This relationship is robust across two generations of Earth system models and is used to reduce the uncertainty of future estimates of the cumulative anthropogenic carbon uptake by up to 53% and the excess heat uptake efficiency by 28%. These results highlight that, for this region, an improved representation of stratification in Earth system models is key to constrain future carbon budgets and climate change projections.
Summary The ocean is warming, losing oxygen and being acidified, primarily as a result of anthropogenic carbon emissions. With ocean warming, acidification and deoxygenation projected to increase for decades, extreme events, such as marine heatwaves, will intensify, occur more often, persist for longer periods of time and extend over larger regions. Nevertheless, our understanding of oceanic extreme events that are associated with warming, low oxygen concentrations or high acidity, as well as their impacts on marine ecosystems, remains limited. Compound events—that is, multiple extreme events that occur simultaneously or in close sequence—are of particular concern, as their individual effects may interact synergistically. In this paper authors assess patterns and trends in open ocean extremes based on the existing literature as well as global and regional model simulations. They discuss the potential impacts of individual and compound extremes on marine organisms and ecosystems and propose a pathway to improve the understanding of extreme events and the capacity of marine life to respond to them. The conditions exhibited by present extreme events may be a harbinger of what may become normal in the future. As a consequence, pursuing this research effort may also help to better understand the responses of marine organisms and ecosystems to future climate change.
Policy relevant message Since the pre-industrial times, marine heatwaves have become 10 x more common and low oxygen extremes have become about 5 x more frequent. Ocean acidity extremes have become essentially near permanent. All three types of extreme events will increase in frequency, magnitude and intensity with continuously rising atmospheric carbon emissions and global temperature.
COMFORT scientist and WP2 co-leader, Stephanie Henson (National Oceanography Centre, Southampton) attended COP26 in Glasgow during the 1st week of the climate action negotiations. Here she tells us about her experience there:
“It was all quite overwhelming, with almost 20,000 attendees. It was strange to be back in such a big crowd after the isolation of Covid! The COP was centred around several areas: pavilions, the Hub and the negotiating rooms. The pavilions were set up in trade show style, each representing a country or theme, with a variety of talks or other activities. I spent a lot of time at the Science Pavilion (no surprise!) which presented the science of climate change in different formats. I also enjoyed visiting pavilions on the themes of resilience, the UN Ocean Decade and biodiversity – but the best coffee was in the Australia pavilion! The Hub was where most of the media action happened, and also live streamed talks from the main negotiating rooms (which ‘Observers’, like myself, could only attend if there was space for us). Overall, it felt a bit like a chaotic circus with a million things happening at once, but I had some fruitful conversations with scientists from other fields, negotiators and business leaders. My abiding memory though will probably be the long (long) queues to access the site every day, the huge climate protests engulfing Glasgow, and wearing a face mask for 14 hours a day! But hopefully, policy makers are now truly hearing the message on climate change and are ready to take the difficult decisions necessary to ensure the goals of the Paris agreement are met.”
Bardon, L. R., Ward, B. A., Dutkiewicz, S., & Cael, B. B. (2021). Testing the Skill of a Species Distribution Model Using a 21st Century Virtual Ecosystem. Geophysical Research Letters, 48(22), e2021GL093455. https://doi.org/10.1029/2021GL093455
Marine plankton communities play a central role within Earth’s climate system, with important processes often divided among different “functional groups.” Changes in the relative abundance of these groups can therefore impact on ecosystem function. However, the oceans are vast, and samples are sparse, so global distributions are not well known. Statistical species distribution models (SDM’s) have been developed that predict global distributions based on their relationships with observed environmental variables. They appear to perform well at summarizing present day distributions, and are increasingly being used to predict ecosystem changes throughout the 21st century. But it is not guaranteed that such models remain valid over time. Rather than wait 100 years to find out, the authors of this study applied a statistical SDM to a complex virtual ocean, and trained it using virtual observations that match real-world ocean samples. This allows them to jump forward to the end-of-century to test the accuracy of our predictions. The SDM performed well at qualitatively predicting “present day” plankton distributions but yielded poor end-of-century predictions. This case study emphasizes both the importance of environmental variable selection, and of changes in the underlying relationships between environmental variables and plankton distributions, in terms of model validity over time.
Marine microbial communities are critical in sustaining ocean food webs. However, these communities will change with climate through gradual or foreseeable changes but likely have much more substantial consequences when sudden and unpredictable. Through a complex mathematical model of marine microbial ecosystem, the authors of this study found that climate change–driven shifts over the 21st century are often abrupt, large in amplitude and extent, and unpredictable using standard early warning signals. Phytoplankton (microscopic marine algae) with unique resource needs are prone to abrupt shifts. These abrupt shifts in biomass, biological productivity, and phytoplankton community structure are concentrated in Atlantic and Pacific subtropics. Abrupt changes in environmental variables such as temperature and nutrients rarely precede these ecosystem shifts, indicating that rapid community restructuring can occur in response to gradual environmental changes, particularly in nutrient supply rate ratios.
Cheung, W. W. L., Frölicher, T. L., Lam, V. W. Y., Oyinlola, M. A., Reygondeau, G., Sumaila, U. R., Tai, T. C., Teh, L. C. L., & Wabnitz, C. C. C. (2021). Marine high temperature extremes amplify the impacts of climate change on fish and fisheries. Science Advances, 7(40), eabh0895. https://doi.org/10.1126/sciadv.abh0895
Extreme temperature events have occurred in all ocean basins in the past two decades with detrimental impacts on marine biodiversity, ecosystem functions, and services. However, global impacts of temperature extremes on fish stocks, fisheries, and dependent people have not been quantified. This study, using a mathematical model, projected that, on average, when an annual high temperature extreme occurs in an exclusive economic zone, 77% of exploited fishes and invertebrates therein will decrease in biomass while maximum catch potential will drop by 6%, adding to the decadal-scale mean impacts under climate change. The net negative impacts of high temperature extremes on fish stocks are projected to cause losses in fisheries revenues and livelihoods in most maritime countries, creating shocks to fisheries social-ecological systems particularly in climate-vulnerable areas. This study highlights the need for rapid adaptation responses to extreme temperatures in addition to carbon mitigation to support sustainable ocean development.
Policy relevant message:
When an annual high temperature extreme occurs in an exclusive economic zone, 77% of exploited fishes and invertebrates therein will decrease in biomass while maximum catch potential will drop by 6%, adding to the decadal-scale mean impacts under climate change. This study highlights the need for rapid adaptation responses to extreme temperatures in addition to carbon mitigation to support sustainable ocean development.
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