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  • English  (9)
  • 1
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    Mixed Layer Depth Promotes Trophic Amplification on a Seasonal Scale (2022)
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    Publication Date: 2022-10-06
    Description: The Humboldt Upwelling System is of global interest due to its importance to fisheries, though the origin of its high productivity remains elusive. In regional physical‐biogeochemical model simulations, the seasonal amplitude of mesozooplankton net production exceeds that of phytoplankton, indicating “seasonal trophic amplification.” An analytical approach identifies amplification to be driven by a seasonally varying trophic transfer efficiency due to mixed layer variations. The latter alters the vertical distribution of phytoplankton and thus the zooplankton and phytoplankton encounters, with lower encounters occurring in a deeper mixed layer where phytoplankton are diluted. In global model simulations, mixed layer depth appears to affect trophic transfer similarly in other productive regions. Our results highlight the importance of mixed layer depth for trophodynamics on a seasonal scale with potential significant implications, given mixed layer depth changes projected under climate change.
    Description: Plain Language Summary: The Humboldt Upwelling System is a fishery‐important region. A common assumption is that a certain amount of phytoplankton supports a proportional amount of fish. However, we find that a small seasonal change in phytoplankton can trigger a larger variation in zooplankton. This implies that one may underestimate changes in fish solely based on phytoplankton. Using ecosystem model simulations, we investigate why changes of phytoplankton are not proportionally reflected in zooplankton. The portion of phytoplankton that ends up in zooplankton is controlled by the changing depth of the surface ocean “mixed layer.” The “mixed layer” traps both the phytoplankton and zooplankton in a limited amount of space. When the “mixed layer” is shallow, zooplankton can feed more efficiently on phytoplankton as both are compressed in a comparatively smaller space. We conclude that in the Humboldt System, and other “food‐rich” regions, feeding efficiently, determined by the “mixed layer,” is more important than how much food is available.
    Description: Key Points: Environmental factors strongly affect plankton trophodynamics on a seasonal scale. Seasonal trophic amplification in the Humboldt system is driven by mixed layer dynamics. Mixed layer depth and food chain efficiency correlate also in other productive regions.
    Description: China Sponsorship Council
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Keywords: ddc:577.7
    Language: English
    Type: doc-type:article
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  • 2
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    Net‐Zero CO2Germany—A Retrospect From the Year 2050 (2022)
    In:  Earth's Future
    Details
    Publication Date: 2022-02-17
    Description: Germany 2050: For the first time Germany reached a balance between its sources of anthropogenic CO2 to the atmosphere and newly created anthropogenic sinks. This backcasting study presents a fictional future in which this goal was achieved by avoiding (∼645 Mt CO2), reducing (∼50 Mt CO2) and removing (∼60 Mt CO2) carbon emissions. This meant substantial transformation of the energy system, increasing energy efficiency, sector coupling, and electrification, energy storage solutions including synthetic energy carriers, sector-specific solutions for industry, transport, and agriculture, as well as natural-sink enhancement and technological carbon dioxide options. All of the above was necessary to achieve a net-zero CO2 system for Germany by 2050.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 3
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    Physical drivers of the recent Southern Ocean carbon uptake in an eddying ocean (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-07-03
    Description: Owing to its cool temperatures and vigorous water mass formation, the strongly eddying Southern Ocean is a key region of ocean CO〈sub〉2〈/sub〉 uptake. In this study we assess the role of 1) wind stress and buoyancy forcing and 2) the representation of mesoscale eddies, in affecting the mean and temporal variations of the Southern Ocean carbon uptake in the past 60 years. We analyze global ocean biogeochemistry simulations based on the NEMO-MOPS and FESOM-REcoM models and ranging from 1° and 0.5° resolutions (where eddies are parameterized) to eddy-rich 0.25° and 0.1° resolutions. The 0.25° model is also used to perform sensitivity experiments to unravel the relative role of wind stress and of buoyancy forcing for the carbon uptake variations. We find that eddy-rich models have steeper isopycnals across the Antarctic Circumpolar Current, which results in higher anthropogenic carbon uptake and storage than in models where eddies are parameterized. This, in combination with a somewhat lower outgassing of natural CO〈sub〉2〈/sub〉, gives rise to a steeper trend of the Southern Ocean carbon uptake in the eddy-rich than in the eddy-parameterized models. Wind stress and buoyancy forcing are the main drivers of an increased outgassing of natural CO〈sub〉2〈/sub〉 over the past decades and drive most of its interannual and decadal variability, with wind stress dominating at subpolar latitudes, and buoyancy forcing in water mass formation regions. However, our experiments indicate that the stalling of the Southern Ocean carbon uptake in the 1990s was mostly driven by a reduction of its anthropogenic carbon uptake.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 4
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    Towards a comprehensive climate impacts assessment of solar geoengineering (2017)
    In:  Earth's Future
    Details
    Publication Date: 2023-07-18
    Description: Despite a growing literature on the climate response to solar geoengineering – proposals to cool the planet by increasing the planetary albedo – there has been little published on the impacts of solar geoengineering on natural and human systems such as agriculture, health, water resources, and ecosystems. An understanding of the impacts of different scenarios of solar geoengineering deployment will be crucial for informing decisions on whether and how to deploy it. Here we review the current state of knowledge about impacts of a solar geoengineered climate and identify major research gaps. We suggest that a thorough assessment of the climate impacts of a range of scenarios of solar geoengineering deployment is needed and can build upon existing frameworks. However, solar geoengineering poses a novel challenge for climate impacts research as the manner of deployment could be tailored to pursue different objectives making possible a wide range of climate outcomes. We present a number of ideas for approaches to extend the survey of climate impacts beyond standard scenarios of solar geoengineering deployment to address this challenge. Reducing the impacts of climate change is the fundamental motivator for emissions reductions and for considering whether and how to deploy solar geoengineering. This means that the active engagement of the climate impacts research community will be important for improving the overall understanding of the opportunities, challenges and risks presented by solar geoengineering.
    Language: English
    Type: info:eu-repo/semantics/article
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  • 5
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    The European Transdisciplinary Assessment of Climate Engineering (EuTRACE): Removing Greenhouse Gases from the Atmosphere and Reflecting Sunlight away from Earth. Final Report of the FP7 CSA project EuTRACE. Funded by the European Union’s Seventh Framework Programme under Grant Agreement 306993. (2015)
    Institute for Advanced Sustainability Studies (IASS)
    Details
    Publication Date: 2023-07-18
    Language: English
    Type: info:eu-repo/semantics/report
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  • 6
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    Achieving Climate Neutrality and Paris Agreement Goals: Opportunities for Ocean-Based Methods of Carbon Dioxide Removal (2022)
    CDRmare
    In:  Science Policy Brief
    Details
    Publication Date: 2023-07-18
    Language: English
    Type: info:eu-repo/semantics/report
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  • 7
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    Evaluating climate geoengineering proposals in the context of the Paris Agreement temperature goals (2018)
    In:  Nature Communications
    Details
    Publication Date: 2023-07-18
    Description: Current mitigation efforts and existing future commitments are inadequate to accomplish the Paris Agreement temperature goals. In light of this, research and debate are intensifying on the possibilities of additionally employing proposed climate geoengineering technologies, either through atmospheric carbon dioxide removal or farther-reaching interventions altering the Earth’s radiative energy budget. Although research indicates that several techniques may eventually have the physical potential to contribute to limiting climate change, all are in early stages of development, involve substantial uncertainties and risks, and raise ethical and governance dilemmas. Based on present knowledge, climate geoengineering techniques cannot be relied on to significantly contribute to meeting the Paris Agreement temperature goals.
    Language: English
    Type: info:eu-repo/semantics/article
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  • 8
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    Sinking of Gelatinous Zooplankton Biomass Increases Deep Carbon Transfer Efficiency Globally (2021)
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    Publication Date: 2021-10-28
    Description: Gelatinous zooplankton (Cnidaria, Ctenophora, and Urochordata, namely, Thaliacea) are ubiquitous members of plankton communities linking primary production to higher trophic levels and the deep ocean by serving as food and transferring “jelly-carbon” (jelly-C) upon bloom collapse. Global biomass within the upper 200 m reaches 0.038 Pg C, which, with a 2–12 months life span, serves as the lower limit for annual jelly-C production. Using over 90,000 data points from 1934 to 2011 from the Jellyfish Database Initiative as an indication of global biomass (JeDI: http://jedi.nceas.ucsb.edu, http://www.bco-dmo.org/dataset/526852), upper ocean jelly-C biomass and production estimates, organism vertical migration, jelly-C sinking rates, and water column temperature profiles from GLODAPv2, we quantitatively estimate jelly-C transfer efficiency based on Longhurst Provinces. From the upper 200 m production estimate of 0.038 Pg C year−1, 59–72% reaches 500 m, 46–54% reaches 1,000 m, 43–48% reaches 2,000 m, 32–40% reaches 3,000 m, and 25–33% reaches 4,500 m. This translates into ~0.03, 0.02, 0.01, and 0.01 Pg C year−1, transferred down to 500, 1,000, 2,000, and 4,500 m, respectively. Jelly-C fluxes and transfer efficiencies can occasionally exceed phytodetrital-based sediment trap estimates in localized open ocean and continental shelves areas under large gelatinous blooms or jelly-C mass deposition events, but this remains ephemeral and transient in nature. This transfer of fast and permanently exported carbon reaching the ocean interior via jelly-C constitutes an important component of the global biological soft-tissue pump, and should be addressed in ocean biogeochemical models, in particular, at the local and regional scale.
    Keywords: 577.1 ; Jelly-C ; carbon ; gelatinous ; zooplankton ; modeling ; transfer efficiency
    Language: English
    Type: map
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  • 9
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    Simulated Future Trends in Marine Nitrogen Fixation Are Sensitive to Model Iron Implementation (2022)
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    Publication Date: 2022-06-17
    Description: Biological nitrogen fixation is an important oceanic nitrogen source, potentially stabilizing marine fertility in an increasingly stratified and nutrient‐depleted ocean. Iron limitation of low latitude primary producers has been previously demonstrated to affect simulated regional ecosystem responses to climate warming or nitrogen cycle perturbation. Here we use three biogeochemical models that vary in their representation of the iron cycle to estimate change in the marine nitrogen cycle under a high CO2 emissions future scenario (RCP8.5). The first model neglects explicit iron effects on biology (NoFe), the second utilizes prescribed, seasonally cyclic iron concentrations and associated limitation factors (FeMask), and the third contains a fully dynamic iron cycle (FeDyn). Models were calibrated using observed fields to produce near‐equivalent nutrient and oxygen fits, with productivity ranging from 49 to 75 Pg C yr−1. Global marine nitrogen fixation increases by 71.1% with respect to the preindustrial value by the year 2100 in NoFe, while it remains stable (0.7% decrease in FeMask and 0.3% increase in FeDyn) in explicit iron models. The mitigation of global nitrogen fixation trend in the models that include a representation of iron originates in the Eastern boundary upwelling zones, where the bottom‐up control of iron limitation reduces export production with warming, which shrinks the oxygen deficient volume, and reduces denitrification. Warming‐induced trends in the oxygen deficient volume in the upwelling zones have a cascading effect on the global nitrogen cycle, just as they have previously been shown to affect tropical net primary production.
    Description: Plain Language Summary: Phytoplankton need nutrients to grow. Two of those nutrients are nitrogen and iron. Climate change projections suggest that in the future there could be less nitrogen supplied to the surface ocean, which might reduce phytoplankton growth. Less phytoplankton growth could impact a wide range of ocean services, like fishing and fossil carbon draw‐down. However, some phytoplankton have the ability to add “new” nitrogen to the surface ocean directly from the atmosphere. In this study, we explore how this biological fixation of new nitrogen might change into the future using three models. These models differ in how iron is represented, but all do equally well in representing the observed nutrient and oxygen distribution. Biological nitrogen fixation slightly decreases with climate change in the very complex iron model and the moderately complex iron model, but it increases strongly (by more than 70% by the year 2100) in the model that does not include iron effects on biology. Our study addresses the importance of iron models and how they can change our view of how the ocean responds to climate change.
    Description: Key Points: Models performing similarly with respect to global NO3, PO4, and O2 distributions yield diverse responses in marine N2 fixation to warming. Marine N2 fixation trends are sensitive to whether iron limits primary production in upwelling regions, for example, the Eastern Tropical Pacific.
    Description: Helmholtz Research School for Ocean System Science and Technology
    Description: New Zealand Ministry of Business, Innovation and Employment
    Description: https://data.geomar.de/downloads/20.500.12085/673e7de0-20ab-4dd3-afe9-c4bfb00b1faf/
    Keywords: ddc:551.9
    Language: English
    Type: doc-type:article
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