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  • 1
    Type of Medium: Book
    Series Statement: Preprints / Koninklijk Nederlands Meteorologisch Instituut 97,30
    Language: Undetermined
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  • 2
    Keywords: Report ; Forschungsbericht
    Type of Medium: Book
    Pages: 51 S , graph. Darst., Kt , 30 cm
    Series Statement: Report / Max-Planck-Institut für Meteorologie 177
    Language: English
    Note: Literaturverz. S. 24 - 25
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  • 3
    Publication Date: 2021-02-08
    Description: Highlights: • Lagrangian ocean analysis is a powerful way to analyse the output of ocean circulation models • We present a review of the Kinematic framework, available tools, and applications of Lagrangian ocean analysis • While there are unresolved questions, the framework is robust enough to be used widely in ocean modelling Abstract: Lagrangian analysis is a powerful way to analyse the output of ocean circulation models and other ocean velocity data such as from altimetry. In the Lagrangian approach, large sets of virtual particles are integrated within the three-dimensional, time-evolving velocity fields. Over several decades, a variety of tools and methods for this purpose have emerged. Here, we review the state of the art in the field of Lagrangian analysis of ocean velocity data, starting from a fundamental kinematic framework and with a focus on large-scale open ocean applications. Beyond the use of explicit velocity fields, we consider the influence of unresolved physics and dynamics on particle trajectories. We comprehensively list and discuss the tools currently available for tracking virtual particles. We then showcase some of the innovative applications of trajectory data, and conclude with some open questions and an outlook. The overall goal of this review paper is to reconcile some of the different techniques and methods in Lagrangian ocean analysis, while recognising the rich diversity of codes that have and continue to emerge, and the challenges of the coming age of petascale computing.
    Type: Article , PeerReviewed
    Format: text
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  • 4
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    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 26 (4). pp. 559-580.
    Publication Date: 2019-08-08
    Description: A primitive equation World Ocean model has been integrated with restoring boundary conditions to reach a steady state. The global distribution of potential temperature, salinity, and meridional streamfunction are consistent with observations. In steady state, the effective freshwater fluxes were diagnosed, and the model has been integrated further prescribing these freshwater fluxes. The ocean circulation undergoes self-sustained oscillations over a wide range of timescales, ranging from decadal to millennium. Most pronounced are self-sustained oscillations with a timescale of 20, 300, and 1000 years. The latter two oscillations are coupled. They consist of density (salinity) anomalies that circulate through the global conveyor belt, periodically enhancing convection in the Southern Ocean and limiting convection in the northern North Atlantic. The timescale is set by the vertical diffusion, which destabilizes the stratification in the Southern Ocean when convection is weak. The 20-yr oscillation is a coupled salinity and sea ice thickness anomaly propagating around Antarctica.
    Type: Article , PeerReviewed
    Format: text
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  • 5
    Publication Date: 2016-09-14
    Description: We discuss potential transitions of six climatic subsystems with large-scale impact on Europe, sometimes denoted as tipping elements. These are the ice sheets on Greenland and West Antarctica, the Atlantic thermohaline circulation, Arctic sea ice, Alpine glaciers and northern hemisphere stratospheric ozone. Each system is represented by co-authors actively publishing in the corresponding field. For each subsystem we summarize themechanism of a potential transition in a warmer climate along with its impact on Europe and assess the likelihood for such a transition based on published scientific literature. As a summary, the ‘tipping’ potential for each system is provided as a function of global mean temperature increase which required some subjective interpretation of scientific facts by the authors and should be considered as a snapshot of our current understanding.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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  • 6
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    IPCC
    In:  In: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth : Assessment Report of the Intergovernmental Panel on Climate Change : Chapter 4. , ed. by Masson-Delmotte, V., Zhai, P., Pirani, A., Connors, S. L., Pean, C., Berger, S., Caud, N., Chen, Y., Goldfarb, L., Gomis, M. I., Huang, M., Leitzell, K., Lonnoy, E., Matthews, J. B. R., Maycock, T. K., Waterfield, T., Yelekçi, O., Yu, R. and Zhou, B. IPCC, Genf, Switzerland, pp. 1-195.
    Publication Date: 2022-01-05
    Type: Book chapter , NonPeerReviewed
    Format: text
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  • 7
    Publication Date: 2023-02-08
    Description: The Atlantic meridional overturning circulation (AMOC) represents the zonally integrated stream function of meridional volume transport in the Atlantic Basin. The AMOC plays an important role in transporting heat meridionally in the climate system. Observations suggest a heat transport by the AMOC of 1.3 PW at 26°N—a latitude which is close to where the Atlantic northward heat transport is thought to reach its maximum. This shapes the climate of the North Atlantic region as we know it today. In recent years there has been significant progress both in our ability to observe the AMOC in nature and to simulate it in numerical models. Most previous modeling investigations of the AMOC and its impact on climate have relied on models with horizontal resolution that does not resolve ocean mesoscale eddies and the dynamics of the Gulf Stream/North Atlantic Current system. As a result of recent increases in computing power, models are now being run that are able to represent mesoscale ocean dynamics and the circulation features that rely on them. The aim of this review is to describe new insights into the AMOC provided by high-resolution models. Furthermore, we will describe how high-resolution model simulations can help resolve outstanding challenges in our understanding of the AMOC.
    Type: Article , PeerReviewed
    Format: text
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  • 8
    Publication Date: 2020-02-10
    Description: The Atlantic meridional overturning circulation (AMOC) represents the zonally integrated stream function of meridional volume transport in the Atlantic Basin. The AMOC plays an important role in transporting heat meridionally in the climate system. Observations suggest a heat transport by the AMOC of 1.3 PW at 26°N ‐ a latitude which is close to where the Atlantic northward heat transport is thought to reach its maximum. This shapes the climate of the North Atlantic region as we know it today. In recent years there has been significant progress both in our ability to observe the AMOC in nature and to simulate it in numerical models. Most previous modeling investigations of the AMOC and its impact on climate have relied on models with horizontal resolution that does not resolve ocean mesoscale eddies and the dynamics of the Gulf Stream/North Atlantic Current system. As a result of recent increases in computing power, models are now being run that are able to represent mesoscale ocean dynamics and the circulation features that rely on them. The aim of this review is to describe new insights into the AMOC provided by high‐resolution models. Furthermore, we will describe how high‐resolution model simulations can help resolve outstanding challenges in our understanding of the AMOC.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 9
    Publication Date: 2022-05-25
    Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of Geophysical Research: Oceans 123 (2018): 3563-3576, doi:10.1029/2017JC013329.
    Description: We investigate the characteristics of the sinking of dense waters in the North Atlantic Ocean that constitute the downwelling limb of the Atlantic Meridional Overturning Circulation (AMOC) as simulated by two global ocean models: an eddy‐permitting model at 1/4° resolution and its coarser 1° counterpart. In line with simple geostrophic considerations, it is shown that the sinking predominantly occurs in a narrow region close to the continental boundary in both model simulations. That is, the regions where convection is deepest do not coincide with regions where most dense waters sink. The amount of near‐boundary sinking that occurs varies regionally. For the 1/4° resolution model, these variations are in quantitative agreement with a relation based on geostrophy and a thermodynamic balance between buoyancy loss and alongshore advection of density, which links the amount of sinking to changes in density along the edge of the North Atlantic Ocean. In the 1° model, the amount and location of sinking appears not to be governed by this simple relation, possibly due to the large impact of overflows and nonnegligible cross‐shore density advection. If this poor representation of the processes governing the sinking of dense waters in the North Atlantic Ocean is a generic feature of such low‐resolution models, the response of the AMOC to changes in climate simulated by this type of models needs to be evaluated with care.
    Description: NWO (Netherlands Scientific Research foundation) VIDI Grant Number: 864.13.011; National Science Foundation Grant Numbers: OCE‐1534618, OCE‐1558742
    Keywords: Ocean circulation ; Climate
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 10
    Publication Date: 2022-05-26
    Description: © The Author(s), 2013. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Climate of the Past 9 (2013): 1111-1140, doi:10.5194/cp-9-1111-2013.
    Description: Both historical and idealized climate model experiments are performed with a variety of Earth system models of intermediate complexity (EMICs) as part of a community contribution to the Intergovernmental Panel on Climate Change Fifth Assessment Report. Historical simulations start at 850 CE and continue through to 2005. The standard simulations include changes in forcing from solar luminosity, Earth's orbital configuration, CO2, additional greenhouse gases, land use, and sulphate and volcanic aerosols. In spite of very different modelled pre-industrial global surface air temperatures, overall 20th century trends in surface air temperature and carbon uptake are reasonably well simulated when compared to observed trends. Land carbon fluxes show much more variation between models than ocean carbon fluxes, and recent land fluxes appear to be slightly underestimated. It is possible that recent modelled climate trends or climate–carbon feedbacks are overestimated resulting in too much land carbon loss or that carbon uptake due to CO2 and/or nitrogen fertilization is underestimated. Several one thousand year long, idealized, 2 × and 4 × CO2 experiments are used to quantify standard model characteristics, including transient and equilibrium climate sensitivities, and climate–carbon feedbacks. The values from EMICs generally fall within the range given by general circulation models. Seven additional historical simulations, each including a single specified forcing, are used to assess the contributions of different climate forcings to the overall climate and carbon cycle response. The response of surface air temperature is the linear sum of the individual forcings, while the carbon cycle response shows a non-linear interaction between land-use change and CO2 forcings for some models. Finally, the preindustrial portions of the last millennium simulations are used to assess historical model carbon-climate feedbacks. Given the specified forcing, there is a tendency for the EMICs to underestimate the drop in surface air temperature and CO2 between the Medieval Climate Anomaly and the Little Ice Age estimated from palaeoclimate reconstructions. This in turn could be a result of unforced variability within the climate system, uncertainty in the reconstructions of temperature and CO2, errors in the reconstructions of forcing used to drive the models, or the incomplete representation of certain processes within the models. Given the forcing datasets used in this study, the models calculate significant land-use emissions over the pre-industrial period. This implies that land-use emissions might need to be taken into account, when making estimates of climate–carbon feedbacks from palaeoclimate reconstructions.
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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