GLORIA

GEOMAR Library Ocean Research Information Access

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    facet.materialart.
    Unknown
    Sea Ice Rheology Experiment (SIREx): 2. Evaluating Linear Kinematic Features in High‐Resolution Sea Ice Simulations (2022)
    Details
    Publication Date: 2022-09-22
    Description: Simulating sea ice drift and deformation in the Arctic Ocean is still a challenge because of the multiscale interaction of sea ice floes that compose the Arctic Sea ice cover. The Sea Ice Rheology Experiment (SIREx) is a model intercomparison project of the Forum of Arctic Modeling and Observational Synthesis (FAMOS). In SIREx, skill metrics are designed to evaluate different recently suggested approaches for modeling linear kinematic features (LKFs) to provide guidance for modeling small‐scale deformation. These LKFs are narrow bands of localized deformation that can be observed in satellite images and also form in high resolution sea ice simulations. In this contribution, spatial and temporal properties of LKFs are assessed in 36 simulations of state‐of‐the‐art sea ice models and compared to deformation features derived from the RADARSAT Geophysical Processor System. All simulations produce LKFs, but only very few models realistically simulate at least some statistics of LKF properties such as densities, lengths, or growth rates. All SIREx models overestimate the angle of fracture between conjugate pairs of LKFs and LKF lifetimes pointing to inaccurate model physics. The temporal and spatial resolution of a simulation and the spatial resolution of atmospheric boundary condition affect simulated LKFs as much as the model's sea ice rheology and numerics. Only in very high resolution simulations (≤2 km) the concentration and thickness anomalies along LKFs are large enough to affect air‐ice‐ocean interaction processes.
    Description: Plain Language Summary: Winds and ocean currents continuously move and deform the sea ice cover of the Arctic Ocean. The deformation eventually breaks an initially closed ice cover into many individual floes, piles up floes, and creates open water. The distribution of ice floes and open water between them is important for climate research, because ice reflects more light and energy back to the atmosphere than open water, so that less ice and more open water leads to warmer oceans. Current climate models cannot simulate sea ice as individual floes. Instead, a variety of methods is used to represent the movement and deformation of the sea ice cover. The Sea Ice Rheology Experiment (SIREx) compares these different methods and assesses the deformation of sea ice in 36 numerical simulations. We identify and track deformation features in the ice cover, which are distinct narrow areas where the ice is breaking or piling up. Comparing specific spatial and temporal properties of these features, for example, the different amounts of fractured ice in specific regions, or the duration of individual deformation events, to satellite observations provides information about the realism of the simulations. From this comparison, we can learn how to improve sea ice models for more realistic simulations of sea ice deformation.
    Description: Key Points: All models simulate linear kinematic features (LKFs), but none accurately reproduces all LKF statistics. Resolved LKFs are affected strongest by spatial and temporal resolution of model grid and atmospheric forcing and rheology. Accurate scaling of deformation rates is a proxy only for realistic LKF numbers but not for any other LKF static.
    Description: DOE
    Description: HYCOM NOPP
    Description: Innovation Fund Denmark and the Horizon 2020 Framework Programme of the European Union
    Description: National centre for Climate Research, SALIENSEAS, ERA4CS
    Description: German Helmholtz Climate Initiative REKLIM (Regional Climate Change)
    Description: Gouvernement du Canada, Natural Sciences and Engineering Research Council of Canada (NSERC) http://dx.doi.org/10.13039/501100000038
    Description: Environment and Climate Change Canada Grants & Contributions program
    Description: Office of Naval Research Arctic and Global Prediction program
    Description: U.S. Department of Energy Regional and Global Model Analysis program
    Description: National Science Foundation Arctic System Science program
    Description: Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659
    Description: https://zenodo.org/communities/sirex
    Keywords: ddc:550.285
    Language: English
    Type: doc-type:article
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 2
    facet.materialart.
    Unknown
    A home-visiting intervention targeting determinants of infant mental health: the study protocol for the CAPEDP randomized controlled trial in France (2012)
    BioMed Central
    Details
    Publication Date: 2012-08-14
    Description: Background: Several studies suggest that the number of risk factors rather than their nature is key to mental health disorders in childhood.Method and DesignThe objective of this multicentre randomized controlled parallel trial (PROBE methodology) is to assess the impact in a multi-risk French urban sample of a home-visiting program targeting child mental health and its major determinants. This paper describes the protocol of this study. In the study, pregnant women were eligible if they were: living in the intervention area; able to speak French, less than 26 years old; having their first child; less than 27 weeks of amenorrhea; and if at least one of the following criteria were true: less than twelve years of education, intending to bring up their child without the presence of the child's father, and 3) low income. Participants were randomized into either the intervention or the control group. All had access to usual care in mother-child centres and community mental health services free of charge in every neighbourhood. Psychologists conducted all home visits, which were planned on a weekly basis from the 7th month of pregnancy and progressively decreasing in frequency until the child's second birthday. Principle outcome measures included child mental health at 24 months and two major mediating variables for infant mental health: postnatal maternal depression and the quality of the caring environment. A total of 440 families were recruited, of which a subsample of 120 families received specific attachment and caregiver behaviour assessment. Assessment was conducted by an independent assessment team during home visits and, for the attachment study, in a specifically created Attachment Assessment laboratory.DiscussionThe CAPEDP study is the first large-scale randomised, controlled infant mental health promotion programme to take place in France. A major specificity of the program was that all home visits were conducted by specifically trained, supervised psychologists rather than nurses. Significant challenges included designing a mental health promotion programme targeting vulnerable families within one of the most generous but little assessed health and social care systems in the Western World.Trial registrationCurrent Clinical trial number is NCT00392847.
    Electronic ISSN: 1471-2458
    Topics: Medicine
    Published by BioMed Central
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 3
    facet.materialart.
    Unknown
    Arctic Sea Ice in CMIP6 (2020)
    Wiley
    In:  EPIC3Geophysical Research Letters, Wiley, ISSN: 0094-8276
    Details
    Publication Date: 2020-05-04
    Description: We examine CMIP6 simulations of Arctic sea‐ice area and volume. We find that CMIP6 models produce a wide spread of mean Arctic sea‐ice area, capturing the observational estimate within the multi‐model ensemble spread. The CMIP6 multi‐model ensemble mean provides a more realistic estimate of the sensitivity of September Arctic sea‐ice area to a given amount of anthropogenic CO2 emissions and to a given amount of global warming, compared with earlier CMIP experiments. Still, most CMIP6 models fail to simulate at the same time a plausible evolution of sea‐ice area and of global mean surface temperature. In the vast majority of the available CMIP6 simulations, the Arctic Ocean becomes practically sea‐ice free (sea‐ice area 〈 1 million km2) in September for the first time before the year 2050 in each of the four emission scenarios SSP1‐1.9, SSP1‐2.6, SSP2‐4.5 and SSP5‐8.5 examined here.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev , info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 4
    facet.materialart.
    Unknown
    The Effects of Non-Normal Flow Rules on Fracture Angles in Viscous-Plastic Sea Ice Models (2020)
    In:  EPIC3AGU 2020 Fall Meeting, Online, 2020-12-01-2020-12-17
    Details
    Publication Date: 2021-02-09
    Description: High-resolution viscous-plastic (VP) sea ice models reproduce the narrow deformations lines observed in the Arctic sea ice, called the Linear Kinematic Features (LKFs). Recent studies showed that standard VP models overestimate the intersection angles between the LKFs when compared to observations. We investigate fracture angles in a uniaxial compression test and two different VP rheology. The first one uses an elliptical yield curve and a normal flow rule. In contrast, the second rheology uses a different elliptical plastic potential that creates a non-normal flow rule. Results show that the non-normality of the flow rule changes the angles of fracture. This new rheology can create fracture angles as low as 22º when the rheology with normal flow rule is limited to angles above 30º. A newly adapted theory – based on one developed from granular material observations – predicts the modeled fracture angles accurately. Using a non-normal flow rule takes longer to solve numerically, but allow reductions of the fracture angle to values within the range of satellite observations and decouples the angle of fracture from the shape of the yield curve.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 5
    facet.materialart.
    Unknown
    Alternative viscous-plastic rheologies for the representation of fracture lines in high-resolution sea ice models (2021)
    In:  EPIC3vEGU21: Gather Online, Online, 2021-04-19-2021-04-30Alternative viscous-plastic rheologies for the representation of fracture lines in high-resolution sea ice models
    Details
    Publication Date: 2021-05-25
    Description: Fracture lines dominate the dynamics of sea ice. They affect the ice mass balance and the heat transfer between the atmosphere and the ocean. Therefore, climate modeling and sea ice prediction require an accurate fracture representation. Most sea ice models use viscous-plastic (VP) rheologies to simulate sea ice internal stresses. One of the issues with these rheologies is that they overestimate the intersection angles between fracture lines, with consequences for the subsequent sea ice drift. In idealized experiments, we investigate the mechanisms linking VP rheologies and fracture angles and assess alternative rheologies for high-resolution modeling. Results show that the definition of the transition between viscous and plastic states is essential for the creation of sharp fracture lines. The fracture angles with Mohr-Coulomb yield curves agree with the Arthur fault orientation theory. Further, rheologies with Mohr-Coulomb yield curves or teardrop yield curves appear to reduce intersection angles. Finally, experiments show that these results are reproduced for different sea ice initial conditions. With rheologies that favor smaller intersection angles, sea ice models move a step closer to accurate sea ice dynamics at high-resolution.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
    Format: application/pdf
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 6
    facet.materialart.
    Unknown
    Modeling sea ice fracture at very high resolution with VP rheologies (2019)
    In:  EPIC3AERC 2019 - The Annual European Rheology Conference, Portorož, Slovenia, 2019-04-08-2019-04-11
    Details
    Publication Date: 2021-02-01
    Description: Recent high resolution pan-Arctic sea ice simulations show fracture patterns that are typical of granular materials but with intersection (fracture) angles wider than those observed from high-resolution satellite images (with a modal value of θ = 20º). In this work, we investigate the mechanism of formation and parameter dependencies of ice fracture in simple numerical uni-axial test on a 8 km x 25 km ice floe at an unprecedented resolution of 25 m for two different Visco-Plastic (VP) yield curves: an elliptical (standard in sea ice models) and a coulombic yield curve both with normal flow rule. In the standard VP model, the simulated angle of fracture is θ=33.9º. The dependence of the angle of fracture on the ice shear strength is also contrary to that of typical granular materials with larger angle of fracture for higher shear strength. In this model, the divergence along the fracture lines (or LKFs) is entirely dictated by the ice shear strength with high shear strength resulting in convergence along LKFs and low shear strength resulting in divergence along LKFs. This is again contrary to typical granular materials. Moreover, the angle of fracture depends on the confining pressure in the uni-axial test with more convergence as the confining pressure increases, again contrary to granular material. In the Coulombic model, the angle of fracture is smaller (θ=23.5º), but the solution is unstable because of the discontinuity between the straight limbs of the yield curve and the elliptical capping. Our results show that while the VP model gives angles of fracture that are visually correct, the bias in the magnitude of the angle of fracture and the physical dependencies of the angle of fracture on mechanical strength parameters and stress fields couple the sea ice mechanical strength parameters, the sea-ice drift, sea-ice deformation (strain-rate) field in an inconsistent way. We consider this evidence to move away from the elliptical yield curve and associative (normal) flow rule.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
    Format: application/pdf
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 7
    facet.materialart.
    Unknown
    Breaking the ice: Fracture angles with viscous-plastic sea ice rheologies (2021)
    In:  EPIC3VI ECCOMAS Young Investigators Conference, Online, 2021-07-07-2021-07-09
    Details
    Publication Date: 2021-07-12
    Description: Arctic sea ice plays a critical role in the climate system. Therefore it needs to be modeled accurately to make precise climate predictions of the current anthropogenic climate change. Most of today’s climate models simulate sea ice motion using a viscous-plastic (VP) rheology with an elliptical yield curve and a normal flow rule [1]. This rheology gives accurate predictions at low resolution but features discrepancies at high resolution when compared to observations. Observations show that narrow lines of deformation dominate the pattern of sea ice motion. Models using the VP rheology feature these fracture lines but overestimate the intersection angles between them [2]. To understand and solve these differences, we study the creation of fracture angles using idealized compression experiments. We test several yield curves and flow rules and investigate their effect on the angles between fracture lines. The results show that: first, the fracture angle depends on the shape of the yield curve as well as the flow rule, in agreement with Roscoe’s angle [3]; second, the elliptical yield curve with normal flow rule cannot create angles lower than 30° in uniaxial compression; finally, implementing a non-normal flow rule can lead to fracture angles as low as 22°. Results also show that sea ice dynamics in models disagree with sea ice observed granular behavior. With the new knowledge gained from these idealized experiments, we can now define new VP rheologies for more accurate sea ice modeling, e.g., with Mohr-Coulomb or teardrop yield curves. REFERENCES: [1] Hibler III WD: A dynamic thermodynamic sea ice model, Journal of physical oceanography. Jul;9(4):815-46, 1979. [2] Hutter, N. and Losch, M.: Feature-based comparison of sea ice deformation in lead-permitting sea ice simulations, The Cryosphere, 14, 93–113, https://doi.org/10.5194/tc-14-93-2020, 2020. [3] Roscoe, K. H.: The Influence of Strains in Soil Mechanics, Géotechnique, 20, 2, 129-170, 1970.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
    Format: application/pdf
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 8
    facet.materialart.
    Unknown
    Landfast sea ice material properties derived from ice bridge simulations using the Maxwell elasto-brittle rheology (2020)
    COPERNICUS GESELLSCHAFT MBH
    In:  EPIC3The Cryosphere, COPERNICUS GESELLSCHAFT MBH, 14(6), pp. 2137-2157, ISSN: 1994-0424
    Details
    Publication Date: 2020-07-28
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 9
    facet.materialart.
    Unknown
    The Future of Sea Ice Modeling: Where Do We Go from Here? (2020)
    AMER METEOROLOGICAL SOC
    In:  EPIC3Bulletin of the American Meteorological Society, AMER METEOROLOGICAL SOC, 101(8), pp. E1304-E1311, ISSN: 0003-0007
    Details
    Publication Date: 2020-09-14
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 10
    facet.materialart.
    Unknown
    A 5 ̊C Arctic in a 2 ̊C World (2016)
    Columbia Climate Center, Earth Institute, Columbia University
    In:  EPIC3Technical report, Columbia Climate Center, Earth Institute, Columbia University, 12 p.
    Details
    Publication Date: 2016-11-23
    Description: The Columbia Climate Center, in partnership with World Wildlife Fund, Woods Hole Research Center, and Arctic 21, held a workshop titled A 5 C Arctic in a 2 C World on July 20 and 21, 2016. The workshop was co-sponsored by the International Arctic Research Center (University of Alaska Fairbanks), the Arctic Institute of North America (Canada), the MEOPAR Network (Marine Environmental Observation, Prediction, and Response), and the Future Ocean Excellence Cluster. The goal of the workshop was to advance thinking on the science and policy implications of the temperature change in the context of the 1.5 to 2 C warming expected for the globe, as dis- cussed during the 21st session of the Conference of the Parties of the United Nations Framework Convention on Climate Change at Paris in 2015. For the Arctic, such an increase means an antic- ipated increase of roughly 3.5 to 5 C. An international group of 41 experts shared perspectives on the regional and global impacts of an up to +5 C Arctic, examined the feasibility of actively lowering Arctic temperatures, and considered realistic timescales associated with such interventions. The group also discussed the science and the political and governance actions required for alternative Arctic futures.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Miscellaneous , notRev
    Format: application/pdf
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER (OA)
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...