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  • 1
    Online Resource
    Online Resource
    Recent multivariate changes in the North Atlantic climate system, with a focus on 2005–2016
    Wiley ; 2018
    In:  International Journal of Climatology Vol. 38, No. 14 ( 2018-11), p. 5050-5076
    Details
    In: International Journal of Climatology, Wiley, Vol. 38, No. 14 ( 2018-11), p. 5050-5076
    Abstract: Major changes are occurring across the North Atlantic climate system, including in the atmosphere, ocean and cryosphere, and many observed changes are unprecedented in instrumental records. As the changes in the North Atlantic directly affect the climate and air quality of the surrounding continents, it is important to fully understand how and why the changes are taking place, not least to predict how the region will change in the future. To this end, this article characterizes the recent observed changes in the North Atlantic region, especially in the period 2005–2016, across many different aspects of the system including: atmospheric circulation; atmospheric composition; clouds and aerosols; ocean circulation and properties; and the cryosphere. Recent changes include: an increase in the speed of the North Atlantic jet stream in winter; a southward shift in the North Atlantic jet stream in summer, associated with a weakening summer North Atlantic Oscillation; increases in ozone and methane; increases in net absorbed radiation in the mid‐latitude western Atlantic, linked to an increase in the abundance of high level clouds and a reduction in low level clouds; cooling of sea surface temperatures in the North Atlantic subpolar gyre, concomitant with increases in the western subtropical gyre, and a decline in the Atlantic Ocean's overturning circulation; a decline in Atlantic sector Arctic sea ice and rapid melting of the Greenland Ice Sheet. There are many interactions between these changes, but these interactions are poorly understood. This article concludes by highlighting some of the key outstanding questions.
    Type of Medium: Online Resource
    ISSN: 0899-8418 , 1097-0088
    URL: Issue
    URL: Article
    DOI: 10.1002/joc.2018.38.issue-14
    DOI: 10.1002/joc.5815
    RVK:
    RA 1000
    Language: English
    Publisher: Wiley
    Publication Date: 2018
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    SSG: 14
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  • 2
    Online Resource
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    Micromechanics of sea ice frictional slip from test basin scale experiments
    The Royal Society ; 2017
    In:  Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences Vol. 375, No. 2086 ( 2017-02-13), p. 20150354-
    Details
    In: Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, The Royal Society, Vol. 375, No. 2086 ( 2017-02-13), p. 20150354-
    Abstract: We have conducted a series of high-resolution friction experiments on large floating saline ice floes in an environmental test basin. In these experiments, a central ice floe was pushed between two other floes, sliding along two interfacial faults. The frictional motion was predominantly stick–slip. Shear stresses, normal stresses, local strains and slip displacement were measured along the sliding faults, and acoustic emissions were monitored. High-resolution measurements during a single stick–slip cycle at several positions along the fault allowed us to identify two phases of frictional slip: a nucleation phase, where a nucleation zone begins to slip before the rest of the fault, and a propagation phase when the entire fault is slipping. This is slip-weakening behaviour. We have therefore characterized what we consider to be a key deformation mechanism in Arctic Ocean dynamics. In order to understand the micromechanics of sea ice friction, we have employed a theoretical constitutive relation (i.e. an equation for shear stress in terms of temperature, normal load, acceleration, velocity and slip displacement) derived from the physics of asperity–asperity contact and sliding (Hatton et al. 2009 Phil. Mag. 89 , 2771–2799 ( doi:10.1080/14786430903113769 )). We find that our experimental data conform reasonably with this frictional law once slip weakening is introduced. We find that the constitutive relation follows Archard's law rather than Amontons' law, with (where τ is the shear stress and σ n is the normal stress) and n  = 26/27, with a fractal asperity distribution, where the frictional shear stress, τ = f fractal T ml w s , where f fractal is the fractal asperity height distribution, T ml is the shear strength for frictional melting and lubrication and w s is the slip weakening. We can therefore deduce that the interfacial faults failed in shear for these experimental conditions through processes of brittle failure of asperities in shear, and, at higher velocities, through frictional heating, localized surface melting and hydrodynamic lubrication. This article is part of the themed issue ‘Microdynamics of ice’.
    Type of Medium: Online Resource
    ISSN: 1364-503X , 1471-2962
    URL: Article
    DOI: 10.1098/rsta.2015.0354
    RVK:
    AX 30011
    Language: English
    Publisher: The Royal Society
    Publication Date: 2017
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  • 3
    Online Resource
    Online Resource
    Impact of Variable Atmospheric and Oceanic Form Drag on Simulations of Arctic Sea Ice*
    American Meteorological Society ; 2014
    In:  Journal of Physical Oceanography Vol. 44, No. 5 ( 2014-05-01), p. 1329-1353
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 44, No. 5 ( 2014-05-01), p. 1329-1353
    Abstract: Over Arctic sea ice, pressure ridges and floe and melt pond edges all introduce discrete obstructions to the flow of air or water past the ice and are a source of form drag. In current climate models form drag is only accounted for by tuning the air–ice and ice–ocean drag coefficients, that is, by effectively altering the roughness length in a surface drag parameterization. The existing approach of the skin drag parameter tuning is poorly constrained by observations and fails to describe correctly the physics associated with the air–ice and ocean–ice drag. Here, the authors combine recent theoretical developments to deduce the total neutral form drag coefficients from properties of the ice cover such as ice concentration, vertical extent and area of the ridges, freeboard and floe draft, and the size of floes and melt ponds. The drag coefficients are incorporated into the Los Alamos Sea Ice Model (CICE) and show the influence of the new drag parameterization on the motion and state of the ice cover, with the most noticeable being a depletion of sea ice over the west boundary of the Arctic Ocean and over the Beaufort Sea. The new parameterization allows the drag coefficients to be coupled to the sea ice state and therefore to evolve spatially and temporally. It is found that the range of values predicted for the drag coefficients agree with the range of values measured in several regions of the Arctic. Finally, the implications of the new form drag formulation for the spinup or spindown of the Arctic Ocean are discussed.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    URL: Article
    DOI: 10.1175/JPO-D-13-0215.1
    DOI: 10.1175/JPO-D-13-0215s2.tex
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2014
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  • 4
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    Online Resource
    Theory, modelling and observations of marginal ice zone dynamics: multidisciplinary perspectives and outlooks
    The Royal Society ; 2022
    In:  Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences Vol. 380, No. 2235 ( 2022-10-31)
    Details
    In: Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, The Royal Society, Vol. 380, No. 2235 ( 2022-10-31)
    Abstract: The marginal ice zone (MIZ) is the dynamic interface between the open ocean and sea ice-covered ocean. It is characterized by interactions between surface gravity waves and granular ice covers consisting of relatively small, thin chunks of sea ice known as floes. This structure gives the MIZ markedly different properties to the thicker, quasi-continuous ice cover of the inner pack that waves do not reach, strongly influencing various atmosphere–ocean fluxes, especially the heat flux. The MIZ is a significant component of contemporary sea ice covers in both the Antarctic, where the ice cover is surrounded by the Southern Ocean and its fierce storms, and the Arctic, where the MIZ now occupies vast expanses in areas that were perennial only a decade or two ago. The trend towards the MIZ is set to accelerate, as it reinforces positive feedbacks weakening the ice cover. Therefore, understanding the complex, multiple-scale dynamics of the MIZ is essential to understanding how sea ice is evolving and to predicting its future. This article is part of the theme issue ‘Theory, modelling and observations of marginal ice zone dynamics: multidisciplinary perspectives and outlooks’.
    Type of Medium: Online Resource
    ISSN: 1364-503X , 1471-2962
    URL: Article
    DOI: 10.1098/rsta.2021.0265
    RVK:
    AX 30011
    Language: English
    Publisher: The Royal Society
    Publication Date: 2022
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    SSG: 5,21
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  • 5
    Online Resource
    Online Resource
    Characterizing Arctic sea ice topography using high-resolution IceBridge data
    Copernicus GmbH ; 2016
    In:  The Cryosphere Vol. 10, No. 3 ( 2016-05-31), p. 1161-1179
    Details
    In: The Cryosphere, Copernicus GmbH, Vol. 10, No. 3 ( 2016-05-31), p. 1161-1179
    Abstract: Abstract. We present an analysis of Arctic sea ice topography using high-resolution, three-dimensional surface elevation data from the Airborne Topographic Mapper, flown as part of NASA's Operation IceBridge mission. Surface features in the sea ice cover are detected using a newly developed surface feature picking algorithm. We derive information regarding the height, volume and geometry of surface features from 2009 to 2014 within the Beaufort/Chukchi and Central Arctic regions. The results are delineated by ice type to estimate the topographic variability across first-year and multi-year ice regimes. The results demonstrate that Arctic sea ice topography exhibits significant spatial variability, mainly driven by the increased surface feature height and volume (per unit area) of the multi-year ice that dominates the Central Arctic region. The multi-year ice topography exhibits greater interannual variability compared to the first-year ice regimes, which dominates the total ice topography variability across both regions. The ice topography also shows a clear coastal dependency, with the feature height and volume increasing as a function of proximity to the nearest coastline, especially north of Greenland and the Canadian Archipelago. A strong correlation between ice topography and ice thickness (from the IceBridge sea ice product) is found, using a square-root relationship. The results allude to the importance of ice deformation variability in the total sea ice mass balance, and provide crucial information regarding the tail of the ice thickness distribution across the western Arctic. Future research priorities associated with this new data set are presented and discussed, especially in relation to calculations of atmospheric form drag.
    Type of Medium: Online Resource
    ISSN: 1994-0424
    URL: Article
    URL: Article
    DOI: 10.5194/tc-10-1161-2016
    DOI: 10.5194/tc-10-1161-2016-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2016
    detail.hit.zdb_id: 2393169-3
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  • 6
    Online Resource
    Online Resource
    Similarity solutions describing the melting of a mushy layer
    Elsevier BV ; 2000
    In:  Journal of Crystal Growth Vol. 208, No. 1-4 ( 2000-1), p. 746-756
    Details
    In: Journal of Crystal Growth, Elsevier BV, Vol. 208, No. 1-4 ( 2000-1), p. 746-756
    Type of Medium: Online Resource
    ISSN: 0022-0248
    URL: Article
    DOI: 10.1016/S0022-0248(99)00456-X
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2000
    detail.hit.zdb_id: 1466514-1
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  • 7
    Online Resource
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    Flow-induced morphological instability of a mushy layer
    Cambridge University Press (CUP) ; 1999
    In:  Journal of Fluid Mechanics Vol. 391 ( 1999-07-25), p. 337-357
    Details
    In: Journal of Fluid Mechanics, Cambridge University Press (CUP), Vol. 391 ( 1999-07-25), p. 337-357
    Abstract: A morphological instability of a mushy layer due to a forced flow in the melt is analysed. The instability is caused by flow induced in the mushy layer by Bernoulli suction at the crests of a sinusoidally perturbed mush–melt interface. The flow in the mushy layer advects heat away from crests which promotes solidification. Two linear stability analyses are presented: the fundamental mechanism for instability is elucidated by considering the case of uniform flow of an inviscid melt; a more complete analysis is then presented for the case of a parallel shear flow of a viscous melt. The novel instability mechanism we analyse here is contrasted with that investigated by Gilpin et al . (1980) and is found to be more potent for the case of newly forming sea ice.
    Type of Medium: Online Resource
    ISSN: 0022-1120 , 1469-7645
    URL: Article
    DOI: 10.1017/S002211209900539X
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 1999
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    detail.hit.zdb_id: 218334-1
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  • 8
    Online Resource
    Online Resource
    Ice Shelf Water plume flow beneath Filchner-Ronne Ice Shelf, Antarctica
    American Geophysical Union (AGU) ; 2007
    In:  Journal of Geophysical Research Vol. 112, No. C5 ( 2007-05-24)
    Details
    In: Journal of Geophysical Research, American Geophysical Union (AGU), Vol. 112, No. C5 ( 2007-05-24)
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2006JC003915
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2007
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    detail.hit.zdb_id: 161666-3
    detail.hit.zdb_id: 161667-5
    detail.hit.zdb_id: 2969341-X
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    detail.hit.zdb_id: 2220777-6
    detail.hit.zdb_id: 3094197-0
    SSG: 16,13
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  • 9
    Online Resource
    Online Resource
    Stability of an ice sheet on an elastic bed
    Elsevier BV ; 2004
    In:  European Journal of Mechanics - B/Fluids Vol. 23, No. 5 ( 2004-9), p. 681-694
    Details
    In: European Journal of Mechanics - B/Fluids, Elsevier BV, Vol. 23, No. 5 ( 2004-9), p. 681-694
    Type of Medium: Online Resource
    ISSN: 0997-7546
    URL: Article
    DOI: 10.1016/j.euromechflu.2003.12.004
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2004
    detail.hit.zdb_id: 2019287-3
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  • 10
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    Online Resource
    Dependence of Sea Ice Yield-Curve Shape on Ice Thickness
    American Meteorological Society ; 2004
    In:  Journal of Physical Oceanography Vol. 34, No. 12 ( 2004-12-01), p. 2852-2856
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 34, No. 12 ( 2004-12-01), p. 2852-2856
    Abstract: In this note, the authors discuss the contribution that frictional sliding of ice floes (or floe aggregates) past each other and pressure ridging make to the plastic yield curve of sea ice. Using results from a previous study that explicitly modeled the amount of sliding and ridging that occurs for a given global strain rate, it is noted that the relative contribution of sliding and ridging to ice stress depends upon ice thickness. The implication is that the shape and size of the plastic yield curve is dependent upon ice thickness. The yield-curve shape dependence is in addition to plastic hardening/weakening that relates the size of the yield curve to ice thickness. In most sea ice dynamics models the yield-curve shape is taken to be independent of ice thickness. The authors show that the change of the yield curve due to a change in the ice thickness can be taken into account by a weighted sum of two thickness-independent rheologies describing ridging and sliding effects separately. It would be straightforward to implement the thickness-dependent yield-curve shape described here into sea ice models used for global or regional ice prediction.
    Type of Medium: Online Resource
    ISSN: 1520-0485 , 0022-3670
    URL: Article
    DOI: 10.1175/JPO2667.1
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2004
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    detail.hit.zdb_id: 184162-2
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