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Pierre Rampal - One of the best experts on this subject based on the ideXlab platform.
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Wave-Ice interactions in the neXtSIM sea-Ice model
The Cryosphere, 2017Co-Authors: Timothy D. Williams, Pierre Rampal, Sylvain BouillonAbstract:Abstract. In this paper we describe a waves-in-Ice model (WIM), which calculates Ice breakage and the wave radiation stress (WRS). This WIM is then coupled to the new sea-Ice model neXtSIM, which is based on the elasto-brittle (EB) rheology. We highlight some numerical issues involved in the coupling and investigate the impact of the WRS, and of modifying the EB rheology to lower the stiffness of the Ice in the area where the Ice has broken up (the marginal Ice zone or MIZ). In experiments in the absence of wind, we find that wind waves can produce notIceable movement of the Ice edge in loose Ice (concentration around 70 %) – up to 36 km, depending on the material parameters of the Ice that are used and the dynamical model used for the broken Ice. The Ice edge position is unaffected by the WRS if the initial concentration is higher (≳ 0.9). Swell waves (monochromatic waves with low frequency) do not affect the Ice edge location (even for loose Ice), as they are attenuated much less than the higher-frequency components of a wind wave spectrum, and so consequently produce a much lower WRS (by about an order of magnitude at least). In the presence of wind, we find that the wind stress dominates the WRS, which, while large near the Ice edge, decays exponentially away from it. This is in contrast to the wind stress, which is applied over a much larger Ice area. In this case (when wind is present) the dynamical model for the MIZ has more impact than the WRS, although that effect too is relatively modest. When the stiffness in the MIZ is lowered due to Ice breakage, we find that on-Ice winds produce more compression in the MIZ than in the pack, while off-Ice winds can cause the MIZ to be separated from the pack Ice.
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Wave-Ice interactions in the neXtSIM sea-Ice model
2017Co-Authors: Timothy D. Williams, Pierre Rampal, Sylvain BouillonAbstract:Abstract. In this paper we describe a waves-in-Ice model which calculates Ice breakage and the wave radiation stress (WRS) that is coupled to the new sea Ice model neXtSIM, which is based on the Elasto-Brittle (EB) rheology. We highlight some numerical issues involved in the coupling, and investigate the impact of the WRS, and of modifying the EB to lower the stiffness of the Ice in the area where the Ice has broken up (the marginal Ice zone, or MIZ). In experiments in the absence of wind, we find that wind waves can produce notIceable movement in loose Ice (concentration around 70 %) – up to 36 km, depending on the material parameters of the Ice that are used, and the dynamical model used for the broken Ice. Swell waves do not produce any movement, as they are attenuated too little to induce a very large WRS. In the presence of wind, we find that the wind stress dominates the WRS, which while large near the Ice edge, decays exponentially away from it. This is in contrast to the wind stress which is applied over a much larger Ice area. In this case (when wind is present) the dynamical model for the MIZ has more impact than the WRS, although that effect too is relatively modest. When the stiffness in the MIZ is lowered due to Ice breakage, we find that on-Ice winds produce more compression in the MIZ than in the pack, while off-Ice winds can cause the MIZ to be separated from the pack Ice.
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Arctic sea Ice velocity field: General circulation and turbulent-like fluctuations
Journal of Geophysical Research. Oceans, 2009Co-Authors: Pierre Rampal, Jérôme Weiss, David Marsan, Mickaël BourgoinAbstract:Using buoy trajectories of the IABP data set, we analyze the Arctic sea Ice velocity field as the superposition of a mean field and fluctuations. We study how the mean field can be objectively defined, using appropriate spatial and temporal averaging scales depending on the season considered: 400 km and 5 1/2 months for winter (i.e., approximately all the polar winter duration), and 200 km and 2 1/2 months for summer (i.e., approximately all the polar summer duration). The mean velocity field shows a strong intra-annual (between winter and the following summer) as well as interannual variability. The fluctuations, i.e., the remaining part of the velocity field after subtracting the mean field, are analyzed in terms of diffusion properties. Although the Arctic sea Ice cover is a solid, we show that the fluctuations follow the same diffusion regimes as the ones predicted for turbulent flows, as observed in geophysical fluids like the ocean or the atmosphere. We found that the integral time and the diffusivity of sea Ice are in the same ranges as those estimated for the ocean, i.e., 1.5 days in winter and 1.3 days in summer and 0.44 x 10(3) m(2)/s for winter and 0.45 x 10(3) m(2)/s in summer, respectively. However, the statistics of the sea Ice fluctuating velocity deviate from classical turbulence theory, as they show exponential instead of Gaussian distributions. Sea Ice velocity and acceleration are intermittent, and both are characterized by a multifractal scaling. The oceanic and atmospheric dynamic forcing cannot explain solely the statistical properties of sea Ice kinematics and dynamics. We argue that sea Ice dynamic is significantly influenced by the interplay of multiple fractures that are activated intermittently within the Ice pack.
Sylvain Bouillon - One of the best experts on this subject based on the ideXlab platform.
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Wave-Ice interactions in the neXtSIM sea-Ice model
The Cryosphere, 2017Co-Authors: Timothy D. Williams, Pierre Rampal, Sylvain BouillonAbstract:Abstract. In this paper we describe a waves-in-Ice model (WIM), which calculates Ice breakage and the wave radiation stress (WRS). This WIM is then coupled to the new sea-Ice model neXtSIM, which is based on the elasto-brittle (EB) rheology. We highlight some numerical issues involved in the coupling and investigate the impact of the WRS, and of modifying the EB rheology to lower the stiffness of the Ice in the area where the Ice has broken up (the marginal Ice zone or MIZ). In experiments in the absence of wind, we find that wind waves can produce notIceable movement of the Ice edge in loose Ice (concentration around 70 %) – up to 36 km, depending on the material parameters of the Ice that are used and the dynamical model used for the broken Ice. The Ice edge position is unaffected by the WRS if the initial concentration is higher (≳ 0.9). Swell waves (monochromatic waves with low frequency) do not affect the Ice edge location (even for loose Ice), as they are attenuated much less than the higher-frequency components of a wind wave spectrum, and so consequently produce a much lower WRS (by about an order of magnitude at least). In the presence of wind, we find that the wind stress dominates the WRS, which, while large near the Ice edge, decays exponentially away from it. This is in contrast to the wind stress, which is applied over a much larger Ice area. In this case (when wind is present) the dynamical model for the MIZ has more impact than the WRS, although that effect too is relatively modest. When the stiffness in the MIZ is lowered due to Ice breakage, we find that on-Ice winds produce more compression in the MIZ than in the pack, while off-Ice winds can cause the MIZ to be separated from the pack Ice.
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Wave-Ice interactions in the neXtSIM sea-Ice model
2017Co-Authors: Timothy D. Williams, Pierre Rampal, Sylvain BouillonAbstract:Abstract. In this paper we describe a waves-in-Ice model which calculates Ice breakage and the wave radiation stress (WRS) that is coupled to the new sea Ice model neXtSIM, which is based on the Elasto-Brittle (EB) rheology. We highlight some numerical issues involved in the coupling, and investigate the impact of the WRS, and of modifying the EB to lower the stiffness of the Ice in the area where the Ice has broken up (the marginal Ice zone, or MIZ). In experiments in the absence of wind, we find that wind waves can produce notIceable movement in loose Ice (concentration around 70 %) – up to 36 km, depending on the material parameters of the Ice that are used, and the dynamical model used for the broken Ice. Swell waves do not produce any movement, as they are attenuated too little to induce a very large WRS. In the presence of wind, we find that the wind stress dominates the WRS, which while large near the Ice edge, decays exponentially away from it. This is in contrast to the wind stress which is applied over a much larger Ice area. In this case (when wind is present) the dynamical model for the MIZ has more impact than the WRS, although that effect too is relatively modest. When the stiffness in the MIZ is lowered due to Ice breakage, we find that on-Ice winds produce more compression in the MIZ than in the pack, while off-Ice winds can cause the MIZ to be separated from the pack Ice.
Adrian Jenkins - One of the best experts on this subject based on the ideXlab platform.
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Marine Ice in Larsen Ice Shelf
Geophysical Research Letters, 2009Co-Authors: Paul R. Holland, Hugh F. J. Corr, David G. Vaughan, Adrian Jenkins, Pedro SkvarcaAbstract:It is argued that Larsen Ice Shelf contains marine Ice formed by oceanic freezing and other mechanisms. Missing basal returns in airborne radar soundings and observations of a smooth and healed surface coincide downstream of regions where an ocean model predicts freezing. Visible imagery suggests that marine Ice currently stabilizes Larsen C Ice Shelf and implicates failure of marine flow bands in the 2002 Larsen B Ice Shelf collapse. Ocean modeling indicates that any regime change towards the incursion of warmer Modified Weddell Deep Water into the Larsen C cavity could curtail basal freezing and its stabilizing influence
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Frazil Ice formation in an Ice shelf water plume
Journal of Geophysical Research: Oceans, 2004Co-Authors: Lars Henrik Smedsrud, Adrian JenkinsAbstract:[1] We present a model for the growth of frazil Ice crystals and their accumulation as marine Ice at the base of Antarctic Ice shelves. The model describes the flow of buoyant water upward along the Ice shelf base and includes the differential growth of a range of crystal sizes. Frazil Ice formation starts when the rising plume becomes supercooled. Initially, the majority of crystals have a radius of similar to0.3 mm and concentrations are below 0.1 g/L. Depending on the Ice shelf slope, which controls the plume speed, frazil crystals increase in size and number. Typically, crystals up to 1.0 mm in radius are kept in suspension, and concentrations reach a maximum of 0.4 g/L. The frazil Ice in suspension decreases the plume density and thus increases the plume speed. Larger crystals precipitate upward onto the Ice shelf base first, with smaller crystals following as the plume slows down. In this way, marine Ice is formed at rates of up to 4 m/yr in some places, consistent with areas of observed basal accumulation on Filchner-Ronne Ice Shelf. The plume continues below the Ice shelf as long as it is buoyant. If the plume reaches the Ice front, its rapid rise produces high supercooling and the Ice crystals attain a radius of several millimeters before reaching the surface. Similar Ice crystals have been trawled at depth north of Antarctic Ice shelves, but otherwise no observations exist to verify these first predictions of Ice crystal sizes and volumes.
Pedro Skvarca - One of the best experts on this subject based on the ideXlab platform.
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Marine Ice in Larsen Ice Shelf
Geophysical Research Letters, 2009Co-Authors: Paul R. Holland, Hugh F. J. Corr, David G. Vaughan, Adrian Jenkins, Pedro SkvarcaAbstract:It is argued that Larsen Ice Shelf contains marine Ice formed by oceanic freezing and other mechanisms. Missing basal returns in airborne radar soundings and observations of a smooth and healed surface coincide downstream of regions where an ocean model predicts freezing. Visible imagery suggests that marine Ice currently stabilizes Larsen C Ice Shelf and implicates failure of marine flow bands in the 2002 Larsen B Ice Shelf collapse. Ocean modeling indicates that any regime change towards the incursion of warmer Modified Weddell Deep Water into the Larsen C cavity could curtail basal freezing and its stabilizing influence
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Ice dolines on Larsen Ice Shelf, Antarctica
Annals of Glaciology, 2002Co-Authors: Robert Bindschadler, Ted A. Scambos, Helmut Rott, Pedro Skvarca, Patricia VornbergerAbstract:ABSTRACT . Ice dolines on the Larsen Ice Shelf, Antarctica, are observed to beelongated depressions a few hundred meters across and up to 19m deep. One-meterresolution imagery is used to quantify these dimensions. Elevation profiles across fivedolines are derivedby photoclinometry. Landsat and radar imagery is also usedto showthatdolinescanforminasinglemeltseasonandpersistforyears.Dolinesoccurinclustersandindirectproximitytosurfacemeltwaterlakes.Fieldobservationssuggestdolinesformby collapse into a subsurface cavity. A direct hydraulic connection with the underlyingocean is believed necessary to drain water that would otherwise collect in dolines. Aformation hypothesis is discussed consistent with these observations and with energy-andhydrostatic-imbalance considerations. INTRODUCTION Doline isageologictermdescribingaroundedhollowthatcanrange in width from 1 to 100m and in depth from ten tohundredsof meters (AGI,1976). Mellor (1960) wasthefirsttosuggest the term Icedoline be applied to depression featuresseen on Ice. Their size, hundreds of meters across, is theprincipal characteristic distinguishing them from
David M. Holland - One of the best experts on this subject based on the ideXlab platform.
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Computing marine-Ice thickness at an Ice-shelf base
Journal of Glaciology, 2002Co-Authors: David M. HollandAbstract:AbstractThe freezing of sea water to the base of an Ice shelf can give rise to large patches of accumulated Ice, a phenomenon known as marine Ice. In this study a numerical method is presented for calculating the thickness of the marine-Ice layer using an Ice- shelf-ocean model. The present-day modeling paradigm of Ice-shelf–ocean interaction usually involves the fixed specification of the Ice-shelf geometry while the ocean circulation in the cavity beneath the Ice shelf evolves freely. This approach relies on several assumptions, such as steady-state Ice-shelf thickness and Ice-shelf flow fields, in order to make reasonable quantitative estimates of the thermodynamic exchange processes occurring at the Ice-shelf base. This paper discusses the impact of these and other assumptions on the estimation of the thickness of the marine-Ice layer. Model simulation results are presented for an idealized Ice-shelf–ocean configuration as a demonstration of the feasibility of the numerical method. A sensitivity analysis is given so as to quantify the relative uncertainty in the marine-Ice thickness that arises from uncertainties in the model input parameters, these being principally the Ice-shelf flow field, the basal accumulation rate and the Ice-shelf thickness field.
