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J S Wettlaufer - One of the best experts on this subject based on the ideXlab platform.
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statistical mechanics and the climatology of the arctic sea ice Thickness Distribution
EGU General Assembly Conference Abstracts, 2018Co-Authors: Srikanth Toppaladoddi, J S WettlauferAbstract:We study the seasonal changes in the Thickness Distribution of Arctic sea ice, g(h), under climate forcing. Our analytical and numerical approach is based on a Fokker–Planck equation for g(h) (Toppaladoddi and Wettlaufer in Phys Rev Lett 115(14):148501, 2015), in which the thermodynamic growth rates are determined using observed climatology. In particular, the Fokker–Planck equation is coupled to the observationally consistent thermodynamic model of Eisenman and Wettlaufer (Proc Natl Acad Sci USA 106:28–32, 2009). We find that due to the combined effects of thermodynamics and mechanics, g(h) spreads during winter and contracts during summer. This behavior is in agreement with recent satellite observations from CryoSat-2 (Kwok and Cunningham in Philos Trans R Soc A 373(2045):20140157, 2015). Because g(h) is a probability density function, we quantify all of the key moments (e.g., mean Thickness, fraction of thin/thick ice, mean albedo, relaxation time scales) as greenhouse-gas radiative forcing, $$\Delta F_0$$ , increases. The mean ice Thickness decays exponentially with $$\Delta F_0$$ , but much slower than do solely thermodynamic models. This exhibits the crucial role that ice mechanics plays in maintaining the ice cover, by redistributing thin ice to thick ice-far more rapidly than can thermal growth alone.
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statistical mechanics and the climatology of the arctic sea ice Thickness Distribution
arXiv: Atmospheric and Oceanic Physics, 2016Co-Authors: Srikanth Toppaladoddi, J S WettlauferAbstract:We study the seasonal changes in the Thickness Distribution of Arctic sea ice, $g(h)$, under climate forcing. Our analytical and numerical approach is based on a Fokker-Planck equation for $g(h)$ (Toppaladoddi \& Wettlaufer \emph{Phys. Rev. Lett.} {\bf 115}, 148501, 2015), in which the thermodynamic growth rates are determined using observed climatology. In particular, the Fokker-Planck equation is coupled to the observationally consistent thermodynamic model of Eisenman \& Wettlaufer (\emph{Proc. Natl. Acad. Sci. USA} {\bf 106}, pp. 28-32, 2009). We find that due to the combined effects of thermodynamics and mechanics, $g(h)$ spreads during winter and contracts during summer. This behavior is in agreement with recent satellite observations from CryoSat-2 (Kwok \& Cunningham, \emph{Phil. Trans. R. Soc. A} {\bf 373}, 20140157, 2015). Because $g(h)$ is a probability density function, we quantify all of the key moments (e.g., mean Thickness, fraction of thin/thick ice, mean albedo, relaxation time scales) as greenhouse-gas radiative forcing, $\Delta F_0$, increases. The mean ice Thickness decays exponentially with $\Delta F_0$, but {\em much slower} than do solely thermodynamic models. This exhibits the crucial role that ice mechanics plays in maintaining the ice cover, by redistributing thin ice to thick ice--far more rapidly than can thermal growth alone.
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theory of the sea ice Thickness Distribution
Physical Review Letters, 2015Co-Authors: Srikanth Toppaladoddi, J S WettlauferAbstract:We use concepts from statistical physics to transform the original evolution equation for the sea ice Thickness Distribution g(h) from Thorndike et al. into a Fokker-Planck-like conservation law. T ...
Marika M Holland - One of the best experts on this subject based on the ideXlab platform.
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influence of the sea ice Thickness Distribution on polar climate in ccsm3
Journal of Climate, 2006Co-Authors: Marika M Holland, Cecilia M Bitz, William H Lipscomb, Elizabeth C Hunke, J L SchrammAbstract:Abstract The sea ice simulation of the Community Climate System Model version 3 (CCSM3) T42-gx1 and T85-gx1 control simulations is presented and the influence of the parameterized sea ice Thickness Distribution (ITD) on polar climate conditions is examined. This includes an analysis of the change in mean climate conditions and simulated sea ice feedbacks when an ITD is included. It is found that including a representation of the subgrid-scale ITD results in larger ice growth rates and thicker sea ice. These larger growth rates represent a higher heat loss from the ocean ice column to the atmosphere, resulting in warmer surface conditions. Ocean circulation, most notably in the Southern Hemisphere, is also modified by the ITD because of the influence of enhanced high-latitude ice formation on the ocean buoyancy flux and resulting deep water formation. Changes in atmospheric circulation also result, again most notably in the Southern Hemisphere. There are indications that the ITD also modifies simulated sea...
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simulating the ice Thickness Distribution in a coupled climate model
Journal of Geophysical Research, 2001Co-Authors: Cecilia M Bitz, Marika M Holland, Andrew J WeaverAbstract:Climate simulations in a global coupled model are investigated using a dynamic-thermodynamic sea ice and snow model with sophisticated thermodynamics and a subgrid scale parameterization for multiple ice Thicknesses. In addition to the sea ice component, the model includes a full primitive-equation ocean and a simple energy-moisture balance atmosphere. We introduce a formulation of the ice Thickness Distribution that is Lagrangian in Thickness-space. The method is designed to use fewer Thickness categories because it adjusts to place resolution where it is needed most and it is free of diffusive effects that tend to smooth Eulerian Distributions. Experiments demonstrate that the model does reasonably well in simulating the mean Arctic climate. We find the climate of the Arctic and northern North Atlantic is sensitive to resolving the ice-Thickness Distribution when comparing the model results to a simulation with a two-level sea ice model. The ice-Thickness Distribution causes ice export through Fram Strait to be more variable and more strongly linked to meridional overturning in the North Atlantic Ocean. The Lagrangian formulation of the ice-Thickness Distribution allows for the inclusion of a vertical temperature profile with relative ease compared to an Eulerian method. We find ice growth rates and ocean surface salinity differ in our model with a well-resolved vertical temperature profile in the ice and snow and an explicit brine-pocket parameterization compared to a simulation with Semtner zero-layer thermodynamics. Although these differences are important for the climate of the Arctic, the effects of an ice Thickness Distribution are more dramatic and extend into the northern North Atlantic. Sensitivity experiments indicate that five ice-Thickness categories with ∼50-cm vertical temperature resolution capture the effects of the ice-Thickness Distribution on the heat and freshwater exchange across the surface in the presence of sea ice in these simulations.
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modeling the thermodynamics of a sea ice Thickness Distribution 1 sensitivity to ice Thickness resolution
Journal of Geophysical Research, 1997Co-Authors: J L Schramm, Marika M Holland, Judith A Curry, Elizabeth E EbertAbstract:A one-dimensional ice Thickness Distribution model is presented to determine the minimum number of ice Thicknesses necessary to resolve the area-averaged annual cycles of ice Thickness and turbulent fluxes. The baseline case includes 40 ice Thickness categories; ice Thickness and area, meltwater ponds, ice salinity and age, snow cover, and surface albedo evolve independently for each ice category. A ridging and ice export parameterization, and a coupled one-dimensional ocean mixed layer model are also included. Sensitivity studies indicate that 16 ice Thickness categories can accurately resolve the baseline annual cycles of area-averaged ice Thickness and the summertime turbulent fluxes in this model, provided that one third of the Thickness categories represent ice thinner than 0.8 m. Resolving the Distribution of ice in this Thickness range is important in simulating the area-averaged ice characteristics. Wintertime values of the turbulent fluxes differ from the baseline by up to 1 W m−2 for fewer than 40 ice Thickness categories. The large difference in turbulent fluxes between open water and ice thicker than 1.6 m makes the area-averaged value sensitive to the number of ice Thickness categories, since this number can affect the categories that are merged, the categories that melt completely, ice that is ridged, and the resolution of the ice Thickness Distribution. This makes an accurate simulation of the baseline wintertime turbulent fluxes difficult. Model simulations with fewer than 40 categories provide a reasonable estimate of the baseline response to a surface longwave heat flux perturbation of greater than 5 W m−2. The annually area-averaged ice Thickness is within 10 cm. The model response to a heat flux perturbation of less than 5 W m−2 is similar for a wide range of ice Thickness categories, since the Thickness Distribution of ice thinner than 1 m is not affected.
J L Schramm - One of the best experts on this subject based on the ideXlab platform.
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influence of the sea ice Thickness Distribution on polar climate in ccsm3
Journal of Climate, 2006Co-Authors: Marika M Holland, Cecilia M Bitz, William H Lipscomb, Elizabeth C Hunke, J L SchrammAbstract:Abstract The sea ice simulation of the Community Climate System Model version 3 (CCSM3) T42-gx1 and T85-gx1 control simulations is presented and the influence of the parameterized sea ice Thickness Distribution (ITD) on polar climate conditions is examined. This includes an analysis of the change in mean climate conditions and simulated sea ice feedbacks when an ITD is included. It is found that including a representation of the subgrid-scale ITD results in larger ice growth rates and thicker sea ice. These larger growth rates represent a higher heat loss from the ocean ice column to the atmosphere, resulting in warmer surface conditions. Ocean circulation, most notably in the Southern Hemisphere, is also modified by the ITD because of the influence of enhanced high-latitude ice formation on the ocean buoyancy flux and resulting deep water formation. Changes in atmospheric circulation also result, again most notably in the Southern Hemisphere. There are indications that the ITD also modifies simulated sea...
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modeling the thermodynamics of a sea ice Thickness Distribution 1 sensitivity to ice Thickness resolution
Journal of Geophysical Research, 1997Co-Authors: J L Schramm, Marika M Holland, Judith A Curry, Elizabeth E EbertAbstract:A one-dimensional ice Thickness Distribution model is presented to determine the minimum number of ice Thicknesses necessary to resolve the area-averaged annual cycles of ice Thickness and turbulent fluxes. The baseline case includes 40 ice Thickness categories; ice Thickness and area, meltwater ponds, ice salinity and age, snow cover, and surface albedo evolve independently for each ice category. A ridging and ice export parameterization, and a coupled one-dimensional ocean mixed layer model are also included. Sensitivity studies indicate that 16 ice Thickness categories can accurately resolve the baseline annual cycles of area-averaged ice Thickness and the summertime turbulent fluxes in this model, provided that one third of the Thickness categories represent ice thinner than 0.8 m. Resolving the Distribution of ice in this Thickness range is important in simulating the area-averaged ice characteristics. Wintertime values of the turbulent fluxes differ from the baseline by up to 1 W m−2 for fewer than 40 ice Thickness categories. The large difference in turbulent fluxes between open water and ice thicker than 1.6 m makes the area-averaged value sensitive to the number of ice Thickness categories, since this number can affect the categories that are merged, the categories that melt completely, ice that is ridged, and the resolution of the ice Thickness Distribution. This makes an accurate simulation of the baseline wintertime turbulent fluxes difficult. Model simulations with fewer than 40 categories provide a reasonable estimate of the baseline response to a surface longwave heat flux perturbation of greater than 5 W m−2. The annually area-averaged ice Thickness is within 10 cm. The model response to a heat flux perturbation of less than 5 W m−2 is similar for a wide range of ice Thickness categories, since the Thickness Distribution of ice thinner than 1 m is not affected.
William H Lipscomb - One of the best experts on this subject based on the ideXlab platform.
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influence of the sea ice Thickness Distribution on polar climate in ccsm3
Journal of Climate, 2006Co-Authors: Marika M Holland, Cecilia M Bitz, William H Lipscomb, Elizabeth C Hunke, J L SchrammAbstract:Abstract The sea ice simulation of the Community Climate System Model version 3 (CCSM3) T42-gx1 and T85-gx1 control simulations is presented and the influence of the parameterized sea ice Thickness Distribution (ITD) on polar climate conditions is examined. This includes an analysis of the change in mean climate conditions and simulated sea ice feedbacks when an ITD is included. It is found that including a representation of the subgrid-scale ITD results in larger ice growth rates and thicker sea ice. These larger growth rates represent a higher heat loss from the ocean ice column to the atmosphere, resulting in warmer surface conditions. Ocean circulation, most notably in the Southern Hemisphere, is also modified by the ITD because of the influence of enhanced high-latitude ice formation on the ocean buoyancy flux and resulting deep water formation. Changes in atmospheric circulation also result, again most notably in the Southern Hemisphere. There are indications that the ITD also modifies simulated sea...
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remapping the Thickness Distribution in sea ice models
Journal of Geophysical Research, 2001Co-Authors: William H LipscombAbstract:In sea ice models with multiple Thickness categories the ice Thickness Distribution evolves in time. The evolution of the Thickness Distribution as ice grows and melts is analogous to one-dimensional fluid transport and can be treated by similar numerical methods. One such method, remapping, is applied here. Thickness categories are represented as Lagrangian grid cells whose boundaries are projected forward in time. The Thickness Distribution is approximated as a linear or quadratic polynomial in each displaced category, and ice area and volume are transferred between categories so as to restore the original boundaries. In simple test problems and in a single-column model with forcing typical of the central Arctic, remapping performs significantly better than methods previously used in sea ice models. It is less diffusive than a scheme that fixes the ice Thickness in each category and behaves better numerically than a scheme that represents the Thickness Distribution as a set of delta functions. Also, remapping converges faster (i.e., with fewer Thickness categories) than the alternative schemes. With five to seven categories the errors due to finite resolution of the Thickness Distribution are much smaller than the errors due to other sources. Linear remapping performs as well as the more complex quadratic version and is recommended for climate modeling. Its computational cost is minimal compared to other sea ice model components.
Adam Wax - One of the best experts on this subject based on the ideXlab platform.
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multiplexed low coherence interferometry instrument for measuring microbicide gel Thickness Distribution
Applied Optics, 2009Co-Authors: Tyler K Drake, Francisco E Robles, Adam WaxAbstract:We present a Fourier-domain, multiplexed low coherence interferometry (LCI) instrument designed for application to intravaginal measurement of microbicidal gel Distribution. Microbicide gels are topical products developed to combat sexually transmitted diseases, such as HIV/AIDS, by acting as delivery vehicles for active drugs and barrier layers to vaginal tissue. Measuring microbicide gel vaginal Distribution is key to understanding the gel's biological effectiveness. This study presents a new LCI system for measuring gel Distribution that uses six multiplexed channels to achieve broad area scanning without the need for a mechanical scanner. The presented results characterize the performance of the Fourier-domain multiplexed LCI system in measuring gel Thickness Distribution. The system demonstrates good optical signal-to-noise ratio, steady performance across all channels, negligible cross talk, and accurate measurement with micrometer scale resolution. The potential impact of using a multiplexed LCI system for in vivo measurements is also discussed.
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multiplexed low coherence interferometry instrument for measuring microbicide gel Thickness Distribution
Biomedical optics, 2008Co-Authors: Tyler K Drake, Francisco E Robles, Adam WaxAbstract:We present a multiplexed low coherence interferometry (LCI) system for in-vivo human vaginal imaging of microbicidal gel Distribution. In-vitro testing demonstrated high accuracy and linearity of LCI in measuring gel coating Thickness up to 500µm.
