Browsing by Author "Samluk, Jesse P."
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Item Full-physics 3-D heterogeneous simulations of electromagnetic induction fields on level and deformed sea ice(International Glaciological Society, 2015-10-01) Samluk, Jesse P.; Geiger, Cathleen A.; Weiss, Chester J.; Jesse P. SAMLUK, Cathleen A. GEIGER, Chester J. WEISS; Samluk, Jesse P.; Geiger, Cathleen A.In this paper we explore simulated responses of electromagnetic (EM) signals relative to in situ field surveys and quantify the effects that different values of conductivity in sea ice have on the EM fields. We compute EM responses of ice types with a three-dimensional (3-D) finite-volume discretization of Maxwell’s equations and present 2-D sliced visualizations of their associated EM fields at discrete frequencies. Several interesting observations result: First, since the simulator computes the fields everywhere, each gridcell acts as a receiver within the model volume, and captures the complete, coupled interactions between air, snow, sea ice and sea water as a function of their conductivity; second, visualizations demonstrate how 1-D approximations near deformed ice features are violated. But the most important new finding is that changes in conductivity affect EM field response by modifying the magnitude and spatial patterns (i.e. footprint size and shape) of current density and magnetic fields. These effects are demonstrated through a visual feature we define as ‘null lines’. Null line shape is affected by changes in conductivity near material boundaries as well as transmitter location. Our results encourage the use of null lines as a planning tool for better ground-truth field measurements near deformed ice types.Item Impact of spatial aliasing on sea-ice thickness measurements(International Glaciological Society, 2015-10-01) Geiger, Cathleen A.; Müller, Hans-Reinhard; Samluk, Jesse P.; Bernstein, E. Rachel; Richter-Menge, Jacqueline A.; Cathleen GEIGER, Hans-Reinhard MÜLLER, Jesse P. SAMLUK, E. Rachel BERNSTEIN, Jacqueline RICHTER-MENGE; Geiger, Cathleen A.; Samluk, Jesse P.; Bernstein, E. RachelWe explore spatial aliasing of non-Gaussian distributions of sea-ice thickness. Using a heuristic model and >1000 measurements, we show how different instrument footprint sizes and shapes can cluster thickness distributions into artificial modes, thereby distorting frequency distribution, making it difficult to compare and communicate information across spatial scales. This problem has not been dealt with systematically in sea ice until now, largely because it appears to incur no significant change in integrated thickness which often serves as a volume proxy. Concomitantly, demands are increasing for thickness distribution as a resource for modeling, monitoring and forecasting air–sea fluxes and growing human infrastructure needs in a changing polar environment. New demands include the characterization of uncertainties both regionally and seasonally for spaceborne, airborne, in situ and underwater measurements. To serve these growing needs, we quantify the impact of spatial aliasing by computing resolution error (Er) over a range of horizontal scales (x) from 5 to 500 m. Results are summarized through a power law (Er = bxm) with distinct exponents (m) from 0.3 to 0.5 using example mathematical functions including Gaussian, inverse linear and running mean filters. Recommendations and visualizations are provided to encourage discussion, new data acquisitions, analysis methods and metadata formats.Item On the uncertainty of sea-ice isostasy(International Glaciological Society, 2015-10-01) Geiger, Cathleen A.; Wadhams, Peter; Müller, Hans-Reinhard; Richter-Menge, Jacqueline A.; Samluk, Jesse P.; DeLiberty, Tracy L.; Corradina, Victoria; Cathleen GEIGER, Peter WADHAMS, Hans-Reinhard MÜLLER, Jacqueline RICHTER-MENGE, Jesse SAMLUK, Tracy DELIBERTY, Victoria CORRADINA1; Geiger, Cathleen A.; DeLiberty, Tracy L.; Corradina, Victoria; Samluk, Jesse P.During late winter 2007, coincident measurements of sea ice were collected using various sensors at an ice camp in the Beaufort Sea, Canadian Arctic. Analysis of the archived data provides new insight into sea-ice isostasy and its related R-factor through case studies at three scales using different combinations of snow and ice thickness components. At the smallest scale (<1 m; point scale), isostasy is not expected, so we calculate a residual and define this as ��� (‘zjey’) to describe vertical displacement due to deformation. From 1 to 10m length scales, we explore traditional isostasy and identify a specific sequence of thickness calculations which minimize freeboard and elevation uncertainty. An effective solution exists when the R-factor is allowed to vary: ranging from 2 to 12, with mean of 5.17, mode of 5.88 and skewed distribution. At regional scales, underwater, airborne and spaceborne platforms are always missing thickness variables from either above or below sea level. For such situations, realistic agreement is found by applying small-scale skewed ranges for the R-factor. These findings encourage a broader isostasy solution as a function of potential energy and length scale. Overall, results add insight to data collection strategies and metadata characteristics of different thickness products.