Browsing by Author "Richter-Menge, Jacqueline A."
Now showing 1 - 3 of 3
Results Per Page
Sort Options
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.Item Spatial and temporal characterization of sea-ice deformation(International Glaciological Society, 2011) Hutchings, J. K.; Roberts, A.; Geiger, Cathleen A.; Richter-Menge, Jacqueline A.; Hutchings, J. K., Roberts, A., Geiger, Cathleen A., Richter-Menge, J.; Geiger, Cathleen A.In late March 2007 an array of GPS ice drifters was deployed in the Beaufort Sea as part of the Sea Ice Experiment: Dynamic Nature of the Arctic (SEDNA). The drifters were deployed in an array designed to resolve four, nested spatial scales of sea-ice deformation, from 10 to 140 km, with the arrays maintaining appropriate shape for strain-rate calculation until mid-June. In this paper, we test whether sea-ice deformation displays fractal properties in the vicinity of SEDNA. We identify that deformation time series have different spectral properties depending on the spatial scale. At the scales around 100 km, deformation is a red-noise process, indicating the importance of the ice-pack surface forcing in determining the deformation rate of sea ice at this scale. At smaller scales, the deformation becomes an increasingly whiter process (it has pink noise properties), which suggests an increasing role of dissipative processes at smaller scales. At spatial scales of 10-100 km, and sub-daily scales, there is no deformation coherence across scales; coherence only becomes apparent at longer scales greater than 100 km. The lack of coherence at small scales aids in understanding previous observations where correlation between 10 km regions adjacent to each other varied widely, with correlation coefficients between 0.3 and 1. This suggests it is not appropriate to think of sea ice as having a decorrelation length scale for deformation. We find that lead scale observations of deformation are required when estimating ice growth in leads and ridging time series. For the two SEDNA arrays, we find coherence between 140 and 20 km scale deformation up to periods of 16 days. This suggests sea-ice deformation displays coherent deformation between 100 km scale and the scale of the Beaufort Sea (of order 1000 km), over synoptic time periods (daily to weekly timescales). Organization of leads at synoptic and larger scales is an emergent feature of the deformation field that is caused by the smooth variation of surface forcing (wind) on the ice pack.