Browsing by Author "Wadhams, Peter"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
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 The relation between Arctic sea ice surface elevation and draft: A case study using coincident AUV sonar and airborne scanning laser(American Geophysical Union, 2011) Geiger, Cathleen A.; Wadhams, Peter; Skourup, H.; Doble, M. J.; Doble, M. J., Skourup, H., Wadhams, P., Geiger, Cathleen A.; Geiger, Cathleen A.Data are presented from a survey by airborne scanning laser profilometer and an AUV-mounted, upward looking swath sonar in the spring Beaufort Sea. The air-snow (surface elevation) and water-ice (draft) surfaces were mapped at 1 x 1 m resolution over a 300 x 300 m area. Data were separated into level and deformed ice fractions using the surface roughness of the sonar data. The relation (R = d/f) between draft, d, and surface elevation, f, was then examined. Correlation between top and bottom surfaces was essentially zero at full resolution, requiring averaging over patches of at least 11 m diameter to constrain the relation largely because of the significant error (similar to 15 cm) of the laser instrument. Level ice points were concentrated in two core regions, corresponding to level FY ice and refrozen leads, with variations in R attributed primarily to positive snow thickness variability. Deformed ice displayed a more diffuse "cloud," with draft having a more important role in determining R because of wider deformed features underwater. Averaging over footprints similar to satellite altimeters showed the mean surface elevation (typical of ICESat) to be stable with averaging scale, with R = 3.4 (level) and R = 4.2 (deformed). The "minimum elevation within a footprint" characteristic reported for CryoSat was less stable, significantly overestimating R for level ice (R > 5) and deformed ice (R > 6). The mean draft difference between measurements and isostasy suggests 70 m as an isostatic length scale for level ice. The isostatic scale for deformed ice appears to be longer than accessible with these data (>300 m).