Analysis of Glacial Change in the Northern Antarctic Peninsula Region Using Photogrammetry
Clearly and robustly documenting global climate change over this past century remains a key goal for
researchers. Polar regions are an ideal place to study change, since they are particularly sensitive to
temperature changes. As part of an International Polar Year (IPY) grant called IPY-ROAM (Research and
Educational Opportunities in Antarctica for Minorities), faculty at the University of Texas at El Paso (UTEP) took
29 underrepresented minority students and teachers on a research expedition to Antarctica over winter break
2007. One goal of the program was to document glacial change along the Antarctic Peninsula over the past
century using photogrammetry, a technique that uses photos to make accurate geographic measurements.
Prior to embarkation, we gathered historic photos of glaciers along our travel route. During the expedition, new
photos were taken within the old photo sites, where we made Global Positioning System (GPS) readings and
accurately measurement angles to the geographic features. The geographic features (including top and
bottom of a glacier) were then mapped onto a Geographical Information Systems (GIS) that allowed us to
determine location, scale and distance to these features on the photos. With the angle and distance, the height
difference between the old and current photo of the glacier was calculated using basic trigonometric functions.
In one case, we determined a 14 m reduction in glacier height from 1934 to 2007. Future work will include
analysis from more glaciers in the region, and to determine if there is a correlation between glacier retreat and
Generalization of the University of Toronto Glacial Systems Model: A New Numerical Framework with Unstructured Grids
We will describe new work relating to the ongoing development and enhancement of the University of Toronto Glacial Systems Model (GSM). Various versions of the GSM have been successfully employed in the past for paleoclimate applications such as the simulation of the glacial history of Greenland. The overall modelling framework has accumulated many advanced features, including the capacity to simulate glacial isostatic adjustment and the logic for automatic neural network optimization of parameters with respect to sparse observational data. The full exploitation and extension of such features has, however, been limited by the software organization of earlier versions of the GSM modelling system. For this reason, we have undertaken to formulate an updated GSM model based on an ocean modelling framework that we developed previously. One of the new features that will come out of this work is the capacity to use unstructured grids in ice-sheet modelling. When spatial domains are discretized using general triangulations, resolution can be arbitrarily enhanced near dynamically crucial ice margins and ice streams. We aim to demonstrate some of the enhanced GSM features in the context of Greenland ice-sheet simulations.
A micro-hydrometeorological study on the Peyto Glacier.
A micrometeorological experiment was conducted in the summer of 2008, at Peyto Glacier, during three periods of dry, warm weather and one of moist, cool weather. The data include a breakdown of net radiation into its short- and long-wave components, as well as wind speed, temperature and humidity profile data for use in bulk transfer estimates of sensible heat and moisture transfer. In addition, a micro-hyrological experiment was conducted, the data comprising sonic sounder measurements of ablation and stage level records of discharge from a supra-glacial catchment. As expected, there is short-term divergence between energy budget and ablation estimates of meltwater production because of weathering crust development. Also, the conversion of stage level data into discharge from a supra-glacial catchment presents challenges, not the least of which is to define the area of the catchment. Nevertheless, it is clear that peak discharge can lag peak meltwater energy input by periods of four to six hours. This suggests that a substantial part of the delay in runoff from a glacierized basin is tied up in ice surface hydrological processes.
Snowpack Variability Across Two Small Watersheds
Snowpack is highly variable across different scales of terrain and with changing land cover. Previous research has used various terrain properties, such as elevation, slope, aspect, northness, occasionally at different resolutions, to estimate the distribution of snowpack properties. Snow depth is among the easiest snowpack properties to measure. The variability of snow depth across two Watershed of differing characteristics is investigated. One watershed is in northern Colorado and the other is on Byers Peninsula of Livingston Island, Antarctica. We use several techniques to quantify variability and show that scaling is more crucial with some methods of quantification than others. We can use some of these methods to determine the resolution of future sampling.
Englacial Stress and Velocity Fields: Comparison of Finite-Element Approximations to Exact Solutions
The quasi-stationary motion of a two-dimensional glacier is considered. For a given transient geometry, glacier ice is treated as an incompressible non-Newtonian fluid to calculate englacial velocity and stress fields. Powerful finite-element software for multiphysical problems, Elmer, is used to solve Stokes equation by treating the stress-dependent effective viscosity in an iterative fashion. The zeroth order (so called Shallow Ice Approximation) stress field is computed and compared to the exact solution. In addition, outcomes of higher- order stress field analyses are compared to other studies such as (i) analytical solution of gravity driven flow down an inclined plane [Paterson, 1994, The physics of Glaciers (3rd ed.), p. 251-253], (ii) analytical englacial stress field [Bahr, 1996, Mathematical Geology 28 (2), p. 229-251], and (iii) analytical transfer functions for velocity field [Gudmundsson, 2003, Journal of Geophysical Research 108 (B5), 2253].
Arctic sea ice Freeboard Heights From ICESat Laser Altimetry
Arctic sea ice extent has been decreasing at a rate of about 10% per decade, since the earliest satellite observations in 1979. This decline is mainly attributed to climate change and variability. The effect of climate change is more pronounced in the Arctic because of the ice-albedo feedback effect which accelerates the melting process. In order to understand the changing Arctic sea ice cover, the change in sea ice volume must be known (both extent and thickness). Sea ice thickness is an important parameter that moderates the heat exchange between the ocean and the atmosphere which affects the Earth's climate. Despite about 200 years of research and observations in the Arctic, detailed observations at large-spatial scales and long continuous time-series are not available. In this study, satellite laser altimetry data from ICESat (NASA's Ice, Cloud, and Elevation Satellite) have been used to estimate Arctic sea ice freeboard heights based on the models of geoid (EIGEN-GL04), ocean tides (AOTIM-5), and mean dynamic topography. Sea ice freeboard can be eventually converted into thickness, if the physical properties of the ice pack are known using hydrostatic equilibrium assumptions. Current limitations in this method are the lack of information on the depth of the overlying snow layer and the uncertainties in the oceanographic models. Sea ice freeboard results from ICESat for mission phases from 2003 to 2008 will be discussed.
Sublimation of snow in low arctic tundra
Sublimation is a difficult process to measure directly and modeling provides only a general quantification of the process over larger areas. Complicated topography provides a range of environments where snow can be eroded and deposited. In this study, located in the Coppermine River basin of the Northwest Territories, Canada, we were interested in quantifying the variability of sublimation loss in the tundra snowpack in a variety of depositional environments. At locations representing the range of depositional environments snowpits were excavated at the end of the snow accumulation period just prior to springmelt in April 2006,07 and 08. At each snowpit individual strata were sampled for water equivalent and chemical analysis. Through these winter periods individual snow events were sampled in Nipher gauges (located 50km southeast of our field site) by Ekati Diamond Mine staff. Water equivalent of each storm was recorded and samples for chemical analysis were shipped south. Weighted mean cation and anion concentrations for each snow season were calculated and compared to the weighted mean cation and anion concentration from each snowpit site. Sublimation will result in water loss but retention of ions thus enrichment of the snowpack samples relative to the 'Nipher' annual snowpack sample was assumed to represent sublimation of the snowpack. Depending on the depositional environment sublimation ranged between 17% and 35%.