Date of Award

2010-01-01

Degree Name

Master of Science

Department

Geology

Advisor(s)

Craig E. Tweedie

Abstract

The Arctic appears to be affected by climate change more so than any other region on Earth. Some of the most significant climate change impacts reported for the Arctic are associated with dramatic shifts in the hydrologic regime of terrestrial ecosystems. Understanding the hydrologic processes that are associated with different components of arctic terrestrial ecosystems is important because water in the form of snow or rain influences a range of properties and processes such as land-atmosphere energy and trace gas fluxes, nutrient cycling, ecosystem dynamics, biodiversity, periglacial processes and surface albedo. Furthermore, plants, animals, and native people of the Arctic depend on these ecosystems and a substantial hydrologic shift could significantly impact provision of ecosystem goods and services and, therefore, natural system and human well being.

A climatic warming and drying trend has been observed in Northern Alaska, near the Iñupiat Village of Barrow as well as elsewhere in the Arctic. Importantly, there remains a great deal of uncertainty as to how coastal tundra ecosystems will respond to such a trend. To assist in addressing this uncertainty, a large-scale, multi-investigator flooding and draining experiment was initiated in summer 2005, and plot to landscape responses of multiple parameters (i.e. soil moisture, plant phenology, and trace gas flux) were measured. The experimental area was situated on the Barrow Environmental Observatory in a vegetated drained thaw-lake basin (DTLB) that was divided into three treatment areas: an experimentally flooded section, an experimentally drained section, and a control section that was not flooded or drained. For this thesis, baseline hydrology data were gathered between 2005 and 2007, prior to the initiation of the flooding and draining experiment. Measurements were continued in 2008 but under experimental conditions (+/- 10 cm flooding/draining respectively). The overarching goal of this thesis is to characterize baseline hydrologic conditions in the experimental DTLB as a contribution to the Biocomplexity Initiative sponsored by the US National Science Foundation.

Climate data from the NOAA Earth Systems Research Lab, (Global Monitoring Division's online U.S. Climate Reference Network) were attained to plot summer climatic conditions at the study site for June-August of years 2005 through 2008. Average precipitation for all years was a few millimeters lower than the average 29 year precipitation reported by the NOAA and average temperature was virtually the same as the 29 year average. Data from an air-borne LIght Detection And Ranging (LiDAR) survey were processed with ArcGIS 9.2 Geographic Information System (GIS) software to develop a Digital Elevation Model (DEM) of the experimental area. ArcHydro, an extension to ArcGIS, was used to locate research infrastructure such as the dikes and model the catchment and drainage network of the study area. Snow depth measurements were taken along a 100m grid in the experimental DTLB. Snow depths were then converted to snow water equivalent measurements (SWE). Averaged over all years, snow depth and SWE fell within the range of other snow depth and SWE measurements in the Barrow region. Seasonal water table depth and thaw depth were collected in each experimental treatment and analyzed, using the statistical software JMP 8, to identify inter-annual and treatment differences. Following initiation of the manipulation, significant differences between the treatments were observed for thaw depth and water table depth. Water table depth was highest (close to the ground surface) in the flooded treatment and lowest (deepest underground) in the control treatment for summer 2007. In 2008, water table was highest in the flooded treatment, but lowest in the drained treatment. Maximum thaw depth occurred in the flooded treatment for summers 2007 and 2008. Minimum thaw depth was recorded in the control treatment in 2007 and the drained treatment in 2008. Confidence curves fit to normalized seasonal time series of pond water levels indicate that ponds, in general, behaved in a uniform manner. A pre and post test of water levels in their respective treatment sections reveals that differences in water levels between each treatment for summers 2005-2008 were not significant. HOBO water level loggers were used to record pond temperature and the average temperature from all ponds was within range of pond temperatures recorded in the 1960's and 1970's. Meyer's evaporation equation was used to calculate evaporation. Results were a few millimeters higher than other evaporation rates for the region. This suggests evaporation may be the primary control on surface hydrology in ponds within the experimental area.

Continued long-term monitoring of hydrologic variables such as the ones observed in this thesis is important because natural and anthropogenic disturbances to hydrology can alter drainage patterns, geomorphic processes, vegetation structure and function, and land-atmoshphere feedbacks. This thesis documented substantial inter-annual variability and long term observations are likely to be needed to determine long term trends.

Language

en

Provenance

Received from ProQuest

File Size

85 pages

File Format

application/pdf

Rights Holder

Edith Jaurrieta de Velasco

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