Undergraduate Honors Theses

Thesis Defended

Spring 2017

Document Type

Thesis

Type of Thesis

Departmental Honors

Department

Geological Sciences

First Advisor

Robert Anderson

Second Advisor

Charles Stern

Third Advisor

Carol Wessman

Abstract

Snow bedforms, which are 3-dimensional features that form in the snow as a result of wind patterns, cover up to 11% of the Earth’s surface annually (Filhol et al., 2015). These features are widespread but have not yet been studied in great depth. Snow bedforms are concentrated at the poles of the Earth, and they therefore cover critical areas that are widely influential for many global processes, including Arctic energy balances, atmospheric and heat exchanges, and sea ice melt rates. These zones are changing rapidly as global temperatures increase, and further study on snow bedforms is essential to improve our understanding of the changing Arctic. Niwot Ridge on the Colorado Front Range proved to be an excellent site to investigate the conditions in which snow bedforms form, because the site is easily accessible and has strong, reliable winter winds. This paper examines the types of snow bedforms that occur on Niwot Ridge and the relative wind speeds and snow ages that lead to the specific formations. The main goal of the study was to quantify the weather conditions under which each type of bedform grows, which is imperative for future modeling of snow bedforms. We correlated the average and gusting wind speeds with the age and the type of bedform, and generated several comprehensive diagrams to illustrate the relationship between these variables. We found that stationary erosional features such as sastrugi formed in snow anywhere from 0-20 days old and under wind speeds of 10-20 m/s, moved only in snow younger than about 2 days with wind speeds from about 6-15 m/s. Depositional features such as dunes and ripples were almost always seen moving, and formed with snow less than two days old and with average wind speeds around 15 m/s. This information was then used to speculate and generate a figure on the conditions under which these bedforms fall. Snow bedforms affect surface roughness and land morphology and thus play a huge role in energy balances across the globe. Correlating weather patterns to snow formations will improve our understanding of how the planet will respond to a warming climate and allow us to infer what changes may come to our larger snow-covered land masses.

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