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Impacts of Glacial Meltwater on Geochemistry and Discharge of Alpine Proglacial Streams in the Wind River Range, Wyoming, USA

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Impacts of Glacial Meltwater on Geochemistry and Discharge of Alpine Proglacial Streams in the Wind River Range, Wyoming, USA Brigham Young University BYU ScholarsArchive Theses and Dissertations 2019-07-01 Impacts of Glacial Meltwater on Geochemistry and Discharge of Alpine Proglacial Streams in the Wind River Range, Wyoming, USA Natalie Shepherd Barkdull Brigham Young University Follow this and additional works at: https://scholarsarchive.byu.edu/etd BYU ScholarsArchive Citation Barkdull, Natalie Shepherd, "Impacts of Glacial Meltwater on Geochemistry and Discharge of Alpine Proglacial Streams in the Wind River Range, Wyoming, USA" (2019). Theses and Dissertations. 8590. https://scholarsarchive.byu.edu/etd/8590 This Thesis is brought to you for free and open access by BYU ScholarsArchive. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. Impacts of Glacial Meltwater on Geochemistry and Discharge of Alpine Proglacial Streams in the Wind River Range, Wyoming, USA Natalie Shepherd Barkdull A thesis submitted to the faculty of Brigham Young University in partial fulfillment of the requirements for the degree of Master of Science Gregory T. Carling, Chair Barry R. Bickmore Stephen T. Nelson Department of Geological Sciences Brigham Young University Copyright © 2019 Natalie Shepherd Barkdull All Rights Reserved ABSTRACT Impacts of Glacial Meltwater on Geochemistry and Discharge of Alpine Proglacial Streams in the Wind River Range, Wyoming, USA Natalie Shepherd Barkdull Department of Geological Sciences, BYU Master of Science Shrinking alpine glaciers alter the geochemistry of sensitive mountain streams by exposing reactive freshly-weathered bedrock and releasing decades of atmospherically-deposited trace elements from glacier ice. Changes in the timing and quantity of glacial melt also affect discharge and temperature of alpine streams. To investigate the effects of glacier ice melt on the geochemistry and hydrology of proglacial streams in the arid Intermountain West, we sampled supraglacial meltwaters and proglacial streams in the Dinwoody Creek watershed in the Wind River Range, Wyoming during late summer 2015, when the contributions of glacier meltwater were highest. Supraglacial meltwater was enriched in 8 trace elements (Cd, Co, Cu, MeHg, Mn, Pb, THg, Zn) relative to proglacial meltwaters. Concentrations of major ions (Mg2+, K+, Na+, 2+ 2- Ca , SO4 ) and the remaining 30+ analyzed trace elements were enriched in proglacial streams relative to supraglacial meltwater. To evaluate the diurnal effects of glacial meltwater on the chemistry and hydrology of proglacial streams, we collected hourly water samples of Dinwoody Creek and deployed loggers to monitor water depth, temperature, and specific conductance (SPC) at 15-min intervals over a 1-week period. The influx of glacial meltwater between 10:00 and 20:00 diluted solute concentrations and affected the relative enrichment/depletion of highly soluble elements (major ions, alkaline earth elements), less than REEs. Stable isotopes of H and O (δD, δ18O) in Dinwoody Creek were more depleted during peak runoff (10:00 – 20:00) than base flow, reflecting contributions from isotopically depleted glacial meltwaters. Looping hysteresis patterns were observed between water depth versus DO, pH, temperature and SPC in glaciated streams. Hysteresis patterns were affected by changes in weather and varied depending on the type of stream (glaciated versus non-glaciated) and the distance to glacier toe. Combination of multiple hydrologic tracers (solute concentrations, high frequency logger data, stable isotopes) shows strong potential to improve estimates of glacial meltwater contributions to Dinwoody Creek. Our results suggest that elevated concentrations of heavy metals in glacier ice melt across the Intermountain West may negatively impact sensitive alpine streams. Keywords: glacier meltwater, geochemistry, diel cycle, trace metals, heavy metals, supraglacial meltwater, proglacial streams TABLE OF CONTENTS TABLE OF CONTENTS .......................................................................................................... iii LIST OF FIGURES ....................................................................................................................v SUPPLEMENTARY MATERIAL ............................................................................................ vi 1. Introduction .............................................................................................................................1 2. Methods ..................................................................................................................................4 2.1 Study Area ........................................................................................................................4 2.2 Sample data collection .......................................................................................................6 2.3 Lab analyses ......................................................................................................................8 2.4 Quality control ..................................................................................................................9 2.5 Statistical Analysis .......................................................................................................... 10 2.5.1 Data normalization.................................................................................................... 10 2.5.2 Nonmetric multidimensional scaling analysis ............................................................ 12 2.5.3 Hystericity analysis ................................................................................................... 13 3. Results .................................................................................................................................. 13 3.1 Stable isotopes from supraglacial and proglacial samples were distinct ............................ 13 3.2 Supraglacial and proglacial meltwaters contained different trace element concentrations . 14 3.3 Multivariate statistics show distinct geochemical groupings by sample type .................... 15 3.4 Trace element geochemistry of glacier-influenced streams differed from a non-glacial stream ................................................................................................................................... 16 3.5 Variations in proglacial stream chemistry over a 24-hour period ...................................... 17 3.5.1 Isotopic composition of Dinwoody Creek changed over 24-hour period .................... 17 3.5.2 Proglacial streams exhibited diel cycling and hysteresis patterns ............................... 18 3.5.3 Solute concentrations varied over 24-hour period ...................................................... 19 3.6 Timing and magnitude of daily water parameter fluctuation varied between glacial and non-glacial streams ................................................................................................................ 20 4. Discussion ............................................................................................................................. 20 4.1 Trace element contributions from atmospheric deposition and local weathering............... 20 4.2 Causes and effects of diel cycling in Dinwoody Creek ..................................................... 23 4.3 High frequency temperature, SPC, and depth loggers characterized differences between the timing and magnitude of runoff in glaciated and non-glaciated streams ................................. 25 4.4 Implications for future studies ......................................................................................... 28 iii 5. Conclusions ........................................................................................................................... 29 References ................................................................................................................................ 31 Figures ...................................................................................................................................... 35 SUPPLEMENTARY MATERIAL ............................................................................................ 48 SUPPLEMENTARY FIGURES ............................................................................................ 48 SUPPLEMENTARY TABLES ............................................................................................. 53 iv LIST OF FIGURES Figure 1. Study area map .......................................................................................................... 35 Figure 2. Study area weather and climate.................................................................................. 36 Figure 3. δ18O and δD composition........................................................................................... 37 Figure 4. Boxplot major elements ............................................................................................. 38 Figure 5. Boxplot selected trace elements ................................................................................. 39 Figure 6. NMS ordination ......................................................................................................... 40 Figure 7. Enrichment/depletion relative to non-glacial stream................................................... 41 Figure 8. Enrichment/depletion REEs relative to chondrite ......................................................
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