Geochemistry of a Chilean glacier watershed for the 2013 Expedition to Cerro Plomo in the Chilean Andes
Written by Alfonso Fernández, Ohio State University, Byrd Polar Research Center, Columbus, OH
Glacier-fed streams emanating from Andean mountain valleys are essential for human welfare and also contain geochemical properties resulting from the many natural processes and phase changes that cycle water through the Earth System. By analyzing the chemical characteristics of the water sampled at various positions in the watershed, we are able to gain insights into these hydrologic pathways, and evaluate how water supply is affected by climate change. As one of the most easily recognizable water stores in nature, glacier ice and snow are key sources for maintaining relatively constant stream flows during dry months. Furthermore, mountain ice and snow significantly contribute to erosion processes that imbue stream runoff and meltwater with chemical compounds that get transported downstream, and can be beneficial for other environments.
The Chile Glacier Quest Team will be able to sample stream waters and sediments as they ascend the valley, and even up to the glacier snow and ice. The purpose of this survey is to establish a baseline of fundamental geochemical characteristics of the water draining the Cepo Valley. This will be an excellent opportunity to test hypotheses about the relative influence of climate, elevation, and bedrock geology.
Back in the lab, we will use different techniques such as ion chromatography and mass spectrometry to analyze the samples for standard chemical properties: water isotopes (Hydrogen-Deuterium and Oxygen); major dissolved cations (Calcium, Magnesium, Sodium, and Potassium) and anions (Fluoride, Chloride, Nitrate, and Sulfate); and nutrients (Ammonia and Phosphate, for example). These characteristics of the water relate to factors like the precipitation sources, what percentage of meltwater feeds the streams, and the local geology. Coupled with glacier- climate modeling, mapping of previous glacier extents in satellite imagery, and subsequent fieldwork, these initial samples will be fundamental to understand whether and how much the snow and glacier ice contribute to water availability changes.
© Copyright 2013 Kurt J. Sanderson unless otherwise noted.