Reconstruction of Past Environmental Changes in Southern Patagonia Using Stable Isotopes

Authors: Kristen Sarna*, Department of Geography, Texas A&M University, Julie Loisel, Department of Geography, Texas A&M University
Topics: Paleoenvironmental Change, Water Resources and Hydrology
Keywords: Paleoclimate reconstruction, stable isotopes, Patagonia, cellulose, peat, Sphagnum magellanicum
Session Type: Poster
Day: 4/11/2018
Start / End Time: 8:00 AM / 9:40 AM
Room: Napoleon Foyer/Common St. Corridor, Sheraton, 3rd Floor
Presentation File: No File Uploaded

Paleoclimate reconstructions allow us to build a better picture of how climate has changed over time. However, relatively little research has been done in the higher latitudes of the southern hemisphere, leaving a gap in our knowledge. Changes in temperature and moisture can have significant impacts on local vegetation growth structure and ecosystem functioning; these changes in hydroclimatic conditions can be traced using stable isotope analysis of carbon (δ13C), oxygen (δ18O), and hydrogen (δ2H) in peat deposits. Here we aim to determine the effects of changes in precipitation amounts and sources of moisture in southernmost Patagonia using peat-core samples collected in 2010. The top 350 cm (~ 4200 cal. BP) of the core was analyzed in 2 centimeter increments. For each horizon, Sphagnum magellanicum moss stems were hand-picked and cleaned. Cellulose from those moss stems was then extracted following the alkaline bleaching method. Samples are currently being analyzed for δ13C, δ18O, and δ2H using a mass spectrometer. On the basis of previous studies and our own surface calibration analysis, we anticipate δ13C values to reflect surface moisture conditions, with cellulose values that are more depleted in the heavier isotope corresponding to wetter conditions (and vice versa). We expect water isotope values (δ18O and δ2H) to reflect changes in the dominant moisture source, with westerly wind flows being depleted in the heavier isotopes but also more impacted by evaporative enrichment. The combination of all three isotopes will allow us to tease apart local (soil moisture) vs. regional (moisture source) environmental effects.

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