Paired δ13C and δ18O Analysis of Distichia muscoides from High Andean Peatlands in Colombia to Constrain Climate Change Since the Little Ice Age
Abstract
Recent climate change has resulted in drastic impacts on the alpine tundra "páramo" in the Colombian high Andes. However, short instrumental records and lack of high-resolution paleoenvironmental data from high elevations hinders our understanding of climate variability, its forcing mechanisms, and its influence on mountain ecology. Here we present a multi-proxy study from two high-elevation peatlands on the interior slope of the Sierra Nevada del Cocuy (6.4°N, 72.4°W) to fill this major knowledge gap. Both peatlands, Chapetona (4,196 m asl) and Cusiri (4,084 m asl), are currently dominated by the vascular cushion forming plant Distichia muscoides (Juncaceae)—found throughout the Andes above 4000 m elevation. We use paired isotopic analysis (δ13C, δ18O) of Distichia α-cellulose, together with a modern process study, to refine a paleoclimate record from the high Andes. The Cusiri peatland shows slow accumulation rates, 2 m over 10,900 years. In contrast, the Chapetona peatland initiated 4,300 years ago, accumulating 4.2 m of peat. Preliminary results from the Chapetona peatland show that Distichia domination started at the end of the Little Ice Age (LIA) and has since accumulated 1.4 m, allowing us to reconstruct a very high resolution isotopic record spanning the end LIA-to-recent climate warming transition. Field observations show consistent differences in Distichia morphology along the cushion edge to top gradient, with leaves progressively becoming smaller as the surface becomes drier. Leaf sample isotope results along this modern Distichia cushion transect show a positive relationship between δ13C and δ18O(R2 = 0.55), indicating greater discrimination against 13CO2 due to moisture stress and resultant higher δ13C values as well as greater evaporative enrichment of δ18O in leaf water on cushion tops. In down-core analysis, we use δ13C to constrain peatland moisture and evaporative conditions, which allows us to distinguish climatic (air temperature, precipitation amount, or moisture sources) from local hydrological controls of down-core δ18O variations. The results will provide one of the first independent peat-based isotopic records to test LIA climate inferences (low temperature and high precipitation) based on nearby glacial moraines and lake-based glacier dynamics in the northern Andes.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMPP23D1526B
- Keywords:
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- 3335 North American Monsoon;
- ATMOSPHERIC PROCESSESDE: 0473 Paleoclimatology and paleoceanography;
- BIOGEOSCIENCESDE: 4914 Continental climate records;
- PALEOCEANOGRAPHYDE: 4938 Interhemispheric phasing;
- PALEOCEANOGRAPHY