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USGS NOROCK EcoLunch Seminar Series

Title: A full Holocene record of water isotopes from syngenetic pore ice in central Yukon Territory

Abstract: Ice core water isotope records are central to knowledge of Quaternary climates, but are restricted to glaciated locales. Millennial-scale knowledge of water isotope variability is largely absent in areas lacking glaciers today. Here we present a new ca. 13,000 year record of water isotopes (δD, δ18O, and d-excess) in central Yukon Territory based on a ~6 m core sequence of pore ice from a perennially frozen, soligenic peatland along the Dempster Highway (65.21°N, 138.32°W). The Dempster pore ice likely reflects late summer and early fall precipitation, and is a reasonable first-order proxy for late summer/early fall temperature due to the strong association between temperature and precipitation isotopes in Arctic and sub-Arctic North America. The Dempster pore ice δD reveals the (late summer/early fall) Holocene Thermal Maximum in this region was centered at ca. 9-7 ka BP, in close agreement with summer/fall insolation curve at 65°N. The last 7,000 years was characterised by a long, insolation-driven cooling trend, with the exception of recent climate warming which has countered this trend and may soon surpass peak Holocene warmth if the current rate of warming is sustained. This study demonstrates a new type of water isotope archive from a northern peatland, and more generally the potential to use syngenetic pore ice in permafrost regions to fill knowledge gaps in Holocene climate and water isotope systematics.

Location: First Floor Conference Room "Madison Room"- NOROCK, 2327 University Way, Suite 2.

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