Long-term precipitation isotopes (δ18O, δ2H, d-excess) at Denali National Park, Alaska: Implications for the Mt Hunter ice core climate record

Theme 1. Environmental protection
Session Name 1.10 Biogeochemical cycles in Arctic forests
Datetime Sep 07, 2018 01:30 PM - 01:45 PM (UTC +3)
Presentation Type Oral
Author(s) Hannah Bailey (University of Oulu, Finland), Eric Klein (University of Alaska Anchorage, USA), Dave Schirokauer (Denali National Park Service, USA), Erich Osterberg (Dartmouth College, USA), Jeffrey Welker (University of Oulu, Finland)
Abstract text

The Arctic hydrologic cycle is undergoing pronounced change. Reduced albedo due to declining sea ice extent is amplifying Arctic temperatures and atmospheric humidity, leading to complex seasonal patterns of synoptic weather, precipitation and evaporation. To better understand the patterns and changes in the Alaskan water cycle we are using a long-term record (1989-2018) of precipitation isotopes (δ18O, δ 2H and d-excess values) from Denali National Park, and applying this modern understanding of the water cycle to resolve historical climates and weather (1900-2010) preserved in a new Denali ice core (Mt. Hunter, 3900 m elevation). For each precipitation event, moisture source regions are identified using the NOAA hybrid single-particle Lagrangian integrated trajectory (HYSPLIT) model coupled with climate reanalysis datasets. Each event is further examined in context of climate variables (e.g. temperature, precipitation amount, relative humidity) and synoptic indices (e.g. the Arctic Oscillation). The data reveal a migrating moisture source region that typically fluctuates between the south (Pacific), west (Bering), and north (Arctic), with characteristic isotopic ‘fingerprints’ unique to each source region. Accordingly, the Mt. Hunter ice core mean annual δ18O and δ 2H records are statistically significantly correlated (p < 0.05) with mean annual temperatures in the North Pacific and Bering Sea from 1900-2010. Our analyses indicates a direct link between atmospheric circulation and the Arctic water isotope cycle, and provide an improved understanding of past, present, and future geochemical changes under variable synoptic conditions.

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