Glaciochemical records from the Saint Elias Mountains, Yukon, Canada
While many paleoclimate records have been recovered from the North Atlantic sector of the Arctic, there is a gap in our understanding of climactic and environmental change in the North Pacific. Glaciochemical records from the St. Elias Mountains spanning an elevation range of three to five km provide a three-dimensional view of the paleo-atmosphere in this region. Three ice cores from Eclipse Icefield provide a high-resolution record of precipitation chemistry in the remote northwestern North America mid-troposphere and allow investigation of spatial and temporal variability in glaciochemical signals. Greater spatial variability is observed for species present as coarse mode dust and sea salt particles than for accumulation mode sulfate and ammonium aerosols or gas phase nitrate. Simultaneous sampling of aerosol and snow chemistry at King Col indicates large enrichments of nitrate and chloride in snow relative to aerosol by scavenging of gas phase nitric and hydrochloric acid. Back trajectories document the transport of Asian dust and anthropogenic emissions, the May 22 eruption plume of Sheveluch, Kamchatka, and sea salt from the Gulf of Alaska to King Col during the sampling period. The Eclipse ice cores provide a record of forest fire activity in Alaska and the Yukon that responds to anthropogenic influences such as the Klondike Gold Rush and natural climate variability such as the Medieval Warm Period. The Eclipse and Mt. Logan ice cores offer a record of regionally significant volcanic eruptions, with at least one-third of the eruptions recorded from Alaskan and Kamchatkan volcanoes. Major tropical eruptions are also recorded. The three Eclipse cores record similar volcanic sulfate fluxes from the largest eruptions such as Katmai, as well as some moderate eruptions. While a bipolar volcanic signal in 1809 is generally attributed to single tropical eruption, dacitic tephra from the Eclipse ice core that is chemically distinct from andesitic 1809 tephra found in Antarctica indicates a second eruption in the Northern Hemisphere at this time. Sulfate flux calculations suggest this eruption contributed little additional sulfate to circum-Arctic ice cores, and therefore had negligible climatic significance.
Geochemistry, Geology, Environmental Sciences
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