An ice core paleoclimate study of Windy Dome, Franz Josef Land (Russia): Development of a recent climate history for the Barents Sea.

摘要

A 315-meter ice core obtained in April-May, 1997 from the summit of Windy Dome, Franz Josef Land in the Russian high Arctic (81°N, 64°E, 509 masl) reflects 772 years of climate variability in the Barents Sea region. Paleotemperatures inferred from oxygen isotope (δ18O) calibration indicate a dramatic and sustained wintertime warming of more than 8°C occurring abruptly around 1910, halting the persistent cold temperatures of the Little Ice Age (LIA, ∼1450 to ∼1870 A.D.). Summer temperatures, related to meltwater formation, rose earlier (∼1850) but only by approximately 0.5°C relative to the LIA mean, consistent with regional tree-ring histories.; The age scale for the finely-sampled Windy Dome ice core was generated by three-parameter (chloride, δ18O, and melt-stratigraphy) reconciled layer counting, guided by the detection of recent nuclear testing horizons and nine known volcanic eruptions, and confirmed by duplicating the cosmogenic record of solar variability. Accordingly, a proposed common time scale based on this superior chronology is presented, that realigns previous Eurasian Arctic ice core records to illustrate a consistent pattern of climate change along the northern Barents continental margin from Nordauslandet, Svalbard to Severnaya Zemlya. While the temporal climate changes fit a global paradigm, it is cautioned that the wintertime fluctuations that occurred here represent a threshold change in the position of the polar front and should be weighted accordingly when considering hemispheric-scale climatology.; Soluble ionic constituents in the ice core reveal a strong signature of anthropogenic emissions by rising sulfate and nitrate levels, and also 20th century agricultural activity via ammonium. The degree of post-depositional modification of core parameters was quantified, with ion fractionation and multi-year percolation indicated to reduce concentrations of more mobile ions (e.g., SO₄2−, Mg2+) by up to 10–15%, and solid-liquid stable isotope fractionation currently responsible for a ∼0.9‰ difference between bubbly and melt-infiltrated ice. Regular oscillations in pH values suggest a succession of “stacked percolation cells” that are sealed and archived every 13–14 years on average. Periodicities of 40–70 years were detected by Singular-Spectrum Analysis (SSA) in several parameters, and the annual signal strength of δ 18O and chloride is shown to be related to the extent of meltwater formation and thereby summer temperatures.