A Coherent Signature of Anthropogenic Nitrogen Deposition to Remote Watersheds of the Northern Hemisphere

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Science  16 Dec 2011:
Vol. 334, Issue 6062, pp. 1545-1548
DOI: 10.1126/science.1212267

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  1. Fig. 1

    Locations and sediment δ15N profiles from Northern Hemisphere lakes grouped by ecotype: temperate/boreal (green circles), alpine (blue circles), and arctic (red circles). Twenty-five of the original 33 lakes were included in the hierarchical model of N isotopic depletion (solid circles). The remaining eight lakes are shown with open circles. The location for the Greenland Summit ice core is indicated with a yellow circle. The solid lines are the median posterior fits to the observed data using the most parsimonious model. The dotted lines are the 2.5 and 97.5% credible limits.

  2. Fig. 2

    Relative change in sediment δ15N from 25 Northern Hemisphere lakes over the past 260 years (inner left ordinate), standardized to a common asymptotic δ15N (C0) of zero. Also shown is the relative change in δ15N-NO3 from the Greenland Summit ice core (outer left ordinate) (11), Haber-Bosch N fertilizer production (right ordinate) (25), and global anthropogenic CO2 (right ordinate, data rescaled by 1/100 for plotting purposes) (26). (Inset) Posterior probability distributions of Y0, describing the timing of onset of declining sediment δ15N.

  3. Fig. 3

    Timing of cumulative changes in sediment δ15N based on model results. Data are the year in which 10, 25, 50, and 75% of the total change in δ15N occurred among the 25 lakes in the analysis.