1. Evidence for an 1859/1860 nitrate spike in the Greenland ice sheet C. M. Laird 1, G. A. M. Dreschhoff 1, T. P. Armstrong 1, 2, A. L. Melott 1, and B. C. Thomas 1, 3 1. Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045 2. Fundamental Technologies, LLC, Lawrence, KS 66046 3. Department of Physics and Astronomy, Washburn University, Topeka, KS 66621

2. Wolff et al, GRL 2012 – Fig. 1

3. A reanalysis of the GISP2 H ice core ECM (Electrical Conductivity Method) and nitrate data around the NO 3 - spike previously dated to late 1859 suggests the feature most likely appears in early 1860.

4. Utilized standard method for absolute dating of ice cores: 1.ECM (volcanism) – establishes marker years 1853, 1854, 1883,… 2.proxies exhibiting annual cycles (e.g. nitrates) - count/interpolate years between markers 3.combining 1. and 2. gives annual dating => Nitrate spike most probably occurs in 1860. Dating Methodology – GISP2 H Core Dreschhoff and Zeller, 1994 1859 or 1860one or two years

5. GISP2 H Core Segment - Dreschhoff and Zeller, 1994 (evenly-spaced samples) 1. Shiveluch (1854) and Krakatau (1883) ECM markers bracket nitrate spike 2. annual nitrate cycles count/interpolate years between markers 3. 1. & 2. => NO 3 - spike most probably occurs in 1860 (not 1862/1863) ECM NO 3 -