Variations in Atmospheric N 2O
Concentration During Abrupt Climatic Changes |
J. Flückiger*, A. Dällenbach*, T. Blunier*,
B. Stauffer*, T. F. Stocker*, D. Raynaud**, J.-M. Barnola**
* Climate and Environmental Physics,
Physics Institute, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland
** CNRS Laboratoire de Glaciologie et Géophysique de l'Environnement (LGGE),
Boîte Postale 96, 38402 St Martin d'Hères Cedex, Grenoble, France.
** CNRS Laboratoire de Glaciologie et Géophysique de l'Environnement (LGGE), Boîte Postale 96, 38402 St Martin d'Hères Cedex, Grenoble, France.
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Published: © by the American Association for the Advancement of Science
Science, 285, 227-230
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Nitrous oxide (N 2O) is an important greenhouse gas that is presently increasing at a rate of 0.25 percent per year. Records measured along two ice cores from Summit in Central Greenland provide information about variations in atmospheric N2O concentration in the past. The record covering the past millennium reduces the uncertainty regarding the pre-industrial concentration. Records covering the last glacial-interglacial transition and a fast climatic change during the last ice age show that the N2O concentration changed in parallel with fast temperature variations in the Northern Hemisphere. This provides important information about the response of the environment to global climatic changes.
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Comparison of our N2O measurements with previously published values for the past 1000 years. Shown are EUROCORE (dark blue circles) and GRIP mean values (light blue diamonds) from this study and the calculated 1sigma band of EUROCORE and GRIP mean values (shaded area). Previously published data are from Lawdome (plus signs) (3), Byrd (open triangles down), Crête (open diamonds), Camp Century (open squares) (4), D57 (open circles) (5), Dye 3 (open triangles up) (6), H15 (red triangles) (7), the South Pole (violet stars) (15) and direct atmospheric measurements from Cape Grim (crosses) (14). Each point of our record is either a single measurement or the mean value of two to six measurements on samples from the same core section. The error bars represent the analytical reproducibility (1sigma). For the age scale, the difference between the age of the air and the surrounding ice has been taken into account (20). The 1sigma band through our data was obtained by a Monte Carlo simulation (25) and marks the range of a likely evolution of the N2O concentration for this period.
GRIP N2O (solid and open circles), del18O (upper trace), and CH4 (lower trace) records for the last glacial-interglacial transition [the GRIP timescale is in years before 1989]. For N2O, the results from all individual samples are plotted together with their analytical uncertainty (1 sigma). We assume that high N2O values (open circles) are caused by artefacts. Solid circles indicates reliable results. Error bars indicate estimated 1 sigma uncertainty (4 ppbv). Measurements that are out of range are marked by arrows at the corresponding time. The light shading denotes the time period of the B/A; the dark shading denotes the YD event. The uncertainty in the difference between ice and gas age (Delta age) and therefore in the comparison of N2O and CH4 to del18O is about 100 years.
GRIP N2O (solid circles, left axis), del18O (upper trace) and CH4 (lower trace) records for the D-O event 8. We assume that high N2O values (open circles and arrow at the corresponding time) are caused by an artefact. For this time period, the uncertainty in Delta Age is better than 300 years. N2O measurements from the Byrd core for the same time period are shown as solid diamonds (right axis). Error bars indicate estimated 1 sigma uncertainty (4 ppbv). The time scale of the Byrd gas record was synchronized to that of the GRIP gas record with an uncertainty of 200 years.
NOAA Paleoclimatology Program / WDC for Paleoclimatology
11 February 2000