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N2O and CH4 variations during the last glacial epoch:
Insight into global processes

Fig. 9. Details of the beginnings of D-O event 12. Click for full image including events 8-12 and 19-20. N2O and CH4 variations during the last glacial epoch: Insight into global processes
Global Biogeochemical Cycles,
Vol. 18, GB1020, January 2004.


Jacqueline Flückiger, Thomas Blunier, and Bernhard Stauffer
Climate and Environmental Physics, Physics Institute,
University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland


Jérôme Chappellaz
CNRS Laboratoire de Glaciologie et de Géophysique
de l'Environnement, Grenoble, France


Renato Spahni, Kenji Kawamura, Jakob Schwander, and Thomas F. Stocker
Climate and Environmental Physics, Physics Institute,
University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland


Dorthe Dahl-Jensen
Niels Bohr Institute, Department of Geophysics, University of Copenhagen, Copenhagen, Denmark

ABSTRACT:
Greenhouse gas measurements along polar ice cores provide important insight into the former composition of the atmosphere, its natural variations, and the responses to fast climatic changes in the past. We present high-resolution nitrous oxide (N2O) and methane (CH4) records measured along two ice cores from central Greenland covering part of Marine Isotope Stages 3 and 4 in the last glacial epoch. The N2O data confirm the hypothesis that N2O shows variations in phase to fast climatic changes observed in the Northern Hemisphere, the so-called Dansgaard-Oeschger (D-O) events. Variations exist not only for events with a long duration (1500 years and more) but also for the shorter ones. The comparison with CH4 unveils interesting differences between the response of CH4 and N2O to D-O events. While the average amplitudes of CH4 oscillations associated with D-O events are similar to those of the Northern Hemisphere summer insolation, the magnitude of the N2O concentration change instead correlates with the duration of the D-O events. The records give further insight into the timing of concentration changes at the beginning of D-O events. They show that for long-lasting events the N2O concentration starts to increase before both the sharp increase in the CH4 concentration and the temperature reconstructed for Greenland.

DATA:
Download the N2O and CH4 data from the GRIP and North GRIP ice cores from the WDC Paleo Archive.

Fig. 2 Dome C long term trends of CO2, CH4, and N2O
Fig. 2. Click for larger image.
(top) NGRIP d18O (S. Johnsen, personal communication, 2003), (middle) CH4, and (bottom) N2O record for D-O events 9 to 12. The numbers of the D-O events are indicated in the top part of the figure. For N2O the 1-sigma uncertainty is given. N2O data, which are assumed to be artifacts according to the method described in Appendix A of the paper, are plotted as open circles. Artifacts that exceed the range of the axes are indicated with arrows at the corresponding age. The values of these artifacts are given in parentheses. In the time period of 43.8 to 44.6 kyr BP, two additional N2O data points are excluded (open triangles) due to their high sensitivity to changes in the parameters of our method to define artifacts (see Appendix A of the paper). To emphasize the atmospheric trend over the whole N2O data set, a spline with a cutoff period of 600 years is shown (solid line) [Enting, 1987]. The best guess of the possible atmospheric trend in the time period of 43.8 to 45.0 kyr BP is indicated as a shaded dashed line. All data are given on a tentative timescale. The ice age scale is closely related to the GRIP SS09sea timescale [Johnsen et al., 2001]. The gas age scale was calculated from the ice age scale for a temperature scenario of a temperature sensitivity of 0.3 per mil/°C according to Schwander et al. [1997]. These tentative timescales will be improved further in the future. However, our conclusions do not depend on the timescale.

Fig. 3 GRIP d18O, N2O, and CH4
Fig. 3. Click for larger image.
(top) GRIP d18O [Dansgaard et al., 1993], (middle) CH4, and (bottom) N2O record covering D-O events 19 and 20. For N2O, the 1-sigma uncertainty is given. N2O data, which are assumed to be artifacts according to the method described in Appendix A of the paper, are plotted as open circles. Artifacts that exceed the range of the axis are indicated with arrows at the corresponding age. The values of these artifacts are given in parentheses. The atmospheric N2O trend is indicated by the spline with a cutoff period of 600 years (solid line) All data are shown on the GRIP SS09 timescale [Johnsen et al., 1995: Schwander et al., 1997 ]. The numbers of the D-O events are indicated in the top part of the figure.

To read or view the full study, please visit the AGU website.
It was published in Global Biogeochemical Cycles, Vol. 18, GB1020, February 2004.


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4 February 2004