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Science 10 February 2006:
Vol. 311. no. 5762, pp. 838 - 840
DOI: 10.1126/science.1121235
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Reports

Late Quaternary Atmospheric CH4 Isotope Record Suggests Marine Clathrates Are Stable

Todd Sowers

Department of Geosciences and the Earth and Environmental Systems Institute, Pennsylvania State University, University Park, PA 16802, USA.


Figure 1 Fig. 1. Characteristic {delta}DCH4 values for various present-day CH4 sources. All the data except the value for the marine clathrates (13) are from (26–28). Present day atmospheric {delta}DCH4 estimates are ~–90 ± 5{per thousand} (29). The enriched atmospheric value is the result of a large KIE (+250 {per thousand}) associated with the primary sink (tropospheric OH) (14). Error bars for each source correspond to the tabulated range of values. SMOW, standard mean ocean water. [View Larger Version of this Image (12K GIF file)]
 

Figure 2 Fig. 2. Results from the last glacial termination as recorded in the GISP II ice core. The upper purple curve is the isotopic temperature (30). The red curve is from the current {delta}DCH4 analyses with 1{sigma} (4.2{per thousand}) error bars. The bottom CH4 concentration curve (green) is from Brook et al. (3). ppb, parts per billion. The increased sample resolution associated with the abrupt CH4 concentration increases associated with the onset of the Bolling/Allerod and the end of the Younger Dryas periods are shown in expanded view in Fig. 3. The present-day {delta}DCH4 value for the Southern Hemisphere (SH) is shown as a horizontal dashed line for reference. [View Larger Version of this Image (34K GIF file)]
 

Figure 3 Fig. 3. Expanded views of three abrupt CH4 concentration events recorded in the GISP II ice core. The isotopic temperature record (30) and atmospheric CH4 concentration record (3) are plotted for reference. The red curves are from the current {delta}DCH4 analyses with 1{sigma} errors at each measured depth. The results from the one-box clathrate-only model are shown for the Younger Dryas simulation with black curves. All data in all three panels are plotted on the same y axes for comparison. [View Larger Version of this Image (27K GIF file)]
 

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