The interpolar CH4 gradient associated with DO#7
Abstract
The atmospheric CH4 concentration has been shown to vary on many timescales. On orbital timescales, CH4 varies with northern hemisphere insolation presumably related to the monsoonal forcing. High resolution CH4 records during MIS 3 illustrate an amazing covariation between CH4 levels and circum north Atlantic climate oscillations with higher CH4 levels characteristic of the warmer interstadial periods. Together these records argue for a strong teleconnection between climate and CH4 emissions likely driven by the extent of global wetlands. Contemporaneous ice core CH4 measurements have shown that the interpolar CH4 gradient (IPG) varies over glacial/interglacial timescales. The magnitude of the IPG reflects the magnitude of CH4 emissions from the Arctic relative to the tropics. Higher IPG values in the past result from enhanced Arcitc CH4 emissions. In order to study the IPG associated with a stadial/interstadial transition, we sampled ~60 ice samples from both the WAIS (West Antarctica) and GISP II (Central Greenland) ice cores covering DO#7 (34-36ka). Samples from the same period from both cores were run on the same day with duplicate samples run on a different day to avoid aliasing the results with day-to-day analytical variability. The average difference between the replicate analyses was ~4ppb for both cores representing less than 1% of the measured values. The mean IPG for the period was 28 ppb with a one sigma standard deviation of 8ppb. Interestingly enough, there is no apparent IPG variation associated with this particular DO event. Previous IPG estimates for stadial/interstadial events suggest elevated IPG values associated with the warm interstadial periods signifying activated boreal wetland emissions. In contrast, our new IPG results for DO#7 suggest that the relative proportion of boreal/tropical CH4 emissions appears to have remained constant through this stadial/interstadial event.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFMPP11D..03S
- Keywords:
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- 0315 ATMOSPHERIC COMPOSITION AND STRUCTURE Biosphere/atmosphere interactions;
- 0429 BIOGEOSCIENCES Climate dynamics;
- 4932 PALEOCEANOGRAPHY Ice cores