Atmospheric methane control mechanisms during the early Holocene

Ji-Woong Yang, Jinho Ahn, Edward J. Brook, Yeongjun Ryu
2016 Climate of the Past Discussions  
Understanding the atmospheric methane (CH<sub>4</sub>) change is crucial to predict and mitigate the future climate change. In spite of recent studies using various approaches for the last ~&amp;thinsp;1000 to 2000 years, control mechanisms of CH<sub>4</sub> still remain unclear, partly because the late Holocene CH<sub>4</sub> budget is comprised of natural and anthropogenic emissions. In contrast, the early Holocene was a period when human influence should have been substantially smaller, so
more » ... at it allows us to elucidate the natural controls under interglacial conditions. Here we present new high resolution CH<sub>4</sub> records of millennial scale CH<sub>4</sub> variability from Siple Dome, Antarctica, covering from 11.6 to 7.7 thousands of years before 1950&amp;thinsp;AD (ka). We observe several local CH<sub>4</sub> minima on a roughly 1000-year spacing. Each CH<sub>4</sub> minimum corresponds to cool periods in Greenland. We hypothesize that the cooling in Greenland forced the Intertropical Convergence Zone (ITCZ) to migrate southward, reducing rainfall in northern tropical wetlands although there is no obvious change was observed in low latitude hydrology corresponding to abrupt CH<sub>4</sub> reduction at ~&amp;thinsp;10.3&amp;thinsp;ka. A high resolution inter-polar difference (IPD) during the early Holocene increased from ~&amp;thinsp;10.7 to 9.9&amp;thinsp;ka, and remained high until ~&amp;thinsp;9.3&amp;thinsp;ka. With a simple three-box model results, our new IPD records suggest that the ratio of northern high latitude to tropical sources increased due to a boreal source expansion following the deglaciation.
doi:10.5194/cp-2016-75 fatcat:uogfhxwn2vdxtbkscz4npqfgdq