Atmospheric methane control mechanisms during the early Holocene
Ji-Woong Yang1, Jinho Ahn1, Edward J. Brook2, and Yeongjun Ryu11School of Earth and Environmental Sciences, Seoul National University, Seoul 08826, South Korea 2College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA
Abstract. Understanding the atmospheric methane (CH4) change is crucial to predict and mitigate the future climate change. In spite of recent studies using various approaches for the last ~ 1000 to 2000 years, control mechanisms of CH4 still remain unclear, partly because the late Holocene CH4 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 that it allows us to elucidate the natural controls under interglacial conditions. Here we present new high resolution CH4 records of millennial scale CH4 variability from Siple Dome, Antarctica, covering from 11.6 to 7.7 thousands of years before 1950 AD (ka). We observe several local CH4 minima on a roughly 1000-year spacing. Each CH4 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 CH4 reduction at ~ 10.3 ka. A high resolution inter-polar difference (IPD) during the early Holocene increased from ~ 10.7 to 9.9 ka, and remained high until ~ 9.3 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.
Yang, J.-W., Ahn, J., Brook, E. J., and Ryu, Y.: Atmospheric methane control mechanisms during the early Holocene, Clim. Past Discuss., doi:10.5194/cp-2016-75, in review, 2016.