11 Millenial-scale Correlation Between Ice-core and Marine Sediment Records

Friday, 25 July 2003
8:00 AM - 12:00 PM

METHANE IN ICE CORES AT MILLENNIAL SCALE : WHICH PART OF THE CLIMATE SYSTEM DOES IT DESCRIBE?

Paper number: 11-7
Program: SYMPOSIA
Time: 10:10 AM – 10:30 AM

Authors

  • Jerome Chappellaz Presenting Author
    Laboratoire de Glaciologie et Géophysique de l'Environnement, St Martin d'Heres Cedex, N/A
  • Jean-Marc Barnola
    Laboratoire de Glaciologie et Géophysique de l'Environnement, St Martin d'Heres Cedex, N/A
  • Amaelle Landais
    Laboratoire des Sciences du Climat et de l'Environnement, Gif sur Yvette Cedex, N/A
  • Ed Brook
    Washington State Univ, Vancouver, WA
  • Jacqueline Flückiger
    Climate and Environmental Physics, Bern, N/A
  • Thomas Blunier
    Climate and Environmental Physics, Bern, N/A
  • Marc Delmotte
    Laboratoire de Glaciologie et Geophysique de l'Environnement, St Martin d'Heres Cedex, N/A

Abstract

Over the last 15 years, increasingly detailed records of atmospheric methane (CH4) mixing ratio have been produced from Antarctic and Greenland ice cores. In addition to its long-term glacial-interglacial variability (typically in the range 350-700 ppbv or parts per billion in volume), these records have revealed millennial scale CH4 changes associated with Dansgaard/Oeschger events in Greenland. As an end-product of a complex biogeochemical cycle, these CH4 fluctuations are clear indicators that millennial climate events were not limited to the circum North Atlantic sector but indeed affected the climate system on a much larger scale.

We will present new CH4 records from the North GRIP and GRIP (Greenland) cores reaching sub-centennial resolution in particular over Marine Isotope Stage 4 ; they show a remarkable correspondence with Greenland climate features, including unnumbered isotopic events. Parallel measurements of N2 and Ar isotopes indicate that Greenland climate and atmospheric methane varied synchronously at sample resolution (~50 yr).

As Greenland ice cores do not yet allow to study older periods than the last interglacial, and thanks to the Greenland/CH4 correspondence observed during the last glacial, detailed Antarctic CH4 records provide a tool to extend the observation of millennial climate events back in time. We will present and discuss the status of such records obtained from the Vostok and Dome C deep ice cores. Although the strong smoothing of atmospheric variations at these low-accumulation sites tamper the amplitude of events, the data at hand do reveal Dansgaard/Oeschger variability during previous glaciations. Coherence and phase studies between CH4 and Antarctic climate suggest that the bipolar see-saw mechanism remained a strong feature of the climate system over the last four climatic cycles.

Causes of natural CH4 changes mostly include continental hydrology (wetland extent and temperature), the atmospheric oxidative capacity and possible hydrate destabilisation. We will discuss the arguments available about the relative contribution of these mechanisms.