Climate of the Past Discussions www.clim-past-discuss.net 1814-9340 1814-9359 2 4 2006 10.5194/cpd-2-371-2006 http://www.clim-past-discuss.net/2/371/2006/ http://www.clim-past-discuss.net/2/371/2006/cpd-2-371-2006.html http://www.clim-past-discuss.net/2/371/2006/cpd-2-371-2006.pdf 371 397 2006-07-07 Quasi-100 ky glacial-interglacial cycles triggered by subglacial burial carbon release N. Zeng Department of Atmospheric and Oceanic Science, and Earth System Science Interdisciplinary Center, University of Maryland, USA A new mechanism is proposed in which climate, carbon cycle and icesheets interact with each other to produce a feedback that can produce quasi-100 ky glacial-interglacial cycles. A key process is the burial and preservation of organic carbon by icesheets. The switch from glacial maximum to deglaciation is triggered by the ejection of glacial burial carbon when icesheets grow to sufficiently large size and subglacial transport becomes significant. Glacial inception is initiated by CO₂ drawdown due to a ''rebound'' from a high but transient interglacial CO₂ value as the land-originated CO₂ invades into deep ocean via thermohaline circulation and CaCO₃ compensation. Also important for glacial inception is the CO₂ uptake by vegetation regrowth in the previously ice-covered boreal regions. When tested using a fully coupled Earth system model with comprehensive carbon cycle components and semi-empirical physical climate components, it produced self-sustaining glacial-interglacial cycles of duration about 93 ky, CO₂ change of 90 ppmv, temperature change of 6°C under certain parameter regimes. Since the 100 ky cycles can not be easily explained by the weak Milankovitch astronomical forcing alone, this carbon-climate mechanism provides a strong feedback that could interact with external forcings to produce the major observed Quaternary climatic variations.