HR: 0800h
AN: OS41A-0595    [Abstracts]
TI: Exploration of the Mechanism Explaining the Emergence of Unforced Millennial Scale Variability in the Bern Climate Model under Glacial Boundary Conditions
AU: * Liu, Y
EM: yrliu@ph.utexas.edu
AF: Department of Physics, University of Texas at Austin 1 University Station C1600, Austin, TX 78712-0264 United States
AU: Jackson, C
EM: charles@ig.utexas.edu
AF: Institute for Geophysics University of Texas at Austin, 4412 Spicewood Springs Rd. #600, Austin, TX 78759-8500 United States
AU: Marchal, O
EM: omarchal@whoi.edu
AF: Woods Hole Oceanographic Institution, MS #22, Woods Hole, MA 02543-105 United States
AU: Stocker, T
EM: stocker@climate.unibe.ch
AF: Climate and Environmental Physics University of Bern, Sidlerstrasse 5, Bern, 3012 Switzerland
AB: Previous efforts have failed to identify unforced modes of variability relevant to millennial scale variability. The best inference from data and modeling studies is that millennial scale variability occurs within the climate system when triggered by pulses of freshwater or through a stochastic resonance mechanism coordinated by a weak (and yet unknown) oscillatory forcing. However, an unforced mode with ~1200 year periodicity emerged within the Bern Climate model when placed under sufficiently strong glacial boundary conditions. The seasonally resolving Bern climate model (Schmittner and Stocker, 1999, J Clim) is composed of a zonally averaged ocean model (Wright and Stocker, 1992, J Clim) coupled to an energy-balance model of the atmosphere that parameterizes the meridional transport of heat and moisture. We shall present the mechanism for this mode of variability. Our leading hypothesis is that the imposition of glacial boundary conditions within the Bern Climate Model alters its stability thresholds and the accessibility to modes of variability that may be excited by the presence of a random forcing.
DE: 3305 Climate change and variability (1616, 1635, 3309, 4215, 4513)
DE: 4500 OCEANOGRAPHY: PHYSICAL
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4926 Glacial
DE: 4962 Thermohaline
SC: Ocean Sciences [OS]
MN: Fall Meeting 2005