Transient simulation of the last glacial inception, Part II: sensitivity and feedback analysis

• Main Authors: Reinhard Calov, Andrey Ganopolski, Martin Claussen, Vladimir Petoukhov, Ralf Greve
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2005
• Subjects: Ice Sheet
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.464.286; http://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/29692/1/CD24-6.pdf

We study the mechanisms of glacial inception by using the Earth system model of intermediate complexity CLIMBER-2, which encompasses dynamic modules of the atmosphere, ocean, biosphere and ice sheets. Ice-sheet dynamics are described by the 3-dimensional polythermal ice-sheet model SICOPOLIS. We have performed transient experiments starting at the Eemiam interglacial, at 126 kyr BP (126,000 years before present). The model runs for 26,000 years with time-dependent orbital and CO2 forcings. The model simulates a rapid expansion of the area covered by inland ice in the Northern Hemisphere, predominantly over Northern America, starting at about 117 kyr BP. During the next 7 kyr, the ice volume grows gradually in the model at a rate which corresponds to a change in sea level of 10 m per millennium. We have shown that the simulated glacial inception represents a bifurcation transition in the climate system from an interglacial to a glacial state caused by the strong snow-albedo feedback. This transition occurs when summer insolation at high latitudes of the Northern Hemisphere drops below a threshold value, which is only slightly lower than modern summer insolation. By performing long-term equilibrium runs, we find that for the present-day orbital parameters at least two