Supplementary information to chapter 5.8: Modelling the end of an interglacial (MIS 1, 5, 7, 9, 11) Claudia Kubatzki*, Martin Claussen**, Reinhard Calov, Andrey Ganopolski Potsdam-Institute for Climate Impact Research PO Box , Potsdam *now at Alfred Wegener Institute Bussestr. 24, Bremerhaven ( ) **now at University of Hamburg and Max Planck Institute for Meteorology

Figures I This first part contains the figures of our book chapter.

Figures II This second part contains supplementary material.

Model: CLIMBER-2.3 is an Earth system model of intermediate complexity („weather“ parameterized, coarse spatial resolution except for the inland-ice module); couples atmosphere, ocean, vegetation, inland ice, carbon cycle; is driven by changes in insolation and CO 2 ; simulation period: several thousands of years.

Glacial inception: At the end of the Eemian interglacial  decreasing summer insolation in the northern hemisphere;  glacial inception in Northern America at about 117 kyBP;  bifurcation (strong positive snow-albedo feedback);  sea-level change about 40m until 100 kyBP.

CO 2 and insolation (Last Glacial Inception):

longitude latitude Last Glacial Inception: ice thickness [m] (Changes since Eemian) 2000 years

Last glacial inception as bifurcation (max. volume lags area by ~ 3 ky)

128 kyBP 117 kyBP 100 kyBP Atlantic ocean meridional overturning circulation

125 kyBP 115 kyBP 100 kyBP 10%90% Tree fraction

Amplification factors: The last glacial inception in the model is mainly caused by changes in the precession. Changes in the ocean surface as well as of vegetation provide a crucial additional, positive albedo feedback. Variations in the atmospheric CO 2 only act as an amplification factor.

Ice-area (North America): Temperature (global annual): Last Glacial Inception: - Precession initiates ice-sheet growth - Obliquity / CO 2 act as amplifiers

Fixed pre-ind or Eemian surface conditions Atm.+ oce.+veg. Atm.+ oce. Atm.+ veg. Atm. interactively simulated, other components fixed

Cold events: At the end of the Eemian interglacial: data show abrupt cooling events, and forest decline in central Europe; reproducable in the model due to changes in the Atlantic overturning circulation, caused by disturbing the North Atlantic freshwater balance.

Stadials D-O events Temperature in Greenland: CLIMBER-2 and NGRIP NGRIP members 2004 Freshwater disturbances („IRDs“)

An ice-free Greenland is a possible second equilibrium state in the model under the insolation forcing of 128 kyr BP. Timing and extent of northern American glaciation at the end of the Eemian, however, do not depend on the size of the Greenland ice sheet during the Eemian.

Sea-level change (difference to pre-industrial): Difference between the two runs resulting from two possible equilibrium states of the Greenland ice sheet

The end of the current interglacial: In the next 50,000 years („natural“ forcing)  only small changes in solar insolation;  insolation variations comparably low as during MIS 11  but no significant expansion of inland ice in the model.

Maximum insolation at 65 o N MIS 1 CO 2 from Vostok Petit et al MIS Berger 1978

meters Inland-ice area MIS 10 MIS kyAP Present Height of inland ice at the end of MIS 10 (343kyBP) Future glaciation ? Sea-level change

Application of our model to a ‘typical GCM setup’: The extent to which time-slice simulations of 115 kyr BP are able to reproduce a transient simulation of the last glacial inception is significantly influenced by use of a high-resolution orography and the atmospheric CO 2 concentration applied. Certain combinations of synchronously-run periods and acceleration of the climate model as compared to the ice-sheet module enable a reasonable reproduction of a fully synchronous run.

Annual temperature (difference to pre-industrial): the transient simulation of the fully coupled model at 115 ka BP, a time slice simulation of 115 ka BP with fixed pre-industrial ice sheets, a time slice simulation of 115 ka BP with interactive inland ice model.

Simulation of the last glacial inception applying different levels of climate vs. ice-sheet model acceleration (coupling period / presetting run time, the black line gives the control run). Global ice volume: