Oliver Elison Timm 1, Malte Heinemann 1, Axel Timmermann 1,4 Fuyuki Saito 3, A. Abe-Ouchi 2,3 Simulating the Last Glacial Termination Using a 3-Dimensional Coupled Climate-Ice-Sheet Model. 1.International Pacific Research Center, University of Hawaii at Manoa, Honolulu, HI, USA 2. Center for Climate System Research, University of Tokyo, Kashiwa, Japan. 3. Research Institute for Global Change, JAMSTEC, Yokohama, Japan. 4. Dept. of Oceanography, University of Hawaii at Manoa, Honolulu, HI, United States.

Oliver Elison Timm 1, Malte Heinemann 1, Axel Timmermann 1,4 Fuyuki Saito 3, A. Abe-Ouchi 2,3 Simulating the Last Glacial Cycle Using a 3-Dimensional Coupled Climate-Ice-Sheet Model. 1.International Pacific Research Center, University of Hawaii at Manoa, Honolulu, HI, USA 2. Center for Climate System Research, University of Tokyo, Kashiwa, Japan. 3. Research Institute for Global Change, JAMSTEC, Yokohama, Japan. 4. Dept. of Oceanography, University of Hawaii at Manoa, Honolulu, HI, United States.

Motivation: Ice-sheet simulations forced with atmospheric boundary conditions Ocean-Atmosphere model simulations with external forcing from greenhouse gases, orbital forcing, and ice- sheets Coupled Ocean-Atmosphere- Ice-sheet simulations with external forcing from greenhouse gases, orbital forcing: Exploring what external forcings and internal feedbacks cause glacial inceptions and terminations

Motivation: Exploring what external forcings and internal feedbacks cause glacial inceptions and terminations Coupled Ocean-Atmosphere- Ice-sheet simulations with external forcing from greenhouse gases, orbital forcing

LOVECLIM-GLIMMER LOVECLIM-IcIES Ice-sheet model GLIMMER * or IcIES + ECBilt – atmosphere T21, L3 t2m precip t2m precip CLIO – ocean sea-ice 3x3, L20 aiaaia aiaaia air-sea fluxes VECODE – vegetation t2m,precip albedo t2m,precip albedo LOCH – Marine carbon cycle aiaaia aiaaia CO 2 fluxes Transient external forcing Freshwater Forcing albedo + orography albedo + orography * Rutt et al., J. Geophys. Res., 114, F02004, Abe-Ouchi et al, Clim. Past., 2007

Ice sheet models: GLIMMER: (Community model developed by Hagdorn, Rutt, Payne, Hebeler)  Thermomechanical 3-d model for grounded ice  Shallow Ice Approximation  Northern Hemisphere in polar stereographic projection ( approx 30N-90N domain), 148x148 grid (100km resolution)  11 sigma levels  Daily PDD scheme  Isostatic bedrock adjustment (~3000a )  Ice calving parameterization IcIES: (“Ice Sheet for Integrated Earth system Studies”, developed by Abe-Ouchi & Saito)  Thermomechanical 3-d model for grounded ice  Shallow Ice Approximation  Northern Hemisphere in 1x1deg lon-lat coordinates (30N-89N, 360x59 grid boxes)  26 sigma levels  Monthly PDD scheme  Isostatic bedrock adjustment (~5000a )  Ice calving parameterization

Modeling Approach Note, we currently apply accelerated orbital and greenhouse gas forcing (factor 10/20) Asynchronous coupling: Ocean-Atmosphere-Vegetation adjusts faster to ice-sheet changes than land ice to climatic changes Surface temperature, precipitation (annual cycle) Surface temperature, precipitation (annual cycle) Surface elevation, albedo, ice mask Surface elevation, albedo, ice mask Surface temperature, precipitation (annual cycle) Surface temperature, precipitation (annual cycle) Surface elevation, albedo, ice mask Surface elevation, albedo, ice mask

Orbital parameters after Berger (1978) time External forcing: Orbital changes Obliquity constant at o. Two orbital forcing Experiments

External forcing: Atmospheric Greenhouse Gas Concentrations CO 2, CH 4, N 2 O derived from Antarctic ice-cores (EPICA EDC) CO 2 : Luethi et al, Nature, 453, CH 4 : Loulergue et al., Nature, 453, 2008 N 2 O: Schilt et al, QSR., 29, 2010 Three experiments with different CO 2 sensitivities in LOVECLIM: Source: IGBP PAGES/World Data Center for Paleoclimatology NOAA/NCDC Paleoclimatology Program Longwave radiation ~ a ln(CO 2 /CO 2_ref ), with CO 2_ref = 356 ppmv (present day)

Initial State Problem: time [ka] NH ice sheet volume [msl] thickness [km] initial ‘LGM’ Ice-sheet model IcIES forced with preindustrial climatology from LOVECLIM (full forcing, not anomaly forcing) initial ‘no ice’

Initial State Problem: time [ka] NH ice sheet volume [msl] initial ‘LGM’ Ice-sheet model IcIES forced with preindustrial climatology From LOVECLIM (full forcing, not anomaly forcing) initial ‘no ice’ thickness [km]

LOVECLIM-GLIMMER Simulation of the last Glacial-Interglacial Cycle (LOVECLIM-GLIMMER) Inception phase around 116kaBP But to weak ice-buildup Last Glacial Maximum around 20kaBP followed by Termination Termination phase extends into Holocene. Note: “Unofficial ICE5g” data for period kaBP from the “Special Bureau for Loading”: * *

LOVECLIM-GLIMMER Simulation of the last Glacial-Interglacial Cycle (LOVECLIM-GLIMMER) 115,000 BP 65,000 BP 20,000 BP 1000 BP

LOVECLIM-GLIMMER/IcIES sensitivity experiments Strong sensitivity to CO 2 forcing Obliquity experiment: Constant obliquity with present-day obliquity (23.44 deg) =>suppressed ice buildup  Reduced summer insolation (shortwave energy) during low Obliquity phases important!

Summary Coupled Ice-sheet-Atmosphere-Ocean-Vegetation glacial cycle experiment: First successful glacial inception and last glacial maximum representation in LOVECLIM-GLIMMER/IcIES This was achieved without bias correction in temperature or precipitation fields Sensitivity experiments highlight the strong dependence of ice-sheet buildup on CO 2 forcing and obliquity cycles. Future improvements: Include thermal and freshwater coupling ice ocean Study the feedback between ice-sheets atmosphere-ocean-vegetation circulation

LOVECLIM-GLIMMER Simulation of the last Glacial-Interglacial Cycle (LOVECLIM-GLIMMER) The coupled system generates millennial-scale variability. Atlantic Meridional Overturning Circulation LOVECLIM-GLIMMER LOVECLIM-IcIES NH ice volume