Paleoclimate Models Chapter 12 The Climate System IPCC

Paleoclimate Models (Chapter 12)

The Climate System (IPCC TAR, Ch. 1)

The Climate System (IPCC TAR, Ch. 1)

Feedbacks Internal couplings through linking processes Amplify or diminish initial induced climate change

Adjustment Time Scales 300 -3000 yr

Climatic Variation and Change Additional Factors 1. Abrupt change - external conditions (e. g. , solar output) - passing a threshold (e. g. ice caps melting) internal feedbacks 2. Multiple climate states from the same external conditions

How can a numerical model represent all of this? Options: • “Full” complexity - short time scales • Simplified - long time scales

Simplified Models • Climate simulation in general - 1960 s • Paleoclimate applications: Barry Saltzman (1931 -2001) e. g. , Saltzman & Maasch (1991)

Simplified Models • Three-variable model for slow climate variability: I = ice mass, = atmospheric CO 2, = mean ocean temperature R(t) = solar variation at 65 ˚N i, I - constants that can distill into 7 tunable parameters

Simplified Models • Three-variable model for slow climate variability: (Saltzman, 1986) CO 2 parameter ( ): from 13 C core data (dashed) and simulation (solid)

Simplified Models • Three-variable model for slow climate variability: (Saltzman, 1986) 18 O: from SPECMAP 18 O (dashed) and simulation (solid)

Intermediate Models Global, 2 -5 dimensional model: • 5˚ latitudinal bands • In each band - 2 continental sectors (Eurasia-Africa, Americas) - 3 ocean sectors (Atlantic, Indian, Pacific) • Circulation dynamics: 2 -level, Q-G - winds at 250 h. Pa, 750 h. Pa - temperature at 500 h. Pa - plus - Hadley Cell transport in tropics • 2 -D ocean model for each basin • Land-atmosphere coupling processes (Crucifix et al. , 2002)

Intermediate Models Simulation versus observations (Crucifix et al. , 2002)

Intermediate Models (Crucifix et al. , 2002)

Intermediate Models Prescribed Changes (Crucifix et al. , 2002)

Intermediate Models Prescribed Changes and Responses (Crucifix et al. , 2002)

Intermediate Models Response (Crucifix et al. , 2002)

Intermediate Models Prescribed Changes Sensitivity (Crucifix et al. , 2002)

Intermediate Models Sensitivity (Crucifix et al. , 2002)

Global Climate Models

Global Climate Models Differing scales: distributed surface properties

Global Climate Models

GCM Simulation Paleo-Simulation Projects: ¬ Cooperative Holocene Mapping Project (COHMAP) ¬ COHMAP extension ¬ Paleoclimate Model Intercomparison Project (PMIP)

GCM Simulation Cooperative Holocene Mapping Project (COHMAP) ¬ NCAR CCM 0 ¬ Prescribed changes in - Insolation - SST - Ice sheets - CO 2 ¬ Time slices every 3, 000 yr (18 k BP, 15 k BP, …) ¬ Perpetual January or July

GCM Simulation Cooperative Holocene Mapping Project (COHMAP) ¬ Ice sheets & cold ocean Þ colder, drier climate Þ intensified jet stream ¬ Amplified annual cycle ¬ Intensified summer monsoons

GCM Simulation COHMAP Extension ¬ NCAR CCM 1 ¬ Computed - SST (slab ocean, prescribed heat transport) - Sea ice - Soil moisture - Seasonal snow ¬ Time slices every ~ 3, 000 yr ¬ Full annual cycle simulated

GCM Simulation (Kutzbach et al. , 1998)

GCM Simulation (Kutzbach et al. , 1998)

GCM Simulation • 25 -yr simulation • Last 5 yr analyzed (Kutzbach et al. , 1998)

GCM Simulation Longitudinal average overturning circulation (mean meridional circulation) (Kutzbach et al. , 1998)

GCM Simulation Present-Day Results Spruce Douglas Fir Sagebrush (Bartlein et al. , 1998)

GCM Simulation Changes with Climate (Bartlein et al. , 1998)

GCM Simulation Paleoclimate Model Intercomparison Project: Tropical Changes @ LGM • 17 GCMs - 9 slab ocean - 8 prescribed SST • Prescribed changes in - insolation - CO 2 - ice sheets

GCM Simulation (Pinot et al. , 1999) PMIP: LGM vs. Present Day

GCM Simulation PMIP: Present Day Sea-surface temperature Land-surface temperature (Pinot et al. , 1999)

GCM Simulation PMIP: Present Day (Pinot et al. , 1999)

GCM Simulation PMIP: Present Day Ocean precipitation Land precipitation (Pinot et al. , 1999)

GCM Simulation (Pinot et al. , 1999) PMIP: LGM vs. PD (30 S - 30 N)

GCM Simulation Paleoclimate Model Intercomparison Project: Tropical Changes @ LGM Top: Sfc T change - prescribed SST RMS spead among models Bottom: Sfc T change - computed SST

GCM Simulation Paleoclimate Model Intercomparison Project: Tropical Changes @ LGM Difference in simulated SST changes from reconstructed changes (LGM-PD)

GCM Simulation PMIP: LGM-PD Comparison with proxies (Pinot et al. , 1999)

GCM Simulation Paleoclimate Model Intercomparison Project: Tropical Changes @ LGM Model changes vs. pollen record Coldest month temperature

GCM Simulation Model changes vs. pollen record Annual surface temperature Paleoclimate Model Intercomparison Project: Tropical Changes @ LGM

Precipitation changes vs. lake records prescribed SST models

Precipitation changes vs. lake records computed SST models

Paleoclimate Models (Chapter 12) END