Paleoclimate ModelsPaleoclimate Models

(Chapter 12)(Chapter 12)

The Climate SystemThe Climate System

(IPCC TAR, Ch. 1)

The Climate SystemThe Climate System

(IPCC TAR, Ch. 1)

Feedbacks

Internal couplings through linking processesAmplify or diminish initial induced climate change

Adjustment Time ScalesAdjustment Time Scales

300-3000 yr

Climatic Variation and ChangeClimatic Variation and ChangeAdditional FactorsAdditional Factors

1.1. Abrupt changeAbrupt change- external conditions (e.g., solar output)external conditions (e.g., solar output)- internal feedbacksinternal feedbacks- passing a threshold (e.g. ice caps passing a threshold (e.g. ice caps

melting)melting)

2. Multiple climate states from the same 2. Multiple climate states from the same external conditionsexternal conditions

How can a numerical model How can a numerical model represent all of this?represent all of this?

Options:Options:

• “ “Full” complexity - short time scalesFull” complexity - short time scales

• Simplified - long time scalesSimplified - long time scales

Simplified ModelsSimplified Models• Climate simulation in general - 1960sClimate simulation in general - 1960s

• Paleoclimate applications: Paleoclimate applications:

Barry Saltzman (1931-2001)Barry Saltzman (1931-2001)

e.g., Saltzman & Maasch (1991)e.g., Saltzman & Maasch (1991)

€

dIdt

= α 1 − α 2cμ − α 3I − α 2κθθ − α 2κθ R(t)

dμdt

= β1 − (β2 − β3θ + β4θ 2)μ − (β5 − β6θ)θ

dθdt

= γ1 − γ2I − γ3θ

Simplified ModelsSimplified Models• Three-variable model for slow climate variability:Three-variable model for slow climate variability:

I = ice mass, I = ice mass, = atmospheric CO = atmospheric CO22, , = mean ocean = mean ocean temperaturetemperature

R(t) = solar variation at 65 ˚NR(t) = solar variation at 65 ˚N

ii, , ii, , II - constants that can distill into 7 tunable parameters - constants that can distill into 7 tunable parameters€

dIdt

= α 1 − α 2cμ − α 3I − α 2κθθ − α 2κθ R(t)

dμdt

= β1 − (β2 − β3θ + β4θ 2)μ − (β5 − β6θ)θ

dθdt

= γ1 − γ2I − γ3θ

Simplified ModelsSimplified Models• Three-variable model for slow climate variability:Three-variable model for slow climate variability:

(Saltzman, 1986)(Saltzman, 1986)

COCO22 parameter ( parameter (): ):

from from 1313C core data (dashed) and simulation (solid)C core data (dashed) and simulation (solid)

Simplified ModelsSimplified Models• Three-variable model for slow climate variability:Three-variable model for slow climate variability:

(Saltzman, 1986)(Saltzman, 1986)

1818O: O:

from SPECMAP from SPECMAP 1818O (dashed) and simulation (solid)O (dashed) and simulation (solid)

Intermediate ModelsIntermediate Models Global, 2-5 dimensional model:Global, 2-5 dimensional model:• 5˚ latitudinal bands5˚ latitudinal bands• In each bandIn each band

- 2 continental sectors (Eurasia-Africa, Americas)2 continental sectors (Eurasia-Africa, Americas)- 3 ocean sectors (Atlantic, Indian, Pacific)3 ocean sectors (Atlantic, Indian, Pacific)

• Circulation dynamics: 2-level, Q-G Circulation dynamics: 2-level, Q-G - winds at 250 hPa, 750 hPawinds at 250 hPa, 750 hPa- temperature at 500 hPatemperature at 500 hPa- plus - Hadley Cell transport in tropicsplus - Hadley Cell transport in tropics

• 2-D ocean model for each basin2-D ocean model for each basin• Land-atmosphere coupling processes Land-atmosphere coupling processes (Crucifix et al., 2002)(Crucifix et al., 2002)

Intermediate Intermediate ModelsModels

Simulation Simulation versus versus observationsobservations

(Crucifix et al., 2002)(Crucifix et al., 2002)

Intermediate ModelsIntermediate Models

(Crucifix et al., 2002)(Crucifix et al., 2002)

Intermediate Intermediate ModelsModels

Prescribed ChangesPrescribed Changes

(Crucifix et al., 2002)(Crucifix et al., 2002)

Intermediate Intermediate ModelsModels

Prescribed ChangesPrescribed ChangesandandResponsesResponses

(Crucifix et al., 2002)(Crucifix et al., 2002)

Intermediate Intermediate ModelsModels

ResponseResponse

(Crucifix et al., 2002)(Crucifix et al., 2002)

Intermediate Intermediate ModelsModels Prescribed Changes - Prescribed Changes -

SensitivitySensitivity

(Crucifix et al., 2002)(Crucifix et al., 2002)

Intermediate Intermediate ModelsModels

SensitivitySensitivity

(Crucifix et al., 2002)(Crucifix et al., 2002)

Global Climate ModelsGlobal Climate Models

Global Climate ModelsGlobal Climate Models

Differing scales: distributed surface properties

PBL

ATMOS

SVAT

Export throughStreamflow

SW/GW

External Forcing

CLASP

Global Climate ModelsGlobal Climate Models

GCM SimulationGCM Simulation

Paleo-Simulation Projects:Paleo-Simulation Projects: Cooperative Holocene Mapping Project Cooperative Holocene Mapping Project

(COHMAP)(COHMAP)

COHMAP extensionCOHMAP extension

Paleoclimate Model Intercomparison Project Paleoclimate Model Intercomparison Project (PMIP)(PMIP)

GCM SimulationGCM SimulationCooperative Holocene Mapping Project (COHMAP)Cooperative Holocene Mapping Project (COHMAP)NCAR CCM0NCAR CCM0Prescribed changes inPrescribed changes in

- InsolationInsolation- SSTSST- Ice sheetsIce sheets- COCO22

Time slices every 3,000 yr (18k BP, 15k BP, …)Time slices every 3,000 yr (18k BP, 15k BP, …) Perpetual January or JulyPerpetual January or July

GCM SimulationGCM Simulation

Cooperative Holocene Mapping Project (COHMAP)Cooperative Holocene Mapping Project (COHMAP)

Ice sheets & cold ocean Ice sheets & cold ocean

colder, drier climatecolder, drier climate

intensified jet streamintensified jet stream

Amplified annual cycleAmplified annual cycle

Intensified summer monsoonsIntensified summer monsoons

GCM SimulationGCM SimulationCOHMAP ExtensionCOHMAP ExtensionNCAR CCM1NCAR CCM1 ComputedComputed

- SST (slab ocean, prescribed heat transport)SST (slab ocean, prescribed heat transport)- Sea iceSea ice- Soil moistureSoil moisture- Seasonal snowSeasonal snow

Time slices every ~ 3,000 yrTime slices every ~ 3,000 yr Full annual cycle simulatedFull annual cycle simulated

(Kutzbach et al., 1998)(Kutzbach et al., 1998)

GCM GCM SimulationSimulation

GCM GCM SimulationSimulation

(Kutzbach et al., 1998)(Kutzbach et al., 1998)

• 25-yr simulation25-yr simulation

• Last 5 yr analyzed Last 5 yr analyzed

GCM GCM SimulationSimulation

(Kutzbach et al., 1998)(Kutzbach et al., 1998)

Longitudinal Longitudinal average average overturning overturning circulation circulation

(mean (mean meridional meridional circulation)circulation)

GCM SimulationGCM Simulation

(Kutzbach et al., 1998)(Kutzbach et al., 1998)

SpruceSpruceGCM GCM SimulationSimulation

(Bartlein et al., 1998)(Bartlein et al., 1998)

Douglas Douglas FirFir

SagebrushSagebrush

Present-Day Present-Day ResultsResults

GCM GCM SimulationSimulation

(Bartlein et al., 1998)(Bartlein et al., 1998)

Changes Changes with with ClimateClimate

Paleoclimate Model Paleoclimate Model Intercomparison Project:Intercomparison Project:Tropical Changes @ LGMTropical Changes @ LGM

• 17 GCMs17 GCMs- 9 slab ocean9 slab ocean

- 8 prescribed SST8 prescribed SST

• Prescribed changes inPrescribed changes in

- insolation- insolation

- CO- CO22

- ice sheets- ice sheets

GCM GCM SimulationSimulation

PMIP: LGM vs. Present DayPMIP: LGM vs. Present Day

(Pinot et al., 1999)

GCM GCM SimulationSimulation

(Pinot et al., 1999)

GCM GCM SimulationSimulation

PMIP: PMIP: Present DayPresent Day

Sea-surface temperature

Land-surface temperature

(Pinot et al., 1999)

GCM GCM SimulationSimulation

PMIP: PMIP: Present DayPresent Day

(Pinot et al., 1999)

GCM GCM SimulationSimulation

PMIP: PMIP: Present DayPresent Day

Ocean precipitation

Land precipitation

PMIP: LGM vs. PD PMIP: LGM vs. PD (30 S - 30 N)(30 S - 30 N)

(Pinot et al., 1999)

GCM GCM SimulationSimulation

Paleoclimate Model Paleoclimate Model Intercomparison Project:Intercomparison Project:Tropical Changes @ LGMTropical Changes @ LGM

GCM GCM SimulationSimulation

Top: Sfc T change - prescribed SST

Bottom: Sfc T change - computed SSTRMS spead among models

Paleoclimate Model Paleoclimate Model Intercomparison Project:Intercomparison Project:Tropical Changes @ LGMTropical Changes @ LGM

GCM GCM SimulationSimulation

Difference in simulated SST changes from reconstructed changes (LGM-PD)

(Pinot et al., 1999)

GCM GCM SimulationSimulation

PMIP: LGM-PDPMIP: LGM-PDComparison with proxiesComparison with proxies

Paleoclimate Model Paleoclimate Model Intercomparison Intercomparison Project:Project:Tropical Changes @ Tropical Changes @ LGMLGM

GCM GCM SimulationSimulation

Model changes vs. pollen record

Coldest month temperature

Paleoclimate Model Paleoclimate Model Intercomparison Project:Intercomparison Project:Tropical Changes @ LGMTropical Changes @ LGM

GCM GCM SimulationSimulation

Model changes vs. pollen record

Annual surface temperature

Precipitation changes vs. lake records prescribed SST models

Precipitation changes vs. lake records computed SST models

Paleoclimate ModelsPaleoclimate Models

(Chapter 12)(Chapter 12)

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