glaciations on mars: response to orbital variations...

Glaciations on Mars:response to orbital variations

inferred from climate modelling,and comparison with Earth.

J.-B. Madeleine1 (jbmlmd@lmd.jussieu.fr)F. Forget1, J. W. Head2, F. Montmessin3, S. Bonelli4

1Laboratoire de Météorologie Dynamique (LMD), CNRS/UPMC/IPSL, France2Brown University, Providence RI 02912, USA3Service d’Aéronomie, CNRS/UVSQ/IPSL, France4Laboratoire des Sciences du Climat et de l'Environnement

(LSCE), IPSL/UMR CEA-CNRS 1572/UVSQ, France.

With the help of Pierre-Yves Meslin, Ehouarn Millour and Cédric Pilorget

International Conference on Comparative Planetology - 11-15 May 2009 - ESTEC, Noordwijk (NL)

Two glacial climate systems

Atmosphere

Cryosphere (ice sheets and glaciers)

Glacier bed

External controls(orbital parameters

and solar variability)

Internal controls

(Plate tectonics, magnetic field)

Biosphere(includinghumans)

Adapted fromAndrews (2006)

Earth and MarsClimate System

(10 to 106 year time scale)

Atmosphere

Glacier bed

Internal controls

Orbital parameters of Earth

Adapted from Paillard et al. (1996)

Today:ε = 23.5°e 0.017∼

Orbital parameters of Mars

Adapted from Laskar et al. (2002)

MARSEarth

Today:ε = 25.2°e 0.093∼

Atmosphere

Glacier bed

Internal controls

Atmosphere

Glacier bed

Internal controls

Cryosphere - Atmosphere

Atmosphere CryosphereChanges inmass balance

Summertemperature

(ablation)

Precipitation(accumulation)

- Orbital parameters:Change the space-time distribution of insolation;

- Radiative transfer:Chemical species (CO2)and aerosols (dust and clouds) change surface temperature.

- Water sourcesFirst control on the amount of water vapor in the atmosphere;

- Lower atmosphere temperature

Controls the amount of water vapor;- Dynamics

Results in cross-front mixing of moisture and condensation;

- Condensation nucleiFavor cloud formation.

Atmosphere

Glacier bed

Internal controls

Atmosphere

Glacier bed

Internal controls

Icethickness

LGM: 21 kyr Today

Contour intervalof 1 km Peltier et al. (1998)

Earth 21 kyr BP: Last Glacial Maximum (LGM)

Earth: CLIMBER-GREMLINS coupled model (S. Bonelli)

CLIMBER 2.3 (Petoukhov et al., 2000)

- climate model of intermediate complexity;- Fast enough to run simulations over thousands of years;- model the major features of the atmosphere-vegetation-ocean system;- Resolution: 51° in longitude, 10° in latitude.

Atmosphere

Icesheet

GREMLINS (Ritz et al., 1997)

- 3D thermo-mechanical ice sheet model;- predicts the vertical temperature profile, basal melting, ice dynamics and isostatic adjustment of bedrock;- Resolution: 45 km in longitude and latitude (cartesian grid)Siegert et al. (2005)

CLIMBER 2.3 (Petoukhov et al., 2000)

- climate model of intermediate complexity;- Fast enough to run simulations over thousands of years;- model the major features of the atmosphere-vegetation-ocean system;- Resolution: 51° in longitude, 10° in latitude.

Model is forced by:1) The orbital parameters (Berger, 1978)2) The atmospheric CO2 content,

measured at the Vostok station(Petit et al., 1999)

3) The amount of dust deposition on the surface, which changes the albedo (Mahowald et al., 1999)

Past CO2concentrations,

Vostok

Start ofthe run

LGMLGM TodaySummer Surface Temperatures (°C)

LGM: ε=22.95° e=0.019 Today: ε=23.5° e=0.017

ObservationsObservations Coupled model results

Peltier et al. (1998)

Ice sheetheight (m)

(Bonelli et al.,2009)

ObservationsObservations Coupled model results

Peltier et al. (1998)

Ice sheetheight (m)

(Bonelli et al.,2009)

Asymmetry over northern Asia

Earth: Asymmetry over Asia: Dust deposition

(Mahowald et al., 2006)

Dust darkening effect (Krinner et al., 2006)

Earth: First conclusions

Glacial-interglacial periods are mainly controlled by summer surface temperatures;

Favorable conditions implied by the orbital parameters are amplified by the CO2 cycle (Eurasian glaciation);

Dust deposition on the seasonal snow cover results in low albedo and melting in northern Asia.

(Bonelli et al., 2009)

Mars: Late Amazonian (< 250–700 Myr) glaciations

Head et al. (2008)

- The latitude dependent mantle (1): m thick layered deposits, above 50° (Head et al., 2003);- Northern mid-latitudes (3,4,5,6,7): valley glaciers and plateau glaciation, km thicknesses;- Tropical mountain glaciers (8): mountain glacial systems, episodes of advance and retreat;

Head et al. (2005, 2008)

MARS EARTH

Tropical mountain glaciers (8): mountain glacial systems, episodes of advance and retreat;

Mars: Late Amazonian mid-latitude glaciation

MARS EARTH

Head et al. (2008)

Northern mid-latitudes (3,4,5,6,7): valley glaciers and plateau glaciation, km thicknesses;

Mars: Late Amazonian mid-latitude glaciation

Mars: The LMD/GCM

Observations

- 3D General Circulation Model;

- Dust cycle: based on a prescribed value of τdust;

- Water cycle: includes water vapor transport and condensation predicted by a microphysical scheme (Montmessin et al, 2005).

Smith et al. (2002)

Summer Fall Winter Spring Summer

Water vapor column, in pr. μm

Mars: The LMD/GCM

Observations

Smith et al. (2002)

Summer Fall Winter Spring Summer

Water vapor column, in pr. μm

Model is forced by:

1) The orbital parameters(Laskar et al., 2002)

1) The atmospheric dust content, inferred from

dust transport simulation

(Newman et al., 2005)

< SAME FORCINGS >

Tharsis tropical mountain glaciers

Forget et al. (2006)

ε=45°, e=0, τdust=0.2, sources=northern polar cap

Summer north-westerlywinds and precipitation

Northern mid-latitude glaciation

Clouds(pr. µm)

WV (pr. µm)

Wind (100 m/s)at 5.6 km

ε=35°, e=0.1, Lp=270°, τdust=2.5, sources=TMG

Today Late Am.

eleine et al. (2

Northern mid-latitude glaciation

(mm/yr)

(mm) (mm)

eleine et al. (2

Dust feedback: Two planets, same component, same physics, different feedback:

− Mars: positive feedbackdust-atmospheric heating feedback (warms the atmosphere and leads to increased water vapor content).

− Earth: negative feedbackdust-albedo feedback (darkens the ice cover and increases ice melting);

Discussion (1)

MODIS-NASA, and Malin et al. (2007)

What about the other components of the two climate systems?

− Cryosphere: Ice-thickness feedback (height of the ice sheet changes the geometry of the atmospheric waves);

Ice-albedo feedback (brighter surfaces and change in the net radiation budget);

Ice-thermal inertia feedback (dampens surface temperature variations and reduces ice sublimation);

Discussion (2)

− Atmospheric dust: Dust lag feedback (on the contrary, a fine layer of dust prevents the underlying ice from sublimating in a low P/T° environment);

− Clouds: Cloud radiative feedback (changes the thermal structure of the atmosphere)

Discussion (3)

Conclusion Ice ages are strongly controlled by ablation on both

planets, but on Mars, precipitation is very sensitive to orbital parameters and atmospheric dust;

GLACIAL EARTH=”COLD”, GLACIAL MARS=”WARM”! Earth model has to be forced by past atmospheric CO2

contents to trigger the Eurasian glaciation; Mars GCM has to be forced by past presumed dust

content to trigger the Northern mid-latitude glaciation;

THRESHOLD-LINKED BEHAVIOR ON BOTH PLANETS! Same components (dust cycle) of the climate system

seem to play a different role in the two glacial cycles:

MARS IS THE ONLY OPPORTUNITY TO STUDY THE SAME COMPONENTS UNDER DIFFERENT CONDITIONS.

glaciations on mars: response to orbital variations...

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