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Do Hesperian plateau channel networks record local or global climate conditions?. Mesoscale simulations with MRAMS of atmospheric response to chaos formation. Edwin Kite (UC Berkeley) Collaborators: Scot Rafkin & Tim Michaels (SwRI) Michael Manga (UC Berkeley). Outline.

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Mesoscale simulations with mrams of atmospheric response to chaos formation

Do Hesperian plateau channel networks record local or global climate conditions?

Mesoscale simulations with MRAMS of atmospheric response to chaos formation

Edwin Kite

(UC Berkeley)

Collaborators:

Scot Rafkin & Tim Michaels (SwRI)

Michael Manga (UC Berkeley)


Outline

Outline climate conditions?

Channels on the Valles Marineris plateau:

formed by chaos storms?

The Mars Regional Atmospheric Modeling

System (MRAMS)

Boundary conditions

Results


Plateau channel networks
Plateau channel networks climate conditions?

1.5km

  • Remarkably late in Martian history

    • Overlie Late Hesperian lavas

    • Main epoch of valley network formation tightly constrained to Late Noachian – Early Hesperian (Fassett & Head, JGR, 2008)

  • Associated with opal, ‘jarosite’ bearing light-toned layered deposits

  • Sometimes inverted relief

  • No HiRISE-resolved clasts

  • Multiple periods of flow; in places, flow direction changed over time

  • Strong evidence for precipitation, not groundwater

    • Drainage density, branching order, tributaries extend to near ridges

    • Phase (rain vs. snow) not clear

  • Local, regional or global climate change?

MOC NA R08-021292

Williams et al., LPSC, 2005

Milliken et al., GRL, 2008; Weitz et al., GRL, 2008

Bishop et al., JGR, 2009; Weitz et al., Icarus, in press


Localized chaos induced precipitation

MEGAOUTFLO hypothesis: Vapor release to atmosphere by chaos outflows produces transient global greenhouse.

- Baker et al., Nature, 1991; Baker, Nature, 2001.

But hydrologic models suggest individual chaos-forming events were small.

- Andrews-Hanna & Phillips, JGR, 2007

Harrison & Grimm, JGR, 2008.

Therefore, a localized response to chaos formation might be expected – mesoscale, not global.

- e.g., Mangold et al., 2008.

Localized, chaos-induced precipitation?


Test location juventae

Area of inverted channels outflows produces transient global greenhouse.

Area of LLD

from Weitz et al., Icarus, in press

OUTFLOW

CHANNEL

spillway

Flooding level

-1000 m

contour

Test location: Juventae

crater

Forced by present-day (Ames) GCM

Pressure 2x present-day

Fixed lake surface temperature and elevation

Surface albedo -> 0.75 when water ice lands

Flooded to -1000m, just below spillway elevation

Grid resolution 8.33 km (finest grid)

approx. 40 CPU-days

50km


Hypothesis test with mrams

  • Hypothesis outflows produces transient global greenhouse.: Given a chaos region filled to spillway with water at 5 deg C,

  • Precipitation location matches mapped light-toned layered deposits

  • Precipitation magnitude can move sediment through mapped inverted channels.

Hypothesis test with MRAMS

Mars Regional Atmospheric Modeling System (Rafkin et al., Icarus, 2001)

 Non-hydrostatic mesoscale model

 Used in landing-site downselect for MER, PHX, MSL

 Boundary conditions supplied by GCM

 Nested grids (8 km resolution on finest grid)

 Water vapor treated as a trace gas

CARMA-derived ice and dust aerosol microphysics

Monin-Obukhov surface flux parameterization

 Modified to include ITS-90 saturation vapor pressure


Atmospheric response

X-Z outflows produces transient global greenhouse.

section

peak ~ 1.4%

42 km

Atmospheric response

460 km

Observed

layered

deposits

Flooded

Juventae

Chasma

floor

MGCM, 1.25 days water release:

Ls = 270°, PCO2 = 2 x PAL

ALL RESULTS

ARE PRELIMINARY


Steady state zone of precipitation has been established

640 km outflows produces transient global greenhouse.

1.25 days

Steady state zone of precipitation has been established

Rates in inverted-

channel area are steady


Precipitation

Area of channels outflows produces transient global greenhouse.

Area of LLD

from Weitz et al., Icarus, in press

Mean ice precip rate in mm/hr

Precipitation

W-directed winds + promontory effect + rapid rainout

Snow

Peak value:

3.96 g/cm^2 in 1.25 days

In 1 Earth year, 1200 g/cm^2

Strong precip on chasm walls

expected

ALL RESULTS

ARE PRELIMINARY


Precipitation is highly localized

Precipitation is highly localized outflows produces transient global greenhouse.


At 2 x pal co 2 conditions on the plateau permit melting of precipitated water ice

Max. air temp from control run outflows produces transient global greenhouse.

Max. surface temp from control run (K)

At 2 x PAL CO2, conditions on the plateau permit melting of precipitated water ice

With albedo 0.7, temperatures are always less than 273.15K.


Modeled precipitation rates are sufficient to move gravel through mapped channels

Modeled precipitation rates are sufficient to move gravel through mapped channels

Perron et al., JGR, 2006

dd =1.33 km-1

PSP_003724_1755


Outstanding issues next steps

  • 1) Physics: through mapped channels

    • Sensitivity tests show a trend of reduced vapor release with reduced grid spacing in z;

    • The model has an inadequately-resolved water vapor concentration boundary layer.

    • Treat water vapor as a bulk constituent of the atmosphere

    • - Pressure & virtual temperature effects of H2Ov (pressure source; different molecular mass)

    • Self-consistent lake thermodynamics

    • Wind-dependent lake surface roughness parameterization from Shieh et al., 1979

    • New locations: Echus & Ganges

  • 2) Geology:

    • Are modelled precipitation rates sufficient to initiate observed channel network?

    • Look for additional inverted channels/layered deposits around chaos rims.

    • Search for opal or jarosite bearing deposits on the plateau far from candidate paleolakes

    • (would disprove the localized-precipitation hypothesis).

Outstanding issues / Next steps


Summary

Summary through mapped channels

Atmospheric response is “hurricane-like”

- Water vapor mass ratio reaches 0.3 (>> trace)

Juventae channels correspond to a local maximum in water-ice precipitation

- No channels in available (CTX) images of the south chasm wall

Water-ice precipitation is highly localized

- Inverted channels on the Valles Marineris plateau far from paleolakes would disprove the localized-precipitation hypothesis

Chaos storms can mobilize sand and perhaps gravel but not boulders.

- Detection of HiRISE-resolvable clasts would be a severe

challenge for the localized-precipitation hypothesis


Backup slides
Backup slides through mapped channels


What is the range of acceptable lake surface temperatures
What is the range of acceptable lake surface temperatures? through mapped channels

  • Vapor -> atm. will be small unless freezing of top of lake can be delayed

    -- 4.18 K for fresh water

  • In model, evaporative cooling ~ 2 KW/m2

    -- Sensible heat cooling < 1% of total cooling

  • Heat sources

    • fracturing mixes reservoirs that are isolated by low permeability

    • Shear heating

    • Clathrate decomposition (?)

    • Most important: volcanic heating

    • Warmest (deepest) water will arrive last (Andrews-Hanna & Phillips, 2007).

McKenzie & Nimmo, Nature, 1999