A WAIS Analog Found on Mars Polar Cap  

Weili Wang1, Jun Li1 and Jay Zwally2

1. Raytheon ITSS, NASA/GSFC, Code 971, Greenbelt, MD 20771, USA.

2. Ocean and Ice Branch, NASA/GSFC, Code 971, Greenbelt, MD 20771, USA.

North Polar Cap

South Polar Cap

Mars X 5 km

X 5 km

Meter

X 5 km

X 5 km

Meter

(Surface topography)

(Surface topography)

(Maximum thickness: ~ 3000 m at the dome)

(meter)

Distance (x5 km)

Dis

tanc

e (

x5 k

m)

North Polar Cap on Mars

Chasma Boreale

Surface topography and flowlines

300 km

AB

Mars Polar Cap

WAIS

A BTheoretical

(Vialov type) ice-sheet profile

Grounding Line

Inland Ice

Ice Stream

Ice Shelf

Chasma Boreale

Ice-Stream Onset(After Bindschadler et al, 2001, The West Antarctic ice sheet )

The location of the transition between inland ice flow (corresponding to a convex-up shape profile) and ice-streaming flow (corresponding to a concave-up shape profile ).

WAISSurface elevation (m)

Surface slope

Driving stress (bar)

Onset

Mars Polar Cap Surface elevation (m)

Surface slope

Driving stress (bar)

Onset

Ice-Sheet Modelling

A flowline model is applied to examine the basal/surface conditions required for maintaining this ice-stream type surface profile.

Model Run I (warm bed)Inputs:

Outputs:

• Flowline geometry• Surface mass balance• Basal temperature (at pressure melting point)• Basal geothermal heat flux

• Distribution of temperature• Distribution of velocity

Model Run II (cold bed)Inputs:

Outputs:

• Flowline geometry• Surface temperature• Basal geothermal heat flux

• Distribution of temperature• Distribution of velocity• Surface mass balance

Surface mass balance (accumulation rate + ablation/sublimation rate)

Basal Melting RateEmergence Velocity

Ice-Sheet Modelling

x

BbUbWsW

x

SsUΜ

Continuity Equation

{{

: 00th

yε

Model Run I (warm bed)

Distance (km)

m/a

m/a

oc

(m)

(m)

(m) Temperature

Horizontal Velocity

Vertical Velocity

(m)

Dynamic Velocity

m/a

(Glen’s flow law)

Distance (km)

m/a

m/a

oc

(m)

(m)

(m) Temperature

Horizontal Velocity

Vertical Velocity

(m)

m/a

Dynamic Velocity

Onset

(Glen’s flow law)

-5-10

Model Run I (warm bed)

Model Run II (cold bed)

Temperature

Horizontal Velocity

Vertical Velocity

Surface mass balance

Distance (km)

m/a

m/a

oc

(m/a

)(m

)(m

)(m

)

Temperature

Horizontal Velocity

Vertical Velocity

Surface Mass Balance

Distance (km)

m/a

m/a

oc

(m/a

)(m

)(m

)(m

) -80-70

Model Run II (cold bed)

Distance (km)

Surface Mass Balance

Basal TemperatureC/m

C/mC/m

Surface Temperature

Blue: x 10-4

Red: x 10-5

Green: x 10-6

(o C)

(m/a

)

Model Run II (cold bed)

Summary:

• The surface topography determined by MOLA data shows an ice-stream type profile through the head of Chasma Boreale.

• “Onset” (the location of the transition between inland ice flow and ice-stream flow) is clearly detected.

• Modelling study indicates that basal melting may have been experienced over the bed of Chasma Boreale at various times in Mars’ history.