29 SEPTEMBER 2007 The Commerce of Climate PHOTO BY ROGER BRAITHWAITE AND JAY ZWALLY.
A WAIS Analog Found on Mars Polar Cap Weili Wang 1, Jun Li 1 and Jay Zwally 2 1. Raytheon ITSS,...
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Transcript of A WAIS Analog Found on Mars Polar Cap Weili Wang 1, Jun Li 1 and Jay Zwally 2 1. Raytheon ITSS,...
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.