Please enable JavaScript.
Coggle requires JavaScript to display documents.
Ice Shelves & G.L. (Amery Ice Shelf (Amery shelf = Trapped btwn 2…
Ice Shelves
& G.L.
Grounding Line
= where ice sheet disconnected from bed
∴ ice becomes afloat
i.e. transition ice sheet/stream to shelf
Antarctica
IS Bed
∴ Ice sheet bed = well below sea level
WAIS / much of Antarctic IS = 'marine ice sheet'
'Foredeepened bed'
deeper inland than at margin
Myr of ice pressing down on bed
WAIS Unstable
due to:
Downsloping bed
Ocean interaction
Grounding
Line Mvmt
Grounding line is not fixed in space
If ice thins enough it will float
∴ Grounding line moves
since ice shelf extent changes
Volume lost
Once ice is floating it has contributed to sea level
∴ Melting will not contribute further
Rapid Ice
Shelf Motion
Ice shelves = amongst fastest moving areas of ice
Flow rate control ? Partly geographical settting of ice shelf
Thwaites Velocity Curiosity
Velocity profile & elevation (ice shape)
from ice stream upstream to ice shelf front
Ice sheet:
Velocity increases as slope steepens seaward
Ice sheet thinning oceanward
Ice shelf
= Curious
Velocity increases as ice flattens & thins
Contradicts theory discussed so far
Amery
Ice Shelf
Amery shelf = Trapped btwn 2 slow moving regions of Antarctica
Slows down close to grounding line
Speeds up toward front / coastal margin as ice thins
Velocity dip - possibly represents buttressing ?
Why ice shelves behave differently
Different material?
No - mostly same material as ice sheets
i.e. ice formed from land forms ice shelves
Differing geographical setting
Setting has changed
Grounded ice - exposed to friction @ bed
Ice shelf = frictionless ∴ weaker at bottom
Ocean beneath shelf
Honey
Analogy
Thick stream through air
Supports itself - will all fall if cut it
Flows fast
Spreads out on plate
Governed by friction - slows mvmt
i.e. grounded ice
Ice shelf = like thick stream
pulling / stretching itself out in
attempt to become as thin as possible
Grounded Ice Velocity ∆
Ice speed-up observed due to ice shelf thinning
in past few decades
e.g. Pine Island, Thwaites E. Ice Shelf/Ice Tongue
How does ice shelf thinning cause ice stream acceleration?