Please enable JavaScript.
Coggle requires JavaScript to display documents.
Antarctic Glaciology 2 (Marine IS Instability Hypothesis (Why unstable…
Antarctic Glaciology 2
Marine IS Instability Hypothesis
Glacier/ice stream
retreating on a reverse slope
→
will continue retreating
after initial foricng
Why unstable feedback?
Ice bed deepens inland
∴ Unstable positive feedback
→
Ever greater area exposed to ocean melting
(submarine melt by warm oceanwater)
With continued retreat into deeper bed,
Result retreat onto reverse bed
increasing flux across grounding line
∴ Grounded ice → Floating ice (shelf)
First elevation maps
From assembled radar seismic & gravity msmts e.g. Weertman 1974
∴ WAIS = biggest threat to global sealevel
'weak underbelly of antarctica'
forcing in AIS - will see WAIS decline/go away most quickly
Indicated WAIS = unstable
Marine
ice sheet
= area of ice with bed lying
below
sealevel
~ sensitive situation
History recap
1960s
Oversnow traverses
= Reconnaisance / exploration
1970s
Airborne reconn
First elev maps
∴ Ice volume --> WAIS Instability hypothesis
1980s/90s
Major field campaigns
Focus: WAIS instability hypothesis
1990s
Little evidence for WAIS instability
No measurements from Amundsen & Bellingshausen Seas though
Directed Field Campaigns 1980s
Focus efforts on coordinated scientific experiments
Weddell Sea Sector
Began field msmt @ Rutford Ice Stream
Rutford ice stream drains into Filchner Ronne Ice Shelf
Spot msmts:
ice shelf thinning
weddell seas oceanography
Siple Coast
Ice Streams
Ice streams
Most ice Q
self-organised into fast flowing channels of ice
Separated by slower areas of ice flow
Test bed for ideas of basal motion (basal sliding, soft sed def)
Discovery:
Ice streams exhibit
cycles of rapid/slow motion
- 'surges'
Satellite Obvs = Revolutionary
Remote sensing facilitated
large, continental-scale obvs
Antarctic - ESA msmts = first
Ice flow velocities - InSAR by ERS
Ice stream satellite insights
Ice streams can switch
on & off
Rapid onset/cessation of ice streaming
= observed by satellites
Lotsa theories wrt driver
Driver: probably f ( water @ ice bed )
InSAR
Interferometric synthetic aperture radar
Ice flow velocity msmts
Showed
self organisation ice flow
into channels of rapid flow
Same msmts decades apart
Revealed
acceleration of some ice streams
e.g. PIG
Satellite Altimetry
Ice surface elevation ∆ (lowering/rising)
All studies agree:
big ∆ @ margins
Greatest ice loss
:
Amundsen & Bellinshausen
sea sectors
Consistent ice loss @ PIG & Thwaites past ~30 years
Greatest ice loss
Amundsen & Bellinshausen
sea sectors
Consistent & worsening ice loss signal (lowering)