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Glacier Mass ∆
Glacier Mass ∆
GRACE
Gravity Recover & Climate Experiment
Measures variations in Earth's gravity field over time
Resolution: coarse
(~300km)
Other mass ∆s also affect record
Limited to major ice sheets
(regions w/large continuous ice extent)
Austfonna Ice Cap, Svalbard
Recent thinning
across ~ 50 km portion from centre to margin
Dynamic thinning
- ice loss area correlates with velocity increase
Elevation ∆ observed from Cryosat (radar altimetry)
Unlikely caused by air temp ∆
--> given thinning only seen at one portion of margin
Convincing evidence K anomaly
IceSat - laser altimetry 2003-2009
shows slower area loss / some gain in K
DEM Photogrammetry (Gardelle 2012)
i.e. differencing 2 high res DEMs
✓ Higher spatial res IceSat
x Less coverage - due to processing (errors of different nature)
Length change (bolch 2012)
Spy photos, Icesat etc
Bolch 2012 cumulative ∆ since 1900 with any data source poss
Karakoram Anomaly
Glaciers in Karakoram = reacting differently
Area loss = much slower
(or gain/thickening in some glaciers)
Different behaviour / glacier type
Karakoram Glaciers
Responding differenlty to forcing applied
Lengthening
THickening (or atleast not thinning)
Icelandic Ice
Cap Surface ∆
High elevations
-
slight thickening
1200km - Warmer air carries more water - thickening
Fringes/ edges
-
signif thinning
Lower elev <1200 km - lotsa thinning (more melt)
Air temp ∆ = likely cause
--> given homogeneity in mass ∆ across regions
GRACE
msmt
= direct msmt of mass ∆
from msmt of ∆ in Earth's gravitational field
Earth's Mass Redistribution
Himalayas
-
exhibit big mass ∆
probs loss ice mass
Canada
Probs reflects isostatic uplift following ice sheet loss kyrs ago
Biggest cause gravity variations
= water movement on Earth
Biggest cause gravity thus mass variations
High Mtn Asia Glacier ∆
Majority Himalayan glaciers
exhibit thinning & retreat
i.e. East/Central/W Himalaya
Karakoram glaciers exhibit
slower area loss or thickening/area gain
Mtn range btwn India/China & Pakistan
Gardelle
2012
Findings suggested NO THINNING (net mass gain) on Karakoram Glaciers