Who Left the Freezer Door Open?

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Who Left the Freezer Door Open?

• Dr. Robert Bindschadler
• Chief Scientist
• Laboratory for Hydrospheric and Biospheric
  Sciences
• NASA Goddard Space Flight Center
• Robert.A.Bindschadler_at_nasa.gov

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Landsat Image Mosaic of Antarcticalima.usgs.gov l
ima.nasa.gov
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Remember

• Most climate models underestimate ice loss
• Less ice in a warmer world
• Ice sheet dynamics will dominate future sea level
  change
• Ice sheets hate water

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(adapted from NSIDC)
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Sea-Level History tells us

• Less ice in warmer climates
• Ice sheets shrink faster than they grow

HIGH
SEA LEVEL
Less ice
More ice
LOW
TEMPERATURE
WARM
COLD
THEN
NOW
Time
? Ice sheet dynamics matters
But we dont know the details
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Sea level has gone up much faster

• Relatively steady over past 6000 yrs (2 mm/yr.)
• Periods of fast rise
• Up to 20 times present rate
• Cant be due to melting alone
• Ice flow dictates rapid sea level rise
• Humans have never dealt with rapid sea level rise

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Sea Level has been Rising
3.1 mm/a
2.0 mm/a
From Church and White, 2006
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Ice Sheets matter NOW
Maldives
B. Richmond, USGS
London
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Earth Science and Applications from Space
National Imperatives for the Next Decade and
Beyond (a.k.a. NRC Decadal Survey)
Key Question 1 (of 6) Will there be
catastrophic collapse of the major ice sheets,
including Greenland and West Antarctica and, if
so, how rapidly will this occur? What will be
the time patterns of sea level rise as a result?
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maximum?
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Sea Level Rise Components
?
Ice Sheets
Ocean Thermal Expansion
Glaciers and Ice Caps
Source IPCC FAR
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Where is the Ice?
East
West
2-6 of all water on Earth 70-80 of all fresh
water on Earth
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6 meter rise--Greenland Ice Sheet is equal to 6
meters
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6 Meter Rise
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Ice Sheets matter Globally
Source CReSIS and NASA
Land area lost by 1-meter rise in sea level
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Impact of 1-meter sea level rise
From Anthoff et al., 2006
An immediate and significant impact on economies
and ecosystems worldwide
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Direct observations tell us
? Ice sheets are changing fast
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Old Greenland Ice Sheet
Sea level Change (mm/a)
0
1
-1
accumulation
450 Gt/a
melting
225 Gt/a
ice flow
225 Gt/a
Approximately in mass balance
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We See

• Thickening in the high elevation interior of
  Greenland
• Big change can be 10
• Climate models get this about right
• Increase in surface melting around perimeter
• Big change can be 50
• Climate models also get this about right
• Large acceleration, retreat and thinning of
  outlet glaciers
• Big change can be 100s
• 210 observed already (Rignot and Kanagaratnam,
  2006)
• Ice flow models cant get this right

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Tomorrows Greenland Ice Sheet
Sea level Change (mm/a)
0
1
-1
accumulation
melting
ice flow
Things could get a little better or a lot
worse Increased ice flow will dominate the future
rate of change
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Declining Health of Greenland
(Source Luthcke et al., unpub.)
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Fastest Flow at the Edges
Interior 1000s meters thick and
slow Perimeter 100s meters thick and fast
Source Rignot and Thomas
Response time and speed of perturbation
propagation are tied directly to ice flow speed
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Accelerating Outlet Glaciers
(Source I. Joughin)
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Recent Rapid Retreat
ice flow
Icebergs leaving Jacobshavns Fjord
Jacobshavns Isbrae
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The most sophisticated ice-flow models cant
reproduce recent outlet glacier behaviorbut
whats responsible?
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Water

1. Causes basal lubrication
2. Causes ice shelf disintegration
3. Causes grounding line melting

Ice sheets HATE water!
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Summer acceleration of Greenlands margins
Glacier flow increases 10-15 Slower ice
increases up to 70
(from Joughin et al., 2008)
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More Melt More Lubrication Faster Flow
Texas
(Source M. Tedesco)
Flow increase is proportional to amount of melt
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Ice Shelf Disintegration
2000 km2 of Larsen Ice Shelf disintegrated in 2
days.
Source T. Scambos
Require gt10,000 years to form Disintegrate in
weeks
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Consequence of Ice Shelf Loss
up to 510 faster in 2 years
up to 400 faster in 2 years
(Scambos et al., 2004)
Newly un-buttressed glaciers accelerate
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400 miles
1000 miles
PIG is moving at one foot per hour and thinning
at over one meter per year
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Cold, fresh water
Warm, salty water

• Melting basal ice ?reduces basal friction
• ?reduces buttressing effect of
  floating ice shelf

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Blogs take you through last field season
http//pigiceshelf.nasa.gov
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Field work takes time.While you wait
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Tidewater glaciers are a good analogue to
anticipate ice sheet future
Muir Glacier, Alaska
Large outlet glaciers are displaying classic
drastic retreat traits similar to Alaskan
tidewater glaciers
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Tidewater Glacier Drastic Retreat
600
400
Altitude (m.a.s.l.)
200
Quasi-stable
Sea level
0
0
10
20
30
40
Distance (km)
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Tidewater Glacier Drastic Retreat
600
400
Altitude (m.a.s.l.)
200
Quasi-stable
retreating
Sea level
0
0
10
20
30
40
Distance (km)
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Tidewater Glacier Drastic Retreat
600
400
Altitude (m.a.s.l.)
200
Quasi-stable
retreating
Still retreating
Sea level
0
0
10
20
30
40
Distance (km)
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Columbia Glacier, Alaska
Helheim Glacier, Greenland
??
2000
1980
Source USGS
1996 aerial photograph
2007 image (GoogleEarth)
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• Central region of Greenland is below sea level
• Jacobshavns Isbrae occupies subglacial channel
  connected to central depression

Russel Huff, Univ. of Colorado
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Antarctica
West Ant.
East Ant.
Nearly all of West Antarctica ice sheet and much
of East Antarctica ice sheet rests on bed below
sea level
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Summary

• Most climate models underestimate ice loss
• Less ice in a warmer world
• Sea level rise will increase
• Ice sheets dynamics will dominate future sea
  level change
• 1 m by 2100
• Ice sheets hate water
• Were working on it

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Antarctica in Hi-Def
http//lima.usgs.gov
Like it REALLY looks!
http//lima.nasa.gov
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About LIMA

• First IPY benchmark data set
• Used 1100 individual Landsat-7 scenes
• Contains over100 Billion pixels
• each pixel the size of half a basketball court
• Data are free (but data set is huge)
• Solutions are being developed
• Helps people become more familiar with Antarctica
  really looks like

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3D with MODIS
3D with LIMA
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Enhanced Versions show Details
30X
10X
3X
No stretch
No stretch
Custom stretch
MODIS MOA
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Complementary Mosaics
LIMA
RadarSat
MOA
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http//lima.nasa.gov

• Lesson plans
• Hands-on samples
• Videos of scientists explaining use of imagery
• Links to gt13,000 Antarctic names
• Flying tour of Antarctica as it really looks

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What is it?
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NASA Quest

• 1000s of students exploring Antarctica

http//quest.nasa.gov/challenges/lima
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Thank you!
Questions?