What are your lakes doing to my glaciers

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What are your lakes doing to my glaciers?

• Ben Smith
• Ian Joughin
• UW-APL polar science center

Funded by NSF grant ANT0636719, With thanks to
Helen Fricker and Bob B. and the ASAIDS project
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Background 1
124 active lakes are known in Antarctica based
ICESat repeat-track analysis More than 280 more
lakes are known to exist, but their activity
level is unknown
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Background 2
-2006-07 drainage of a pair of lakes in the Byrd
Glacier catchment was associated with a 10,
1-year speedup in glacier flow -Prior to WAIS
2009, no other concurrent lake-drainage and
velocity measurements were available
Question to be answered -Is the Byrd glacier
response typical for lake drainage
events? -What are the chances that any observed
change in glacier speed is due to an unobserved
lake drainage?
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Two interesting lakes
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Cook lakes
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Spring, 1800 GMT
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Mid summer, 2200 GMT
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Cook lake volume estimates

• Upper lake discharged 4 km3 of water in 2 years,
  or about 63 m3/s
• Large discharge from upper lake coincides with
  much smaller filling at the lower lake
• Timing of lower-lake filling uncertain by 6
  months
• Drainage between late 2006 and late 2008

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Upper lake
Lower lake
Potential basin?
Cook IS
Grayscale Hydro potential, Contours surface
height
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Measuring Cook Ice Shelfs dynamic response
Landsat feature tracking on Cook Ice
Shelf --Comparisons between pairs of images
320-420 days apart give 10 m/yr
resolution --Main limitations are a lack of
bedrock control points, and cloudy
conditions MAMM and ALOS SAR data also give
velocities -MAMM velocities show poor coherence,
may not be well controlled
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Lambert glacier lake
A lake beneath the Eastern tributary to Lambert
glacier drained from before 2003 until mid-2006
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Lambert glacier lake
ICESat shows 0.8 km3 drainage, ending in mid
2006. Landsat, Radarsat and ALOS velocities
available
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Recovered ice speeds
-No significant speed variation between 2000 and
2004, or between draining and drained conditions
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Conclusions

• No significant speed-up in Lambert glacier
  results from a flood of 0.8 km3 over 2.5 a
• Possibly reflects channel formation over longer
  periods.
• Possible ice-speed variations in Cook glacier
• Resulted from the largest flood seen in
  Antarctica between 2003 and 2009
• Further ice speed measurements needed to confirm
  ice speeds prior to 2007
• Glacier speed sensitivity to water inputs is
  likely to depend on flood volume, duration, and
  water distribution at the bed during the flood
• More comparisons like these are need to identify
  patterns with different glacier types.
• Answers to previous questions
• What are your lakes doing to my glaciers?
• It depends on the glacier
• Is the Byrd glacier response typical for lake
  drainage events?
• No- responses depend on the glacier.
• What are the chances that any observed change in
  glacier speed is due to an unobserved lake
  drainage?
• Small, although more observations are needed.

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Mid summer, 500 GMT