Iceberg Scouring

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Iceberg Scouring
By Tony Zwink
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What is it?

• Plough marks made by icebergs keels as they
  pass over lake or sea beds.
• Scour Dimensions
• Depth- 20m
• Width- 250m
• Length- Several Km

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Features

• Deep Pits caused by grounding.
• Scoured berms that can reach 6m.
• Chaotic criss cross patterns.

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Case study

• J.A. Dowdeswell did a study on the East
  Greenland Shelf involving present day scouring.
  (1992)

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Results

• About 18 km3 of icebergs are calved from the
  Scorsby Sund Fjord system each year. (Satellite)
• These icebergs cause severe scouring and can have
  keels up to 550m below the surface.
• Iceberg scouring inversely related to water
  depth.

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Iceberg Keel Size

• J.A. Dowdeswell did a study on the keel size
  of icebergs in the Antarctic. (2007)
• INSERT IMAGE

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Iceberg Keel Sizes

• Keel sizes dependant on the thickness of the ice
  shelf
• Melt a few meters a year
• Only a few scours found below 500-600m

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Why are they Important?

• Paleoclimate indicators
• Economics
• Biologic effects

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Case Studies

• J. Winsemann conducted a study on glacial Lake
  Rinteln (2003) and found iceberg scours preserved
  in the lake fan deposit.

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Stratigraphic Cross Sections
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Series of Events
Shows Paleoclimate as well as stratigraphic
history!
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Case Studies

• Article by Jenna Hill studied iceberg scours off
  the South Carolina coast using bathymetric and
  side scan sonar. (2008)
• Alternative Hypothesis
• Fishing
• Paleochannels
• Density driven gravity flows

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Evidence of Icebergs?

• Grounding Pits
• No change in volume from the berm to the trough
• Piles of sediment at the end of scour tracks
• String and circular depressions indicate skipping
  and bobbing

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Paleoclimate Indicator?

• Present current flow

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Case Studies

• D. Gerdes, H. Lee conducted studies of the
  scouring effects on deep sea life. (2001, 2003)

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Huge Effect on Seafloor Life
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Economic Effects

• Sea floor excavation (glory holes)
• Often several well heads placed in the same
  hole. Directional drilling.
• Cost!!

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References