Difference between revisions of "Ice observations"

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Ice breakup is either mechanical or thermal  
 
Ice breakup is either mechanical or thermal  
  
Ice definitions (from NWS Alaska Pacific River Forecast Center)
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==Ice definitions (Reference: NWS Alaska Pacific River Forecast Center)==
Ice chunks: smallest size of ice
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*Ice chunks: smallest size of ice
Ice pans: medium sized ice
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*Ice pans: medium sized ice
Ice sheet: large size ice
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*Ice sheet: large size ice
Shorefast ice
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*Shorefast ice
Bottomfast  / anchor ice
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*Bottomfast  / anchor ice
Frazil ice
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*Frazil ice
Pre-breakup
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== Pre-breakup ==
unbroken ice: continuous ice surface that has few cracks
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*unbroken ice: continuous ice surface that has few cracks
Rotten ice:  weak ice that appears brown or black
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*Rotten ice:  weak ice that appears brown or black
Arched ice:  Ice that is attached to the banks which rises in the center of the channel due to increased flow beneath the ice, causing melt water to collect in channels along banks
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*Arched ice:  Ice that is attached to the banks which rises in the center of the channel due to increased flow beneath the ice, causing melt water to collect in channels along banks
Shifted ice:  large ice sheets that have moved short distances from their original locations as rising water levels create wider areas of open water into which the ice can move
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*Shifted ice:  large ice sheets that have moved short distances from their original locations as rising water levels create wider areas of open water into which the ice can move
Moving Ice / Breakup
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==Moving Ice / Breakup==
Ice run: continuous length of moving ice
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*Ice run: continuous length of moving ice
Breakup front: location along river in between moving and stationary ice
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*Breakup front: location along river in between moving and stationary ice
The ice breakup front may stall out temporarily while moving downstream like an inchworm, this is not an ice jam.  A significant amount of ice run accumulating upstream from the location where the breakup front stopped due to an obstruction (sharp bend, constriction, island, bridge, etc.) is an indication of an ice jam.  If an ice jam is observed, estimate the height.
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*The ice breakup front may stall out temporarily while moving downstream like an inchworm, this is not an ice jam.  A significant amount of ice run accumulating upstream from the location where the breakup front stopped due to an obstruction (sharp bend, constriction, island, bridge, etc.) is an indication of an ice jam.  If an ice jam is observed, estimate the heights.
Flooding:  water that has gone over the banks and covered areas of lands that are normally dry.
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*Flooding:  water that has gone over the banks and covered areas of lands that are normally dry.
Post breakup
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==Post breakup ==
Ice or debris run:  a length of river channel containing moving ice or debris
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*Ice or debris run:  a length of river channel containing moving ice or debris
Stranded ice:  ice pushed onto the banks or side channels that is left behind after the ice has cleared out of the main channel
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*Stranded ice:  ice pushed onto the banks or side channels that is left behind after the ice has cleared out of the main channel
Field notes:   
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== Field notes:  ==
Describe breakup daily
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*Describe breakup daily
Estimate the size of the ice (length, width, thickness, height above water level)
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*Estimate the size of the ice (length, width, thickness, height above water level)
Estimate the speed of the ice
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*Estimate the speed of the ice

Latest revision as of 09:11, 12 April 2010

Ice breakup is either mechanical or thermal

Ice definitions (Reference: NWS Alaska Pacific River Forecast Center)

  • Ice chunks: smallest size of ice
  • Ice pans: medium sized ice
  • Ice sheet: large size ice
  • Shorefast ice
  • Bottomfast / anchor ice
  • Frazil ice

Pre-breakup

  • unbroken ice: continuous ice surface that has few cracks
  • Rotten ice: weak ice that appears brown or black
  • Arched ice: Ice that is attached to the banks which rises in the center of the channel due to increased flow beneath the ice, causing melt water to collect in channels along banks
  • Shifted ice: large ice sheets that have moved short distances from their original locations as rising water levels create wider areas of open water into which the ice can move

Moving Ice / Breakup

  • Ice run: continuous length of moving ice
  • Breakup front: location along river in between moving and stationary ice
  • The ice breakup front may stall out temporarily while moving downstream like an inchworm, this is not an ice jam. A significant amount of ice run accumulating upstream from the location where the breakup front stopped due to an obstruction (sharp bend, constriction, island, bridge, etc.) is an indication of an ice jam. If an ice jam is observed, estimate the heights.
  • Flooding: water that has gone over the banks and covered areas of lands that are normally dry.

Post breakup

  • Ice or debris run: a length of river channel containing moving ice or debris
  • Stranded ice: ice pushed onto the banks or side channels that is left behind after the ice has cleared out of the main channel

Field notes:

  • Describe breakup daily
  • Estimate the size of the ice (length, width, thickness, height above water level)
  • Estimate the speed of the ice