Topic 10 Ice and Fog
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Transcript of Topic 10 Ice and Fog
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Topic 10Ice and Fog
GEOL 2503Introduction to Oceanography
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Ice
• Ice is fresh water, pure H2O • Dissolved materials are left behind in the
surface water• Remaining surface water has increased
salinity (same amount of salt, less liquid water)
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Sea Ice
Frozen ocean surface water
Photos from the International Ice Patrol photo gallery: http://www.uscg.mil/lantarea/iip/Photo_Gallery/Category.shtml
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Land Ice
• Earth's ice cover formed on land as the result, principally, of the freezing of precipitation
• Takes water from one reservoir (ocean) and moves it to another (land)
• Changes the volume of water in oceans (and sea level)
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Ice Sheets
• Regional, extensive covering of land ice• Antarctic—largest• Greenland—second largest• Sometimes referred to simply as glaciers,
but there are also small glaciers in mountains and elsewhere that are not ice sheets
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More Ice Terms
• Fast Ice—sea ice anchored to land mass, doesn’t move
• Ice Floe—sea ice not anchored, moves with currents
• Iceberg—broken off chunks of land ice
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Icebergs
• Ice is about 10% less dense that liquid water
• So only about 10% floats above water• “tip of the iceberg”
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Icebergs off Greenland
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12
3
Iceberg photos from IIP:
1. Coast Guard plane
2. Tabular iceberg
3. World’s tallest iceberg, 550 feet
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Notice the latitude at which the Titanic sank. Since then, the sea surface has warmed enough that today there are no icebergs south of about 45 degrees north latitude
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Life of an Iceberg
This is the basic drift of an average iceberg during its 2-3 year life cycle.
The numbers correspond to the next few slides showing the different stages of the iceberg's life in more detail.
12
65
4
3
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Birth (very large iceberg)
Photo of glaciers on Greenland's West Coast which produces most of the icebergs that drift down into the north Atlantic shipping lanes.
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Childhood (large to very large icebergs)This photo shows winter off of Baffin Island, and the many very large icebergs that spend the early part of their "lives" there.
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Teen (medium icebergs)
Here is the rugged coastline of Labrador, where large icebergs often ground themselves or break up into smaller pieces as they continue traveling south.
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Young Adult (medium rolling or breaking-up icebergs)
This picture shows the St. John's, Newfoundland area, where medium-sized icebergs continue to break up and roll through shipping lanes and past oil rigs.
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Old Age (small icebergs)When the iceberg reaches this stage it is often small in size (also called a growler) from years of melting and breaking up. Once icebergs reach old age, they quickly
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Water Cycle of an Iceberg(see next slide)
• The life cycle of the iceberg is also a key part of nature's water cycle. • First, water in the ocean (including water from the small melted
icebergs) evaporates and forms clouds. • Some of those clouds are then carried by the wind over the country of
Greenland where the cold air causes them to condense. • This condensation causes the clouds to release the water as
precipitation in the form of snow. • This snow fall builds for thousands of years, and then compresses to
form glaciers. • Due to their immense weight the glaciers are then forced down to the
ocean by gravity. • As they reach the ocean pieces of the glacier break off and fall into the
ocean, creating icebergs. • The iceberg goes through its life cycle, travels through the ocean,
grows smaller over time and then once again melts, starting the water cycle all over again.
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The water cycle of an iceberg (see previous slide)
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Iceberg Shapes
• 1. Tabular (Flat)• 2. Wedge• 3. Dome• 4. Blocky• 5. Dry-docked (Connected under water)• 6. Pinnacled (Pointed) • 7. Non-tabular (Anything else)
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1. Tabular (Flat)
2. Wedge
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3. Dome
3. Blocky
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5. Dry-docked (Connected under water)
6. Pinnacled (Pointed)
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7. Non-tabular (Anything else)
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Fog• Cloud at ground level• Form when air can’t hold all the water
vapor (cool air can’t hold as much as warm)
• Fog/clouds are liquid water—droplets• Three types
– Advective– Radiative– Sea Smoke
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Advective Fog
• Warm air, saturated with water vapor• Moves over colder water• Blanket of fog forms at surface of water• Tends to persist• Grand Banks• San Francisco
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Radiative Fog
• Warm days, cold nights• Earth surface cools at night• So does air above surface• Moisture in air condenses at night• Forms low-lying, thick fog• Dissipates as air warms, water evaporates• Also called “radiation fog”
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Sea Smoke
• Dry, cold air• Moves over warmer water• Water warms air above it• Air picks up moisture from water• Warmed air rises rapidly• Air cools, water vapor condenses• Forms ribbons of fog
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How sea smoke forms
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Ice Fog
• forms when the air temperature is well below freezing
• composed entirely of tiny ice crystals that are suspended in the air
• will only be witnessed in cold Arctic / Polar air
• Generally the temperature will be 14 F or colder in order for ice fog to occur.
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Ice fog
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Freezing Fog• Occurs when the water droplets that the fog is
composed of are "supercooled“• Supercooled water droplets remain in the liquid
state until they come into contact with a surface upon which they can freeze
• Any object the freezing fog comes into contact with will become coated with ice.
• The same thing happens with freezing rain or drizzle.
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Freezing fog