OCN 5401 Chapter 2 Stratification Instructor: Dr. George A. Maul [email protected] / X 7453.
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Transcript of OCN 5401 Chapter 2 Stratification Instructor: Dr. George A. Maul [email protected] / X 7453.
Water is a Unique Molecule
SpecificHeat (Cp)
calories/gram/ºC
joules/kg/kelvin
Water 0.9998 4186
Air 0.2404 1006
Granite 0.192 804
Ice Floats!!!
Amount of heat added to or released from one gram of water during a change of state.
How much heat is 2260 Joules?
Of what significance is this addition or loss
of heat during evaporation and
precipitation?
Depos
ition
How much heat is 2260 Joules?Heat (H) = mass (m) ∙ specific heat
(Cp) ∙ Temperature change (∆T)
H = m ∙ Cp ∙ ∆T
Assume m = 1 kg = 1 liter H2O
∆T = ?
x1000 km3 % of total
Ocean 1,400,000.0 95.96
Cryosphere 43,400.0 2.97
Groundwater 15,300.0 1.05
All other reservoirs: 93.2* 0.02
Lakes* 9.0Rivers* 1.7Soil Moisture* 65.0Atmosphere* 15.5Biosphere* 2.0
Inventory of water at Earth’s surface (from Berner and Berner, 1987)
Seasalts
What is salinity?
Grams of salt in one kilogram saltwater
Bonaire, N.A.
28m
56m
If we evaporate the ocean, how thick a layer of salt would
be left behind?
84m
Consider a column 5000 m by 1 m2 square. For S=35‰, salt content is ~35 kg·m-3, density of salt is ~2.1 g·cm-3.
Could the ocean hold more salt?
Great Salt Lake, Utah. Salinity range 50 to 270‰
A two-layered fluid
A16 T-S Diagram• Iceland-0º• 0º - 30ºS• 30ºS – South Georgia Island
Depth zones in the ocean Why do these profiles appear as they do?
𝑆=1𝜌𝜕 𝜌𝜕 𝑧
The previous figure is an average distribution of temperature, salinity and density. However, the surface values are variable with both latitude and season. Here we see the average annual temperature by latitude.
Why do they differ?
Oceanic Internal Waves
Brunt-Väisälä Frequency
pycnocline follower
http://ice.nasa.gov/aboutCryosphere/
What about the Cryosphere?
Why do icebergs float? Who was Archimedes?
Sea Ice
How high does an iceberg float?
We’ll need the hydrostatic equation again
p = ρ∙g∙z
pup = pdown
287 B.C. to 212 B.C. Buoyancy Force Fb = g V dρ
What maritime disaster precipitated the formation of the International Ice Patrol?
Blowing up Icebergs?!
A. Southern hemisphere B. Northern hemisphere.
Seasonal extent of sea ice
How much frozen water is in sea ice?Sea ice is 0.1% of the total volume of ice on Earth
How much of Earth is covered with sea ice?
2/3 of Earth’s permanent ice cover is sea ice. This is approximately 5-6% of the surface area of Earth.
Of what significance is sea ice in the Earth System?
What happens if it all melts?
What happens if more forms?
Please note the size of the sheets of ice breaking off!
Approximately 1000 km3 of glacial ice enters the sea each year as icebergs. (Can you put this number in perspective?)
How wide is Florida?
How much heat to melt sea ice? Sea ice is 0.1% of Cryosphere
or
0.043 x 106 km3 or 43 x 1018 g of ice.
For ice at 00C to water at 00C 330J/g or 79 cal/g ice is required.
Total heat required to melt sea ice is 1.45 x 1022 J
or
for the whole Cryosphere is 1.45 x 1025 J.
For perspective, world energy consumption is approximately
4 x 1020 J/year
One PB&J sandwich is about 1 million Joules!!
OCN 5401
Questions?
Chapter 2
