the whole earth course chapter 9 hydrosphere 2 the cryosphere instructor: dr. george a. maul...
TRANSCRIPT
The Whole Earth Course
Chapter 9
Hydrosphere 2
The Cryosphere
Instructor: Dr. George A. Maul
[email protected] / X 7453
http://www.panoramas.dk/fullscreen2/full22.html
Outline of the Class
• Earth’s Cover of Ice and Snow• Glaciers• Glaciated Landscapes• Sea Ice• Periglacial Landscapes and Permafrost• Summary
What is the Cryosphere?
• Sea, lake, and river ice• Glaciers• Ice sheets• Ice caps• Ice shelves• Frozen ground such as permafrost
Last time we said that Earth’s Cryosphere is 43,400,000 km3
In-class Calculation:How tall would a 1 km x 1 km tower of 4.3x107 km3 stand?
What is the distance to the sun?
Volume = Height x Length x Width
4.3x107 ÷ 149.6x106 =
HOW BIG IS THE CRYOSPHERE?
Approximately 3% of all the water in the hydrosphere is contained in the Cryosphere.
WHERE DO WE FIND THE CRYOSPHERE?
Glaciers cover about 10% of land area.
Permafrost is another 20% of land area.
HOW MUCH IS SEA ICE?
Two-thirds of Earth’s permanent ice cover;
one-thousandth of Earth’s total ice volume.
Average snow cover in the northern hemisphere (%) during December 1992, based on data received (left) from a microwave sensor aboard a satellite.
Maximum 1979-1995What is a microwave
satellite sensor?
Today’s ice and snow coverage
MICROWAVE SENSORSDefense Meteorological Satellite Program – DMSP
Scanning Multichannel Microwave Radiometer - SMMR
DMSP SMMR Image
Motion of Arctic Sea Ice
http://www.youtube.com/embed/hC3VTgIPoGU?rel=0
How would Earth’s temperature change if the ice coverage changed?
414 EARTHSUN
GHE TAC
Q
QGHE: What is the greenhouse effect?
CSUN: What is the solar constant?
A: What is Earth’s albedo?
4: Where does the ¼ come from?
What is ?
IN CLASS CALCULATION:
CSUN: What is the solar constant?
SUNSUNEarth
SUNSUN C
r
rT
2
24
4
4
where
4281067.5 KmWx
If TSUN = 5775 K, CSUN = ?
rsun= 696,000 kmrEarth-SUN=149,600,000 km
Why the ¼ in our equation?
Energy in: π r2
Energy out: 4π r2
By-the-way: Q is a flux, i.e. amount per unit area per unit time
𝐽𝑚2𝑠
=𝑊𝑚2
Units?
IN CLASS CALCULATION:
How would Earth’s temperature change if the albedo changed from 30% to 29%?
4%)30(30.01
4 AEARTHSUN
GHE TC
Q
4%)29(29.01
4 AEARTHSUN
GHE TC
Q minus
)(30.029.04
4%)29(
4%)30( AEARTHAEARTH
SUN TTC
If TEARTH(A=30%) = 288K, TEARTH(A=29%) = ?
Pressure Melting Point of Ice
0
500000
1000000
1500000
2000000
2500000
-25-20-15-10-50
Temperature (Celsius)P
res
su
re (
mil
lib
ars
)
Ice movement over meltwater has less friction than over frozen surfaces.
What is the pressure (p) at the base of a 10,000 m thick glacier?
p = ρ∙g∙h
IN CLASS CALCULATION:
What is the pressure (p) at the base of a 10,000 m thick glacier?
What are the units?
What is the pressure melting point at the base of the glacier?
-25-20-15-10-500
50000000
100000000
150000000
200000000
250000000
Pressure Melting Point of Ice
Temperature (Celsius)
Pre
ssu
re (p
asca
ls)
So the ice melts at -8°C
Effects of glaciers on Earth’s surface are significant. Can you contrast the effects of streamflow and glaciers on sediment transport?
Hint: Which one sorts sediments during transport?
FeedbackWhich is positive feedback and which is negative feedback?
http://www.atmosedu.com/Geol390/feedbacks.htm
IN CLASS CALCULATION:
How high does an iceberg float?
We’ll need the hydrostatic equation again
p = ρ∙g∙hp – pressure, ρ – density, g – gravity, h – height
ρseawater=1025 kg·m-3 ρice=917 kg·m-3
(ρgh)water = (ρgh)ice so hice = ?
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?
Who cares?
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?
http://oceanexplorer.noaa.gov/edu/learning/player/lesson12/l12la1.html
Towing Icebergs
Step 2: curtain icebergStep 1: circle iceberg Step 3: tow iceberg
How much heat to melt sea ice?
What about the Cryosphere?Sea ice is 0.1% of Cryosphere
or
0.0434 x 106km3 or 39.4 x 1018 g of ice.
For ice at 00C to water at 00C 330J/g or 79 cal/g is required.
Total heat required to melt sea ice is 1.3 x 1022 J,
or
for the whole Cryosphere is 1.3 x 1025 J.
For perspective, world energy consumption is approximately
4 x 1020 J/year
One PB&J sandwich is about 1 million Joules!!
Transect along western Atlantic Ocean showing water masses and general circulation processes.
What happens if sea ice melts here?
What happens if sea ice forms here?
Post Script: Greenland Sea Deep Water Warming
http://www.sciencedaily.com/releases/2013/09/130925102833.htm
Summary
• Cover of Ice, Snow, and Permafrost is 30%• Glaciers: temperate and polar• Glacier mass = accumulation - ablation• Glaciated Landscapes: Plow, File, and Sled• Sea Ice: >60% of area, 0.1% of volume• Permafrost covers >20% of land surface