The Whole Earth Course

Chapter 9

Hydrosphere 2

The Cryosphere

Instructor: Dr. George A. Maul

gmaul@fit.edu / 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.

Past Glaciation

Ice cover changes Earth’s Albedo (A)

Who Cares?

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

Climate Change: Arctic Sea Ice

Motion of Arctic Sea Ice

http://www.youtube.com/embed/hC3VTgIPoGU?rel=0

Antarctic Ice

“Facts matter” Stephen Breyer

Associate Justice, US Supreme Court

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 ?

Stefan-Boltzmann Law

Q=

Units?

Circa 1879

Plank’s LawIλ

λ

What is QGHE ?

𝑄𝐺𝐻𝐸=𝜎 𝑆𝑡𝑒𝑓𝑎𝑛−𝐵𝑜𝑙𝑡𝑧𝑚𝑎𝑛𝑛×𝑇 4

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

Albedo: Today’s value A=30%

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%) = ?

Contorted medial moraines of Susitna Glacier in Alaska.

Glaciers

Where do we find glaciers?

28m

How thick can glaciers be?

How thick is 3000 m?

What is the height of the Crawford Building?

Main features of a valley glacier.

An expanded view of the effects of glacial ice on the geosphere.

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

Changes in a Glacier

Evolution of glacial carved

landforms

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?

Major glacial landforms in USA

Periglacial Landforms, Permafrost, Tundra

Tundra Extent

TundraPeriglacial Landform

Permafrost

FeedbackWhich is positive feedback and which is negative feedback?

http://www.atmosedu.com/Geol390/feedbacks.htm

Why do icebergs float? Who was Archimedes?

Sea Ice

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 = ?

What maritime disaster precipitated the formation of the International Ice Patrol?

Blowing up Icebergs?!?!

Pancake Ice – discovery of the Ekman Spiral.

Seasonal extent of sea ice in A. Southern hemisphere, and B. Northern hemisphere.

Florida Tech Student deploying FIT-built ROV under Arctic Ice

What is an ROV?

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

Next TimeChapter 10 – the oceans

70.8% of the Whole Earth’s Surface