IPY/NSTA Web Seminar: The Fragile Ice LIVE INTERACTIVE LEARNING @ YOUR DESKTOP Thursday, May 3, 2007...

IPY/NSTA Web Seminar:

The Fragile Ice

LIVE INTERACTIVE LEARNING @ YOUR DESKTOP

Thursday, May 3, 2007

7:00 p.m. to 8:00 p.m. Eastern time

Snow: a Winter’s Tale- or -

Evidence of the Past from Snow on the Ground

Mary Albert, Ph.D.Army Cold Regions Research & Engineering Laboratory

andDartmouth Thayer School of Engineering

International Polar Year

Take the pulse of the poles. Biggest effort in 50 years

• Arctic observing network• Life in extreme environments• Polar ice sheets• Education and outreach• www.us-ipy.gov (U.S.)• www.ipy.org (International)

A “beehive” of activity

http://www.us-ipy.gov/

http://www.ipy.org/

Snow characteristicsAntarctica from space

BPRC Ohio State

M. Albert for NSTA 2007

Ice sheets hold evidence of changing climate. Snow in your yard has evidence of changing weather.

http://earthobservatory.nasa.gov/Study/RampingUp/Images/RAMPmosaic_5km.jpg

• What causes different layers in snow on the ground?• What causes changes in snow crystals once they are

on the ground?• How can snow on the ground give evidence of past

weather?


Falling Snow


No two snow crystals falling from the sky are alike. But are they all dendritic, like the Christmas tree ornaments?

Yes No

Falling Snow

Libbrecth & Rasmussen, 2006

The shape of falling snow crystals depends on temperature and humidity in the atmosphere.


Snow layer formation


Layers of snow on the ground are from different depositional events. They provide evidence about different snow (or rain!) storms.

Snow on the ground

Colbeck et al, 1990

Snow crystal shape changes in time due to metamorphism.

Crystals become more faceted when there is a strong temperature gradient across the layer.


Which layer in this snow pack has faceted crystals?

Snow on the ground


Snow on the ground

Colbeck et al, 1990

Snow crystals get more rounded as they experience warmer conditions.


A temperature gradient is a difference in temperature between two points a certain distance apart.


At temperatures below freezing, why would a temperature gradient cause metamorphism?

Snow crystals contract as it gets colder

Snow crystals expand as it gets colder

Water vapor moves and

condenses on crystals

Surface chemistry

changes the grain shape

This difference in vapor pressure causes the vapor to diffuse from the region of higher vapor pressure to the region of lower vapor pressure.

Warmer air can hold more water vapor than colder air.

So warmer air has higher vapor pressure than colder air.

warmercolder


warmercolder


Summary

Do snow crystals change when there is no change in temperature?

Yes No


How do snow layers behave throughout the winter and into spring?


Sprayed-on dye helps to show snow layering

Before After


(m)


Air

tem

per

atu

re

(C)

Some of the layers are labeled.

Which layer(s) will change first due to changing weather?

Layer 1 Layer 7 All of them


When the snow melts, do all layers melt at the same time ?

Surface snow changes the most in response to changing weather.


The top layer shows the most change due to changing weather.


During much of the melt season, surface melt percolates through melt channels in the snow.


Subsurface layers remain intact through much of the winter, providing evidence about the storm that created them.


Evidence of the Past in Snow• Snow on the ground gives evidence of past weather.

• The snow near the top of the snow pack changes first, in response to changes in the weather.

• Snow crystal properties give evidence of warming or cooling weather in the recent past.

• The International Classification for Snow on the Ground (Colbeck et al 1990) is a guide you can use for metamorphism clues: http://www.crrel.usace.army.mil/techpub/CRREL_Reports/reports/Seasonal_Snow.pdf

• Understanding how nature works helps us to use clues to learn about the past.

• You can be a weather detective with your class by making notes of daily weather & snowfall over time. Then dig a snow pit and look at the snow layers to see how the evidence of weather found in the snow pack correlates with your notes of the observed weather.


http://www.crrel.usace.army.mil/techpub/CRREL_Reports/reports/Seasonal_Snow.pdf

NASA


Ice sheets hold evidence of past climate.The surface conditions reflect current climate, and layers within in

the ice contain evidence of the past. Evidence of climate thousands to hundreds of thousands of years ago hides deep in the ice sheet, waiting for ice coring science to unlock the clues.

Follow IPY science on these web sites:

www.ipy.govwww.ipy.org

Follow our scientific traverse across Antarctica at:

http://traverse.npolar.no

See teachers in the field at:www.polartrec.com

http://www.ipy.gov/

http://www.ipy.org/

http://traverse.npolar.no/

http://www.polartrec.com/

http://earthobservatory.nasa.gov/Study/RampingUp/Images/RAMPmosaic_5km.jpg

http://www.elluminate.com

Elluminate logo

http://learningcenter.nsta.org

NLC screenshot

National Science Teachers AssociationGerry Wheeler, Executive Director

Frank Owens, Associate Executive Director Conferences and Programs

Al Byers, Assistant Executive Director e-Learning

LIVE INTERACTIVE LEARNING @ YOUR DESKTOP

NSTA Web SeminarsFlavio Mendez, Program Manager

Jeff Layman, Technical CoordinatorSusan Hurstcalderone, Volunteer Chat Moderator

IPY/NSTA Web Seminar: The Fragile Ice LIVE INTERACTIVE LEARNING @ YOUR DESKTOP Thursday, May 3, 2007...

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