Lab 3a: The present - University of Texas at Austin



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Lab 8 (follows lab 6 part 2): The Glaciers and Ice Sheets in the Climate System

NOTE:

For home work, please answer all PROBLEMs in this lab on a separate sheet of paper!

INTRODUCTION:

So far we have learned a good deal about glaciers and their importance in the Earth’s climate history during Icehouse eras. This lab is designed to consolidate what we have learned. The students are advised to read Chapter 2 (p. 44-47), Chapter 3 (p. 58, 63, 66), Chapter 10 (p. 210-233), and Chapters 11-15 for further information.

Today we are in an Icehouse era, in which glaciers comprise 2% of the Earth’s total water and about 80% of the fresh water in the world. Ice covers approximately 10% of the world’s land surface (not including oceans). The cryosphere (the frozen part of the world) has a major influence on the Earth’s climate. In order to persist, glaciers require cold temperatures, land, and adequate frozen precipitation. Therefore, the size of glaciers is affected by global climate. These cause and effect relationships make glaciers a dynamic and poorly understood feedback mechanism in the global climate.

What are glaciers?

• Glaciers are masses of permanent ice which are able to flow under their own weight.

So to have a glacier of your very own you need:

• Enough ice to last to and through the summer melting season

• The ice in your glacier needs to be flowing under its own weight.

We like to think of two types of glaciers:

Valley Glaciers

Length: 1-100’s of km

Width: 1- 10’s of km

Thickness: 10’s to 100’s k

Melted at base

Uniform temperature throughout (freezing point)

Respond to climate change on scale of 10’s to 100’s of years

Ice Sheets

Length & width: 100’s – 1000’s of km

Thickness: 500-1000’s meters

Often frozen at base

More complex temperature profile

Continental scale

Respond to climate change on scale of 1000’s of years

Source of image:

(Photographed by M. Schmeltz)

[pic]

This picture is form the Italian Alps (very near Austria). And was taken in mid September. Mass balance is a measure of Ice Accumulated – Ice Lost. When Ice melts / sublimates, the particles trapped within the ice remain. So where there is a positive mass balance (accumulation > ablation (loss)) the glacial surface remains white throughout the summer and fall. However where there is a negative mass balance (ablation > accumulation), the dust (which does not melt) gets concentrated at the surface, causing a noticeable darkening. The line which divides accumulation and ablation is known as the equilibrium altitude line (ELA). There were flurries on the day this picture was taken so assume that it is the end of the ablation season.

PROBLEM 1:

Assuming that this picture was taken at the end of the ablation season (summer), draw the boundary between the accumulation zone and the ablation zone (also known as the ELA). See Picture above for answer.

PROBLEM 2:

In the Photo below, compare the relative sizes of the accumulation zones (really white) with the size of the ablation zones (speckled white).

How does the future look for these glaciers? See Below for ELA.

The future of these glaciers looks rather bleak as the ablation zone is much bigger than the accumulation Area. These glaciers are shrinking.

[pic]

(M. Schmeltz September 13, 2002)

[pic]

Just relax a moment and experience the call of the wild.

Massive minus points if you don’t relax for a moment, but check it out:

Glaciers on the far peak

U-shaped valleys

Hanging valleys

Glacial polish

Everyone covered with silt

PROBLEM 3: EAST ANTARCTICA—ICE CORES:

Here’s what’s up. As of March 2002, the ice core record now extends to Ca 720,000 years ago. However this data is still unpublished so we’ll focus on a more accessible published record from Vostok Station -- the coldest place on the face of the Earth.

(NOTE: Problems 3a to 3f follow below in text)

[pic]

SOURCE:

Petit, J. R.;Jouzel, J.;Raynaud, D.;Barkov, N. I.;Barnola, J. M.;Basile, I.;Bender, M.;Chappellaz, J.;Davis, M.;Delaygue, G.;Delmotte, M.;Kotlyakov, V. M.;Legrand, M.;Lipenkov, V. Y.;Lorius, C.;Pepin, L.;Ritz, C.;Saltzmann, E.;Stievenard, M..  " Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica "   Nature London, Jun 03, 1999, Vol.   399, Issue   6735, p   429-436

3a) All right this graph is rather busy, so we’ll walk you through it.

First of all: compare the bottom X-Axis (age) to the top X-Axis (depth). Since age in ice increases with depth, you can put two labels on the same axis. This relationship, however is not a straight line. So on which axis (age or depth), are the intervals regular evenly spaced? The labels are evenly spaced for the “age” axis. Kind of confusing eh? They use the δ180 to calibrate the age. Deeper/older ice thins considerably under the weight of all that ice above.

3b) “Insolation” (the bottom line) is a measure of how much energy the earth’s surface receives. The bottom line measures the amount of energy received during summer at 65°N. Using your text and the notes, what was the approximate latitude of the Northern Hemisphere ice sheets during the last glacial maximum? (a few words)

Most of the ephemeral Northern Hemisphere Ice sheets were centered at 65°N

3c) Why is R. Petit (the guy who created this famous diagram) linking the δ18O record to the strength of Northern Hemisphere summers? (1 sentence)

Strong N. Hemisphere summers melt and Kill ice sheets.

3d) Does the atmospheric concentration of CO2 appear to rise before the temperature rises or after?

The two appear to rise almost concurrently, usually CO2 in front

3e) Does the atmospheric concentration of CH4 appear to rise before the temperature rises or after?

CH4 rises after temperature rises in some cases. Isn’t this interesting? However there are times when it rises concurrently with temperature—VERY FAST RESPONSE TIME

3f) Give a short paragraph describing the patterns inherent in these records and their relation to climate processes:

What I want people to notice:

1. The abruptness with which a major glacial period ends

2. How quickly an interglacial period ends

3. The relative stability of the climate during Interglacial periods.

4. The wild climate fluctuations of climate during Glacial periods

5. The Excellent correlation between Temperature and CH4 and C02.

[pic]

PROBLEM 4: WEST ANTARCTICA: Larsen Ice shelf:

Short term oscillation or long term climate change?

(NOTE: Problems 4a to 4f and additional instruction follow below in text)

Go to the web page:



go to the link “view animation” for Animation of Larsen B breakup, 31 January to 7 March 2002 “(1/2 way down screen on left just above the grey box),

Or: click this link to view the movie of ice sheet break-up.

To learn more about the break-up of the Larsen Ice shelf, go back and use the links under “press releases” for:

• “University of Colorado”

• “British Antarctic Survey”

[pic]

4a) What theory has been proposed to explain the collapse of the Larsen Ice Shelf?

Warmer temperatures lead to pools of liquid water on the surface which then propagate downward through natural weakness in the ice shelf.

4b) Does this theory relate to climate change? How/how not?

Certainly the regional climate of the Antarctic Peninsula has warmed sharply in the last 50 years. Indeed this region is experiencing some of the largest increases in temperature of any place on the planet. However we only have 50 years or so of records so . . .

4c) A sediment core from this area suggests that the ice shelf has been stable since before the Last Glacial Maximum? Does this evidence change your decision?

Enter the proxies! The type of sediment which forms underneath an ice shelf is dramatically different form the sediment which forms under open water. Think of all the differences: Exposure to light, surface mixing, salinity. A full treatise is not necessary, but it should suffice to say that this level of warming has not been seen at this location in a very long time.

4d) Does the collapse of the Larsen Ice Shelf lead DIRECTLY to sea level rise? Why or why not? NO. The melting of floating ice does not add to sea level. Ice shelves are floating.

4e) Might the collapse of the Larsen Ice Shelf INDIRECTLY lead to sea level rise?

YES! The ice shelf used to hold back the glaciers which fed it. Now that the ice shelf is gone, those glaciers are flowing up to 3 times as fast and they just keep getting faster. That’s land ice flowing into the oceans and that is sea level rise

4f) Finally, where is the Larsen Ice Shelf relative to the bulk of the Antarctic ice. How does this distance compare to the distance between Austin and Chicago (1800 km)?

The Larsen Ice shelf is about as far away from The bulk of the interior ice as Austin is to Chicago. What happens in one part of Antarctica is not always directly connected to the rest of the continent. The Antarctic Peninsula is known as the “Banana Coast” of Antarctica.

PROBLEM 5: Wrapping it all up:

Why are satellites and air photographs used to further our understanding of large ice sheets?

Put Simply: Ice Sheets are HUGE and harsh environments we need equipment capable of surveying large tracts in relatively short periods of time. Satellites can give us the big perspective needed to understand these complicated parts of the world during times when 1000 member teams can not be there. These techniques are also LOW IMPACT.

PROBLEM 6:

Go to:



and tell me the coolest thing that you find (this requires 1 sentence)

There is a lot of neat things that happen with the light at high latitudes. And Antarctic people are COOL!

References:

Paterson, W. S. B. The physics of glaciers,, 1994

Petit, J. R., Jouzel, J., Raynaud, D., Barkov, N. I., Barnola, J. M., Basile, I., Bender, M.;Chappellaz, J., Davis, M., Delaygue, G., Delmotte, M., Kotlyakov, V. M., Legrand, M., Lipenkov, V. Y., Lorius, C., Pepin, L., Ritz, C., Saltzmann, E., Stievenard, M.. "Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica", Nature, Jun 03, 1999, Vol.  399, Issue  6735, p. 429-436.

Rignot E, Vaughan DG, Schmeltz M, Dupont T, MacAyeal D. “Acceleration of Pine Island and Thwaites Glaciers, West Antarctica.”, Annals of Glaciology, Vol. 34, 2002.

Oerlemans, J., Anderson, B., Hubbard, A., Huybrechts, P., Johannesson, T., Knap, W. H.;Schmeits, M., Stroeven, A. P., van de Wal, R. S. W., Wallinga, J., Zuo, Z.. "Modelling the response of glaciers to climate warming", Climate Dynamics, Apr 01, 1998, Vol.   14, Issue   4, p. 267-274.



Schmeltz, Majorie “Photos”

The National Snow and Ice Data Center

Andrew Shepherd,1* Duncan J. Wingham,1 Justin A. D. Mansley,1 Hugh F. J. Corr2 Inland Thinning of Pine Island Glacier, West Antarctica SCIENCE Volume 291, Number 5505, Issue of 2 Feb 2001, pp. 862-864.

The Institute for Geophysics

This lab was funded in part by

Utrecht University, Institute for Marine and Atmospheric Research, Utrecht, Netherlands

The South Tyrolean board of tourism

And a travel grant from Arno P. (Dutch) Wendler Professional Development Fund.

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