Download Lab 3a: The present

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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:
http://www.phys.uu.nl/%7Ewwwimau/education/karthaus02/photos/excursion/Pages/Ima
ge12.html (Photographed by M. Schmeltz)
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.
(M. Schmeltz September 13, 2002)
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)
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.
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:
http://nsidc.org/iceshelves/larsenb2002/
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”
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:
http://www.gdargaud.net/Antarctica/AntarSky.html
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.
http://nsidc.org/iceshelves/larsenb2002/
Schmeltz, Majorie “Photos”
http://www.phys.uu.nl/%7Ewwwimau/education/karthaus02/photos/excursion.html
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.