STEM
Ice Sheets and Sea Level -- Concerns at the Coast (Teachers Guide)
Roughly 153 million Americans (~53%
of the US population) live in coastal counties.
World wide some 3 billion people live within 200
km of the ocean (world population in 2007 6.6
Billion).
If the Greenland Ice sheet (equal to
about 6 meters of global sea level) and the East
and West Antarctic Ice Sheets (equal to about
64 meters of global sea level) were to melt
completely, coastal areas would be flooded up
to 70 meters (230 ft) above present. Geologists
have determined that in the geologic past, these
ice sheets have been known to melt back
dramatically and sometimes even disappear
during intervals when Earth’s climate was
warmer than it is now.
With green house gases now driving
us into a warmer world, our concern is to
estimate how high sea level might get over the
next few decades to centuries. Scientists from a
number of disciplines are now focused on this
issue in order to provide realistic predictions of
sea level rise and inform policy makers about
the need for wise and sensible coastal
management in the US and throughout the
world. Glaciologists, in particular, are studying
physical processes happening at the base of the
ice sheets and how rates of glacial flow into
the sea are changing. On the other hand, ice
shelves are floating ice bodies and their
collapse does not contribute to sea level rise;
however, they are known to buttress outlet
glaciers which drain the large ice sheets into
the sea. The loss of these ice sheets would
have a significant impact on sea level.
Moreover, atmospheric scientists are trying to
narrow uncertainties in the rates of global
warming, especially in the polar regions because
this directly influences glacier mass balance.
Changes in global sea level as projected
into the future are not entirely driven by melting
ice sheets, but also involves the thermal
expansion of the world’s surface ocean due to
increases in surface water temperature (i.e., an
increase in surface water volume as water
expands). Even more complex is the fact that
the position of the land relative to the sea is also
not fixed in many parts of the world. For
example due to the annual deposition of tons of
sediment at the mouth of the Mississippi River,
the coast of Louisianna is isostatically sinking
due the shear weight of the accumulating
sediment pile making up the Mississippi River
delta complex. This sinking further increases
the rise of sea level along the Gulf coast. Other
deltaic parts of the word share the same fate
(e.g., Amsterdam, Nile Delta, Bangladesh etc.).
Ultimately, we would like students to think about
the following questions during this exercise:
 What controls the elevation of the sea
against the shore? What causes it to go up
or down over thousands of years? What
causes it to go up or down over days,
months?
 How much did sea level rise at the end of
the last glaciation? At what rate did it rise
when the last great ice sheets disappeared?
 What factors contribute to sea level rise
today? Are glaciers and ice sheets the only
cause?
 How do city planners and coastal managers
observe and measure sea level rise?
 Does sea level rise at the same rate
everywhere? What types of coastal areas
are more vulnerable than others?
 How stable are the largest ice sheets on our
planet?
 What knowledge is needed to decrease
uncertainties in future projections? What
career possibilities are there to study and
mitigate coastal issues? How much more
information is needed before we act?
 How do we best manage our coastlines as
sea level rises? What choices may be
necessary?
Objectives
 Students will construct graphs showing the
relationship between ice sheet melting and
sea level rise during the last deglaciation.
 Students will interpret the graphs to
determine the rate at which sea level rose
during the last deglaciation.
 Students will use a graph of future
projections of sea level to trace the sea level
displacement on 3 types of coastlines (this
will help to assess societal vulnerability).
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A STEM ED Program at the University of Massachusetts, funded by the National Science Foundation and supported
by the Climate System Research Center in conjunction with the International Polar Year
STEM
Students can research, discuss and debate the
implications and policy issues facing cities and
countries with gradual sea level rise.
Equipment
Student guides
Rulers
Graph paper
Pencils
Alley et al. 2005, Science, 21 Oct issue.
Rahmsdorf, 2007, Science, 19 January issue
Methods:
1. Start with introducing the concept of global
warming and the questions listed in “Before
we Begin” on the student sheet. Also be
sure the students are familiar with the
concepts of the Green House Effect and
why/how sea level might change over time.
Even cycles of the moon, of course,
influence the tides which are significant in
some parts of the world.
2. Allow the students to plot the data in Table 1
on the student sheet (sea level rise of the
past 20ka). Their data will start to look like
the one shown below. This can be done
either by hand, or by using a program such
as excel to plot all the data. From this plot
(and fig. 4 below) they can consider the rate
of sea level rise in meters/thousand years,
centimeters per hundred years and
millimeters/year. Then they can consider
how fast sea level has risen over the past
few decades. You could skip the plotting
part and just have the students use these
graphs to pick off information to determine
the rates of sea level rise.
This figure shows sea level rise since the end of the last glacial episode
based on data from Fleming et al. 1998, Fleming 2000, & Milne et al. 2005.
(Wikipedia Commons)
www.umassk12.net/ipy
A STEM ED Program at the University of Massachusetts, funded by the National Science Foundation and supported by the
Climate System Research Center in conjunction with the International Polar Year
STEM
Standard Sea level curve from Fairbanks, R.G., 1989, A 17,000-year glacio-eustatic
sea level record: influence of glacial melting rates on the Younger Dryas event and
deep-ocean circulation: Nature, v. 342, p. 637-642. 07 Dec.
www.umassk12.net/ipy
A STEM ED Program at the University of Massachusetts, funded by the National Science Foundation and supported by the
Climate System Research Center in conjunction with the International Polar Year
STEM
3. Next ask the students to color in on the
three provided maps where the shore line
would be for 1 m (~3 ft) rise of sea level as
suggested by some for 2100. In a different
color they can show the additional areas
covered by the sea if sea level rose by 6 m
(which would take thousands of years).
How much shoreline retreat can they predict
on average for each of the three map areas
and what controls might there be on the rate
of retreat. The “analysis” questions can be
completed individually, in small groups or as
a whole class.
More advanced ideas:
4. More advanced groups might consider
researching the types of structures used by
engineers to slow down or prevent coastal
erosion.
5. Students could also consider the thermal
expansion of the ocean mixed layer as sea
surface temperatures increase. Add in a
plot of the density of water vs. temperature,
the volume of the ocean mixed layer and
how that layer would change with a
hypothetical change in 1° C.
Sea Level Estimates from Rahmsdorf, 2007. If this relationship between global mean
surface temperature and global mean sea-level rise is applied to the IPCC temperature
projections for the year 2100, it yields a sea-level rise of 0.5 to 1.4 m -- substantially
higher than estimates reported by the IPCC (2007). But current sea level rise is tracking
on the upper portion of this curve.
Important Links
http://www.realclimate.org
http://tidesandcurrents.noaa.gov/sltrends/sltrends.shtml
http://coastalmanagement.noaa.gov/czm/czma_vision.html
http://www.ipcc.ch/ipccreports/ar4-wg1.htm (especially chapter 5)
http://www.pik-potsdam.de/~stefan/Publications/Nature/rahmstorf_science_2007.pdf
www.umassk12.net/ipy
A STEM ED Program at the University of Massachusetts, funded by the National Science Foundation and supported by the
Climate System Research Center in conjunction with the International Polar Year
STEM
Vocabulary
Glacier Mass Balance
The balance between accumulation on a glacier (by snowfall) and ablation (melting, sublimation,
calving). If a glacier has a positive mass balance, it will advance and if its mass balance is negative, it
will retreat.
Green house effect
Greenhouse gasses (including CO2 and methane) are transparent to incoming short wave radiation, but
absorb the long wave radiation that is reflected by the Earth. This traps radiation inside the Earth’s
atmosphere and leads to a general warming.
Ice sheet
Land-based ice that covers the landscape across large areas. Examples include the Greenland ice
sheet and the East and West Antarctic ice sheets. Melting of ice sheets would cause sea level to rise.
Ice Shelves
A thick platform of ice that is floating on the ocean, but attached to land (grounded). Since this ice is
floating (much like ice cubes in a glass of water), melting will not increase sea level but could allow
glaciers that flow onto the ice shelves to calve and melt rapidly.
Outlet Glacier
In this sense, a glacier that flows from an ice sheet out onto an ice sheet or directly into the ocean.
Storm surge
Winds circulating around a low pressure storm system will literally push water against the shore line as
the storm advances. This mound of water can be devastating especially when it occurs during a high
spring tide.
Thermal expansion of water
As water (warmer than ~4°C) increases in
temperature, its density will decrease. This
decrease in density will essentially push some
water molecules further apart from each other
leading to a larger volume occupied by the same
number of molecules.
Isostatic Sinking (isostasy)
The tendency for continental crust to sink into
the asthenosphere when weight is added. This
extra mass can be due to things like glacier
growth or sediment deposition in deltas.
http://www.seafriends.org.nz/oceano/beachdam.htm
www.umassk12.net/ipy
A STEM ED Program at the University of Massachusetts, funded by the National Science Foundation and supported by the
Climate System Research Center in conjunction with the International Polar Year