Name:_____________________________________________ Class Period
DIRECTIONS: Find the link on my webpage (internet activities page) titled Physical
Oceanography Day 1. Read through the word document and circle the correct word
or phrase below.
Webquest Day 1
1.
______ °C
2. ______ °C at high latitudes.
3. [(West) (East)]
4. [(lower) (higher)]
5. Describe in general the patterns of ocean SST and latitude on our globe
6. [(along the equator) (in the subtropical ocean basins) (at high latitudes)].
7. [(greater precipitation than evaporation) (greater evaporation than
precipitation)].
8. [(central North Pacific) (northern South Atlantic) (southern North Atlantic)].
9. [(Atlantic) (Pacific) (Indian) (Arctic) (Southern)] Ocean.
10. [(lowest) (middle) (highest)]
11. _______ meters.
12. [(increases) (decreases) (is constant)]
13. [(2.2) (3.8) (9.8)]
14. [(2.4) (4.7) (12.5)]
15. [(32.1) (33.7) (34.5)].
16. [(1.0259) (1.0264) (1.0275)] g/cm3.
17. [(increase) (decrease)]
DataStreme Ocean Current Ocean Studies 3B
FRESH WATER, OCEAN WATER, AND SEA ICE
Do Now:
1. Print this file and Image 1, but also remain connected or log-on again to
complete the Investigation.
2. Print the Weekly Ocean News file. (Note: check the DataStreme Ocean website
during the week in the event that new ocean news stories have been added.)
To Do Investigation:
1. Read Chapter 3 in the DataStreme Ocean textbook and respond to the Chapter
Progress Questions in the DataStreme Ocean Study Guide Investigations.
2. Complete the introductory portion of Investigation 3B in the Online Ocean
Studies Investigations Manual. [Do not complete the Applications portion of the
Investigation.]
3. Complete the Current Ocean Studies B - Thursday from the course website.
Go to the Online Ocean Studies Manual - Investigation 3B now
WELCOME BACK: Procedure continued from Ocean Studies Investigations Manual,
Investigation 3B.
Sea ice covers about 7% of the world ocean on average. The large expanse of sea ice is of
great importance in Earth's climate system because it reflects most incoming solar
radiation and it functions as a solid insulating layer between the ocean and atmosphere.
Formation and melting of sea ice also greatly impact the salinity and density of seawater.
Additionally, biological activity varies considerably in those areas which experience
seasonal ice cover.
How does ice form in water bodies in the open environment? The freezing process begins
at the water's surface as heat energy is transferred upward to the colder atmosphere and
space. Ice, whether frozen fresh water or seawater, is less dense than the liquid from
which it forms. Hence, ice floats. As seen in Figure 1 in the first part of this investigation,
fresh water freezes at 0 °C in the coldest surface water which is less dense than the
underlying warmer water.
Research vessel in Antarctic sea ice. (©Robert Massim, NSIDC User Services)
1. In seawater with salinities greater than 24.7, the coldest water is also the densest,
causing it to sink until it reaches a level below which water density is greater
because of increased salinity (or, in shallow areas, until it reaches the bottom).
The water cooled at the ocean surface convects downward producing a layer of
water that is uniform in both temperature and salinity. In Figure 3 of the first part
of this investigation, the nearly isothermal layer of Antarctic surface seawater
reached a depth of approximately [(50) (100) (200)] m.
2. Additional cooling of the surface isothermal layer in Figure 3 would probably
result in ice formation. The freezing of seawater is initially in the form of frazil
ice, composed of myriads of tiny separate ice crystals and fragments. With
additional loss of heat the crystals freeze together. Under calm conditions a sheet
of ice can form; in rough water, ice grows from a dense suspension of frazil. With
continued loss of heat energy upward, the sea ice gradually freezes downward.
Unlike fresh water, seawater does not have a specific freezing point, that is, it
does not completely freeze at the same temperature. Growing ice crystals exclude
substances that are in solution in the liquid. Dissolved salts become more and
more concentrated in the remaining liquid. The higher salinities in the resulting
brine lower its temperature of freezing. Some of the brine is encapsulated within
ice crystals, but most brine is trapped in the spaces between neighboring crystals.
Especially when air temperatures are well below zero, the captured brine migrates
downward towards the higher water temperatures below. Eventually, the highdensity brine drains into the water beneath the ice. In the process, the sea ice
freshens (lower salinities when melted) while the underlying ocean water
becomes more saline and [(more) (less)] dense.
3. The extent of sea ice in Arctic and Antarctic regions is expansive, but undergoes
considerable seasonal change. Image 1 portrays the most recent reported extent of
sea ice in the Northern and Southern Hemispheres. The data are provided by the
National Snow and Ice Data Center (NSIDC). In both views, the geographic pole
is at the center and the total area covered by sea ice is reported below the map
view. A comparison of the two maps shows that in August 2007, more sea ice
exists in the [(Northern) (Southern)] Hemisphere.
4. This hemisphere with more sea ice in August 2007 is in its _________ season.
Compare maximum and minimum amounts of sea ice extent in Earth's polar region by
going to the "National Snow and Ice Data Center's Cryospheric Climate Indicators" at:
http://nsidc.org/data/seaice_index/. (For larger views of the images appearing on this
website, click on the individual images.) Scroll down and click on "Animated Images."
Set the Hemisphere choice to "Northern," Year to "2006," month to "September," and
Image to "Sea Ice Extent." Also click on "Slower." [Allow time for loading. Once
animation has started, use the buttons above the image to stop, reverse or forward the
monthly images.] Go through the 12 months of September 2006 through August 2007
one-by-one to view seasonal changes. In the images, the view is circumpolar and the
North Pole is located in the center. Noting the total extent of sea ice indicated at the
bottom of the image, print out the months of maximum and minimum sea ice extent in
the Northern Hemisphere. Follow the same procedure for the Southern Hemisphere,
finding and printing out the months of minimum and maximum sea ice extent.
When answering the following, if more than one month has the same reported maximum
or minimum value, indicate the first month of occurrence.
In the Northern Hemisphere:
5. Month(s) of maximum sea ice extent is (are) ___________.
6. Total sea ice extent is ________ million square km.
7. Month(s) of minimum sea ice extent is (are) ___________.
8. Total sea ice extent is ________ million square km.
In the Southern Hemisphere:
9. Month(s) of maximum sea ice extent is (are) ___________.
10. Total sea ice extent is ________ million square km.
11. Month(s) of minimum sea ice extent is (are) ___________.
12. Total sea ice extent is ________ million square km.
13. Based on the September 2006- August 2007 data, times of maximum sea ice
extent occur in the Northern and Southern Hemispheres at about [(the same time
of year) (a half-year apart)].
14. Times of minimum sea ice extent occur in the Northern and Southern
Hemispheres at about [(the same time of year) (a half-year apart)].
15. Based on the September 2006- August 2007 data, times of maximum and
minimum sea ice extent in the two hemispheres occur [(during the same months
of the year as) (two to three months later than)] their respective winter and
summer solstices.
16. Assuming the data in Items 6 to 13 are representative of maximum and minimum
sea ice extent from year to year, it appears that a larger percentage of the [(Arctic)
(Antarctic)] sea ice melts back in the summer.
17. Controls which influence the distribution of sea ice in polar regions include
variations in the receipt of solar radiation, distribution of land and water, and
atmospheric and oceanic forcing. Of major importance is the relative locations of
land and ocean. In the [(Arctic) (Antarctic)] the land is poleward and the ocean is
equatorward.
18. In the [(Arctic) (Antarctic)] the ocean is poleward and the land is equatorward.
Optional: Go to the following for a detailed discussion of sea ice distribution and
seasonality: http://seis.natsci.csulb.edu/rmorris/seaice/distrib.htm.
Looking for more information on the formation and decay of sea ice? Visit
http://www.arctic.noaa.gov/essay_wadhams.html. Or, if you want to follow North
Atlantic ice bergs in season (or via archives), go to the International Ice Patrol at:
http://www.uscg.mil/lantarea/iip/home.html.
As summarized in this week's Supplemental Information file, there is life in sea-ice
environments. For more on this topic, go to: Arctic Sea Ice: Channels of Life,
http://www.oceanexplorer.noaa.gov/explorations/02arctic/background/sea_ice/sea_ice.ht
ml; Is there life in a desert of ice?,
http://www.arctic.noaa.gov/essay_krembsdeming.html.
Record your responses to items in Current Ocean Studies investigations 3A and 3B on the
COS Answer Form for transmission to your course mentor.
Instructions for Communications with Mentor:
After completing this week's applications, transmit the following work to your LIT
mentor by Monday, 24 September 2007, or as coordinated with your mentor:
1. Chapter 3 Chapter Progress Response Form from the DataStreme Ocean Study
Guide binder, or the DataStreme Ocean website.
2. Investigations 3A and 3B Investigations Answer Form , from the DataStreme
Ocean Study Guide binder, or the DataStreme Ocean website.
3. Current Ocean Studies activities 3A and 3B COS Answer Form.
Back to DataStreme Ocean website
©Copyright 2007, American Meteorological Society
Northern and Southern Hemisphere Sea Ice Extents
August 2007