INGOMAR MIDDLE SCHOOL SCIENCE   ICE CAP          NAME: ______________________
DataStreme Ocean: SeaWifs Images  Sea Surface Temp        Period: ___ Date: ______Score_____/20
Sea Surface Heights  Earth Image    Ice Extent  EET Chapters  Ocean Temp  World Ocean Data Sets  Sea Salinity

On average, about 7% of the world ocean is covered by sea ice. The large expanse of sea ice is of immense importance climatically because it reflects most incoming solar radiation and it is a solid insulating layer between the ocean and atmosphere. The formation and melting of sea ice also has great impact on 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 atmosphere and space. Ice, whether frozen fresh water or seawater, is less dense than the liquid from which it forms. So, it floats. Fresh water freezes at 0 °C in the coldest surface water which is less dense than the underlying warmer water.

1. J Sea Salinity 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 to produce an isothermal layer of water of uniform salinity. In Figure 3 of the first part of this investigation, the nearly isothermal layer of Antarctic seawater reached a depth of approximately ______ m.

 

2. Additional cooling of the isothermal layer in J Sea Surface Temp 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.

3. J World Ocean Data Sets  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 high-density 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) (less)] saline and [(more) (less)] dense.

4. J"Sea Ice Index“ The extent of sea ice in Arctic and Antarctic regions is expansive, but undergoes considerable seasonal change. J"Sea Ice Index“ portrays the most current reported extent of sea ice cover in the polar regions. In both views, the geographic pole is in the center and the total area covered by sea ice is reported below the map view. They show that in _____________ (month and year), more sea ice exists in the [(Northern) (Southern)] Hemisphere. This hemisphere with more sea ice is currently in its _________ season. Ice Extent

5.J"Sea Ice Index“ Compare maximum and minimum amounts of sea ice extent in Earth's polar regions by clicking on "Index Archives" near the top of the site listed above. When the new Index Archives page appears, click on "Extent, Concentrations, Anomalies, Trends, Plots" under the heading "Single Images." Set the Hemisphere choice to "Northern," Year to "2004," month to "January," and Image to "Sea Ice Extent." Finally, click on "Show Image" bar. Go through the 12 months 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.

6. Times of maximum sea ice extent occur in the Northern and Southern Hemispheres at about [(the same time of year) (a half-year apart)]. Times of minimum sea ice extent occur in the Northern and Southern Hemispheres at about [(the same time of year) (a half-year apart)].
   
    

7.      Times of maximum and minimum sea ice extent in the two hemispheres occur [(during the same month of) (more than two months later than)] their respective winter and summer solstices.

 

8.      Assuming the data in Item 12 is representative of maximum and minimum sea ice extent from year to year, it appears that there is a larger percentage of the [(Arctic) (Antarctic)] sea ice that melts back in the summer.

 

9.      Controls which influence the distribution of sea ice in the Polar Regions include variations in the receipt of solar radiation, the distribution of land and water, and atmospheric and oceanic forcing. Of major importance are the relative locations of land and ocean. In the [(Arctic) (Antarctic)] the land is poleward and the ocean is equator ward, whereas in the [(Arctic) (Antarctic)] the ocean is pole ward and the land is equator ward.

10.   Go to the following for a Jdetailed discussion of sea ice Jdistribution and seasonality:
Comments: _____________________________________________________________________

 

11.  JEET Chapters: Go to JAnalyzing the Antarctic Ozone Hole.
Click on Case Study, read information
then click on Step-by-Step Instructions (Tools and Data)   
Lastly click on Part 2-Open and Explore Ozone Images.

12.   Next do Part 3-Highlight

13.                                          and Measure the Ozone Hole

14.  Finally do Part 4- Start Excel then Import

15.                                                            and Graph the Data obtaining a printout.

Looking for more information on the formation and decay of sea ice? Visit  North Atlantic ice bergs in season (or via archives), go to the International Ice Patrol .

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; Is there life in a desert of ice?,