Arctic Sea Ice. Background Information

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1 Arctic Sea Ice Objectives 1. Students will construct graphs of the extent of sea ice over time. 2. Students will use technology to analyze data and draw conclusions about natural phenomena in the Arctic 3. Students will use data to explain the relationship between natural occurrences and changes to world climate Background Information Water cycle diagrams often summarize the water cycle in a qualitative way, noting reservoirs and flows. Reservoirs are places where water is "stored", or where it stays for some period of time. The oceans, glaciers and ice caps, lakes, and the atmosphere are some examples of reservoirs. Flows or pathways are the routes water takes between reservoirs. Evaporation moves water from the oceans to the atmosphere. Precipitation moves liquid (rain) or solid (snow) water from the sky back to Earth's surface. Snowmelt runoff turns solid water into a liquid that flows down rivers to the sea. The amount of time that water spends, on average; in a reservoir is called reservoir time. Note that "water", in this context, means the chemical substance H 2 O, whether in liquid, solid, or gaseous form. Water in oceans and lakes is, of course liquid; but it is solid ice in glaciers, and gaseous water vapor in the atmosphere.

2 How much water is there in the water cycle? A quantitative look at the water cycle adds context to a water cycle diagram. For example, the oceans are by far the largest reservoir, containing between 1.35 and 1.4 x 10 9 km 3 of water; this is more than 95% of the water in the cycle. And how much of it is moving from place to place? The rate of a flow, commonly expressed as cubic kilometers per year, can be measured worldwide. For example, total global precipitation is about 505,000 km 3 per year. How long does water spend in one place or another? Reservoir time is highly variable, depending on the type of reservoir. For example, water stays in the atmosphere for only nine days on average. By contrast, once water reaches the ocean, it stays put for a very long time - an average of more than 3,000 years. It is important to realize that reported residence times are averages, and that the actual residence time for a given water molecule may be far from the average. Water vapor that reaches the stratosphere may remain there for a long time; water that flows into warm, shallow coastal waters from a river may evaporate and leave the ocean very quickly. A few highlights of where water spends its time are below. Atmosphere: The residence time for water in the atmosphere is a brief nine days; the shortest of any major reservoir. Ice Sheets: Water spends thousands, tens of thousands, or even hundreds of thousands of years in a frozen state in an ice sheet before returning to other parts of the water cycle. (For example, the oldest ice found in Antarctica is about 900,000 years old.) Glaciers: Water resides in glaciers for less time than it does in ice sheets, often about years. Snow: Water spends around 2 to 6 months as seasonal snow. Each year approximately 11,000 km 3 of water is in snow; about the same amount melts into water. A little water cycle accounting: The overall water cycle "contains" between 1,386,000,000 and 1,460,000,000 km 3 of water in various states (liquid, solid, or gaseous). The vast majority of it, between 96.5 and 97.25%, is in the oceans. Only about 3% of Earth's water is fresh water. About 2/3 of that is frozen in the ice sheets near the poles and in glaciers. About 90% of the polar ice sheet and glacial ice is in Antarctica; most of the rest is in Greenland; a tiny fraction is locked up in mountain glaciers elsewhere. Most of the rest of the

3 fresh water is underground. Less than 1% of fresh water is on the surface in lakes, wetlands, and rivers. About 80% of rain falls directly into the ocean. However, more water leaves the ocean via evaporation than enters the ocean as precipitation. The opposite is true on land: less water evaporates over the land than falls onto land as precipitation. Evaporation of water from the land happens directly from lakes, puddles, and other surface water. And water also makes its way into the atmosphere via plants and a process called transpiration. Collectively, the water evaporated from the land and from plants is called evapotranspiration. Higher rates of evaporation over the ocean and more precipitation over the land would present an imbalance if it were not for river runoff that transports water from land to ocean. The accounting only works out if the amount of runoff that flows in rivers to the ocean makes up for most of this imbalance. Standards New York State STANDARD 1 Analysis, Inquiry, and Design Students will use mathematical analysis, scientific inquiry, and engineering design, as appropriate, to pose ques- tions, seek answers, and develop solutions.

4 STANDARD 2 Students will access, generate, process, and transfer information, using appropriate technologies. 1.2g Earth has continuously been recycling water since the outgassing of water early in its history. This constant recirculation of water at and near Earthʼs surface is described by the hydrologic (water) cycle. 2.1b The transfer of heat energy within the atmosphere, the hydrosphere, and Earthʼs interior results in the formation of regions of different densities. These density differences result in motion. 2.1i Seasonal changes can be explained using concepts of density and heat energy. These changes include the shifting of global temperature zones, the shifting of planetary wind and ocean current patterns, the occurrence of monsoons, hurricanes, flooding, and severe weather. Hypothesis What is the relationship between the extent of sea ice and time in years? Independent Variable Dependent Variable Procedure 1. Go to Mr. Mac s Science Classes 2. Click on. 3. Click on Changing Climate e-portfolio. 4. Click on Arctic Sea-Ice Data. 5. Construct a graph using Microsoft Excel. Follow the instructions below: a. Open up the Arctic Sea Ice Data using Microsoft Excel. b. For your assigned month or months, highlight the data and click on Charts. c. Select X Y (Scatter). d. Select Smooth Marked Scatter. e. Once your graph has been created, select Chart to move chart to new sheet and label it by month. f. Add Trendline by clicking on one of the points on the graph, and right click on a particular point. g. Make sure your graph is labeled by month, and scale your graph so that the y-axis maximum is set to 20, and y-axis minimum is set to Save as a PDF file and upload your completed graph to Google Docs, make sure you load it using your name and the date assigned. 7. Share with everyone in class. Find your block and share with the class.

5 Analysis and Conclusion 1. What is the largest reservoir of water and how much water does it hold? What is the reservoir time at this location? 2. How does the reservoir time of water in a glacier compare to in the ocean? 3. Based on the data and graph on the extent of sea ice, what pattern or trend do you notice? 4. Give a scientific explanation for the trends that you observed in your graph. 5. Compare your graph to others, what pattern or trend do you notice?

6 6. Give a scientific explanation for the trends that you observed in comparing the graphs from other groups. 7. Based on the data and graphs from the entire class, what is your conclusion? Does it agree or disprove your hypothesis? Explain. 8. Explain how you think it would be different from sea ice data taken from Antarctica. Links Arctic Sea Ice animation