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Grade level: 9-12
Theme: water cycle
Flat Tool: http://ourocean.jpl.nasa.gov/AQUARIUS/chp2.jsp
GoogleEarth Interface Tool: http://aquarius.jpl.nasa.gov/AQUARIUS_DEV/chp2.jsp

Create global maps of mean conditions for any month at designated depths (down to 1500m) using the pull-down menus. Monthly time-series graphs of salinity, temperature, or density can be plotted by selecting up to six locations (by clicking on the map or typing latitude/latitude information into the fields below). These time-series graphs can also represent up to six different depths. Plotted data will also be shown in a table that is easily downloaded (e.g., into Excel). Sources include interpolated atlas data or actual measurements from the database.

Focus Questions | Flat Tool Tutorial

Grade level: 9-12
Theme: water cycle
Activity: http://www.tos.org/hands-on/teaching_phys_concepts.pdf

Activity 1.6: Convection Under Ice (p. 10). In oceanography, density is used to characterize and follow water masses as a means to study ocean circulation. Many processes are caused by or reflect differences in the densities of adjacent water masses or differences in densities between fluids and solids. Plate tectonics and ocean basin formation, deep-water formation and thermohaline circulation, and carbon transport by particles sinking from surface waters to depth are a few examples of density-driven processes. This activity is designed to highlight links to oceanic processes.

In the left panel in the photo at right, an ice block floats in tap water because the density of ice is lower than that of freshwater. As the ice melts, however, cold, colored meltwater sinks to the bottom because it is denser than the tap water. Warmer water from the bottom is then displaced and upwells, resulting in a convective flow visible in the dye patterns. Ice melting in the center of the tank is analogous to a convection "chimney" formed in the open ocean, while ice melting at the tank's edge is analogous to a chimney on a continental shelf (near a land mass). Such chimneys in the ocean, created and sustained by convective processes, appear as "columns" of mixed water that flow downwards. For a given set of oceanic and meteorological conditions, open-water convection tends to entrain (mix with) more of the surrounding waters than does convection near a land mass. The open-ocean case therefore results in downwelled water that is less dense.

In the right panel, the ice block floats in dense, salty water. As the ice melts, only a small amount of dye sinks because the density of the saltwater is greater than the density of the newly melted, fresh, ice-cold water. Most of the meltwater accumulates in a surface layer on top of the denser salt layer.

Read the Background section (p. 4-5) of Chapter 1 (Density) in preparation for this activity.

Note: Even though this experiment focuses on temperature only, it can be used to discuss how salinity, like temperature, affects the density of ocean water.

Grade level: 9-12
Theme: water cycle
Activity: http://www.tos.org/hands-on/teaching_phys_concepts.pdf

Activity 1.5: Effect of Stratification on Mixing (p. 9-10). In open ocean regions (with the exception of polar seas), the water column is generally characterized by three distinct layers: an upper mixed layer (a layer of warm, less-dense water with temperature constant as a function of depth), the thermocline (a region in which the temperature decreases and density increases rapidly with increasing depth), and a deep zone of dense, colder water in which density increases slowly with depth.

Mixing of stratified layers requires work. Without energetic mixing (e.g., due to wind or breaking waves), the exchanges of gases and nutrients between surface and deep layers will occur by molecular diffusion and local stirring by organisms, which are slow, ineffective modes of transfer. The energy needed for mixing is, at a minimum, the difference in potential energy between the mixed and stratified fluids. Therefore, the more stratified the water column, the higher the energy needed for vertical mixing.

Density is fundamentally important to large-scale ocean circulation. An increase in the density of surface water, through a decrease in temperature (cooling) or an increase in salinity (ice formation and evaporation), results in gravitational instability (i.e., dense water overlying less-dense water) and sinking of surface waters to depth. Once a sinking water mass reaches a depth at which its density matches the ambient density, the mass flows horizontally, along "surfaces" of equal density. This process of dense-water formation and subsequent sinking is the driver of thermohaline circulation in the ocean. It is observed in low latitudes (e.g., the Gulf of Aqaba in the Red Sea, the Gulf of Lions in the Mediterranean Sea) as well as in high latitudes (e.g., deep water formation in the North Atlantic).

This experiment looks at the energy required to mix two layers. Students should read the Background section (p. 4-5) of Chapter 1 (Density) in preparation for this activity.

Flash Video | QuickTime Movie

Grade level: 9-12
Theme: water cycle
Video: melting_ice_03.flv

Two thirds of the fresh water on Earth is frozen in the world's ice fields. If that ice melts, seas will rise. If all of that ice were to melt, sea level would rise worldwide by 70 meters. No one expects all of that ice to melt anytime soon, but even the meter of sea level rise that many scientists predict for the next century could have dramatic consequences.

Lora Koenig: "Even though the polar regions seem very far from a lot of people's day to day life, they are very important. Because they are regions that cool our earth. And as they change, they're going to cause larger changes throughout the rest of the globe." (source)

Grade level: 9-12
Theme: water cycle
Video: melting_ice_02.flv

It's important to understand how the world's ice sheets form, how they change over time, and how fast they are moving into the sea. That's where researchers like NASA's Lora Koenig come in. She recently spent three months in Greenland studying the composition of those ice sheets. All ice sheets and glaciers start as snowfall. Those tiny flakes get compressed by the weight of more snow above, and eventually become dense masses of ice.

Lora Koenig: "What we're seeing right now on the ice sheets and glaciers is that they are shrinking in size. And as glaciers on land are shrinking overall, that contributes a little bit to sea level rise. And we are worried that as we see warming over the ice sheets, and increased melting over the ice sheets, that they are going to start contributing much more to sea level rise." (source)

Grade level: 9-12
Theme: water cycle
Video: melting_ice_04.flv

Josh Willis: "A lot of people live in coastal areas. Coastal places that have beaches. As sea level rises, then beaches begin to erode and we begin to lose wetlands. A lot of different ecologically-sensitive regions lie along the coastline, and as sea level rises, these get flooded (and) the ecosystems, of course, change. And so all of this can have big consequences for people and especially people who live near the coast."

Josh Willis: "As the great ice sheets in Antarctica and Greenland begin to melt and break up due to global warming, we really might experience very rapid sea level rise; three or four times as fast as the rate that we see today. So predicting this rate out into the future is very tricky because we really don't know when the ice sheets might break up and how fast they will when they do. So predicting future sea level rise is one of the great scientific problems of the future." (source)

Grade level: 9-12
Theme: water cycle
Video: melting_ice_01.flv

The ice is melting. The seas are rising. Little by little, in most parts of the world, the ocean is overtaking the land. Most of us don't think much about sea level rise, but it's one of the biggest signs that humans are affecting the Earth's climate. And it's something worth watching. So the big question is, are we facing a doom and gloom scenario?

Josh Willis: "I prefer not to think about climate change and global warming in terms of doom and gloom scenarios, so much as a change in our planet. Our planet's definitely changing, and we're definitely causing it. So we're going to have learn to deal with some of these changes. But in addition, we're going to have to learn how to make a slightly smaller footprint on our planet."

Josh Willis: "Sea level is rising effectively because of global warming. As the planet heats up, two things happen to the ocean. One is that the temperature of the water increases. And as that happens, the water actually expands and takes up more room. The other thing that happens is that ice that was on land in the form of glaciers and ice sheets begins to melt and as that runs off into the ocean, it increases the water in the ocean, and it actually raises sea level as well. (source)

Grade level: 9-12
Theme: water cycle
Article: documents/21.1_schmitt.pdf

Articles in this salinity-themed Oceanography issue articulate the potential of our rapidly expanding ability to measure salinity to enhance understanding of the global water cycle.

Read and discuss the first three sections (p. 12-15) of this article.

Grade level: 9-12
Theme: water cycle
Video: salt_of_earth_02.flv

Susan Lozier: "And the atmosphere and the ocean, both being fluids of the earth, really work together. We consider them sort of equal partners in the redistribution of this heat on the planet. So when those warm waters are returning, as they're moving up to the higher and higher latitudes then, they're releasing that heat to the atmosphere. Then the winds blow over the ocean, they pick up that heat and those winds over the Atlantic Ocean are moving from the North American continent to the European continent."

Jeff Halverson: "It takes perhaps a thousand years for the water to cycle through the deep ocean. So we say the oceans have a memory. They're like a tape recorder. Things that happen now will still be manifest hundreds of years in the future as that cold water moves through this giant circulation."

Susan Lozier: "So if there's any change to that overturning circulation, that means that Northern Europe and the British Isles would be robbed of that heat due to those waters that are returning to the high latitudes." (source)

Grade level: 9-12
Theme: water cycle
Video: salt_of_earth_01.flv

Susan Lozier: "And it seems a little odd in a way because salt is really a molecule in the ocean water, but collectively, that salinity plays a role in the ocean circulation."

It's these differences in salinity that play a role in the processes that affect weather, climate, sea life, and the whole ocean system itself. And not all oceans have the same salinity. In fact, the North Atlantic Ocean tends to be the saltiest, much more than the Pacific.

Susan Lozier: "The salt in the ocean affects its density, just like the temperature affects its density, and the density, meaning the amount mass per volume, is going to then impact where the water goes as it circulates throughout the globe."

Jeff Halverson: "Differences in temperature and salt content of the water cause some areas of water to sink and some areas of water to rise. And so we tend to see the sinking water at the poles, the water rising back up at the equator, and if you connect the two together, what you have is an overturning that is deep in the ocean. It's like a big conveyor belt that operates in the ocean."

This overturning moves warm water from the tropics toward the poles, and cold water from the poles toward the tropics. In this way the overturning regulates earth's climate. (source)

Grade level: 9-12
Theme: water cycle
Video: Aerosol_Sources_Full_Seq_640x360.flv

Aerosols are complex particles; they occur in nature and can also be generated by human activity. One important new area of aerosol research involves how aerosols impact clouds. Without aerosols, clouds could not exist. Aerosol particles serve as condensation nuclei for water vapor in the atmosphere. Atmospheric water molecules are drawn to aerosol particles like magnets, forming water droplets and eventually creating a cloud. The introduction of a larger number of aerosols will modify cloud's natural properties, leading to an accumulation of water droplets that are smaller in size but greater in number. Clouds play an important role in regulating Earth's climate; aerosol-rich air masses generate clouds that are bigger, brighter, and longer lasting.

Aerosols can occur in nature, but they can also originate from human activity. This animation provides an introduction to four of the varied sources of atmospheric aerosols: cities, forest fires, the ocean, and deserts. This animation shows the different sources of aerosols, how they mix in the Earths atmosphere, and finally disappear by creating sediment or raining out.

Of particular interest is the role of the oceans: salts from the sea spray serve as condensation nuclei. In this animation, sea salt spray aerosols rise into the sky, follows the path downwards to the source (the ocean), and back up into the sky where the aerosols gather in a cloud. (source)

Grade level: 9-12
Theme: water cycle
Video: water_cycle_ipod_640x480.m4v.flv

This animation shows one molecule of water completing the hydrologic cycle. Heat from the sun causes the molecule to evaporate from the ocean's surface. Once it evaporates, it is transported high in the atmosphere and condenses to form clouds.

Clouds can move great distances and eventually the water molecule will fall as rain or snow. Ultimately, the water molecule arrives back where it started...at the ocean. (source)

Grade level: 9-12
Theme: water cycle
Video: water_everywhere_02.flv

Paula Bontempi: "The water evaporates and goes into the atmosphere, and then it doesn't necessarily just turn around and fall as rain or snow."

Condensation is the process by which water vapor molecules cool, stick together, and become liquid again in cloud formation. This often happens high in the atmosphere where the temperature is much lower than it is near the surface.

Paula Bontempi: "What happens in the atmosphere is, just like we have currents in the ocean, we have winds in the atmosphere that actually, to some extent, drive what goes on in the ocean currents. Materials in the atmosphere can travel a great distance, sometimes a quarter of a way around the world, just until they get to the point where they actually turn into rain or snow and thereby fall back to the ocean or fall back to the land. This is called precipitation. If the water molecule falls on the land as snow, it may be stored for a very long period of time in a polar ice sheet or mountain glacier, depending on climate conditions."

Matt Rodell: "When rain falls or the snow melts, typically the next place it goes, it infiltrates the soil. So soil is not solid. It's not like a rock, there are pore spaces that can be filled with water and typically there is a certain amount of water in the soil at all times. If soil was completely dry, plants wouldn't be able to grow." (source)

Grade level: 9-12
Theme: water cycle
Video: WC_precipitation_IPOD.m4v.flv

This animation displays the intensity of precipitation as it flows around the globe, showing heavy precipitation in orange/yellow and light precipitation in purple. This video is a clip taken from Water, Water Everywhere which incorporates audio not included in this clip.

Water regulates climate, storing heat during the day and releasing it at night. Water in the ocean and atmosphere carry heat from the tropics to the poles. The process by which water moves around the earth, from the ocean, to the atmosphere, to the land and back to the ocean is called the water cycle.

This animation was created using data from the GEOS-5 atmospheric model on the cubed-sphere, run at 14-km global resolution for 30-days. Variables animated here include evaporation, water vapor and precipitation. This animation is time synchronous throughout the animation to allow cross fades during compositing. (source)

Grade level: 9-12
Theme: water cycle
Video: water_everywhere_01.flv

Water is all around us, and its importance to nearly every process on earth cannot be underestimated. It is the only compound that can be found naturally as a liquid, gas, and solid. The process by which water moves around the Earth, from the ocean to the atmosphere to the land, and back to the ocean, is called the water cycle. Water regulates climate, storing heat during the day and releasing it at night, and carries heat from the tropics to the poles, by sea and by air.

Let's follow a single molecule of water, beginning in the ocean, through the paths it might take before eventually winding up right where it started - back in the big blue sea. The fuel for this journey will be provided by our planet's prime energy source: the sun. During the day, the sun heats up the air and ocean surface, causing water molecules to evaporate. Evaporation occurs when a liquid molecule of water escapes into the air as a gas.

This scientific visualization shows how water evaporation, indicated in turquoise, is driven by the energy of the sun. Notice how the rate of evaporation pulses over land: it speeds up during the day and almost disappears at night. Over the ocean, evaporation appears to remain constant, both day and night. Water in the air in gas form is known as water vapor. The molecule is now fresh water, having left the ocean salt and other particles behind. (source)

Grade level: 9-12
Theme: water cycle
Video: Evap_and_clock_IPOD.m4v.flv

This animation of evaporation shows how heating from the sun causes increased evaporation over land during the day. This video is a clip taken from Water, Water Everywhere which incorporates audio not included in this clip.

Water regulates climate, storing heat during the day and releasing it at night. Water in the ocean and atmosphere carry heat from the tropics to the poles. The process by which water moves around the earth, from the ocean, to the atmosphere, to the land and back to the ocean is called the water cycle.

This animation was created using data from the GEOS-5 atmospheric model on the cubed-sphere, run at 14-km global resolution for 30-days. Variables animated here include evaporation, water vapor and precipitation. This animation is time synchronous throughout the animation to allow cross fades during compositing. (source)

Grade level: 9-12
Theme: water cycle
Video: WC_evaporation_IPOD.m4v.flv

This animation of evaporation shows how heating from the sun causes increased evaporation over land during the day. This video is a clip taken from Water, Water Everywhere which incorporates audio not included in this clip.

Water regulates climate, storing heat during the day and releasing it at night. Water in the ocean and atmosphere carry heat from the tropics to the poles. The process by which water moves around the earth, from the ocean, to the atmosphere, to the land and back to the ocean is called the water cycle.

This animation was created using data from the GEOS-5 atmospheric model on the cubed-sphere, run at 14-km global resolution for 30-days. Variables animated here include evaporation, water vapor and precipitation. This animation is time synchronous throughout the animation to allow cross fades during compositing. (source)

Grade level: 9-12
Theme: water cycle
Video: WC_vapor_IPOD.m4v.flv

This animation portrays the flow of atmospheric water vapor around the world. This video is a clip taken from Water, Water Everywhere which incorporates audio not included in this clip.

Water regulates climate, storing heat during the day and releasing it at night. Water in the ocean and atmosphere carry heat from the tropics to the poles. The process by which water moves around the earth, from the ocean, to the atmosphere, to the land and back to the ocean is called the water cycle.

This animation was created using data from the GEOS-5 atmospheric model on the cubed-sphere, run at 14-km global resolution for 30-days. Variables animated here include evaporation, water vapor and precipitation. This animation is time synchronous throughout the animation to allow cross fades during compositing. (source)

Grade level: 9-12
Theme: water cycle
Video: WC_SST_IPOD.m4v.flv

This animation of sea surface temperature shows the transport of heat along the ocean's surface. This video is a clip taken from Water, Water Everywhere which incorporates audio not included in this clip.

Water regulates climate, storing heat during the day and releasing it at night. Water in the ocean and atmosphere carry heat from the tropics to the poles. The process by which water moves around the earth, from the ocean, to the atmosphere, to the land and back to the ocean is called the water cycle.

Data for this animation was derived from a model run of ECCO's Ocean General Circulation Model of heat along the ocean's surface. (source)

Grade level: 9-12
Theme: water cycle
Video: WC_rivers_IPOD.m4v.flv

In this animation, pulsing of the global rivers highlights the flow of water from the continents back into the oceans. This video is a clip taken from Water, Water Everywhere which incorporates audio not included in this clip.

Water regulates climate, storing heat during the day and releasing it at night. Water in the ocean and atmosphere carry heat from the tropics to the poles. The process by which water moves around the earth, from the ocean, to the atmosphere, to the land and back to the ocean is called the water cycle. (source)