Ocean Layering: Density, Temperature, Salinity, and ... Ocean Layering: Density, Temperature,...
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Ocean Layering: Density, Temperature, Salinity, and Circulation Sylvia Cole, Scripps Institution of Oceanography Maureen Quessenberry, University City High School Summary We developed a 3-4 day unit on the vertical structure of the ocean that gives students the opportunity to work with actual data, learn about the global circulation, and learn about some of the smaller scale features that stir and mix the ocean. The unit uses ship-based observations on a global scale and observations north of Hawaii from an ocean robot, the autonomous underwater glider Spray, as application activities. Lesson 1: Density and the Ocean Lesson 2: Deep Currents, Stirring, and Mixing Lesson 3: Glider Observations Density & Salinity Students investigate how salinity effects density through a hands on lab activity. The sink / float lab includes one object that will float in salt water and sink in fresh water. Students conclude that salt water is denser than fresh water. Stirring and Mixing Students use clay to create a model of the ocean. Different colors represent different types of water: Warm and cold water Fresh and salty water Polluted and unpolluted water Water full of organisms and water none Water with nutrients and water without A slice through the clay gives information about what happened to the clay. Similarly, a slice through the ocean gives information about what has happened to the ocean. So What? Dense water sinks to the bottom of the ocean, slowly spreads out, and slowly rises back to the surface. This circulation is sometimes referred to as the global conveyor-belt circulation. Liquids can sink and float A density column demonstration introduces students to the idea that liquids can have different densities and can sink and float on top of each other. The ocean is like a density column with the lightest water on top and the heaviest water on the bottom. Learning Goals • Students will be able to describe vertical currents and currents near the bottom of the ocean on a global scale. • Students will be able to explain vertical layers of the ocean in temperature, salinity, and density. • Students will be able to explain why temperature and salinity change more near the surface than at depth. Misconceptions • All ocean currents are caused by tides • The deep ocean never changes and doesn’t move • The ocean has the same salinity everywhere Context for Use This activity was designed for a 9 th grade earth science class, and would also be appropriate for middle school students. There are three 55-minute lessons and one 20-minute quiz. This unit was taught after an atmospheric section and a short unit on the surface circulation of the ocean. Students were familiar with the concepts of density, energy, waves, and the atmospheric circulation as well as the surface circulation of the ocean and what the ocean transports. Atlantic Sections Students complete a short activity using sections of temperature and salinity in the Atlantic. Students see that not all of the water on the bottom is the same, and can trace where water has come from using salinity. Spray Gliders: autonomous ocean robots Gliders have no propulsion mechanism and use buoyancy to control their depth in the water by pumping oil into and out of an external bladder. The glider moves forward in the water as it dives up and down because of the wings. It is ~6 ft long and weighs ~100 lbs. North Pacific Sections 16 sections of temperature and salinity were obtained from July 2007 - December 2009 along a line north of Hawaii. It crosses through the center of the surface gyre. Science Standards We focus on teaching California science standard 5d: “Students know the properties of ocean water, such as temperature and salinity, can be used to explain the layered structure of the ocean, the generation of horizontal and vertical ocean currents, and the geographic distribution of marine organisms.” Schematic of the global conveyor-belt circulation after the popular one by W. S. Broecker*. Water sinks in a few spots near the poles, spread out horizontally, and rises up slowly everywhere else. *Broecker, W S, 1987. The biggest chill. Natural History Magazine, Vol. 97, pp. 74- 82. Blue and yellow colors have been stirred around, and green colors have been mixed together. Sampling the global ocean One way oceanographers sample the ocean is to take slices through it with a ship, stopping every 50 km and dropping instruments down to the bottom. The R/V Melville, pictured at right, is one of the ships used to sample the ocean. From 1990-1998, several slices through the ocean were taken as part of an international effort to observe the global ocean. Some of these sections have been observed prior to and after as well. Water is collected in bottles and brought back to the surface for analysis. Above: sections of temperature and salinity in the Atlantic. Left: The red line shows where this section is located. Gliders have a satellite antenna in their wings, which allows data to be sent back to the scientists and instructions to be sent to the glider. The glider travels 5.5 km horizontally in 5.5 hours for each 1000 m dive. The small horizontal spacing of dives allows smaller-scale features to be studied. Students use six of the sections from different seasons and years to look at ocean layering and some of the smaller scale features. Density Column Ocean Salt water density > Object density Object density > Fresh water density Salt water density > fresh water density Cold deep current Warm surface current Latitude (°) 24 26 28 30 32 34
Transcript of Ocean Layering: Density, Temperature, Salinity, and ... Ocean Layering: Density, Temperature,...
Ocean Layering: Density, Temperature, Salinity, and CirculationSylvia Cole, Scripps Institution of Oceanography Maureen Quessenberry, University City High School
SummaryWe developed a 3-4 day unit on the verticalstructure of the ocean that gives students theopportunity to work with actual data, learn aboutthe global circulation, and learn about some ofthe smaller scale features that stir and mix theocean. The unit uses ship-based observations ona global scale and observations north of Hawaiifrom an ocean robot, the autonomous underwaterglider Spray, as application activities.
Lesson 1: Density and the Ocean Lesson 2: Deep Currents, Stirring, and Mixing Lesson 3: Glider Observations
Density & Salinity
Students investigate how salinityeffects density through a handson lab activity. The sink / float labincludes one object that will floatin salt water and sink in freshwater. Students conclude thatsalt water is denser than freshwater.
Stirring and Mixing
Students use clay to create a model of the ocean.Different colors represent different types of water:
Warm and cold waterFresh and salty waterPolluted and unpolluted waterWater full of organisms and water noneWater with nutrients and water without
A slice through the clay gives information aboutwhat happened to the clay. Similarly, a slicethrough the ocean gives information about whathas happened to the ocean.
So What?
Dense water sinks to the bottom of the ocean, slowly spreads out,and slowly rises back to the surface. This circulation is sometimesreferred to as the global conveyor-belt circulation.
Liquids can sink and float
A density column demonstration introduces students to the idea thatliquids can have different densities and can sink and float on top of eachother. The ocean is like a density column with the lightest water on topand the heaviest water on the bottom.
Learning Goals• Students will be able to describe vertical currentsand currents near the bottom of the ocean on a globalscale.
• Students will be able to explain vertical layers of theocean in temperature, salinity, and density.
• Students will be able to explain why temperature andsalinity change more near the surface than at depth.
Misconceptions• All ocean currents are caused by tides
• The deep ocean never changes anddoesn’t move
• The ocean has the same salinityeverywhere
Context for UseThis activity was designed for a 9th grade earth scienceclass, and would also be appropriate for middle schoolstudents. There are three 55-minute lessons and one20-minute quiz. This unit was taught after anatmospheric section and a short unit on the surfacecirculation of the ocean. Students were familiar with theconcepts of density, energy, waves, and theatmospheric circulation as well as the surface circulationof the ocean and what the ocean transports.
Atlantic Sections
Students complete a shortactivity using sections oftemperature and salinity in theAtlantic. Students see that not allof the water on the bottom is thesame, and can trace where waterhas come from using salinity.
Spray Gliders: autonomous ocean robots
Gliders have no propulsion mechanism anduse buoyancy to control their depth in thewater by pumping oil into and out of anexternal bladder. The glider moves forward inthe water as it dives up and down because ofthe wings. It is ~6 ft long and weighs ~100 lbs.
North Pacific Sections
16 sections of temperatureand salinity were obtainedfrom July 2007 - December2009 along a line north ofHawaii. It crosses throughthe center of the surfacegyre.
Science StandardsWe focus on teaching Californiascience standard 5d: “Studentsknow the properties of ocean water,such as temperature and salinity,can be used to explain the layeredstructure of the ocean, thegeneration of horizontal and verticalocean currents, and the geographicdistribution of marine organisms.”
Schematic of the globalconveyor-beltcirculation after thepopular one by W. S.Broecker*. Water sinksin a few spots near thepoles, spread outhorizontally, and risesup slowly everywhereelse.
*Broecker, W S, 1987. Thebiggest chill. Natural HistoryMagazine, Vol. 97, pp. 74-82.
Blue and yellow colors have beenstirred around, and green colorshave been mixed together.
Sampling the global ocean
One way oceanographers samplethe ocean is to take slices through itwith a ship, stopping every 50 kmand dropping instruments down tothe bottom. The R/V Melville,pictured at right, is one of the shipsused to sample the ocean.
From 1990-1998, several slicesthrough the ocean were taken as partof an international effort to observe theglobal ocean. Some of these sectionshave been observed prior to and afteras well.
Water is collected inbottles and brought backto the surface for analysis.
Above: sections of temperature and salinity in the Atlantic.Left: The red line shows where this section is located.
Gliders have a satelliteantenna in their wings, whichallows data to be sent back tothe scientists and instructionsto be sent to the glider. Theglider travels 5.5 kmhorizontally in 5.5 hours foreach 1000 m dive. The smallhorizontal spacing of divesallows smaller-scale featuresto be studied.
Students use six of the sections from different seasons and yearsto look at ocean layering and some of the smaller scale features.
Density Column Ocean
Salt water density >Object density
Object density >Fresh water density
Salt water density > fresh water density
Cold deep current
Warm surface current Latitude (°)
24 26 28 30 32 34
