MS - ESS2.C (D) - Water on Earth - FINAL (CJT 1/31/2014)

DCI: ESS2.C (D) Variations in density due to variations in temperature and salinity drive a global pattern of interconnected ocean currents.

PE: MS-ESS2-6 Develop and use a model to describe how unequal heating and rotation of the Earth cause patterns of atmospheric and oceanic circulation that determine regional climates.

[Clarification Statement: Emphasis is on how patterns vary by latitude, altitude, and geographic land distribution. Emphasis of atmospheric circulation is on the sunlight-driven latitudinal banding, the Coriolis effect, and resulting prevailing winds; emphasis of ocean circulation is on the transfer of heat by the global ocean convection cycle, which is constrained by the Coriolis effect and the outlines of continents. Examples of models can be diagrams, maps and globes, or digital representations.] [Assessment Boundary: Assessment does not include the dynamics of the Coriolis effect.]

The ideas we see in this standard are: 

- temperature differences and salinity differences cause variations in the density of ocean water

- the differences in density drive global ocean currents

So, we have already focused on water in the atmosphere.  We can use what we did there as a model for what we are going to do here - but basically every one of our questions should relate directly back to density.  The PE mentions uneven heating, which would cause the temperature difference, but not salinity.  So, salinity does not relate to the PE, but should still be a part of our questions.  We will be concentrating on what drives ocean currents, how ocean currents relate to climate, and that the Coriolis effect and the outlines of continents affect the ocean current. 

Possible Question Starters: 

"Thermal differences in ocean water create movement because - "

correct answer - cold water is more dense than warm water

incorrect answer - cold water moves faster than warm water 

A similar question could be asked about salinity. Maybe in the other direction.
"Ocean currents move because of differences in density due differences in temperature of ocean water, and what other feature?"
correct answer - salinity (concentration of salt)

"A map of sea surface temperatures is provided. 

Warmer water is less dense than colder water. Based on this information, and the map provided, it could be predicted that, as a general trend, ocean water  - 

will rise near the Equator
will be less dense at the poles
will flow from west to east
?

- Probably another question about Coriolis effect and how that messes things up.