1. Physical Oceanography Density

2. Measured in mass/volume (g/mL) Is the major factor in water circulation and distribution of plankton Controlled by temperature and salinity Measured with a hydrometer

4. Why Does Ice Float? Water molecules push apart during freezing, increasing the volume. Since the mass is unchanged, but the volume is larger the ice has a lower density than the surrounding water and it floats. Ex) water: 1.00 g/1.00 mL = 1.00 g/mL density ice: 1.00 g/1.10 mL = 0.90 g/mL density

5. Liquid WaterFrozen Water

7. If sea water has a salinity of 35 ‰, then it will freeze at -1.94 °C. If ice freezes rapidly, salt pockets are trapped in it – this makes it very brittle and is called ‘first-year ice.’ Salt pockets migrate downward and out, making ice ‘fresher’ as it gets older; this also makes the ice much stronger.

11. Generalities about Density 1.Normal salt water has a density between 1.01 and 1.03 g/mL 2.Density increases with depth 3.Density increases as temperature decreases 4.Density increases as salinity increases

12. 5.Water is normally stratified (in layers) based on density Q: Is it possible to have a layer of warm ocean water below a layer of cold ocean water?

13. A: Yes. If the warm water has a greater salinity than the cold water, this makes it more dense. Also, if two water masses have the same density but have different temperatures, then one must have a higher salinity than the other.