test

Water on Water

Ava Alexander and Ashukem Taku
Opportunity X @River Glen School

Teacher: Ms Kendall Bell

Theory behind
‘Water on Water’

● The water of the oceans is not uniform.
● Ocean water temperature has big difference

● Ocean water salinity also has big
difference

● Thermohaline Circulation: in the deep ocean,
differences in seawater density drive huge masses
of water circulate around the globe

● Higher salinity → higher density
● Higher temperature → lower density

What happens when
layers of water at

different densities are
brought together?

The Experiments

1. Add salt and food coloring to water
2. Red bottle has one salt density; Blue bottle

has another salt density.

3. Flip one bottle on top of another bottle
4. Watch how salt water mix
5. Each test is repeated three times

How to change density of saltwater?

1. With fixed water temperature at 20
celsius, we change water salinity 0 ppt,
18 ppt, 36 ppt, by adding 0tsp, 1tsp, 2tsp
of salt to 10 oz of water

2. With fixed salinity at 36 ppt, we change
water temperature from room
temperature at 20 celsius to cold
temperature at 4 celsius

The Results

At room temperature (20°C) TOP BOTTLE

BOTTOM Salinity 0 ppt 18 ppt 36 ppt
BOTTLE 0 ppt Mixed quickly Mixed quickly
18 ppt N/A
36 ppt 156 sec 226 sec
Did not mix after Mixed quickly
240 sec N/A
104 sec
Slowly mixed a little Slowly mixed a little
305 sec 220 sec N/A

At 36 ppt salinity TOP BOTTLE
Temperature 4 °C 20 °C

4 °C N/A Slowly mixed a little
20 °C 240 sec
BOTTOM
BOTTLE Mixed quickly
199 sec
N/A

Observations

● Salt water of different density mix
initially, then float on each other.

● When top bottle has a higher density,
it quickly mixes with bottom bottle.
○ Top bottle has higher salinity, with
same temperature
○ Top bottle has lower temperature,
with same salinity

More Observations

● When top bottle has a lower density,
it mixes very slowly or does not mix
○ Top bottle has lower salinity, with
same temperature
○ Top bottle has higher temperature,
with same salinity

● The larger difference of the density,
the longer it takes to reach
equilibrium.

Conclusions

● The experiments demonstrate how
Thermohaline circulation works
○ Salt water of different density mix
initially, then float on each other
○ If higher density salt water is on top,
then it will sink down.
○ If lower density salt water is on top,
then it will not sink down or it will
take very long to sink down

● When the density difference is larger,
then it takes longer to mix.

Future Work

◎ How to prevent Thermohaline Circulation
Shutdown ?
◉ Thermohaline circulation shutdown is
caused by global warming, as melted ice
delutes salty sea water in the North
Atlantic Ocean
◉ Then cold water stays on the surface,
does not sink to deep water, hence
stops Thermohaline circulation
◉ This would cause severe climate change