IGCSE Marine section 1.4. Tides and currents

 The syllabus for 1.4 is:

Candidates should be able to:

 1 outline how high and low tides, and spring and neap tides, are produced by the gravitational effects of the Moon and Sun on the bodies of water on the Earth 

2 describe how to measure tidal amplitude 

3 describe oceanic currents as the continuous movement of sea water in a particular direction 

4 state that oceanic currents are caused by prevailing winds, the spinning of the Earth, tides and changes in water density 

5 describe a gyre as a large system of circular oceanic currents 

 6 state the locations of the five main oceanic gyres 

 7 state that oceanic currents and gyres circulate water around the World Ocean

 8 describe the formation of rip currents and the dangers they present to swimmers

 9 describe how to measure current speed and direction

My video on the syllabus:

The immense power of tides

Tides:

As we talked about in section 1,1, Gravity keeps the earth locked in the orbit of the sun, and the gravity of the earth keeps the moon in a stable orbit.

The moon and the sun both have an effect on our oceans, as their gravity pulls on the ocans of the earth, causing a bulge of water closest to the moon. Also, earths centrifugal forces causes a smaller bulge in the oceans on the opposide side.

This bulge of water move round as the earth spins. This causes the water levels on the oceans to rise and fall in a stady pattern, known as the tidal pattern.

The tidal rang changes during the month, as both the moon and the sun pulls on our oceans. When the moon and sun are alligned, the pull is strongest, and we get spring tides (The biggest tides). When they are on a right angle to eaxch other, we get the smallest tide, the Neap tide.

Tidal range:

Currents:

A currenbt is a continious flow of water in a particular direction.

Surface currents come from the direction of the wind, and are then deflected by the spin of the earth (The corolis effect is not syllabus but it is mighty nteresting)

when currents hit landmasses, they change direction. On the southern hemisphere, currents movecounter clockwise, thile they move clockwise on the northern hemisphere.

Surface currents circulating n the ocean form Gyres in most of our oceans, and they also tend to form the garbage patches we see.

Deep currents are formed by change in density in the sea water. Colder water with more salt is more dense than fresher water that is warmer. That means that cold water will sink, and this causes big currents at the ocean floor.

This video is a great review of currents:

Rip currents:

A rip current is a dangerous type of currents that can form at a beach, and swimmers get caught in them every year, sometims with fatal results

Meassuring currents:

To meassure a current, you need to know 2 things, speed and direction.

The most simple way is to follow an object in the surface.
With modern GPS sensors, this have become a lot easier.

Index can be found here