What are ocean currents ,Tides and waves?
Answers
Waves - periodic changes in the water surface height caused by the wind. The height of the waves is a function of the speed of the wind and the distance over which the wind blows (the fetch). Waves caused by the local wind are called, wait for it, wind waves. A strong storm elsewhere can send substantial waves long distances - this is called the swell. If you look at the NOAA marine forecast (as I do before sailing) you will often see the heights, direction, and periods of wind waves and swells, which often come from different directions.
Tide - periodic change in the ocean level caused by the gravity of the moon and sun. Some places have 2 similar/identical tides every day, others have two different tides. Nautical charts typicaly show the lowest normal water levels in each area - Mean Low Water, or Mean Lower Low Water for places with two different tides. In some places, like the Mediterranean, the tide is barely noticeable. In others, like the Bay of Fundy in Nova Scotia, it can be 10’s of meters.
Current - directional flow of water. If you sit in a boat with no propulsion, the boat will be swept along with the current. This can be caused by:
Gravity of the earth- rivers flow downhill; the current is stronger when the elevation drops more steeply
Tide (gravity of the moon and sun) - To create high and low tides, there are flood and ebb currents bringing the water in and pulling it out. In places where an outgoing river current meets an incoming flood tide, watch out for rough water with short, steep waves
Long term large scale oceanographic/meterological phenomena - the Gulf Stream, the Agulhas current