The oceans regulate the temperature of land (of our globe) in two ways :
through oceanic currents which flow in them due to blowing of winds and rotation of earth.
through convection currents which flow in deep sea due to difference in temperature.
Let us discuss it in detail. When wind blows over the surface of an ocean, it causes the water to flow from one place to another. Similarly, when the earth rotates, it also causes the sea-water to flow along a particular path. This flow of water in the ocean from one place to another is called oceanic current. Also, at the greater depth in the oceans, the temperature difference between different points causes the water to flow. This flow of water due to oceanic currents and convection currents carries heat from lower latitudes to higher latitudes and regulates the temperature of land. It is because of this regulation that the temperature difference between any two points in the ocean is never more than 10°C.