Question

Why warm and cold currents meet and visibility is reduced

Answer 1

The warm air has the moist air present in it. When a cold current comes from a near by area and gets in contact with the warm current, the moist air gets condense and thick air is formed which is also known as fog through which clear view is not possible 

Answer 2

Currents are movements of ocean water in a continuous flow. They are created largely by surface winds and partly by temperature and salinity gradients, Earth's rotation, and the gravitational effects of the sun and moon.

A warm current may have moist air along with it. This moist air condenses when it comes in contact with the cold air travelling along with the cold current. This condensation is fog which reduces the visibility.