Currents are affected by three factor. The moon pushes water away from the saltier. The surface water...... with water that rises from deep down. Ocean currents are also .... by salt levels. When sea water enters the Arctic or Antarctic,the water vools, evaporates and becames...... . In the tropics, the water is blown by atmospheric ....... . The most well-known current is the ....... current. Since the Gulf Stream flows more quickly than other currents,ships use it to sail from west to east.