Can ocean currents be caused by differences in salinity?

Yes

Explanation:

This is because salinity is one of the factors that affect ocean currents through a process called Thermohaline circulation. The higher the salinity of the ocean , the denser the water bodies and vice versa.

Other factors that affect ocean currents include density of the water body and temperature.

ocean expansion, global warming is melting icebergs and causing water levels to rise.