a) This is brought forth by surface wind currents and their clashing—this is a convergence of the two boundaries .
b) The interaction between the ocean’s surface and the circulation of the lower atmosphere or surface winds is the primary cause of the surface currents in the oceans.
c) The anomalies in their salinities and the speed of the currents transports heat therefore affecting climate in big-scales.
The salinities of the oceans may have appeared to be constant because some of the particles of Chlorine ions evaporate, but then particles of Sodium ions remain in the bodies of water. Such discrepancies could be attributed from freshwater evaporation, addition of freshwater on the salty bodies, and also freezing and thawing. Low salinity is found in cold seas, particularly during the summer season when ice melts. High salinity is found in the ocean ‘deserts’ in a band coinciding with the continental deserts. Due to cool dry air descending and warming up, these desert zones have very little rainfall, and high evaporation. The Red Sea located in the desert region but almost completely closed, shows the highest salinity of all (40ppt) but the Mediterranean Sea follows as a close second (38ppt). Lowest salinity is found in the upper reaches of the Baltic Sea (0.5%). The Dead Sea is 24% saline, containing mainly magnesium.
Wind-driven surface currents head polewards from the equatorial Atlantic Ocean, cooling all the while and eventually sinking at high latitudes , forming North Atlantic Deep Water. This dense water then flows into the ocean basins. While the bulk of it upwells in the Southern Ocean, the oldest waters in the North Pacific. Extensive mixing therefore takes place between the ocean basins, reducing differences between them and making the Earth’s ocean a global system. Therefore, of the water on the Pacific was last at the surface in 408 A.D.