Click here to see a graph showing their monthly temperatures. Use an atlas to find other pairs of U.S. cities with about the same latitude, one on the west coast and the other on the east coast. Plot these data on a graph, similar to the graph for San Francisco and Norfolk . The salinity of near-surface ocean water varies from place to place. The crystal structure of ice cannot hold much salt, therefore when water freezes, the surrounding liquid water becomes more saline.
Fresh water comes into the ocean primarily as rain and snow, and runoff from rivers and melting ice.
Many regions are affected by processes that both increase and decrease salinity. For example, near the margins of continents, dry winds blow off landmasses and increase salinity via high evaporation. In these same areas, salinity is decreased by the influx of freshwater from nearby rivers. In general, the higher ocean salinities occur in the centers of ocean basins, where trade winds evaporate water and rain is rare.