By NASA Earth Observatory, 10/23/20
Global sea level has been rising at a rate of 0.1 inches (3.3 millimeters) per year in the past three decades. The causes are mostly the thermal expansion of warming ocean water and the addition of fresh water from melting ice sheets and glaciers. But even as the sea takes up more space, the elevation of the land is also changing relative to the sea. What geologists call vertical land motion—or subsidence and uplift—is a key reason why local rates of sea level rise can differ from the global rate. California offers a good example of how much sea level can vary on a local scale.