I can only list a few regular «goings on'that I KNOW affect sea
level; I'm
certain that there are others: Change in overall temperature of the oceans (a few millidegrees / mm), plate tectonics, slit from rivers, erosion of seashores, extraction of ground water which ultimately returns to the oceans, marine life and its products building up the ocean floors, melting land ice, undersea discharges of a variety of «
stuff» from literally hundreds of thousands of sources, often
at temperatures in the 1 - 2 thousand degree range, which we are only now beginning to notice, wind carrying dust from the land and dropping it on the ocean.