Sea-level measurements from tide gauges

This chapter describes some aspects of the measurement of sea level using tide gauges. By “sea level” we mean “still water level”, the level of the sea surface which occurs due to processes in the ocean such as the tides, storm surges, tsunamis, or mean sea-level changes, but not the high-frequency changes due to wind waves. What is referred to as “sea level” in the UK is usually called “water level” in the USA. By “tide gauge” we mean “sea-level recorder”, as the instrument measures changes in level due to all processes and not just the tide. However, the traditional name has been retained.