Phenology Files: February 2023

phenology fi-ˈnä-lə-jē n 1 : a branch of science dealing with the relations between climate and periodic biological phenomena (such as bird migration or plant flowering) 2: periodic biological phenomena that are correlated with climatic conditions.

King Tides

A lot of us heard the term “king tide” being used throughout the winter. This non-scientific term is used to describe an abnormally high tide, generally above the highest water level of an average high tide.

The changing of tides is controlled by the gravitational pull between Earth and the moon. Certain astronomical events amplify that pull and cause king tide conditions. These astronomical events also help us predict when king tides are coming.

One of these events is called a perigean spring tide. Let’s break down that mouthful – it’s a combination of two things that cause more gravitational pull on the tides:

  • Perigree: when the moon is a position that is especially close to Earth
  • Spring tides: Higher tides caused by the moon and sun being in alignment. This happens twice during the lunar cycle, the new moon and the full moon.
Courtesy of NOAA.

Another event that can cause a king tide is when the Earth is in a position called perihelion, which simply means the time when it’s closest to the sun. This is generally in early January, this year it was on January 4th.

The Salish Sea experienced king tides at the ends of November, December, and January. Why is this important? King tides can often cause coastal flooding, especially when they are magnified by winter storm events.

Like a crystal ball, king tides can give us a glimpse at our future. With sea level rise, the water level reached by a king tide will become that of a regular high tide in the future. With this information, communities can be better informed about the coming changes and make decisions about shorelines and infrastructure.

Want to report king tide conditions? Check out the MyCoast: Washington app!