If you have been on the island this week, or following the news on island happenings, you are well aware that we have been experiencing “King Tides” this week. Tuesday’s high tide was the third highest recorded since 1935, when the National Weather Service began collecting this information. So what exactly is a King Tide?Put simply, a King Tide is just an exceptionally High (and low) tide. These tides occur a just a few times a year, but to understand why, I think it is easiest to start with a brief explanation of how the tides occur.
Tides are the rise and fall of sea levels caused by the combined effects of gravitational forces of the the moon, sun, and rotation of the Earth. Tides are tied (groan) to the lunar cycle, with the highest (and lowest) tides happening every 14 days, at the new and full moons. This large tide swing is referred to as a spring tide, while those occurring during the first and third quarters of the lunar cycle see the smallest tide swing and are called neap tides. Spring tides occur when the sun and moon are directly in line with the earth and their gravitational pulls work in concert. Neap tides occur when the sun and moon are at right angles to the Earth, weakening their gravitational pull on the earth because it is coming from two different directions.
The Moon’s orbit around the Earth is elliptical, which causes the Moon to be closer to the Earth and farther away at different times. When the moon is at its closest point to the Earth during a spring tide, it increases the large tide swing seen during these tides even further. Only happening three or four times a year, these exceptionally high and low tides are referred to colloquially as King Tides. These King Tides frequently cause coastal flooding, especially when the area is experiencing storms or long bouts of rain, as we had been earlier in the week.
One additional note. As we already know, tides are based on the lunar day, which is longer than the Earth day because the moon orbits in the same direction as the Earth spins. Because of this, tides change every 6 hours and 12 minutes, for a total of 48 minutes later than on the previous day.