Call for Citizen-Scientist King Tide Watchers

The University of Washington Sea Grant Program is asking the public to report on local king tides in mid-January by submitting photographs of local waterfront locations. The collected data is intended to assist scientists and planners measure the impact of sea level rise and storm surges on the environment and infrastructure.

“King tide” is an informal name for an unusually high tide. Tides rise and fall because of the gravitational pull of the moon and sun and are amplified by local geography, like that of South Puget Sound. A king tide is said to occur when certain astronomical variables combine with local atmospheric elements — such as high wind or low pressure.

PREDICTED KING TIDES FOR HENDERSON BAY Jan. 13 7:16 a.m. 15.5 feet Jan. 14 7:58 a.m. 15.6 feet Jan. 15 8:39 a.m. 15.6 feet

The highest tides of each lunar cycle (approximately 27 days, 7 hours and 43 minutes) occur when the moon is full or new and aligned with the sun, combining their gravitational effects to create what is called a spring tide.

Three or four times a year the moon’s orbit brings it closer than average to Earth, a position called perigee. When spring tides coincide with the moon in perigee, the moon has a greater than average pull on the oceans, causing higher than average high tides that are called perigean high tides.

Higher tides also regularly occur in early January each year when the Earth is closest to the sun — a position called perihelion.

The most useful photos of tidal impact are those where the tide height can be gauged against familiar landmarks, like buildings, roads, sea walls and piers. Photos can be submitted to mycoast.org/wa.