The Cosmic Origin of King Tides

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Stormy, unpredictable seas are a magnificent sight along our coast as the winter rolls in, bringing with it huge waves and high winds. While raging seas are not uncommon, a raging sea with a King Tide promises to be a sight to behold. Such high tides occur only a handful of times each year, bringing excitement, danger, and an incredible display of the ocean’s power.

What creates a mighty King Tide? To understand that, we must look far, far beyond the ocean to the source of the tides themselves: the Moon and the Sun. The gravitational pull of the Moon and Sun on the Earth and ocean causes tides across the world. The Moon influences the tides more because it is closer to the Earth. The tide itself is the advancement and withdrawal of the seawater level along a coastline in a continuous, alternating pattern. Coastal regions generally experience two tidal bulges every day. However, the tides are not the same every day. The time of day that the tide is high or low or the typical two highs and two lows is influenced by the lunar cycle. Unlike a solar day, a lunar day is 24 hours and 50 mins long due to the moon and Earth rotating in the same direction and axis. So, tidal highs occur every 12 hours and 25 mins, shifting the high or low tide time each day.

So the Moon is causing some changes in our day to day tides – but that’s not all; there are more inconsistencies up there in space to mention. The orbit of the Earth around the sun is not a perfect circle; it is more of an oval that we call an ellipse. The Moon orbits the Earth in an ellipse as well. So, not only is the Earth’s orbit not a perfect circle, but neither is the Moon’s. Are you still with me? Since these orbits are not perfect circles, there are times throughout the orbits when the Moon and Sun are closer to or farther from the Earth. The closest point to Earth in orbit is called the perigee, and the furthest point is called the apogee.

Throughout the lunar orbit, the Moon has the most significant pull on the ocean during a new moon or a full moon. When the Moon is new, it aligns almost perfectly between the Earth and Sun and when the Moon is full, it also aligns with the Earth and Sun on the opposite side of the Earth. In both cases, the Moon’s gravitational pull works with the sun’s gravity to cause the most extreme high tides called spring tides. Seven to fourteen days after a spring tide, the Moon and Sun are at 90° angles to each other, which is when their gravitational force on the ocean is the weakest causing very low tides, called neap tides

All of this cosmic dancing comes together a few times each year to create tidal wonderment. When a full or new moon occurs while the Moon is at its perigee (closest point to Earth), we get an extra-strong gravitational pull from the Moon being so close and in line with the Sun’s gravitational pull. These circumstances create exceptionally high tides called Perigean-Spring Tides, or King Tides. In North America, the Earth is closest to the sun during the winter, so when the Moon and Sun work together to cause a spring tide, the gravitational pull is the strongest of the year. Therefore, winter is often when we see our most exceptional King Tides during our stormy winters.

While we have learned to be extra cautious of coastal areas during King Tides and raging seas, what about the life beneath the waves? What else is affected by this cosmic marine phenomenon? The tides’ rhythmic pattern has created a unique ecosystem zone generated and maintained by the tides, known as the intertidal zone. A multitude of species have evolved to thrive in different areas of the intertidal, adapting to the rewards and the dangers of spending various amounts of time both in and out of the water. Most species tolerate spending a little more or less time submerged during extreme high tides and weather. However, King Tides can always be more powerful and destructive when paired with storms and winter winds, leaving the most resilient species washed ashore. Beyond the intertidal one, not many species are as affected by extreme tides, except one.

One mysterious fish species called a grunion (Leuresthes tenuis) has developed amazing synchronicity with spring tides and spawning patterns. Grunions are found along the Pacific coast from California to Mexico and exclusively spawn during spring tides when they can lay their eggs at the beach’s highest possible section. After a few weeks, the next spring tide stirs up the sand again, prompting the eggs to hatch and wash down into the ocean. They are one of very few species that appear to be living in near-perfect sync with spring tides, and we are still learning about how they know exactly when the cosmos aligns and the spring tides will occur.

As the King Tides wash in this winter, remember that the planets have quite literally aligned for such events to occur. But be cautious and stay safe out there, always observe the ocean from a safe, generous distance.

“Tidal effects are mysterious and dark in the soul, and it may well be noted that even today the effect of the tides is more valid and strong and widespread than is generally supposed.” – J. Steinbeck, The Log from the Sea of Cortez.

 

Written by: Jordan Hawkswell

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