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Tides and Water Levels
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Changing Angles and Changing Tides |
As weve just seen, the Earth's two tidal bulges are aligned with the positions of the moon and the sun. Over time, the positions of these celestial bodies change relative to the Earths equator. The changes in their relative positions have a direct effect on daily tidal heights and tidal current intensity.
As the moon revolves around the Earth, its angle increases and decreases in relation to the equator. This is known as its declination. The two tidal bulges track the changes in lunar declination, also increasing or decreasing their angles to the equator. Similarly, the suns relative position to the equator changes over the course of a year as the Earth rotates around it. The suns declination affects the seasons as well as the tides. During the vernal and autumnal equinoxesMarch 21 and September 23, respectivelythe sun is at its minimum declination because it is positioned directly above the equator. On June 21 and December 22the summer and winter solstices, respectivelythe sun is at its maximum declination, i.e., its largest angle to the equator (Sumich, J.L., 1996).
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