Water science news, explainers, and statistics covering freshwater, hydrology, lakes, rivers, groundwater, ice, and Earth’s connected water systems.
The epipelagic zone extends from the sea surface to roughly 200 meters (656 feet). Oceanographers also call it the sunlit or euphotic zone because enough solar energy reaches much of this layer to support photosynthesis. The 200-meter figure is a useful global convention. The working depth changes with water clarity and the angle of the…
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Flood current moves water toward shore or up an estuary, ebb current moves it away from shore or down an estuary and slack water is the interval around a current reversal when speed is near zero. These phases describe horizontal tidal motion, not the vertical height of the tide. Many coasts pass through flood, slack…
Storm surge is the abnormal rise of seawater produced by a storm above the predicted astronomical tide. Storm tide is the total water level resulting from the combination of storm surge and the astronomical tide. Waves can rise above both measurements and drive water farther inland. The distinction separates the storm’s contribution from the water…
A rip current is a concentrated flow of water moving away from shore through the surf zone. “Rip tide” is an inconsistent term that scientists and safety agencies generally avoid. It may be used informally for a rip current or for a strong tidal flow through an inlet, but those are different processes. Calling the…
