Water science news, explainers, and statistics covering freshwater, hydrology, lakes, rivers, groundwater, ice, and Earth’s connected water systems.
A marine protected area is the broad category; a marine reserve is a highly protected type within it. An MPA can allow fishing, boating, tourism or other uses under site-specific rules. A reserve generally prohibits extracting or destroying natural resources, which is why it is often called a no-take area. The names are not perfectly…
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A freshwater estuary is a coastal transition where river water mixes with the water of a large freshwater lake. The Great Lakes contain the best-known North American examples. They resemble marine estuaries in their sheltered mouths, shifting water levels and rich wetlands, but they lack the persistent salt gradient created where a river meets the…
An ocean thermocline is a layer where temperature falls rapidly with increasing depth. It lies between warmer, wind-mixed surface water and the colder water below. Rather than marking a fixed depth everywhere, the thermocline shifts with latitude, season, weather and ocean circulation. The temperature change affects water density, vertical mixing, nutrient supply, oxygen distribution and…
The SOFAR channel is a deep-ocean layer that guides low-frequency sound over very long distances. Its full name is the Sound Fixing and Ranging channel. Sound bends toward the depth where its speed is lowest, so waves released near that axis can remain trapped instead of quickly escaping toward the surface or seafloor. The channel…
