What is the thermocline and why does it matter?
A hidden thermal wall in the ocean separates warm surface waters from the frigid deep, trapping most marine life above it.
The answer
The thermocline is a layer of ocean water where temperature drops rapidly with depth, typically found between 200 and 1,000 meters in tropical and temperate seas. Above the thermocline, surface waters warmed by the sun can reach 20 to 30 degrees Celsius, while below it, temperatures plunge to near-freezing 1 to 4 degrees Celsius. This sharp density gradient acts as a barrier, inhibiting vertical mixing between surface and deep waters and effectively trapping nutrients in the deep ocean. The thermocline also affects sonar propagation, submarine warfare tactics, and the distribution of marine life, as most commercially important fish species live above it.
Source: Oceanography Textbook (Talley et al.)
- thermocline
- ocean temperature
- ocean layers
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