Which is the definition of the thermocline?

a.
the thermocline is the boundary between colder ocean water near the surface and warmer ocean water at greater depth.

b.
the thermocline is the boundary between warmer ocean water near the equator and colder ocean water near the poles.

c.
the thermocline is where warm ocean currents sink to become cold ones.

d.
the thermocline is the boundary between warmer ocean water near the surface and colder ocean water at greater depth.

B.
The thermocline is the boundary between warmer ocean water near the equator and colder ocean water near the poles.

As snow becomes compressed , air between the flakes gets trapped. The process involving trapping of air occurs during burial of snow layers and  is generally not complete  until the bubbles are about 60 meters or more below the surface.Once the bubbles have formed, they act as the time capsules of the atmosphere when they were trapped. By extracting the air from the bubble in ice cores, changes in the past can be studied . Studies of these changes show the dramatic increase of  what are called greenhouse gases such as carbon dioxide, caused by human use of fossil fuels, as well as natural changes that accompany glacial climate