Desperately need some help!

[Aisha T]

Hi all,

 

I have been told to do a presentation on a topic that I have no idea about, and can't find much info on! I tried googling and all but it wasn't much help. The question is:

 

Why does it take so long for deep ocean waters to circulate through the hydrologic cycle? What happens to substances that contaminate deep ocean water or deep aquifers in the ground?

 

From the little knowledge i've got, I think the reason deep ocean waters take so long to circulate is because the deeper part of the ocean is colder. Colder because less sunlight reaches it. But, then it its colder shouldnt the density be less and it should rise to the top ?:s I could be wrong, as im pretty new to this subject. Any help would be highly appreciated.

 

Thank you .

[mooeypoo]

The idea is right up to the part about the density. Think about it, Aisha, deep ocean water are cold because sunlight doesn't reach it (that much is true) but also, they are very deep underwater... they have the weight of a huge body of water above them -- a lot of mass is pressing them down, which increases pressure, and why the density is higher.

 

Does this make sense? You might be able to look up things more easily now.

[TonyMcC]

But, then it its colder shouldnt the density be less and it should rise to the top ?:s I could be wrong, as im pretty new to this subject. Any help would be highly appreciated.

 

Thank you .

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Sea water is at its most dense at about 4 degrees celsius, which is pretty cold.

[Aisha T]

The idea is right up to the part about the density. Think about it, Aisha, deep ocean water are cold because sunlight doesn't reach it (that much is true) but also, they are very deep underwater... they have the weight of a huge body of water above them -- a lot of mass is pressing them down, which increases pressure, and why the density is higher.

 

Does this make sense? You might be able to look up things more easily now.

 

Thank you so much mooeypoo, really appreciate your help. Ok so, i looked it up and realised that the density of water increases as temprature decreases till a certain temp(4). So, water at the bottom doesnt circulate because its cold and dense, it has a lot of mass above it hence increasing the pressure, also is it right to say the kinetic eneryg of the molecules is less due to low temprature so less movement?

 

Any other reasons possible?

 

I've tried to look up the second part of the question, but haven't really found information related to it. Could you maybe give me a hint or two?

 

Thanx