< p >简单的对这个问题的回答是,冰冷的海水的密度比温暖的海水,这水池和填空深海海洋。< / p > < p >的水满了深海海洋来自极地。这是一个1990年代的温度在大西洋,检索从< a href = " http://sam.ucsd.edu/whp_atlas/atlantic_index.html " rel = " noreferrer " > WOCE大西洋Atlas < / >: < / p > < p > < a href = " https://i.stack.imgur.com/EicYM.jpg " rel = " noreferrer " > < img src = " https://i.stack.imgur.com/EicYM.jpg " alt = "在这里输入图像描述" / > < / > < / p > < p >你可以看到最冷的水是来自南极地区(深蓝色的东西情节的左边)和传播。< / p > < p >如果你看看1990年代盐度相反(策划)你可以看到水从北极不冷,但是很咸(黄色部分的情节从右手边,坐在上面的水来自南极洲北部)。< / p > < p > < a href = " https://i.stack.imgur.com/RsY0S.jpg " rel = " noreferrer " > < img src = " https://i.stack.imgur.com/RsY0S.jpg " alt = "在这里输入图像描述" / > < / > < / p > < p >考虑海洋的密度时,重要的是要记住,海洋不是装满水,瓶里装的是< em > < / em >海水。海水海水包含< a href = " https://en.wikipedia.org/wiki/Salinity " rel = " noreferrer " >每公斤大约35克的盐的海水< / >。因此,海水的密度取决于< a href = " https://en.wikipedia.org/wiki/Seawater /媒体/文件:WaterDensitySalinity.png”rel = " noreferrer " >温度和盐度< / >。你可以写成< / p > < p > <跨类= " math-container " > $ $ \ρ= T + \ \αβS $ $ < / span > < / p > < p >为我们需要足够正确。(小之外,还取决于压力和密度系数<跨类= " math-container " > \α< / span >和美元<跨类= " math-container " > \β< / span >取决于美元压力、盐度、温度和——你可以看到这个的等值线的曲率密度< a href = " https://en.wikipedia.org/wiki/Seawater /媒体/文件:WaterDensitySalinity.png”rel = " noreferrer " >这个数字< / >。真正理解海水的密度是一个巨大的事业。)< / p > < p >盐使另外两个非常重要的事情:< / p > < ol > <李>随着海水变冷,它越来越密集的(但< span class = " math-container " > \α< / span >美元在低温下会很小,所以盐度真的占据了密度)< /李> <李>海水冻结在~ 2°C < /李> < / ol > < p >这是为什么我们看到水-0.4°C蔓延远离南极在图的左下角。表面附近的时候天气比较冷,但是当它沉没携入的周围的液体,和热身。< / p > < p >这解释了我们如何得到冷水进深渊,但为什么不地热热流只是温暖呢?< / p > < p >的原因地热热流不加热深海海洋是它太小了。 The geothermal heat flux is up to ~0.5 W/m$^{2}$. By comparison, heat fluxes at the surface of the ocean range from -200 W/m$^{2}$ to 200 W/m$^{2}$ (where positive means into the ocean in both cases). The surface heat fluxes and ocean dynamics simply overwhelm the much much smaller geothermal heat flux. Lots of models include a heat flux through the ocean floor, but because it is so small the abyssal ocean remains cold. Here's an example of the heat budget from an ocean model that includes a flux of heat through the seafloor. So, not much hard maths in there, but I'm not sure we need it.