引子

Introduction

大海中波浪翻滚，我们常常听到某某洋流或者海流。那么，海流与洋流是否有差异呢？海面的海流我们能轻易推断出是由海风引起的，那么海面下是否仍然存在海流呢？如果有，那么在没有海风的海面下，海流是怎么产生的呢？

We can often hear about so-and-so “洋流”or “海流”. So, is there a difference between “海流” and “洋流”? We can easily deduce that currents at the surface are caused by sea breeze, but are there still currents below the surface? If so, how are currents generated under the surface of the sea where there is no sea breeze?

基本概念

Basic Concept

海流又称洋流，两者实为一个东西，是海水因热辐射、蒸发、降水、冷缩等而形成密度不同的水团，再加上风应力、地转偏向力、引潮力等作用而大规模相对稳定的流动，它是海水的普遍运动形式之一。海洋里有着许多海流，每条海流终年沿着比较固定的路线流动。它像人体的血液循环一样，把整个世界大洋联系在一起，使整个世界大洋得以保持其各种水文、化学要素的长期相对稳定。

“海流” and “洋流” are actually the same thing. It is a water mass with different densities due to thermal radiation, evaporation, precipitation and cold shrinkage which is a kind of large-scale and relatively stable flow of seawater for the wind stress, geostrophic deflection force and tidal attraction force. There are many currents in the ocean, and each current flows along a relatively fixed route throughout the year. It is like the blood circulation of the human body, linking the whole world ocean together, so that the whole world ocean can maintain the long-term relative stability of its various hydrological and chemical elements.

海流成因

Causes of Currents

海流的形成基本分为风海流，密度流与补偿流。

The formation of currents is basically divided into wind current, density current and compensation current.

● 风海流

● Wind Current

海面上的风力驱动，形成风生海流。由于海水运动中粘滞性对动量的消耗，这种流动随深度的增大而减弱，直至小到可以忽略，其所涉及的深度通常只为几百米，相对于几千米深的大洋而言是一薄层。海流形成之后，由于海水的连续性，在海水产生辐散或辐聚的地方，将导致升、降流的形成。

Wind-driven current is formed by the wind on the sea surface. Due to the depletion of momentum by viscosity in the movement of seawater, this current weakens with increasing depth until it is negligible, and the depth involved is usually only a few hundred meters, which is a thin layer compared to the ocean of several thousand meters deep. After the formation of currents, the continuity of seawater will lead to the formation of upwelling and downwelling where the seawater produces dispersion or convergence.

● 密度流

● Density Current

不同海域海水温度和盐度的不同会使海水密度产生差异，从而引起海水水位的差异，在海水密度不同的两个海域之间便产生了海面的倾斜，造成海水的流动，这样形成的海流称为密度流。

The difference of seawater temperature and salinity in different seas will cause the difference of seawater density, which will lead to the difference of seawater level, and the inclination of sea surface between two seas with different seawater density will cause the flow of seawater.

● 补偿流

● Compensation Flow

当某一海区的海水减少时，相邻海区的海水便来补充，这样形成的海流称为补偿流。补偿流既可以水平流动，也可以垂直流动，垂直补偿流又可以分为上升流和下降流，如秘鲁寒流属于上升补偿流。

When the seawater in one sea area decreases, the seawater in the adjacent sea area comes to replenish it, and the resulting current is called the compensation current. Compensation current can flow both horizontally and vertically, and vertical compensation currents can be divided into upwelling and downing, for example, the Peru Current is an upwelling compensating current.

海流发电

Sea Current Power Generation

目前对于海流的利用主要针对于海流发电的研究。在海洋运动中，海流则对地球的气候和生态平衡扮演着重要的角色。海流循着一定的路线周而复始地运动着，其规模比起陆地上的巨江大川则要大出成千上万倍。海水流动可以推动涡轮机发电，为人们输送绿色能源。中国的海流能源也很丰富，沿海海流的理论平均功率为1.4亿千瓦。

At present, the use of ocean current mainly focuses on the research of power generation. In the ocean movement, current plays an important role in the Earth’s climate and ecological balance. And the ocean currents follow a certain course, and their scale is thousands of times larger than that of huge rivers on land. The flow of sea water can drive turbines to generate electricity and deliver green energy to people. China is rich in ocean current energy, with a theoretical average power of 140 million kilowatts of coastal currents.

投稿者：张炜峰 硕士研究生

审核导师：沈义俊 教授