What is the difference between longshore current and longshore drift?

As a marine science expert with a focus on coastal dynamics, I can explain the difference between longshore current and longshore drift. Longshore current is a type of nearshore movement of water that runs parallel to the coastline. This current is typically caused by the angle at which waves approach the shore. When waves break at an angle, they create a water flow that moves along the beach, carrying sediment with it. The size and strength of the longshore current can vary depending on the wave conditions and the shape of the coastline. Longshore drift, on the other hand, refers to the movement of sediment, such as sand, along the shoreline in the direction of the longshore current. This sediment transport is a result of the energy exerted by the waves and the longshore current working together. Longshore drift can significantly shape and reshape beaches over time. Now, let's translate that into Chinese: 作为一名专注于海岸动力学的海洋科学专家，我可以解释沿岸流和沿岸漂移之间的区别。 沿岸流 是一种沿着海岸线平行方向的近岸水流运动。这种流通常是由波浪接近海岸的角度引起的。当波浪以一定角度破碎时，它们会产生沿着海滩移动的水流，并携带沉积物。沿岸流的大小和强度可以根据波浪条件和海岸线的形状而变化。 沿岸漂移 则是指沉积物（如沙子）沿着海岸线在沿岸流的方向上移动。这种沉积物搬运是由波浪和沿岸流共同作用的结果。沿岸漂移可以显著地塑造和重塑海滩。

The longshore current is part of the longshore transport that moves sand and sediment down the coastline, but there is also another process that contributes to the longshore transport called beach drift, or longshore drift. Beach drift is defined as the progressive movement of sand and sediment along the beach.