Tides at the Shore

What do the tides do?

They move entire water column as opposed to the winds that are moving just the surface waters.

What does tidal flow near the bed experience? What does this create?

It experiences frictional resistance. This frictional resistance of flow over bed creates shear

Describe speed of flow at the bottom to the top

Speed of flow is slower at the bottom and then speed of flow will increase as you move further away from the bed

What is shear? What does it cause?

It is change in water velocity with depth and it causes instability and turbulent mixing

What is turbulent mixing limited to? What is the exception of this?

It is limited to the bottom boundary layer. The exception is that this bottom boundary layer can grow all the way up to the surface if flow is shallow enough.

Where does boundary-layer turbulent mixing extend to?

Surface in shallow water but doesn’t out in the ocean basin because it is too deep

What is boundary layer turbulent mixing doing to near shore water?

It is causing nearshore water to be colder and nutrient rich because it is bringing nutrients that have been liberated from the sediment to the surface and colder water from the bottom. This affects primary productivity.

Why is tidal mixing important?

It breaks down stratification and mixes cold water upwards (mixes heat) and nutrients are mixed upwards (mixes nutrients such as carbon and oxygen)