January 31, 2023
upwelling in san diego

Upwelling in San Diego – A Coastal Phenomenon

Upwelling is more of an inconvenience to surfers than anything else. Especially an upwelling in San Diego because we get accustomed to milder water temperatures surfing here!

In this post, learn all about when upwelling in San Diego happens, what does upwelling mean, what causes an upwelling, and other places upwelling occurs in the world.

By the end, you’ll fully understand why and when upwelling occurs.

What Does Upwelling Mean?

To answer what does upwelling mean, I find it’s best to start with a basic upwelling science definition. In this first section, we’ll start with that basic foundation.

In its simplest form, upwelling is when the warmer surface water is replaced with deeper cold water. Think about it like this. When you are swimming, the water is warmest on the surface. When diving below the surface, you can actually feel the water become cooler. The deeper you go, the colder it gets. With upwelling, that colder water is simply brought to the surface displacing the warm water on top.

In summary, that is what upwelling means – a simple swap of the different ocean water temperature layers.

What Causes Upwelling?

Now that we know what upwelling is, let’s find out what causes upwelling.

To begin, the ocean surface is warmest on days with less wind. The lack of wind causes the lower and upper ocean layers not to mix. When a wind blows across the ocean surface (generally parallel to the coastline); this causes the warmer surface water to move and mix the water layers. As a result, this warm layer on top is replaced with a cold layer below. This entire affect causes upwelling to occur.

what causes upwelling
An illustration to what causes upwelling

When Does Upwelling Occur?

The upwelling California season occurs most frequently during the Spring. Although, an upwelling can happen just about any time you get a cross directional wind. The reason upwellings are most common in Spring is that a North Pacific High sits off the coast this time of year. As storms drop through the Great Basin, this creates those strong wind flows which lead to upwelling in San Diego and across California. Summertime is the other time of year when upwelling can periodically occur. Although, not as often.

The other phenomenon that upwelling in San Diego will lead to is May Gray and June Gloom. As the cold water rises to the surface in these Spring months, it will contribute to that dense coastal fog that sits along the coast all morning.

Where Does Upwelling Occur?

Upwelling can occur on just about any coastline. However, there are a few select coastlines where upwellings are most common. They include the California coastline, Northwest Africa, Southern Africa, Peru/Chile, and Somalia. Upwellings are most associated with major coastal currents.

Surfing During Upwelling in San Diego

As surfers, one thing we can typically count on is the ocean temperature in San Diego being pretty consistent throughout the year. We know the winter is coldest and summer is warmest.

However, when we get an upwelling in San Diego during Spring or particularly summer, the average expected ocean temperature is thrown out the window. If you are accustomed to balmy 70° one summer day, you will be in for a shock after an upwelling occurs. The temperature can drop by as much as 10° – yikes!

When this happens, it’s time to check your rubber and put on a thicker wetsuit. My wetsuit guide will help you choose the correct wetsuit based on the current water temperature. Fortunately, the cooler water temps as a result of an upwelling only last a few days before the normal surface ocean temperature returns. If you need to gear up to stay warm during days like this, check my guide to stay warm in the ocean.

where does upwelling occur
Be sure to check the water temperature when upwelling occurs!

In summary, check the water temperature before you paddle out to be sure a sudden temperature drop has not occurred. Surfline is also helpful for this.

Conclusion on Upwelling in San Diego

Upwellings are completely natural events. They are nothing to be concerned about. Upwelling in San Diego is simply an inconvenience when you were hoping to enjoy surfing in warmer water!

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