Tag Archives: Upwelling

Winter: It’s Here But What Is It?

It’s getting cold! The wind is starting to blow! Rain is falling! The grass is starting to grow! The waves are getting bigger! IT’S WINTER!!

WinterBut what exactly is winter?

There are two kinds of winter, astronomical winter— having to do with the position of the earth and the sun ranging from the winter solstice to the vernal equinox— and meteorological winter— based on the annual temperature cycle and the calendar.

In California this manifests in shorter days, cooler temperatures, increased rainfall and onshore winds. Many animals begin to migrate south to  winter in warmer climates or find food.

Just as seasons affect life on land, changes are brewing in the oceans as well. Relative changes in sunlight, day length, wind and ocean temperature all impact phytoplankton— small, plant-like organisms at the base of our ocean’s food web— eventually working its effects throughout the ecosystem.

In the summertime, the dominant California Current sweeps cold cool nutrient rich water from the Alaska current down along the west coast while winds generally blow north to south. Because of the Coriolis Effect these winds veer westward and surface water is pushed offshore. As this water moves westward deeper, nutrient rich water rises to replace the migrating water in a process known as upwelling. In areas where upwelling occurs, phytoplankton blooms are common, attracting fish and other ocean life to the area.

As winter approaches, the wind shifts direction and the California Current meanders westward to be replaced by the northerly flowing Davidson Current. Strong winds from the south pull surface water to build up along coastal margins, resulting in downwelling— essentially the opposite of upwelling where warm surface water sinks down. Even though surface water temperatures may drop rapidly with the arrival of winter, deeper waters (below 200 feet) can actually become warmer due to the mixing with warmer surface waters and the northerly Davidson Current. This warming of deep water could benefit bottom dwelling fish which breed during the winter months.

Many beaches also undergo drastic changes. In the winter larger and more frequent waves pick up sand from the beach and move it offshore, sometimes forming sandbars that buffer beaches from storm erosion. Beaches can become rocky or appear to  disappear! But don’t worry, when the summer returns gentler waves bring the sand back on to the beach just in time to lay out and soak up the sun. Just don’t forget to wear sunscreen!!

By Sachiko Lamen







What’s Up with Upwelling?

It’s a universal understanding amongst all fishermen (and women!) that there are good fishing days, and most definitely bad fishing days. Sometimes all it takes is being in the right place at the right time or maybe even sporting some good ocean karma. There is, although, some technicality and logic behind it all to ensure the most optimum of catching days. It may be hitting up the right location, using the right bait, or stalking bait-balls offshore all afternoon. But what initially attracts the fish to congregate in these places? The obvious answer is food, which could be from a variety of sources. One of those sources is upwelling.

coastalupwellingUpwelling occurs all throughout the globe and in different natures. Essentially what happens is surface water along coastal shores is being pushed offshore by the influence of steady winds. As this happens, the pushed out surface water is being replaced by bottom water that is being drawn up through a current. This bottom water is cold and high in nutritious goodies. We see this exactly at the equator where trade winds blow from east to west drawing water away from South America and towards Indonesia. Prime fishing spots are located just off the coast of Ecuador and Peru. nutrientupwellingAlternatively along the California coastline, winds blow southward from Alaska towards Baja. Here, coastal waters, with the influence of the earth’s rotation, are instead pushed out 90 degrees from the direction of the wind and travel out into the Pacific. We call this process Ekman Transport where our rotating earth creates a force that drags the wind-induced currents to the right in the northern hemisphere. This is reversed in the southern hemisphere where it would travel to the left of the wind. We don’t see this happen at the equator, although, because the earth is wider and spins faster there. Ultimately, the same result occurs where water is transported away from the coast and cold, nutrient-rich waters from the bottom are moved to the surface.

This transport of nutritious bottom water along the California Coast promotes prime fishing, especially for local fisheries in our area. The next time you go fishing and can’t find that trusty bait ball of yours, stick close to the shore. Also keep in mind how this natural process might change this upcoming year with El Niño. Typically, strong dissipation in coastal upwelling is observed more south around the equator during this type of event, but we may see some changes along the Southern California coast.

Written By: John Cornett

Photo Credits:
Coastal Upwelling – https://www.climate.gov/news-features/features/upwelling-crisis-ocean-acidification
Nutrient Upwelling – http://oceanservice.noaa.gov/facts/upwelling.html

Upwelling: Movement in the Ocean

Upwelling is a process that involves cold, nutrient rich water being brought up to the surface.  At the equator, upwelling is a regular occurrence due to the combination of the Earth’s rotation and the wind mostly blowing from East to West.  This constantly pushes air along the equator and results in water being pushed away from the equator and towards both the Northern and Southern hemispheres.  As the surface water is forced outwards from the equator, water from below rises up to take its place.  This water is typically cold and full of nutrients.

Upwelling can also occur along coastlines.  When wind blows south along the California coast, the friction along the surface of the water combined with the rotation of the Earth cause the surface water to be pushed out away from land.  Again, deeper water comes to the surface bringing with it nutrients and cooler water temperatures.  In some places, upwelling can even affect the weather.  In places such as San Francisco, the cool water temperatures brought by upwelling can cause air temperatures to drop and result in even more dense fog.

The combination of the rotation of the Earth and the friction between the various layers of water, result in overall transportation of water by 90 degrees in a different direction than the wind.  In the northern hemisphere, water is moved 90 degrees to the right and in the southern hemisphere the same affect results in water moving to the left.  This process is called the Ekman transport.

For more information on the Ekman transport visit: http://oceanmotion.org/html/background/ocean-in-motion.htm


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