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!!
But 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