Seasons in the Sea - A month-by-month guide to Central California sea life

Section contents:

Windy ocean: Image credit-David Clague, MBARI

Winds, waves, and currents

in November and December

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Diver-at-work symbol (c) Kim Fulton-Bennett This page under construction.
Here are some of the topics that will be covered in this chapter. More text and images will eventually be added to this section. Thank you for your patience.

Physical processes in November and December:

  • The "Oceanic Season" typically comes to an end in November, when the southward-flowing California Current weakens, meanders, and moves westward, up to 100 miles from the coast. Within 30-60 miles of the coast, the California Current is replaced near the coast by the northward-flowing Davidson Current (and its deeper component, the "California Undercurrent." The Davidson Current reaches maximum strength and December and January. Thus, the winter months are known as the "Davidson Current Season."
  • In late fall, low pressure systems begin to sweep southward from the Gulf of Alaska and collide with the Pacific High. At first the high rebuilds after each storm. But as November progresses, the Pacific High moves farther east and weakens, gradually allowing low pressure systems to pass farther south, until they begin to affect the Central Coast.
  • Strong southerly winds during winter storms generate northerly currents that augment the northward flow of the Davidson Current. However, within the kelp beds and in the surf zone, powerful swells from the northwest can generate strong currents that generally flow toward the southeast.
  • Southerly storm winds stir up the nearshore waters, causing "downwelling," as surface waters are mixed with deeper water. The result is that water from the surface down to about 150 feet becomes relatively uniform in temperature and salinity ("well mixed").
  • Water temperatures at the sea surface and near the coast drop rapidly in November, as solar heating of the surface waters is reduced and warm oceanic water is mixed with colder deep water.
  • Surprisingly, deeper waters (below 200 feet) may actually become warmer in winter than at other times of year, due to mixing with warmer surface waters and the influence of the Davidson Current. Thus, the water over the seafloor of the outer continental shelf reaches its warmest temperatures of the year in December and January. This warmer water may benefit bottom fish that release and brood eggs during the winter months.
  • December and January generally bring the strongest rains and southerly storm winds, the largest waves, and the deepest, most turbulent mixing of the nearshore waters.
  • Storm runoff from rivers and streams introduces a layer of fresh water and sediment (as well as pollutants) into coastal waters. In some cases, these plumes nurture unique communities of microscopic algae and animals.
  • Between storms, clear weather and dry winds from the north or northeast are likely (like the Santa Ana winds in Southern California, but colder). These winds may cause upwelling, but the water brought up from the depths may not be high in nutrients, so it may not result in algal blooms. Other times high pressure builds over the Central Coast for several days, bringing sunny days with light winds, and some of the nicest beach weather of the year.
  • Coastal areas that are especially foggy during the summer (e.g. Moss Landing) may be relatively sunny during winter, and south-facing areas that are sunny in the summer may experience more rain and clouds in winter.

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