Seasons in the Sea - A month-by-month guide to Central California sea life
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Windy ocean: Image credit-David Clague, MBARI

Winds, waves, and currents

in September

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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 September:

  • September is the peak of the "Oceanic Season," which typically runs from August to October.
  • Ocean conditions are relatively calm, with light winds and relatively warm, clear, blue, open-ocean water from the California Current flowing into the coastal waters.
  • Surface water temperatures often reach maximum levels for the year in late September (avg about 14-15 deg C).
  • The water column is strongly stratified, with a relatively thin (35-70 feet thick) layer of warm water at the surface. Underneath this warm surface layer is a distinct boundary (the "thermocline") and then much colder water.
  • The California Current becomes weaker and flows closer to the coast. The southward-flowing California Current mostly affects the surface waters down about 50 m below the surface. Below this, colder, saltier water from the California Undercurrent may flow slowly northward.
  • Occasional periods of strong northwest winds and upwelling occur (bringing pulses of cold water to the surface), but they are much less frequent than in July or August.
  • Tides around tend to be less extreme around the Fall Equinox (and Spring as well), so strong tidal currents are less common in September. This means that water in the kelp beds, intertidal areas, and estuaries stays relatively calm and warm. Among other things, this means young, recently-settled animals are less likely to be swept off rocks and will grow relatively rapidly (many young animals grow more rapidly in warmer water - up to a point).
  • Along the open coast, the sunlit surface waters contain very low concentrations of the nutrients needed for algal blooms (e.g. nitrate and iron), except sometimes for a day or two following late-season upwelling events, which become less common as the month progresses.
  • Non-wind-driven upwelling (caused by internal waves or tidal currents around the outer edge of the continental shelf, for example) may become more important than wind-driven upwelling.

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