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 June

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The Pacific High dominates coastal weather

By June, the a large "bubble" of warm air known as the Pacific High becomes relatively strong and stationary over the Pacific Ocean between California and Hawaii. Storms track northward toward the Aleutians or Pacific Northwest, but rarely move as far south as the California border.

Coastal fog and high clouds blanket coast

The Pacific High, especially that quadrant closest to the California coast, is a breeding ground for clouds and overcast. On satellite images in June, you can see a continuous layer of clouds blanketing the northeast Pacific Ocean. As storms pass north of the area, they allow this layer of clouds to thicken and move toward the coast. Where these clouds reach the coast, they create coastal fog. But the "marine layer" is typically only one thousands feet thick or less, so it is blocked by coastal mountain ranges, though it does flow around these ranges, and into low-lying areas such as the San Francisco Bay and Salinas Valley.

The marine layer moves toward the coast at night, as warm air rises from the sun-warmed hills and inland areas. The fog usually reaches its maximum inland extent just before dawn.

Note: Many years ago I sailed to Hawaii on a small sailboat. We had been told that we would be able to steer the boat by following the contrails of all the tourist jets heading toward the islands. I also learned how to calculate my latitude by celestial navigation - measuring the height of the sun above the horizon. We made the crossing in 19 days, but we rarely saw the sun, let alone any contrails. Thank goodness we also had a satellite navigation system on board.

Winds and upwelling weaken near coast but remain strong over outer coastal waters

Within about 10 miles of shore, the winds may be somewhat lighter in June, especially in the morning hours, when fog often blankets the coast. However, the strong northwest winds still howl over the waters over continental shelf, from about 10 to 50 miles offshore.

Note: This difference between coastal and open ocean winds may explain why computer models (which are typically less accurate for nearshore waters) suggest that upwelling should be strongest in late June, whereas measurements along the coast suggest that upwelling is strongest in late May.

In the center of Monterey Bay, the lowest average water temperatures (111.5 to 12.5 deg C), highest nitrate concentrations (7.5 to 20 uM), and saltiest water (.5-33.7 salinity units) of the year typically appear in late May or early June. All of these are indicators that large amoungs of water have been upwelled from several 300 to 500 feet below the ocean (northwest of Santa Cruz) and then carried along the coast toward Monterey Bay. This suggests that in late May or early June, upwelling brings up water from deeper below the surface than at other times of year. At this same time of year, the spring diatoms are reproducing at their fastest rate all year.

Within the waters of the California Current, 50 to 100 miles offshore, the year's strongest northwest winds and highest concentrations of nitrate (the "fertilizer" that helps diatoms bloom) appear in early June. However, the highest concentrations of chlorophyll (which reflects that amount of diatoms in the water) were typically seen in late June.

Note: Some of these diatoms may have initially bloomed closer to the coast earlier in the month, and were subsequently crried away from the shore by upwelling-induced currents.

California current flows closer to coast

During June, surface currents within about 10 miles of the coast flow strongly southward following upwelling events, then surge northward when upwelling subsides. After strong upwelling events, plumes of upwelled water may also flow away from the coast.

Farther offshore, the California Current flows in a meandering pattern from north to south along the sea surface. However, in deeper water (say, below 1,000 feet), below the continental shelf break, the California undercurrent continues to flow northward, and often reaches maximum velocity in June. [Need to confirm that the CALIFORNIA CURRENT FLOWS CLOSEST TO SHORE IN JUNE-JULY]

Exreme tides in June

Because of the seasonal alignment of the sun and moon, June sees some of the most extreme high and (especially) low tides of the entire year, at the time of the full moon closest to June 21, the summer solstice. Because this is not a stormy time of year (and low atmospheric pressure is not contributing to the rise of the ocean, as it sometimes does during winter storms) these tides don't usually cause problems for humans. However, if the extreme tides coincide with a large south swell, some beach houses and highways with southerly exposure may be flooded.

However, June's extreme tides do provide opportunities for spawning marine organisms. For example, in the coastal ocean, the extreme tides of June can also generate strong internal waves along the continental shelf break and edges of Monterey Canyon. As described in Chapter 4, such internal waves can also move microscopic drifting animals toward rapidly toward shore.

Extreme tides also generate strong tidal currents in coastal estuaries. Such currents can sweep young fish and drifting larvae into or out of these coastal nursery areas. These same currents also erode banks and uproot marsh vegetation, carrying it out to sea or depositing it at the high tide line. In either case, this debris provides food for a variety of crabs, worms, clams, and other "detritus" eaters.

You might expect that the extreme low tides of June could cause problems for animals in the tidepools because the hot summer sun and strong winds would dry them out. However, the extreme low tides of June always occur in the morning hours, when the weather at the coast is typically cool, foogy, and calm.

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