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Wednesday, January 16, 2013

King Tide Reveals Scientific Semantics and Seldom Seen Sea Sights

BY SUZANNE GULDIMANN

King tides have been in the news lately, as some of the highest tides of the year arrived last week. The term, which originated in Australia and New Zealand, only recently made its way into California vernacular.
In Australia, the king tide originally referred to the single highest daytime tide of the year that frequently coincides with the weeks around Christmas. In the U.S. the term appears to be synonymous with all of the highest spring tides.
Spring is the traditional term for the highest tide of every month, named not for the season, but for the verb, in the sense of springing forth.
King tides can be dramatic and even potentially dangerous when the tide coincides with winter storm-generated surf and swells. The January king tide in Malibu was uneventful, due to an almost complete lack of wave activity but it did offer Malibu beachgoers a spectacular afternoon low tide and an opportunity to learn more about how tides work.
Approximately twice a month, during the new moon and the full moon, when the Sun, Moon and Earth align—a phenomenon known by the vowel-free term syzygy, the tidal force generated by the sun and moon reaches its peak, causing a spring tide, defined by NOAA as “waters that are higher than average, low waters that are lower than average, ''slack water' time that is shorter than average and stronger tidal currents than average.”
The opposite of a spring tide is called a “neap tide,” or neaps, from the Old English word “nopflod.” The origins of the word are unknown, but it may share its root with the ancient Greek loan-word napus, thought to mean “rounded” and still in use today in the Latin name for the turnips, a vegetable that is still known in Scotland as “neeps.”
A neap tide occurs after the first or third quarter of the moon when there is the least difference between high and low water.
The word tide reportedly also has its roots in old English, where it once was synonymous with time. The word still lingers in archaic terms like “noontide” and “yuletide.”
There is approximately a seven-day interval between springs and neaps—the highest and lowest tides of the lunar month.
The difference in height between high and low waters over about half a day varies in a two-week cycle, according to NOAA. Tides can be predicted with accuracy and charted in advance, but the height and time of the tide varies slightly along the the length of the coast.
For Malibu beachgoers, a Santa Monica Bay tide calendar is essential. Calendars for the Santa Monica Bay with the high and low tide shown as a graph are widely available at bookstores and bait shops. Websites like the National Weather Service, forecast.weather.gov, and www.watchthewater.org offer easy access to daily tide times.There are also a number of apps that offer local tide charts.
Malibuites who like to keep tabs on the tides may be interested in a citizen science project that seeks to document the impact from the highest tides.
The recently formed California King Tides Initiative encourages members of the public to document the highest seasonal tides (or king tides) that occur along the state’s coast.
“These photographs help us visualize the impact of rising waters on the California coast, the California King Tides Initiative website states. “Our shores are constantly being altered by human and natural processes and projections indicate that sea level rise will exacerbate these changes. The images offer a living record of the changes to our coasts and shorelines and a glimpse of what our daily tides may look like in the future as a result of sea level rise.”
“While tides themselves are not affected by climate change, the climate and weather do influence coastal sea levels through storm surges, the El Niño/La Niña-Southern Oscillation and Pacific Decadal Oscillation cycles and other factors, the CKTI website states. “Resulting high tides from a c combination of these conditions can cause widespread damage from flooding and erosion.” More information on the initiative is available at californiakingtides.org
The next spring tide occurs Feb. 7-9, and almost qualifies to be a king tide, with a 6.5-foot high tide at 7:18 a.m. on Feb. 8 and 8:04 a.m. on Feb. 9, and a -1.4 low tide at 2:16 p.m. on Feb. 8 and 2:54 p.m. on Feb. 9, coinciding with the new moon. Beachgoers who miss the February tides will have to wait for May for the next “king tide.”

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