Weather Watch

World’s oceans are rich with salts

The first time I swam in the ocean, I gulped a mouthful of saltwater. That experience made an everlasting impression on me.

President John F. Kennedy said, “All of us have in our veins the exact same percentage of salt in our blood that exists in the ocean, and, therefore, we have salt in our blood, in our sweat, in our tears.”

Think of the ocean as a soup that contains nearly every element present in Earth’s crust and atmosphere.

The prehistoric seas must have been only slightly salty, but over thousands of years, rain has slowly eroded the rocks that make up Earth’s crust.

You see, water is a powerful solvent and can dissolve more substances than almost any other liquid. The dissolved minerals and salts from these rocks are carried by streams and rivers to the ocean. It’s estimated that these streams and rivers carry about 4 billion tons of dissolved salts to the ocean annually. Volcanoes and hydrothermal vents also contribute along with glaciers that slowly grind the earth.

Out over the ocean, the sun’s light combined with Earth’s winds evaporates enormous amounts of seawater into nearly pure water vapor in the atmosphere. It’s been estimated that about 80,000 cubic miles of water evaporates from the ocean each year. Just 1 cubic mile of ocean contains 1.1 trillion gallons of water and about 25 pounds of gold!

If the seas were not replenished by rain, snow and runoff from rivers and glaciers, the ocean would evaporate completely in about 4,000 years.

As the water evaporates and changes from a liquid to a gas (water vapor), it leaves behind the dissolved salts and minerals because water forms a gas at a much lower temperature than the minerals and salts do. If you had a blowtorch, you could heat the mineral and salt particles to their melting point, and eventually they would evaporate, too.

This process has produced a lot of salt in the ocean. In fact, if all the salt was removed from the ocean it would form a 500-foot-thick crust over the Earth’s land surface.

The vast majority of these salts ions are chloride followed by sodium which make up 85 percent of the total dissolved salts in the ocean and combined to form table salt.

Speaking of cooking, you might notice that salt attracts moisture. Seawater evaporates more slowly than freshwater. Swimmers may notice that freshwater evaporates quickly from the skin but seawater lingers.

Off the Central Coast, the average concentration of salt (salinity) ranges between 32 and 35 parts per thousand. Over days or weeks of prolonged rain, when the local streams and creeks are flooded, I’ve seen the salinity levels in Morro Bay dropped to less than 10 parts per thousand. Low salinities levels also occur near the North and South Poles during their summer months where the ocean is diluted by melting ice.

The most salty water in the ocean occurs in areas with hot air temperatures, low relative humidity levels and little to no river or stream runoff. Salinity levels can reach more than 40 parts per thousand in the Red Sea and the Persian Gulf, where rates of evaporation are high.

For comparison, the salinity level in the Great Salt Lake in Utah ranges from 50 to 270 parts per thousand and the Dead Sea is a very salty 337 parts per thousand. With salinity levels this high, you float like cork.

Will the seas keep getting saltier as time goes on? Recent studies indicate that about the same amount of salt probably is deposited as sediment on the ocean bottom and eventually deposited back into the Earth’s crust by way of the subduction fault zones as salts are brought in by rivers. However, with a warming atmosphere and hydrosphere that may be causing excessive ice sheet melting in the polar regions, lower salinity levels in the world’s oceans could be in store for the future.

Today’s weather report

The upper-level ridge responsible for the first 100-degree plus days this year in the North County has moved east, allowing the coastal marine layer to deepen and move onshore this morning. The marine stratus will quickly burn off from the coastal valleys later this morning and from most of the beaches by this afternoon.

Today’s maximum temperatures should only reach the 50s along the northwesterly-facing beaches (Morro Bay, Los Osos, Montaña De Oro and the Nipomo Mesa); the low 60s along the westerly-facing beaches (Pismo Beach); and the high 60s along the southwesterly-facing beaches (Cayucos, Avila and Shell beaches). Maximum temperatures should reach the mid-70s in the coastal valleys and the low 90s in the North County.

The marine layer will redevelop tonight and spread inland by Monday morning.

A cool and wet late season 1,007-millibar low pressure system will move into Northern California on Monday and produce rain as far south as Monterey Bay by Monday afternoon. Heavy rain and thunderstorms are expected across the northern Sierra with snow levels ranging between 6,500 and 8,000 feet.

As this cold front passes over the Central Coast on Monday night with increasing clouds and drizzle, a strong 1,033-millibar Eastern Pacific High will build in behind the front and produce gusty northeasterly (offshore) winds Tuesday morning. These offshore winds will produce clear skies and much warmer temperatures along the beaches.

However, by the afternoon hours the winds will shift out the northwest and increase to fresh gale the strong gale force (39 to 54 mph) levels with gust to 60 mph along the coastline. Very windy indeed! These onshore winds will spread cool marine air throughout San Luis Obispo County by Tuesday afternoon, keeping temperatures from getting too warm.

Another round of northeasterly (offshore) winds will develop Wednesday morning, shifting out the northwest by Wednesday afternoon. Once again these northeasterly (offshore) winds will keep the coastal stratus out to sea.

For the remainder of the school and workweek, night and morning low clouds and fog will develop along the beaches and in the coastal valleys. Temperatures will remain slightly below seasonal values.

Surf report

Today’s 5- to 7-foot northwesterly (300-degree deep-water) sea and swell (with a 7- to 13-second period) will continue at this height and period through tonight.

A 3- to 5-foot northwesterly (300-degree deep-water) swell (with an 8- to 11-second period) will develop along the Pecho Coast on Monday.

Fresh gale the strong gale force (39 to 54 mph) northwesterly winds along the coastline will generate an 8- to 10-foot northwesterly (310-degree deep-water) sea and swell (with a 5- to 9-second period) Tuesday through Wednesday.

A 5 to 7 foot northwesterly (310-degree deep-water) sea and swell (with a 5- to 8-second period) is forecast along our coastline Thursday, decreasing tho 4 to 6 feet Friday. Arriving from the Southern Hemisphere:

A 1- to 2-foot Southern Hemisphere (195-degree deep-water) swell (with an 18- to 20-second period) will reach our shore today, building to 2 to 4 feet (with a 16- to 18-second period) Monday.

A 1-foot Southern Hemisphere (215-degree deep-water) swell (with a 22-second period) will arrive along our coastline hursday, increasing to 1 to 2 feet (with an 18- to 20-second period) Friday.

A large storm is forecast to develop off New Zealand on Wednesday. Swell from the storm could arrive along our coastline on June 15 and 16.

Seawater temperatures

Still no relief in sight, relentlessly blowing northwesterly winds have produced a great amount of upwelling along the immediate coastline. Seawater temperatures will range between 48 and 51 degrees through most of next week.

Awarding bright minds

The winners of the 2012 PG&E Bright Minds Scholarship were selected last week. Craig Martineau of Templeton High School was surprised when his grandparents holding a banner marched in during his advanced placement psychology class and announced that he won the scholarship. Martineau is a standout athlete who plays both baseball and soccer and is also student body vice president. The scholarship is worth $30,000 a year, renewable for four additional years. To read more, visit www.pgecurrents.com.

John Lindsey is a media relations representative and meteorologist for PG&E. He is a local weather expert and has lived along the Central Coast for more than 25 years. To subscribe to his daily weather forecast or ask him a question, email him at pgeweather@pge.com.

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