Winter in the Sanctuary

By Stefan Marti

Heavy surf pounds the Pacifica pier.
Photo: MojosCoast

As winter storms surge in from the Pacific, bringing massive waves and powerful ocean currents, and rivers flood with mountain sediment and urban debris, the coast of our Sanctuary is alive, shifting and eroding in the fierce rain and surf, redefining itself to the new ocean-land environment.

And while we hunker down indoors with a hot cup of tea, local birds embrace the intense storms, the wild gusts of the downpours.  Outside the FMSA office, gulls dance in the dark sky and sanderlings scurry across wind-swept beaches.  Twenty-seven miles west on the barren rocks of the Farallon Islands, murres are busy scaling cliffs, prospecting for nests.

Many seabirds including northern fulmars, black-legged kittiwakes and rhinoceros auklets winter in the area. Despite the heavy rains, storms are mild here compared to the icy gales of Alaska.

Meanwhile, below the giant swells on the ocean surface, elephant seals dive through the frigid waters—some of them at sea for over six months—working their way towards the beaches of Año Nuevo, Point Reyes or the Farallon Islands.  It’s time for a quick haul out, some bloody fights and a raucous mating season. 

Also, the last gray whales are migrating through the Sanctuary on their annual journey down the Pacific coast.  By February, the straggling whales will reach the warm waters off Baja California to reunite with the new mothers and young.

"Winter is a dynamic time in the Sanctuary,” says Farallones Visitor Center Naturalist Peter Winch. “It provides a great arena for the unexpected.  Last January, we had a pod of resident orcas from the Pacific Northwest visit us.”

This year on the 26th of January, we will be heading out to the Farallon Islands on a whale watching trip.

Our Changing Beaches

With the heavy winter storms, California beaches are particularly active.  Waves pounding the shore are constantly shifting and moving sand.

On the California coastline, most beach sand comes from river and stream runoff, not from cliff erosion. When rivers flood after big storms, a great deal of sand and sediment flows to the ocean. Around 80 to 95 percent of beach sand is river derived.

Once sand arrives at the shoreline, waves and wave-induced currents move it onto the beaches and along the shore.  The alongshore movement of sand or littoral drift depends on the direction of the wind and waves.

During winter, storms generally come from the northwest, so there is a southward shift of sand down the coast of California. 

In some low-lying parts of the coast, after sand has washed onto beaches, it slowly moves inland with the onshore flow of winds. In these areas sand dunes will occur.  If there are steep cliffs on the coastline, preventing sand from moving inland, sand will continue drifting south.

Most of this sand eventually funnels into deep submarine canyons.  Numerous underwater canyons such as the La Jolla and Monterey Canyon extend out from the California coastline.  As sand drifts southwards, it eventually drops into these deep basins and washes away from the shore. Hence the beaches in California are not growing larger.

The majority of coastal erosion occurs when heavy storms coincide with high tides, and rains have already loosened up the coastal terrain.  In such conditions, a large amount of sand and sediment can be washed into the sea.

At river mouths, the ocean floor is also changing shape. Sandbars build up and expand during the winter months.  Surfers are often the first to notice the transforming breaks as waves roll to shore.

Along with sand and sediment, a great deal of human waste flows down our streams and rivers.  Fertilizers, car oil and plastic debris wash down tributaries and into the sea, often ending up on our beaches. In addition, oil from past spills will stir up in storms, finding its way back to the shore.  After heavy winter rains, it is especially important to clean our beaches, before wildlife gets entangled or mistakes the debris for food.

Exploring the Sanctuary

Every winter, plants and animals in California welcome the heavy rains.  And though rainy season may seem like a time for staying indoors, the cool clear skies before and after each storm are often the best times to view the Farallon Islands from San Francisco.

With the influx of wildlife just off our coast, winter can be one of the most exciting times of the year.  Just watching the monster waves break at Ocean Beach can be a wondrous sight.

“Just ask any surfer,” says Peter Winch, “and they will tell you the best time of the year is from September through March, when big swells roll in from distant storms in the Pacific."

 

Photo Credits: MojosCoast