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Physical Setting
Regional View
From a regional perspective, Oregon's ocean area is a part of a larger oceanographic region that extends from about Vancouver Island south to Cape Mendocino, California. This region, called
the Northern California Current Ecoregion, is defined by certain patterns in ocean currents, seasonal conditions, topography, and marine life.
 
Shaded relief map of eastern Pacific Ocean basin and western U.S. and Canada
Seafloor elevation model photo.
This elevation model shows the depth of the seafloor as shades of blue and gray and land elevations as shades of yellow and red. Note that the seafloor of the Juan de Fuca plate, north of the Mendocino escarpment that runs west from Cape Mendocino CA, is shallower than the seafloor of the Pacific plate to the south. The continental shelf is the narrow gray feature along the coastline. This model is courtesy of the Center for Environmental Visualization, University of Washington.





From a so-called "basin perspective," the Oregon ocean area is a small segment of a much larger region affected by oceanographic and atmospheric forces that operate across the entire Northeast Pacific Ocean. The West Wind Drift, a large ocean current flowing westward across the Pacific Ocean from Japan, encounters the landmass of North America in the area roughly from southern British Columbia to the central Oregon coast. Water masses are then forced either north [pole-ward], into the counter-clockwise currents of the Alaska Gyre in the Gulf of Alaska, or south [equator-ward], generally parallel to the coastline, in the broad California Current.

The California Current
From a larger view of the Northeast Pacific Ocean, Oregon's ocean area is a small segment of a larger ocean region influenced by the California Current, a broad current that flows southward nearly 1500 miles past Oregon, California and Baja California and is a transition zone between colder subarctic waters of the Gulf of Alaska and subtropical waters off Baja California.
 
The California Current is 500 to 1,000 miles wide and flows 2.5 to 5 miles per day, although strong northwest winds, usually in late spring and summer, can reinforce the flow and double the speed. A narrow, relatively fast undercurrent, the Davidson Current, flows pole-ward below 600 feet. In winter, southwesterly storms reinforce the Davidson Current so that it flows northward 6 to 12 miles per day even at the surface and displaces the southward California Current offshore.
 
Satellite image of chlorophyll concentrations in eastern Pacific OceanThis satellite image shows concentrations of chlorophyll, microscopic plants called phytoplankton that turn sunlight into food energy at the ocean's surface. Red and orange is most chlorophyll, blue and purple is least. This image clearly shows the California Current off the west coast of North America as a narrow zone of high chlorophyll concentration. This image also shows how small the California Current is in relation to the eastern rim of the Pacific Ocean.

Environmental Forces
Environmental conditions in this California Current ecoregion--and Oregon's coastal ocean--are highly variable on many scales of time, from high tide to low tide, from winter to summer, from year to year, over many decades, and even over centuries or thousands of years. Short term episodic events lasting several days, such as storms, or even a year or two, such as El Niño/La Niña, also influence physical and biologic conditions in Oregon's ocean. All of these environmental conditions are influenced by oceanographic and atmospheric phenomena that affect the entire the Northeast Pacific Basin.

Atmospheric forcing
Anyone spending time on the Oregon coast will understand the effect of the weather on ocean conditions, whether winter storms pounding the shore with wind and rain from the south and south west, or chilly winds blowing out of the northwest and kicking up white-cap waves on a summer afternoon. These two patterns dramatically affect the ocean environment from the shoreline all the way across the continental shelf.

Spring and Summer: Upwelling
A large high-pressure atmospheric cell builds near the Aleutian Islands in late spring and sets up dry, clear weather during the summer in the Pacific Northwest. This high pressure causes warmtemperatures inland, which draws strong winds from the north, reinforcing the speed of the southward-flowing California Current. Because of the Earth's rotation, this south-flowing surface water is pushed offshore, away from the coast. In its place, colder, deeper, nutrient-laden waters are drawn into the surface layer near the shore where the spring and summer sunlight cause an explosion of microscopic plant life. This phenomenon is called upwelling and the microscopic plants or phytoplankton it feeds are the source of the rich marine ecosystems along the Pacific coast. Strong upwelling events are essential to mixing nutrients and marine life across the continental margin in great swirls and eddies of water.
 
Satellite images of sea surface temperature off Oregon coast
These two images show sea surface temperatures, blue is coldest water and red is warmest. On the left, a summer upwelling event reveals cold up-welled water near the coast with filaments streaming offshore. On the right, the same region without upwelling shows the relatively warm surface water of the California Current moving much closer to shore. Graphic courtesy of PISCO, the Partnership for Interdisciplinary Studies of Coastal Oceans, at Oregon State University.
 
 
 
 
 
 

Fall and Winter: Storms
From late fall to early spring, a low pressure atmospheric cell moves into the Gulf of Alaska, spawning fierce storms that blow on-shore from the west and southwest. These storms drive surface waters northward along the coast and push surface waters into the nearshore and estuaries, forcing ocean water to sink or down-well near the shore. During this time the northward-flowing Davidson Current, which is submerged during the summer, moves to the surface. Fall and winter rain storms can affect the nearshore zone when coastal rivers discharge large volumes of freshwater laden with sediment and debris, as well as dissolved minerals and other nutrients from watershed.Weather satellite image of eastern Pacific Ocean and western U.S.

NOTE: For a global animated forecast of the wave energy being generated in the Pacific Ocean basin by atmospheric forces, see this excellent website hosted by Scripps Institute of Oceanography. It may take a while to load.
 
This weather satellite image shows a typical winter storm track blowing clouds, rain, and wind onto the Oregon coast from the southwest. Courtesy of the Oregon Climate Service.
 
 
 
 
 

The Columbia River Plume
The Columbia River, which is driven by atmospheric conditions, has an immense influence on the surface water conditions of the Pacific Ocean of the Pacific Northwest in all seasons. Although the various pulses of water entering the ocean have been dampened somewhat by dams built in the past 50 years, the freshwater signature of the river remains significant. In early summer snowmelt from the mountains of the Columbia River watershed arrives at the salty, dense ocean water, creating a surface lens of lower-salinity water traceable as a plume spreading west and south in the California Current as far south as Cape Mendocino [~400 mi]. Jets, squirts, eddies, and other surface complexities in the California Current make the boundary between the Columbia River Plume and surrounding ocean water highly variable and biologically productive. Many species of fish, seabirds, and marine mammals follow these nutrient-rich "fronts" or boundaries during the summer months. In the winter, winter storms and the Davidson Current drive the river's freshwater volume from rain and snowmelt runoff northward and shoreward along the Washington coastline. Columbia River freshwater can dominate the estuarine environments of Willapa Bay and Grays Harbor and is detectable inside the Straits of Juan de Fuca and northward along Vancouver Island.

El Nino/La Nina
Planet Earth is a natural system of many complexities that operate over many different time scales. One such complexity that made headlines during the late 1990s is the phenomena of El Niño and La Niña, popular names for conditions that arise from variability in large atmospheric conditions over the tropical Southwester Pacific Ocean.
 
Images of sea surface temperatures for El Niño and La Niña phases of Southern Oscillation. These two images show the alternate phases of El Niño [top] and La Niña [bottom]. The very warm waters of El Niño, shown in white graded into red, extend eastward along the equator to the Americas, and then north along the coast of Mexico and the United States to about Vancouver Island. In the La Niña phase, cool waters [shown in purple and blue] prevail across the equatorial region and cooler temperatures show along the west coast of North America. TOPEX/POSEIDON image from NASA's Jet Propulsion Laboratory.
 
Called the El Niño/Southern Oscillation or ENSO, these phenomena were not well known as part of large-scale atmospheric dynamics until the past several decades. But climate records in tree rings, ice cores, sediments, and archaeological or cultural records reveals that these climatic events have occurred frequently, but not predictably, since at least the last Ice Ages. Indeed, a major El Niño episode in 1982-83 stimulated scientists worldwide to research its origins and effects, and to develop a global network of instruments to predict and monitor future episodes. The El Niño/La Niña of the late 1990s was therefore monitored and studied more closely than any pervious event and became part of popular culture.
 
An El Niño results from a breakdown in the strong winds that blow westward along the Equator and hold back a large bulge of very warm seawater near Indonesia. When these winds cease to blow, the bulge of heated water slowly surges eastward across the tropical Pacific toward the Americas. As it encounters the landmass South America in the vicinity of Peru, the warm water is deflected northward toward Central and North America, as well as southward. Warmer ocean temperatures as well as increases in sea surface height can result as far north as the Pacific Northwest. In addition, the atmospheric shifts that trigger El Niño also cause major atmospheric patterns over the Pacific Ocean to shift, thus affecting the location and direction of weather patterns. As a result, the Pacific Northwest was drier and warmer during the El Niño event, although not as direct consequence of warmer ocean water.
 
La Niña is the opposite phase where cooler waters prevail across the tropical Pacific, again with effects on ocean conditions of the entire Pacific Ocean basin and weather conditions worldwide.
There are numerous informative websites on climate change and El Niño. Click on these to see more detailed information and wonderful images.
A publication of the Pacific Northwest Coastal Ecosystem Regional Study [PNCERS], published in 1997, contains a chapter on climate variability (pdf) that affects the Pacific Northwest coastal region.

Topographic forcing
Anyone standing on a bluff peering westward across the seascape is likely to picture the ocean as vast and deep. And it is, for the most part. The Pacific Ocean is thousands of miles wide and many miles deep, the largest water body on Planet Earth. 300 miles off the Oregon coast it is over two miles deep.
But near the coast, along the edge of the continent, things are very different. Plate tectonics, great geologic forces that shape our planet, has squeezed the continental margin of the Pacific coast into a narrow ledge no more than 40 miles wide. This ledge, formed from crumpled sediments uplifted by the collision of North America plate and the remnant Juan de Fuca plate, was eroded and submerged by the rising ocean after the last Ice Age. Thus the shelf is a mere 600 to 800 feet deep at the seaward edge.
  • A good explanation of the plate tectonics of the Pacific Northwest.
  • Images of the seafloor [NEED LINK] adjacent to U.S. coastal areas, including Oregon
  • A research paper on "super-scale slumps" [NEED LINK] along Oregon's continental margin. Note: this site may take extra time to load.
Although wide and deep judged on a human scale, the continental shelf off the Pacific coast is a shallow, narrow edge condition of an enormous ocean where immense water masses collide with and respond to the physical presence of the land and the seafloor. The continental edge of the Pacific coast is not smooth. Shoreline capes, submerged banks, rocks and islands, and submarine canyons all affect the flow of the California Current.

Capes
Picture the edge of a river and the effects of a rock or a log at the water's edge on the current moving by. Picture Cape Blanco, on the southern Oregon coast, which extends into the Pacific Ocean more than 30 miles farther than Cape Kiwanda, 165 miles to the north. Cape Blanco, like Cape Mendocino and Point Conception farther south, forces the southward-flowing California Current westward, offshore, introducing instabilities such as plumes and eddies that can extend a hundred miles and influence conditions many hundreds more.

 Natural color satellite image of Cape Blanco, Oregon Satellite image of sea surface temperature off western U.S.
  Cape Blanco is near the center of this satellite image that shows the Oregon coast from just north of the Siuslaw River to the mouth of the Smith River just south of the Oregon California border   This satellite image mosaic shows sea surface temperature in July, 1988 along the Oregon and northern California coasts. Coldest, upwelled water is shown in blue while warmest water is shown in red. Note how cold upwelled water is pulled offshore in eddies, plumes, and other features, and mixed into the southward flowing California Current. Images courtesy of Ted Strub, Oregon State University
 
These water features are clearly seen on remotely sensed satellite images. They can be detected as water temperature anomalies, cold water upwelled nearshore and swirled out across the shelf. They can be detected as chlorophyll anomalies, phytoplankton blooming in the nutrient-rich water and then mixed in filaments and patches far from shore. These dynamic water features provide transport mechanisms for nutrients, eggs, larvae, and fish across the entire shelf.

Banks
Seafloor features also force ocean currents into unstable conditions. For instance, Heceta Banks, 25 miles west of the mouth of the Siuslaw River, rises 350 feet above the edge of the continental shelf to within 250 feet of the ocean surface. During the last Ice Age, some 13,000 years ago, sea level was about 600 feet lower and the banks were hills at the end of a wide peninsula. The ancient ocean shore has been detected by detailed mapping along the western edge Heceta Banks. As great ice sheets melted and sea level rose, the banks became first an island, and finally a submerged bank. Now, its mass and depth cause the California Current to flow over or around it, introducing eddies and other instabilities that affect areas far downstream and along the Oregon coast.

Other features
Underwater canyons at the edge of the continental shelf, such as the Astoria Canyon or Rogue River Canyon, set up their own upwelling conditions that concentrate nutrients into an area of topographic relief thus driving a high level of biologic productivity. Clusters of rocks such as Orford Reef, just south of Cape Blanco, with their kelp forest canopy, slow the flow of ocean currents and retain water masses, as well as small fish, eggs, and larvae for a period of time.

Nearshore
Oblique aerial image of Cape Arago and Coos Bay, OregonRoughly speaking, the nearshore zone of the Oregon coast may be divided into three kinds of shores:

The image to the right shows these three kinds of shores: the rocky headland in the middle of the image is Cape Arago, the light-colored area extending to the top at the right are the sand dunes of the Oregon Dunes National Recreation Area, and the blue region to the right of the dunes is part of the Coos Bay estuary. These nearshore types and how the OCMP deal with them are described elsewhere in this site