Surf's Up: Exploring the Complexities of Oceanic Cycles 

Jim Nestler Distinguished Faculty Lecture
December, 5 2004

About the Author

References

Tonight I hope to do what a science educator should do: increase your understanding of the natural world.  I hope to accomplish this goal by examining cycles, mainly involving the oceans, and by combining several things that I enjoy and that for me are fun: some history, some climatology, some oceanography, and even some biology. 

I mention that these things are fun for me. As Katharine Graham wrote, "To love what you do and feel that it matters - how could anything be more fun?"  Personally I believe that it is important to have fun with what you do, as long as it does matter.  And I think that an hour or so from now when we are done, you will agree that these things we will discuss do matter. 

Tonight we will discuss cycles. I first became aware that cycles existed during my sophomore year in high school.  My English teacher, Mr Garey, had the audacity to make us read and learn Shakespeare.  I remember learning and reciting the famous  "All The World’s A Stage" from Shakespeare’s "As You Like It".  Shakespeare (and Mr. Garey) discussed life as a cycle, starting as an infant and child, and ending in many ways as an infant and child.  And I remember being intrigued with this concept of the cycles of life. 

I came to Walla Walla College my sophomore year, and I learned that other organisms besides humans have cycles too.  I examined  plant life cycles, and learned terms such as "gametophyte", "sporophyte", "mitosis", "meiosis", "haploid", and "diploid".  I learned that these cycles existed also for animals.  I studied biochemical cycles that occur WITHIN organisms, such as Krebs Cycle, beta oxidation cycle, urea cycle.  I learned that some cycles are GLOBAL in nature, including the carbon cycle, nitrogen cycle, water cycle. 

Tonight I want us to spend our time learning about larger oceanic cycles, cycles that are macroscale in nature.  We will focus on cycles that affect the northern hemisphere and thus may have a direct effect on us. 

First, let’s review some basics: for example, what makes the wind? 

Cycles of Air Movement: Hadley Cells, Coriolis Effect, and Prevailing Winds

Let us start by examining cycles of air movement, which actually were first proposed in 1735 by George Hadley.  The sun is the source of energy powering the wind.  Solar radiation strikes the earth, and the sun’s rays and energy are most concentrated at the equator (slide 3).  This solar energy heats the air that is above the equator.  This warm air is less dense than the cold air above, and the warm air begins to rise.  As is rises it cools, loses its moisture, and the equatorial regions receive abundant rainfall.  This cooled air reaches an altitude at which it no longer rises, but is pushed aside, north and south, as more warm air above the equator rises.  This cooled air, moving north and south, soon falls, moves north or south along the earth’s surface, becomes warm and moist, and the cycles continue.  These air cycles or "cells" occur between 0^o (the equator) and 30^o, between 30^o and 60^o, and between 60^o and 90^o (the poles), both north and south of the equator. 

But these air cells do not move only up-and-down and north-and-south, but are deflected by the rotation of the earth in an easterly direction (slide 4).  The 19th-century French engineer-mathematician Gustave-Gaspard Coriolis first proposed this deflection in 1835 and we refer to it as the Coriolis Effect.  Air moving from the equator, either north or south, will be deflected to the east.  In the northern hemisphere air (and also water) typically will flow in a clockwise direction, while in the southern hemisphere it will flow in a counterclockwise direction.  And in case you ask, the Coriolis Effect DOES NOT play a role in determining which way the water in your toilet, sink, or tub will flow.  But it does affect the direction of global air and water movement. 

With this understanding of Hadley Cells and the Coriolis Effect, we can look at the prevailing patterns of surface winds on the earth (slide 5).  Surface winds will tend to move in a clockwise direction in the northern hemisphere and a counterclockwise in the southern hemisphere.  Winds along the equator typically blow toward the west.  Winds across North America, the northern Atlantic Ocean, and also Europe typically blow toward the east.  These prevailing wind directions will play pivotal roles in the cycles we will examine, starting with a name we have all heard, a cycle often called El Niño. 

El Niño and La Niña 

The event we commonly call El Niño goes by several names: El Niño/La Niña, El Niño Southern Oscillation, ENSO.  First we will examine the events during a "normal" year in the Pacific Ocean (slide 6).  Surface winds at the equator typically blow from east to west as we previously saw.  The warm equatorial waters are literally blown toward the western Pacific and pile up.  Ocean temperature is higher in the western Pacific than in the central or eastern Pacific, and precipitation is higher as well.  In the eastern Pacific an upwelling of cold water brings nutrients and cool temperatures to the coastal regions of South America.   

What happens during an El Niño event?  We see that the normal wind pattern changes significantly (slide 7).  The westerly flow of equatorial winds weakens, and sometimes even reverses.  The warm water normally pushed to the west now can move east.  The central and eastern Pacific Ocean become warmer and experience greater precipitation.  In addition, the cold upwelling that normally bathes the coast of South America diminishes, along with the nutrients carried by the upwelling.  The western Pacific experiences decreases precipitation and increased drought conditions.  This El Niño condition typically persists for 12-18 months, and occurs every three to four years. 

During La Niña the equatorial prevailing winds strengthen, pushing the warm waters even farther to the west.  The western Pacific experiences higher temperatures and greater precipitation, while the eastern Pacific experiences cooler temperatures and more upwelling of cold water. 

What effect do these events have on our weather in North America?  El Niño typically results in warmer and drier than normal conditions in the north (slide 9), while the south experiences cooler and wetter conditions.  La Niña causes the opposite (slide 10), with cooler and wetter conditions in the north, and warmer and drier conditions in the south. 

This cycling of El Niño has been a "hot" topic (no pun intended), especially the ability to predict when climatic events might occur.  By studying historical events, we know that El Niño has been a naturally occurring event for a very long time, and we can use past data in an attempt to predict the future.  

A recent study examined temperature records for the previous 150 years¹ (slide 11).  By examining "sea surface temperature (SST) anomalies" we can see when El Niño (high temperatures) and La Niña (low temperatures) have occurred.  The authors of this study used this historical data to predict when these events occur.  Their computer models using data six months in advance of a particular event had an 80% correlation with actual events.  They had a 60% correlation with data from 12 months in advance, and 40% correlation with data from 24 months in advance.  The bottom line is that scientists can predict fairly accurately up to two years in advance when these climatic events might occur.   

But these El Niño/La Niña events are not the only oceanic cycles that occur in the Pacific Ocean or that affect our climate here in Walla Walla.  

Pacific Decadal Oscillation (PDO)

A second cycle is the Pacific Decadal Oscillation (PDO), identified in 1996 by Nate Mantua, a climatologist at the University of Washington.  While El Niño is caused by changes in the southern and equatorial Pacific Ocean, the PDO characterizes changes in ocean temperature in the northern Pacific.  The PDO cycles between a "positive" phase and a "negative" phase (slide 12).  During the positive phase warm water bathes the west coast of North America, while cold water predominates in the central and western part of the north Pacific.  During the negative phase, cold water occurs next to the west coast of North America, with warmer waters occurring in the central and western areas of the north Pacific.  In addition to location, the PDO differs from El Niño in regards to the time length, with cycles lasting 20-30 years.   

How might El Niño events and PDO affect our weather?  What can we expect during the winter of 2004-05 in Walla Walla?  Currently (December 2004) we are experiencing a slight El Niño and a positive phase of the Pacific Decadal Oscillation.  In combination these events are predicted to cause a warmer and drier than normal winter in the Pacific Northwest (slide 13).  By "warmer" we do not imply that no cold weather will occur.  Similarly, by "drier" we do not imply zero precipitation.  But in a few months we will be able to look back at the winter of 2004-05 and see that conditions were warmer and drier than normal.  But then again, this pattern is becoming more normal during the past 10-20 years. 

So we see at least two cyclic phenomena occurring and affecting the Pacific Ocean.  Do we see similar events occurring in other oceans, maybe the Atlantic?  Yes. 

North Atlantic Oscillation (NAO)

Now we will examine the North Atlantic Oscillation (NAO), the major contributor to climate conditions in the north Atlantic region, including the east part of North America, all of Europe, and even northern Asia.  The NAO is a large seesaw in air pressure between a high pressure system off the west coast of southern Europe and northern Africa, and a low pressure system near Iceland (slide 15).  We will see that the high and low pressure systems will change, sometimes becoming stronger and sometimes becoming weaker. 

The NAO cycles between a positive phase and a negative phase.  In the positive phase, the higher pressure system is higher than normal and the low pressure system is lower than normal (slide 16).  This large pressure gradient causes more and stronger storms to cross the Atlantic Ocean on a more northerly track, following the prevailing winds (discussed earlier with slide 5).  Northern Europe and eastern North America experience a wet winter, while southern Europe has a hot and dry winter.  During the negative phase of the NAO the high pressure is not very high and the low pressure is not very low.  This reduced pressure gradient causes fewer and weaker storms to cross the Atlantic Ocean on a southerly track.  Southern Europe experiences a wet winter, while northern Europe and the east coast of North America have a relatively dry winter. 

We saw how El Niño and the Pacific Decadal Oscillation can cycle through time, and the North Atlantic Oscillation is no exception.  For the past 150 years the NAO has cycled repeatedly between its positive and negative phase (slide 16). 

Do more of these "oscillations" affect our climate?  We will briefly examine one more. 

Arctic Oscillation (AO)

The Arctic Oscillation refers to a spinning air mass centered over the North Pole and Arctic Ocean.  It too has a positive phase and negative phase (slide 17).  During the positive phase the air mass has a rapid circulation, "trapping" the cold air in the arctic region.  During the negative phase the air mass has a slower circulation, and cold air can "escape", leading to colder than normal temperatures in North America, Europe, and Asia.  Records for the past 55 years show a cycling between these positive and negative phases of the Arctic Oscillation. 
 

We have now examined four different cycles involving the movement of air over the oceans:  El Niño, Pacific Decadal Oscillation, North Atlantic Oscillation, Arctic Oscillation.  Now we will look at the movement of water in the oceans. 

Cycles of Ocean Currents

Surface ocean currents typically follow the same pattern as air movement, with clockwise cycling in the northern hemisphere and counterclockwise cycling in the southern hemisphere due to the Coriolis Effect (slide 18).  Some exceptions occur, primarily due to currents being deflected by land masses.  We will pay particular attention to events in the north Atlantic, events involving the Gulf Stream and the movement of warm water from tropical regions to the north.   

We can fairly easily observe and track the horizontal movement of water, but we need to realize that water also can move vertically.  This vertical movement is affected by temperature and salinity, both of which can affect water density (slide 19).  As warm water moves towards a colder environment it loses heat, becomes cooler, and thus is more dense.  This cold, dense water sinks, moves along the ocean floor back toward the warmer climates.  At this point it warms, becomes less dense, and rises to the surface to again begin this vertical cycling.  Salinity also affects water density and thus cycling.  Fresh water is less dense than salt water.  If, for example, large amounts of ice (comprised of fresh water) were to melt, increasing the fresh water content of colder regions, the cold water would be less dense than the incoming warm salty water, and would no longer sink.  The vertical cycling would cease.  Both temperature and salinity are important components of this vertical cycling. 

Let us now more closely examine the Gulf Stream, and the movement of warm tropical water toward the colder northern climates of the Atlantic Ocean (slide 20).  The Gulf Stream originates off the coast of Florida, where the Florida Current (from the Gulf of Mexico) and the Antilles Current (coming past Cuba and the Bahamas) combine.  The Gulf Stream is a large river of seawater, about 60 miles wide, a mile deep, and flowing at a speed of about five miles per hour.  It flows along the coast of the U.S. past Cape Hatteras, then moves across the Atlantic Ocean to northern Europe carrying a significant quantity of heat.  This warm, high salinity water enters the cold climate of the north Atlantic (slide 21), loses heat and cools, and becomes more dense.  This cold, dense water sinks at two locations, off the coast of Greenland and north of Scandinavia in the Arctic Ocean.  Together these sinking plumes off Greenland and in the Arctic form deep water that plays an important role in global oceanic circulation, acting as the "engine" that drives both surface and deep currents.  This cycling due to the driving force of sinking water is referred to as "Thermohaline Circulation", since both temperature ("thermo") and salinity ("haline") can affect water density and its ability to sink. 

The Gulf Stream and thermohaline circulation have a significant effect on climate in the northern hemisphere, especially for Europe.  As the warm Gulf Stream water flows north and releases its heat, the prevailing surface winds blowing from west to east pick up this heat and carry it to Europe (slide 22, animation).  Thus the climate in many parts of northern Europe are much warmer than they would be if the Gulf Stream and thermohaline circulation somehow ceased. 

Great Ocean Conveyor Belt

We see that the warm water comes from somewhere and the cold water goes somewhere to the south of the equator.  Where?  Is the Gulf Stream, this thermohaline circulation, part of an even larger cycling of water?  We can expand our horizons and examine the Great Ocean Conveyor Belt. 

Thermohaline circulation is the engine that drives a worldwide cycling of water, ranging from the northern hemisphere to the southern hemisphere, from the Atlantic Ocean to the Pacific, Indian, and Antarctic Oceans (slide 23).  Warm water sinks and cools in the north Atlantic, travels deep along the sea floor to the Pacific and Indian Oceans, warms and rises, and flows on the surface before reaching the Atlantic and starting the entire cycle again.  How important is this Great Ocean Conveyor Belt?  A recent study² (slide 24) suggests that this global cycling of water is crucial for the worldwide distribution of nutrients and the maintenance of three quarters of all life in the oceans. 

We need to reiterate that this cycling is driven by the sinking of cold water in the north Atlantic, and that this vertical cycling is affected by both temperature and salinity; water density is the crucial engine.  If salinity is fairly constant from the surface down to deep water, we find a large amount of water cycling and a large heat loss (slide 25).  In the northern Atlantic this heat is important for maintaining mild climates in both Europe and North America.  If, on the other hand, a layer of fresh water was on top of the ocean, the less dense fresh water would not sink.  Vertical water cycling and heat loss would occur at the surface only, and little heat would be released.  So a layer of fresh water in the north Atlantic Ocean could have a significant effect on climate, potentially leading to colder temperatures in Europe and North America.  As long as salinity and temperature remain as they are, thermohaline circulation, the Gulf Stream, and the Great Ocean Conveyor Belt should remain as they are.  But are salinity and temperature remaining constant? 

Changes in Salinity

Salinity in the Atlantic Ocean has been changing significantly in the past 30-40 years³ (slide 26).  Water near the equator, at the origin of the Gulf Stream, has become more salty since 1970.  Conversely, water in the north Atlantic and Arctic Oceans have become significantly more fresh in the same time period, especially in the areas where water normally sinks as part of thermohaline circulation.  What might be causing these opposite changes in salinity in these two locations? 

The increased salinity in the tropical regions appears to be caused by two factors: decreased precipitation and increased evaporation (due to increased winds and solar radiation; slide 27).  The reduced salinity in the northern Atlantic Ocean is a result of increased precipitation, increased continental fresh water runoff, and increased fresh water from Arctic ice.  The overall cause of these changes in both regions is an increase in temperature. 

Cycles of Earth’s Temperature

If changes in salinity are hypothesized to be a result of increased temperature, we need to determine if changes in temperature have occurred.  Reliable surface temperature measurements have been recorded using thermometers for about 140 years (slide 28).  Starting in the early 1900s the earth’s average temperature began to increase steadily, reaching the highest levels in the past ten to fifteen years.  An examination of ocean temperatures during the previous 60 years (slide 29) demonstrates the same trend⁴.  Increased temperatures and ice melting are prominent especially in the Arctic region⁵, where summer permanent ice has decreased up to 20% in the past 30 years (slide 30), leading to the decreased salinity in the north Atlantic.  What is the overall trend in the northern hemisphere?  A recent study combines data from many studies and sources, and concludes that an increase in temperature has been occurring for at least the last 100-150 years⁶ (slide 31).  But what if we look even farther back?  Do we see significant changes in our planet’s temperature? 

The earth’s temperature certainly has not remained constant, but has experienced significant increases and decreases throughout its history.  Change and cycling of temperature are natural phenomena.  While we have measured temperatures with thermometers for about 140 years, to look back farther in time we use different techniques such as tree rings, ice cores, and coral.  Many studies have demonstrated that these methods can be extremely accurate in determining temperatures going back 1,000 years.  And we see that for most of the previous 1,000 years temperature was lower than it is today (slide 32), with an increase starting about 100-150 years ago.   

But can we look back even farther in time?  Yes, we can, and we see the earth’s temperature has cycled for a very long time.  Recent studies⁷ have examined two different ice cores and two different marine sediments (slide 33).  Each of these independent studies demonstrate the cycling of temperature that has occurred over periods of up to 800,000 years, and the temperature profiles of all four studies line up precisely.  We are confident that temperature cycles are natural.  Why do we bother looking to the past?  As Winston Churchill said, "The farther back we can look, the farther forward you are likely to see." 

What Causes These Changes in Temperature?

If temperature has cycled naturally for a very long time, why are we concerned about the apparent increase that is occurring currently?  Scientists have three concerns.  The first is the speed of the temperature increase.  This rate of increase during the past 20-30 years is faster than ever measured.  The second concern is the cause of the temperature changes.  The largest component causing these changes is related to certain chemicals in the atmosphere.  These chemicals, such as carbon dioxide, nitrous oxide, sulfur, and methane, have the ability to "trap" heat, preventing its escape into space (slide 34).  Less solar energy escapes, and temperatures increase.  Have these chemicals been increasing?  Yes (slide 35).  The concentration of each of these chemicals has increased, especially starting in the 1800s, due to increases in human-produced pollution.  Their increase is tightly correlated with the temperature increase. 

We looked at historical records of temperature and saw that it naturally cycles over long time scales.  Do we see the same with the gases?  We will examine one, carbon dioxide.  Carbon dioxide levels have been measured in the Vostok Ice Core, in Antarctica (slide 36).  Data from this ice core demonstrate that carbon dioxide levels in the atmosphere have cycled, naturally, for a very long time, at least 400,000 years.  Carbon dioxide levels increase and decrease even without human influences.  However, the maximum carbon dioxide levels historically do not reach the levels currently measured in the atmosphere.  Even though carbon dioxide levels cycle naturally, the influence of humans has put carbon dioxide concentrations at levels never previously attained. 

What effect might this increased carbon dioxide have?  How might the increased carbon dioxide be related to temperature?  Changes in carbon dioxide concentrations and temperature are tightly linked, both in the relatively short term (1,000 years, slide 37) and also in the long term (300,000 years, slide 38).  The relationship between carbon dioxide and temperature has been occurring for a very long time⁸. 

Temperature,  Thermohaline Circulation, and the Great Ocean Conveyor Belt

Changes in thermohaline circulation also are highly associated with changes in temperature⁹.  Deep water movement in the north Atlantic was almost completely eliminated at the same time that a rapid change in temperature occurred (slide 39).  This elimination may have been caused by changes in salinity and the resulting changes in water density (see slides 25-27)¹⁰.  As discussed previously, this thermohaline circulation is the engine that drives the entire Great Ocean Conveyor Belt (slide 40).  Thus, changes in earth’s temperature may be directly linked to significant alterations in oceanic cycles. 

A recent Hollywood movie addresses this issue.  In "The Day After Tomorrow" thermohaline circulation shuts down due to increased temperatures.  In a matter of hours, giant freezing hurricanes turn the northern hemisphere into a mass of ice.  Most of this movie is scientific fantasy, created merely to entertain.  How in the world can increased temperatures cause freezing conditions?  It makes no sense!  Or does it?  The underlying scientific premise is credible, makes sense, and deserves our attention (slide 41, animation). 

1.  Increased temperatures cause more Arctic melting, more fresh water in the north Atlantic, and reduced thermohaline circulation (slides 19 and 25).

2.  This reduced thermohaline circulation leads to a reduction in the Gulf Stream, and its heat is no longer carried north (slides 20-22).

3.  Temperatures in North America and especially Europe decrease significantly. 

This reduced temperature would occur not in a matter of hours as in the movie, but over a period of 10-20 years, and would persist for 20-50 years before temperatures again began to increase (slide 42).  We have evidence that such events have happened before: "The farther back we can look, the farther forward you are likely to see." 

Effects of These Changes

If these events have cycled naturally for a very long time, why are we concerned about the apparent increase that is occurring currently?  The third reason is the effects these events may have.  What are the long term consequences, especially in regards to human activities?  Studies completed this year (2004) may help to answer these questions^11,12,13.   

An increase in temperature is predicted to cause increased precipitation and flooding in certain regions (slide 43) including southern Asia, the Pacific islands, the southern coasts of South America and the African continent, and the west coast and southeast of the U.S.  While floods will occur in these areas, other regions will experience drought and accompanying reduction in crop production (slide 44):central Asia, northern Europe, central Africa, and central North America.  An increase in diseases such as malaria, dengue fever, hantavirus, and cholera is predicted in eastern Australia, southeast Asia, the northern half of South America, and western North America (slide 45).  When these affected areas are combined (slide 46), they encompass regions containing more than 70% of the earth’s population, most of whom would be affected directly. 

Who Can Understand This Complexity?

These cycles we have examined are extremely complex.  We certainly do not understand all of the causes and consequences of even a single cycle, never mind all of the interactions.  El Niño, Pacific Decadal Oscillation, North Atlantic Oscillation, Arctic Oscillation, Thermohaline Circulation, Great Ocean Conveyor Belt.  How do we make sense of all of these?  Can we?  I don’t know. 

Fortunately we have a God Who does (slide 47).  For we know that without Him nothing was made (John 1:1-3), including these cycles.  Does this belief mean that God actually dictates the minute details of these cycles on a daily basis?  Humanity has and to some extent continues to attribute earth’s physical phenomena to a direct manifestation of God’s actions. 

God causes the sun to rise in the east and set in the west (slide 48, Matthew 5:45). 

God makes the rainbow in the sky (slide 49, Genesis 9:13). 

God makes the winds to blow (slide 50, Amos 4:13). 

God causes storms, and droughts, and floods (slide 51, Job 12:15). 

These physical phenomena that we used to ascribe as a direct manifestation of God’s actions we can now explain scientifically, many involving the cycles we have examined.  But our ability to unravel the natural laws that govern these phenomena does not in any way remove or diminish the power and ability of our God.  We know that these cycles and the forces affecting them are incredibly powerful and complex.  But our God is even more powerful, more complex, more than we imagine.  In fact, we do not have the ability to imagine how powerful and complex God is. 

Do I believe in a personal God Who traded His life for mine, and Who is coming again as promised?  Absolutely.  Do I believe that without Him nothing was made that was made?  With every cell of my body.  But I sure do not know HOW he made everything.  None of us do, and I am not sure that we can.  Even Ellen White states that His creation is beyond our ability to imagine or comprehend (slide52), "His creative power is as incomprehensible as His existence" (Patriarchs and Prophets, page 113).  We would be placing human constraints on God if we said we knew and fully understood how He created. 

In addition to not knowing HOW He created, I also have to admit not knowing WHEN He created.  By insisting and demanding that God created in a certain way, at a certain point in history, during a particular time period, we again are placing human limits on a limitless God (slide 53).  Who are we to tell God how and when He did things?  How can we discuss the concept of WHEN in the context of our God for whom time has no meaning?  How can we discuss the concept of WHEN for our God Who is the Alpha and Omega, the Beginning and the End (Revelation 22:13), a God for whom a day is like a thousand years and a thousand years like a day (2 Peter 3:8)?  Our God is so much more powerful and complex than we have the ability to imagine, much more powerful and complex than any human limits we may place upon Him. 

I do not pretend to have all of the answers.  None of us should.  But we certainly can and should continue to explore the complex and cyclic nature of this earth, in the confidence that our God Who does have all of the answers is in control (slide 54, Psalm 90:2).  The study of the natural world is fascinating.  The study of the natural world is fun.  The study of the natural world does matter.