Wednesday, June 1, 2016

The Gulf Stream - Part I

From time to time we get questions or comments that require more space then within our comments sections, so we try to answer them in a complete article, such as this one. 
    This question had to do with an article we wrote recently about “When Did South America East of the Andes Develop?” and specifically about the Gulf Stream.
    Comment: I am quite curious about this. Is there any data showing the Gulf Stream did not exist prior to 34 AD? Was the European climate much colder prior to that?
As a tangent to this, how large was the Atlantic/Pacific connection through Central America? Was it large enough to allow the Atlantic Equatorial currents to pass though, or would some (or most) of it be redirected through the Gulf and up the eastern coast?”
Michael R.

Response: Looking out at the ocean, one often sees a seemingly infinite series of waves, as far as the eye can see, transporting water from one place to the next. This is an optical illusion, since waves actually do not travel like that, but move about in a circular motion, much like a buoy or seabird floating on the surface, and when it encounters a surface object, it appears to lurch forward and upward with the wave, but then falls down and back in an orbital rotation as the wave continues by, ending up in the same position as before the wave passed. However, if one imagines a wave of water itself following this same pattern, it is easier to understand ocean waves as simply the outward manifestation of kinetic energy propagating through seawater. In reality, the water in waves doesn’t travel much at all. The only thing waves do transmit across the sea is energy.
    In addition, where waves are clearly seen crashing down dramatically onto shore, it is nothing more than the wave’s orbital motion being disturbed by the seafloor. As a wave passes through water, not only does the surface water follow an orbital motion, but a column of water below it completes the same movement. The approach of the bottom in shallow areas causes the lower portion of the wave to slow down and compress, forcing the wave’s crest higher in the air. Eventually this imbalance in the wave reaches a breaking point, and the crest comes crashing down as wave energy is dissipated into the surf.
So where does a wave's energy come from? There are a few types of ocean waves and they are generally classified by the energy source that creates them. Most common are surface waves, caused by wind blowing along the air-water interface, creating a disturbance that steadily builds as wind continues to blow and the wave crest rises. Surface waves occur constantly all over the globe, and are the waves you see at the beach under normal conditions and are the currents that drive movement across the seas, including those that allow for such things as “drift voyages.”
    Adverse weather or natural events often produce larger and potentially hazardous waves. Severe storms moving inland often create a storm surge, a long wave caused by high winds and a continued low pressure area. Storm surges are a minor disturbance in deep water, often less than one meter high, but intensify as they move into shallower water. Submarine earthquakes or landslides can displace a large amount of water very quickly, creating a series of very long waves called tsunamis. Storm surges and tsunamis do not create a typical crashing wave, but rather a massive sea-level rise upon reaching shore and can be extremely destructive to coastal environments as well as human settlements.
In fluid dynamics, wind waves, or wind-generated waves, are surface waves that occur on the free surface of oceans, seas, lakes, rivers, and canals or even on small puddles and ponds. They result from the wind blowing over an area of fluid surface
    What is important in understanding the currents affected by the throughway (passage) in the Panama Isthmus area is that: 1) Many submerged landfalls, shoals, reefs, even islands, can alter the flow of the water, creating undersea currents even though the surface water appears unchanged; and 2) A surface flow over an extended shallow area, no matter how large, does not alter the kinetic energy passing over this submerged area since it picks up and continues once past the submerged area. Since the depth of the water being affected does not extend below about 9 or 10 feet, if the submerged area is no higher than that, the water would appear unchanged, though the strength of the surface movement will be affected in two ways: 1) the deeper area is altered to move according to what obstruction blocks or alters its path, and 2) the surface area continues on as though nothing is happening beneath the surface even though the movement of the current is slowed and altered to some degree. 
    Thus we have the Humboldt Current, bringing cold water northward along the west coast of South America, the bulge of Peru pushing that current seaward or to the west, and completing what is called the South Pacific Gyre (South Equatorial Current) which moves in a counter-clockwise direction; the same thing is happening in the north, with the North Pacific Gyre (North Equatorial Current) moving clockwise, both nearly joining, and moving westward around the equator toward the west.
The Gulf Stream, on the other hand, was not affected so much by the water flowing through the Panama area or passage, since the Yucatan, Cuba, Haiti/Dominican Republic, Puerto Rico, etc., all tended to block that movement of water into the Caribbean Sea through the passage and direct it down into the northeastern area of South America, which at the time, would have been a large opening (Yellow Arrow) in what is now Eastern Colombia and Western Venezuela, which was then underwater, and into the Pabasian Sea,which would have passed out into the Atlantic around today’s Amazon Sea mouth, and/or into the Paranense Sea, helping to keep that central and eastern part of South America submerged.
    This, by the way, when cut off, i.e., when Panama rose upward to block this passage of water, the source of the Pebesian Sea, Paranense Sea and Paranan Sea would have been diminished. On the other hand, any of those waters coming in through the passage escaping the movement (Yellow Arrow) into the Pebasian Sea would have been caught in the northward movement between the Yucatan and Cuba into the Gulf, bent around Apolochee Bay and back down around the tip of Florida through the Straits of Florida and into the Gulf Stream, which begins upstream of Cape Hatteras (well out to sea off the North Carolina coast and beyond the Pamlico Sound (a 70-mile-long sand bank that begins at Cape Lookout and curves eastward out into the Atlantic to Hatteras Island, then turns back and runs to Virginia Beach) into the North Atlantic Drift (along the North Atlantic Subtropical Gyre) moving, according to the Mariano Global Surface Velocity Analysis a significant amount of warm water poleward (toward the North Pole) in a meandering 2 mile per second current—actually, as the Gulf Stream reaches Cape Hatteras, the cold Labrador Current that flows from the north separates it from the coast. At this confluence, the warm Gulf Stream waters combine with the cold winds accompanying the Labrador Current, forming one of the densest concentrations of fog in the world.
The bottom line is, the Gulf Stream’s warmth would not have been affected, nor would it’s course, though before the passage was cut off,  it might well have moved faster with the extra current pouring into the south current; however, no such records would be available of that prior to the crucifixion of Christ. Whether or not Leif Erickson’s Iceland and Greenland were warmer than after the crucifixion, or England, Norway or beyond is unknown.
(See the next post, "The Gulf Stream-Part II," for more of the stream itself and how it was affected, if at all, by the earlier existence of the Panama Throughway).

1 comment:

  1. Thank you. I'm not sure why I hadn't considered that when the Panama opening existed, the seas covering the interior of South America would also be a path for ocean currents directed that way.