Feb 2
Liberal Arts Blog — Ocean Currents — the Surface, the Deep, the Gulf Stream
Liberal Arts Blog — Wednesday is the Joy of Science, Engineering, and Technology Day
Today’s Topic — Ocean Currents — the Surface, the Deep, the Gulf Stream
So what are the coolest things about oceans that you know that the rest of us may not? What are the most important things to know about the oceans that every 5th, 8th, 12th grader should? I can remember pathetically little about anything I ever learned about the oceans so this morning I decided to take a quick refresher course. Experts — please chime in. Correct, elaborate, elucidate.
SURFACE OCEAN CURRENTS — wind driven — what gives?
1. Temperature differentials drive pressure differentials and pressure differentials drive winds.
2. Temperature differentials on the earth are principally driven by the shape of the earth which determines the angle at which the sun’s light strikes.
3. The other factor is the rotation of the earth which causes the “Coriolis” effect. This in turn causes the Ekman Spiral.
NB: “If the Earth did not rotate and remained stationary, the atmosphere would circulate between the poles (high pressure areas) and the equator (a low pressure area) in a simple back-and-forth pattern. But because the Earth rotates, circulating air is deflected. Instead of circulating in a straight pattern, the air deflects toward the right in the Northern Hemisphere and toward the left in the Southern Hemisphere, resulting in curved paths. This deflection is called the Coriolis effect. It is named after the French mathematician Gaspard Gustave de Coriolis (1792–1843), who studied the transfer of energy in rotating systems like waterwheels. (Ross, 1995).”
The Ekman spiral: “When surface water molecules move by the force of the wind, they, in turn, drag deeper layers of water molecules below them. Each layer of water molecules is moved by friction from the shallower layer, and each deeper layer moves more slowly than the layer above it, until the movement ceases at a depth of about 100 meters (330 feet).” Ekman (1874–1954) was a Swedish scientist.
DEEP OCEAN CURRENTS — “Thermohaline” — the “global conveyor belt”
1.“In the Earth’s polar regions ocean water gets very cold, forming sea ice. As a consequence the surrounding seawater gets saltier, because when sea ice forms, the salt is left behind.”
2. “As the seawater gets saltier, its density increases, and it starts to sink. Surface water is pulled in to replace the sinking water, which in turn eventually becomes cold and salty enough to sink.
3. “This initiates the deep-ocean currents driving the global conveyer belt.”
GULF STREAM — “more powerful than the wind” (Ponce de Leon log. 1512) Part of the “North Atlantic gyre” — one of five gyres
1. “European discovery of the Gulf Stream dates to the 1512 expedition of Juan Ponce de Leon, after which it became widely used by Spanish ships sailing from the Caribbean to Spain.”
2. From the Ponce de Leon log: “A current such that, although they had great wind, they could not proceed forwards, but backwards….the current was more powerful than the wind.”
3. The current veers eastwards at about the 36 latitude and then splits at about latitude 40 into two — the Northern Atlantic Drift and the Canary Current which goes down to Senegal in Africa.
NB: The Gulf Stream is part of the North Atlantic Gyre (see fourth link below). Its northern acceleration is driven by “western intensification” (fifth link below).
The western currents of ocean basins are stronger than the eastern because “the Coriolis effect is stronger in the latitudes of the westerlies than in the latitudes of the trade winds. Transport of surface waters toward the western boundary of the ocean basins causes the ocean-surface slope to be steeper on the western side (versus eastern side) of a gyre (in either hemisphere). A steeper ocean-surface slope translates into a faster geostrophic flow on that side of the gyre.” The American scientist who figured this out was Henry Stommel (1920–1992). (See last link below.)
The Ekman Spiral — Currents: NOAA’s National Ocean Service Education
Thermohaline Circulation — Currents: NOAA’s National Ocean Service Education
North Atlantic Gyre — Wikipedia
Ocean Motion : Definition : Wind Driven Surface Currents — Western Boundary Currents
QUOTE OF THE MONTH:
“In my walks, every man I meet is in some way my superior and in that I can learn of him.” Ralph Waldo Emerson
A LINK TO THE LAST FOUR YEARS OF POSTS ORGANIZED BY THEME:
PDF with headlines — Google Drive
ATTACHMENT BELOW:
#1 A graphic guide to justice (9 metaphors on one page).
#2 “39 Songs, Prayers, and Poems: the Keys to the Hearts of Seven Billion People” — Adams House Senior Common Room Presentation, 11/17/20
PDF with headlines — Google DriveY
OUR TURN
Please share the coolest thing you learned this week related to science, engineering, or technology. Or, even better, the coolest or most important thing you learned in your life related to science and engineering.
This is your chance to make someone else’s day. Or to cement in your mind something that you might otherwise forget. Or to think more deeply about something dear to your heart. Continuity is key to depth of thought.
