[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:06.55,0:00:07.99,Default,,0000,0000,0000,,In 1992,
Dialogue: 0,0:00:07.99,0:00:12.21,Default,,0000,0000,0000,,a cargo ship carrying bath toys \Ngot caught in a storm.
Dialogue: 0,0:00:12.21,0:00:14.65,Default,,0000,0000,0000,,Shipping containers washed overboard,
Dialogue: 0,0:00:14.65,0:00:20.84,Default,,0000,0000,0000,,and the waves swept 28,000 rubber ducks \Nand other toys into the North Pacific.
Dialogue: 0,0:00:20.84,0:00:22.70,Default,,0000,0000,0000,,But they didn’t stick together.
Dialogue: 0,0:00:22.70,0:00:23.98,Default,,0000,0000,0000,,Quite the opposite–
Dialogue: 0,0:00:23.98,0:00:27.31,Default,,0000,0000,0000,,the ducks have since washed up \Nall over the world,
Dialogue: 0,0:00:27.31,0:00:29.56,Default,,0000,0000,0000,,and researchers have used their paths
Dialogue: 0,0:00:29.56,0:00:33.73,Default,,0000,0000,0000,,to chart a better understanding\Nof ocean currents.
Dialogue: 0,0:00:33.73,0:00:36.49,Default,,0000,0000,0000,,Ocean currents are driven \Nby a range of sources:
Dialogue: 0,0:00:36.49,0:00:40.04,Default,,0000,0000,0000,,the wind, tides, changes in water density,
Dialogue: 0,0:00:40.04,0:00:43.07,Default,,0000,0000,0000,,and the rotation of the Earth.
Dialogue: 0,0:00:43.07,0:00:47.73,Default,,0000,0000,0000,,The topography of the ocean floor \Nand the shoreline modifies those motions,
Dialogue: 0,0:00:47.73,0:00:49.36,Default,,0000,0000,0000,,causing currents to speed up,
Dialogue: 0,0:00:49.36,0:00:52.20,Default,,0000,0000,0000,,slow down, or change direction.
Dialogue: 0,0:00:52.20,0:00:55.03,Default,,0000,0000,0000,,Ocean currents fall into \Ntwo main categories:
Dialogue: 0,0:00:55.03,0:00:58.29,Default,,0000,0000,0000,,surface currents and deep ocean currents.
Dialogue: 0,0:00:58.29,0:01:00.05,Default,,0000,0000,0000,,Surface currents control the motion
Dialogue: 0,0:01:00.05,0:01:02.66,Default,,0000,0000,0000,,of the top 10 percent \Nof the ocean’s water,
Dialogue: 0,0:01:02.66,0:01:06.23,Default,,0000,0000,0000,,while deep-ocean currents mobilize \Nthe other 90 percent.
Dialogue: 0,0:01:06.23,0:01:07.93,Default,,0000,0000,0000,,Though they have different causes,
Dialogue: 0,0:01:07.93,0:01:10.96,Default,,0000,0000,0000,,surface and deep ocean currents \Ninfluence each other
Dialogue: 0,0:01:10.96,0:01:15.16,Default,,0000,0000,0000,,in an intricate dance that keeps \Nthe entire ocean moving.
Dialogue: 0,0:01:15.16,0:01:16.18,Default,,0000,0000,0000,,Near the shore,
Dialogue: 0,0:01:16.18,0:01:19.64,Default,,0000,0000,0000,,surface currents are driven \Nby both the wind and tides,
Dialogue: 0,0:01:19.64,0:01:24.50,Default,,0000,0000,0000,,which draw water back and forth \Nas the water level falls and rises.
Dialogue: 0,0:01:24.50,0:01:29.77,Default,,0000,0000,0000,,Meanwhile, in the open ocean, wind is the \Nmajor force behind surface currents.
Dialogue: 0,0:01:29.77,0:01:31.52,Default,,0000,0000,0000,,As wind blows over the ocean,
Dialogue: 0,0:01:31.52,0:01:34.51,Default,,0000,0000,0000,,it drags the top layers \Nof water along with it.
Dialogue: 0,0:01:34.51,0:01:37.48,Default,,0000,0000,0000,,That moving water pulls on \Nthe layers underneath,
Dialogue: 0,0:01:37.48,0:01:39.70,Default,,0000,0000,0000,,and those pull on the ones beneath them.
Dialogue: 0,0:01:39.70,0:01:43.20,Default,,0000,0000,0000,,In fact, water as deep as 400 meters
Dialogue: 0,0:01:43.20,0:01:47.03,Default,,0000,0000,0000,,is still affected by the wind \Nat the ocean’s surface.
Dialogue: 0,0:01:47.03,0:01:51.34,Default,,0000,0000,0000,,If you zoom out to look at the patterns \Nof surface currents all over the earth,
Dialogue: 0,0:01:51.34,0:01:54.82,Default,,0000,0000,0000,,you’ll see that they form \Nbig loops called gyres,
Dialogue: 0,0:01:54.82,0:01:57.58,Default,,0000,0000,0000,,which travel clockwise \Nin the northern hemisphere
Dialogue: 0,0:01:57.58,0:02:00.43,Default,,0000,0000,0000,,and counter-clockwise \Nin the southern hemisphere.
Dialogue: 0,0:02:00.43,0:02:02.62,Default,,0000,0000,0000,,That’s because of the way \Nthe Earth’s rotation
Dialogue: 0,0:02:02.62,0:02:06.63,Default,,0000,0000,0000,,affects the wind patterns that\Ngive rise to these currents.
Dialogue: 0,0:02:06.63,0:02:08.28,Default,,0000,0000,0000,,If the earth didn’t rotate,
Dialogue: 0,0:02:08.28,0:02:10.74,Default,,0000,0000,0000,,air and water would simply \Nmove back and forth
Dialogue: 0,0:02:10.74,0:02:12.82,Default,,0000,0000,0000,,between low pressure at the equator
Dialogue: 0,0:02:12.82,0:02:14.61,Default,,0000,0000,0000,,and high pressure at the poles.
Dialogue: 0,0:02:14.61,0:02:16.35,Default,,0000,0000,0000,,But as the earth spins,
Dialogue: 0,0:02:16.35,0:02:20.86,Default,,0000,0000,0000,,air moving from the equator to the \NNorth Pole is deflected eastward,
Dialogue: 0,0:02:20.86,0:02:24.51,Default,,0000,0000,0000,,and air moving back down \Nis deflected westward.
Dialogue: 0,0:02:24.51,0:02:27.30,Default,,0000,0000,0000,,The mirror image happens \Nin the southern hemisphere,
Dialogue: 0,0:02:27.30,0:02:29.23,Default,,0000,0000,0000,,so that the major streams of wind
Dialogue: 0,0:02:29.23,0:02:32.79,Default,,0000,0000,0000,,form loop-like patterns \Naround the ocean basins.
Dialogue: 0,0:02:32.79,0:02:35.68,Default,,0000,0000,0000,,This is called the Coriolis Effect.
Dialogue: 0,0:02:35.68,0:02:40.13,Default,,0000,0000,0000,,The winds push the ocean beneath \Nthem into the same rotating gyres.
Dialogue: 0,0:02:40.13,0:02:43.79,Default,,0000,0000,0000,,And because water holds onto heat \Nmore effectively than air,
Dialogue: 0,0:02:43.79,0:02:48.30,Default,,0000,0000,0000,,these currents help redistribute \Nwarmth around the globe.
Dialogue: 0,0:02:48.30,0:02:49.86,Default,,0000,0000,0000,,Unlike surface currents,
Dialogue: 0,0:02:49.86,0:02:55.01,Default,,0000,0000,0000,,deep ocean currents are driven primarily \Nby changes in the density of seawater.
Dialogue: 0,0:02:55.01,0:02:57.33,Default,,0000,0000,0000,,As water moves towards the North Pole,
Dialogue: 0,0:02:57.33,0:02:58.50,Default,,0000,0000,0000,,it gets colder.
Dialogue: 0,0:02:58.50,0:03:01.04,Default,,0000,0000,0000,,It also has a higher \Nconcentration of salt,
Dialogue: 0,0:03:01.04,0:03:05.96,Default,,0000,0000,0000,,because the ice crystals that form \Ntrap water while leaving salt behind.
Dialogue: 0,0:03:05.96,0:03:08.80,Default,,0000,0000,0000,,This cold, salty water is more dense,
Dialogue: 0,0:03:08.80,0:03:09.95,Default,,0000,0000,0000,,so it sinks,
Dialogue: 0,0:03:09.95,0:03:12.62,Default,,0000,0000,0000,,and warmer surface water takes its place,
Dialogue: 0,0:03:12.62,0:03:17.08,Default,,0000,0000,0000,,setting up a vertical current called \Nthermohaline circulation.
Dialogue: 0,0:03:17.08,0:03:21.56,Default,,0000,0000,0000,,Thermohaline circulation of deep water \Nand wind-driven surface currents
Dialogue: 0,0:03:21.56,0:03:26.32,Default,,0000,0000,0000,,combine to form a winding loop \Ncalled the Global Conveyor Belt.
Dialogue: 0,0:03:26.32,0:03:29.49,Default,,0000,0000,0000,,As water moves from the depths of \Nthe ocean to the surface,
Dialogue: 0,0:03:29.49,0:03:32.61,Default,,0000,0000,0000,,it carries nutrients that nourish the \Nmicroorganisms
Dialogue: 0,0:03:32.61,0:03:35.73,Default,,0000,0000,0000,,which form the base of many \Nocean food chains.
Dialogue: 0,0:03:35.73,0:03:39.31,Default,,0000,0000,0000,,The global conveyor belt is the\Nlongest current in the world,
Dialogue: 0,0:03:39.31,0:03:41.31,Default,,0000,0000,0000,,snaking all around the globe.
Dialogue: 0,0:03:41.31,0:03:44.91,Default,,0000,0000,0000,,But it only moves a few \Ncentimeters per second.
Dialogue: 0,0:03:44.91,0:03:49.46,Default,,0000,0000,0000,,It could take a drop of water \Na thousand years to make the full trip.
Dialogue: 0,0:03:49.46,0:03:52.100,Default,,0000,0000,0000,,However, rising sea temperatures are \Ncausing the conveyor belt
Dialogue: 0,0:03:52.100,0:03:54.96,Default,,0000,0000,0000,,to seemingly slow down.
Dialogue: 0,0:03:54.96,0:03:57.75,Default,,0000,0000,0000,,Models show this causing havoc with \Nweather systems
Dialogue: 0,0:03:57.75,0:03:59.62,Default,,0000,0000,0000,,on both sides of the Atlantic,
Dialogue: 0,0:03:59.62,0:04:02.86,Default,,0000,0000,0000,,and no one knows what would happen if it \Ncontinues to slow
Dialogue: 0,0:04:02.86,0:04:05.15,Default,,0000,0000,0000,,or if it stopped altogether.
Dialogue: 0,0:04:05.15,0:04:09.14,Default,,0000,0000,0000,,The only way we’ll be able to forecast\Ncorrectly and prepare accordingly
Dialogue: 0,0:04:09.14,0:04:13.83,Default,,0000,0000,0000,,will be to continue to study currents \Nand the powerful forces that shape them.