How do ocean currents work? - Jennifer Verduin

2,458,246 views ・ 2019-01-31

TED-Ed


Tafadhali bofya mara mbili manukuu ya Kiingereza hapa chini ili kucheza video.

Translator: Julie Mbeyella Reviewer: Nelson Simfukwe
00:06
In 1992,
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Mwaka 1992
00:07
a cargo ship carrying bath toys got caught in a storm.
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Meli ya mizigo iliyobeba shehena ya Vichezeo vya kuogea ilipatwa na dhoruba.
00:12
Shipping containers washed overboard,
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Makontena ya kusafirishia shehena yakapotea kwenye maji,
00:14
and the waves swept 28,000 rubber ducks and other toys into the North Pacific.
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Mawimbi yalisomba bata wa raba na vichezeo vinginevyo kwenye bahari ya Pacific ya kaskazini.
00:20
But they didn’t stick together.
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Lakini havikukaa pamoja.
00:22
Quite the opposite–
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Tofauti kabisa--
00:23
the ducks have since washed up all over the world,
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Bata hao wametapakaa Dunia nzima,
00:27
and researchers have used their paths
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Na wachunguzi wametumia njia yao
00:29
to chart a better understanding of ocean currents.
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Kuelewa zaidi mikondo ya Bahari.
00:33
Ocean currents are driven by a range of sources:
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Mikondo ya bahari inaendeshwa na vitu vingi:
00:36
the wind, tides, changes in water density,
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Upepo,mawimbi,mabadiliko kwenye wiani,
00:40
and the rotation of the Earth.
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Na mzunguko wa Dunia.
00:43
The topography of the ocean floor and the shoreline modifies those motions,
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Topografia ya sakafu ya bahari na ufukwe vinaongeza hiyo mizunguko,
00:47
causing currents to speed up,
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Kusababisha mikondo iongeze spidi,
00:49
slow down, or change direction.
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Kupunguza spidi au kubadili muelekeo.
00:52
Ocean currents fall into two main categories:
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Mikondo ya bahari imegawanyika kwenye makundi makuu mawili:
00:55
surface currents and deep ocean currents.
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Mikondo ya juu na mikondo ya ndani ya bahari.
00:58
Surface currents control the motion
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Mikondo ya juu ina dhibiti mwendo
01:00
of the top 10 percent of the ocean’s water,
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Wa asilimia 10 ya maji ya bahari,
01:02
while deep-ocean currents mobilize the other 90 percent.
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Wakati mikondo ya ndani inadhibiti asilimia 90 iliyobaki.
01:06
Though they have different causes,
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Japo yanasababishwa na vitu tofauti,
01:07
surface and deep ocean currents influence each other
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Mikondo ya juu na ya ndani inashabiana
01:10
in an intricate dance that keeps the entire ocean moving.
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Ni dansi ambayo inaifanya bahari itembee.
01:15
Near the shore,
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Karibu na fukwe,
01:16
surface currents are driven by both the wind and tides,
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Mikondo ya bahari ya juu inaendeshwa na upepo na mawimbi,
01:19
which draw water back and forth as the water level falls and rises.
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Ambayo inavuta Maji ndani na Nje pale ambapo kiwango cha maji kinapungua na kuongezeka.
01:24
Meanwhile, in the open ocean, wind is the major force behind surface currents.
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Wakati huo huo,kwenye bahari upepo ndio nguvu kubwa ya mikondo ya juu.
01:29
As wind blows over the ocean,
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Upepo unapovuma juu ya bahari,
01:31
it drags the top layers of water along with it.
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Unaenda na maji ya juu,
01:34
That moving water pulls on the layers underneath,
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Maji yanayotembea yavuta vilivyomo chini,
01:37
and those pull on the ones beneath them.
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Na hizo zinavuta za chini yake.
01:39
In fact, water as deep as 400 meters
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Maji yenye kina kirefu cha Mita 400
01:43
is still affected by the wind at the ocean’s surface.
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Bado yana athiriwa na upepo wa juu ya bahari.
01:47
If you zoom out to look at the patterns of surface currents all over the earth,
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Ukiangalia kwa karibu muundo wa mikondo ya juu ya bahari ya Dunia nzima,
01:51
you’ll see that they form big loops called gyres,
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Utaona kwamba inatengeneza vitanzi vikubwa vinavyoitwa gyre,
01:54
which travel clockwise in the northern hemisphere
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Inayosafiri upande wa saa kaskazini mwa ulimwengu
01:57
and counter-clockwise in the southern hemisphere.
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Na kwa kurudi kusini mwa ulimwengu.
02:00
That’s because of the way the Earth’s rotation
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Hiyo ni sababu ya jinsi Dunia inavyozunguka
02:02
affects the wind patterns that give rise to these currents.
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Inaingilia muundo wa upepo inayoleta hii mikondo.
02:06
If the earth didn’t rotate,
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Kama Dunia isingezunguka,
02:08
air and water would simply move back and forth
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Maji na hewa vingeenda mbele na nyuma
02:10
between low pressure at the equator
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Kutoka sehemu yenye presha ndogo ikweta
02:12
and high pressure at the poles.
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Na presha kubwa kwenye fito.
02:14
But as the earth spins,
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Lakini Kadri Dunia inavyozunguka,
02:16
air moving from the equator to the North Pole is deflected eastward,
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Hewa kutoka ikweta kwenda kwenye fito ya kaskazini inageukia mashariki,
02:20
and air moving back down is deflected westward.
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Na hewa inayoelekea chini inageukia magharibi.
02:24
The mirror image happens in the southern hemisphere,
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Tofauti yake inatokea kwenye ulimwengu wa kusini,
02:27
so that the major streams of wind
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Ili kusudi mito mikubwa ya upepo
02:29
form loop-like patterns around the ocean basins.
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Inatengeneza miundo ya vitanzi karibu na mabonde ya bahari.
02:32
This is called the Coriolis Effect.
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Hii inaitwa ifekti ya coriolis.
02:35
The winds push the ocean beneath them into the same rotating gyres.
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Upepo unasukuma bahari chini yake kwenye gyre za kuzunguka.
02:40
And because water holds onto heat more effectively than air,
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Na sababu maji yanashika moto upesi kushinda hewa,
02:43
these currents help redistribute warmth around the globe.
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Hii mikondo inasaidia kugawanya joto duniani.
02:48
Unlike surface currents,
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Tofauti na mikondo ya juu,
02:49
deep ocean currents are driven primarily by changes in the density of seawater.
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Mikondo ya ndani inaendeshwa na tofauti ya wiani wa maji ya bahari.
02:55
As water moves towards the North Pole,
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Maji yanavyoelekea fito ya kaskazini,
02:57
it gets colder.
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Yanakuwa na baridi.
02:58
It also has a higher concentration of salt,
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Pia yanakuwa na chumvi nyingi,
03:01
because the ice crystals that form trap water while leaving salt behind.
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Sababu ile barafu inayoshikilia maji wakati inaacha chumvi nyuma.
03:05
This cold, salty water is more dense,
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Haya Maji ya baridi yenye chumvi ni mazito zaidi
03:08
so it sinks,
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Kwahiyo yananuka,
03:09
and warmer surface water takes its place,
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Na Maji ya uvugu vugu yanachukua nafasi yake.
03:12
setting up a vertical current called thermohaline circulation.
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Kutengeneza mkondo wa wima unaoitwa mzunguko wa thermohaline
03:17
Thermohaline circulation of deep water and wind-driven surface currents
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Mzunguko wa thermohaline wa maji ya ndani na yanayoendeshwa na upepo wa Mkondo wa bahari wa juu
03:21
combine to form a winding loop called the Global Conveyor Belt.
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Unajiunga kutengeneza kitanzi cha upepo kinachoitwa Global Conveyor Belt.
03:26
As water moves from the depths of the ocean to the surface,
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Maji yanavyohama kutoka ndani ya bahari kwenda juu.
03:29
it carries nutrients that nourish the microorganisms
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Yanabeba virutubishi ambavyo vinasaidia kukuza viumbe hai
03:32
which form the base of many ocean food chains.
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Ambayo inatengeneza msingi wa cheni nyingi za chakula baharini.
03:35
The global conveyor belt is the longest current in the world,
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Mkondo wa Global Conveyor belt ndo mrefu zaidi duniani,
03:39
snaking all around the globe.
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Ukizunguka dunia nzima.
03:41
But it only moves a few centimeters per second.
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Lakini unazunguka sentimita chache kwa sekunde.
03:44
It could take a drop of water a thousand years to make the full trip.
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Inaweza ichukua tone la maji miaka 1000 kufanya safari yote.
03:49
However, rising sea temperatures are causing the conveyor belt
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Japokuwa Levo za joto la bahari zinazopanda zinasababisha ukanda wa conveyor
03:52
to seemingly slow down.
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Kupunguza spidi.
03:54
Models show this causing havoc with weather systems
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Modeli zinaonesha hii inasabisha ma tatizo kwenye hali ya hewa
03:57
on both sides of the Atlantic,
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Kwenye pande zote za Atlantic,
03:59
and no one knows what would happen if it continues to slow
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Na hamna anayejua nini kitatokea ikiendelea kupunguza spidi
04:02
or if it stopped altogether.
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Au ikisimama kabisa
04:05
The only way we’ll be able to forecast correctly and prepare accordingly
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Njia pekee tutakayoweza tabiri sawasawa na kujiandaa vizuri
04:09
will be to continue to study currents and the powerful forces that shape them.
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Ni Kwa kuendelea kusoma mikondo na nguvu zote zinazosababisha mikondo kuwepo.
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