Transcript 2.36 Deep Ocean Currents

Deep Ocean Currents
(Great Ocean Conveyer Belt)
Differential Solar Heating
Deep Ocean Currents
• There are areas in the oceans where
surface water becomes denser than the
water below it and sinks
• This causes a system of slow deep water
currents
• In order for sea level to remain constant, if
water sinks in one area, it must rise
somewhere else
• Areas where deep water rises to the
surface are called areas of upwelling
Sinking of Surface Water
• Surface water sinks in areas where warm,
salty water is carried toward the poles by
currents
• This water cools and becomes cold, salty
water which makes it denser than the
water below it
• So it sinks forcing deep water to flow away
from that area thus starting the deep
current
Example
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Tropical Atlantic is very salty
Gulf Stream moves this water north
Water cools along the way
By the time it reaches the area between
Iceland and Europe, it has cooled
enough to become very dense
• Surface water sinks to the bottom –
feeding deep currents
North Atlantic Deep Water
Formation
Great Ocean Conveyor Belt
• The deep current system connects all the
oceans
• Called the Great Ocean Conveyor
• Has enormous effects on:
– World climate (heat transfer)
– Fishing industry (upwelling areas are great
fishing grounds)
Great Ocean Conveyor Belt
Conveyor and Climate Change
• Scientists are concerned that global
warming could affect the ocean
conveyor system and make abrupt
climate change more likely
• Melting of ice is making polar seas less
salty
• This could interfere with sinking –
slowing down the conveyor
• On the other hand, tropical waters are
becoming saltier or denser
• Ultimate result??? Can’t be sure
• The following illustration describes the flow pattern of the major
subsurface ocean currents. Near surface warm currents are drawn in
red. Blue depicts the deep cold currents. Note how this system is
continuously moving water from the surface to deep within the oceans
and back to the top of the ocean.
• One complete circuit of this flow of sea water is estimated to take about
1,000 years.
• the ocean "conveyor belt", refers to the cycle in which surface
waters sink, enter deep water circulation, then resurface after slowly
flowing through the deep ocean.