The Sea Around Us,
Lecture 7,
2 Feb 2016
Ocean & Atmospheric Circulation, It’s all about HEAT
Here Comes the Sun!
Around the Sun, REM
Under the Sea
Timeflies Tuesday
A drop in the ocean
Ron Pope
Read: Course web site, Lecture Notes and Reading
• Two links to required reading/veiwing
Read: Course web site, Lecture Notes and Reading
• Two links to required reading/veiwing
Opportunity for undergrad students to sail on a
short research cruise:
http://usoceandiscovery.org/stemseas-2/
• OLA3 Due Today!
• Quiz 1 will be available for full review on
Thursday, Feb 4
• Quiz 1 results: Mean score was 79.9
What drives atmospheric
and ocean Circulation?
Let’s examine how the spatial distribution of energy receipt and how
the resulting temperature gradient drives ocean and atmospheric
convection
We’ll see how the winds (atmospheric circulation) drives circulation of
ocean Surface Water!
The North Pacific
Gyre is the home of
the Great Pacific
Garbage Patch.
•
https://sites.google.com/site/gre
atpacificgyre/
Global "Thermohaline" Circulation
Circulation of ocean water driven by
temperature and salinity differences
The Ocean "Conveyor Belt"
The "Conveyor"
system is a very
generalized view
of the work done
by surface and
deep circulation in
mass and heat
transfer.
Sinking of cold
dense waters at
high latitude
Return of warm
surface waters to
replace them
The Sea Around Us
My Job in Geosc040
100 Thomas…
Wait for clicker
questions Help
is on the way!
CLASS
Energy from the Sun!
http://earthguide.ucsd.edu/earthguide/diagrams/greenhouse/
Energy Transfer to and from the Oceans
Three types of heat transfer:
•Radiation
Direct transmission from
source with or without a
medium
Energy Transfer to and from the Oceans
Three types of heat transfer:
•Radiation
Direct transmission from
source with or without a
medium
•Advection or Convection
Transport of material and its
heat. Density-bouyancy
driven movement of fluid
Energy Transfer to and from the Oceans
Three types of heat transfer:
•Radiation
Direct transmission from
source with or without a
medium
•Advection or Convection
Transport of material and its
heat. Density-bouyancy
driven movement of fluid
•Conduction
Heat transfer by molecular
motion. Only works for
bodies in direct contact.
Think about Solar Radiation Reaching the Sea Surface
Albedo=30%
Radiation Balance for the Earth
Solar Radiation Reaching Sea Surface
(considers loss of reflected energy by clouds, etc.)
Units are Watts/meter2--compare incoming patterns to outgoing in next slide
Long-wave (infrared) radiation out
Notice that higher energy loss values are association with tropics (warm),
and values near the pole exceed incoming solar (previous slide).
Seasonal variations, but the
equatorial regions receive
more heat YEAR IN and
YEAR OUT!
Radiation Balance for the Earth
N. Pole
The Sun heats
Earth more at
the equator
than at the
poles!
equator
Did you see
this link on the
course web
site?
S. Pole
Fig. 6.12
Radiation Balance for the Earth
Earth's radiation
balance is
approximately at
"steady state”
(comparing one
year to the next)
That is:
outgoing rad=
incoming rad
(units are in percent
of total radiation
either incoming
(solar) or outgoing
(long-wave)
Albedo=30%
Don’t worry about numbers, but note complexity
Note role for latent
heat transfer
• A temperature
gradient is created
from low (warmer)
to high (colder)
latitude
• This drives heat
transfer
But how is this heat
transferred?
The Ocean-Atmosphere Connection, Winds & Surface Currents
Today’s in-class iClicker exercises:
A) Full credit if you answer 75% or more of
the questions
B) If there are 10 questions and you
answer at least 8 of them you’ll get full
credit for today (100%)
C) If you answer the question correctly
you’ll get a bonus point, up to a
maximum of 105% for today’s in-class
exercise
D) All of the above (this is the correct
answer, choose D!)
What drives
atmospheric
and ocean
Circulation?
Average Sea Surface Temperatures
Strong
Temperature
gradient
Cold poles
Hot tropics
So, the Temperature Pattern is
Determined by Solar Energy Receipt
but Must be Modified by Heat Transport
\
The Pattern of Surface Water Ocean Circulation
Ocean Currents Transfer Heat
Winds transfer heat too!
GLOBAL ATMOSPHERIC CIRCULATION (WINDS)
Large Scale Winds Transfer Heat, Note Air Pressure Zones
GLOBAL ATMOSPHERIC CIRCULATION (WINDS)
Large Scale Winds Transfer Heat, Note Air Pressure Zones
Notice that this
diagram shows
3D wind pattern.
Rising air over
the equator
flows north and
south
Wind and Ocean Currents are driven by heat imbalance
Wind and Ocean Currents are driven by heat imbalance
Wind and Ocean Currents are driven by heat imbalance
GLOBAL ATMOSPHERIC CIRCULATION (WINDS)
Large Scale Winds Transfer Heat, Note Air Pressure Zones
Warm air rises
LOW Pressure
S
0
N
Warm air rises
Rising air is replaced
30° S
LOW
Pressure
0
Winds blow
in toward low
pressure
30° N
Air cools, sinks
Air cools, sinks
Warm air rises
LOW Pressure
30° N
0
30° S
GLOBAL ATMOSPHERIC CIRCULATION (WINDS)
Large Scale Winds Transfer Heat, Note Air Pressure Zones
Notice that this
diagram shows
3D wind pattern.
Rising air over
the equator
flows north and
south
GLOBAL ATMOSPHERIC CIRCULATION (WINDS)
Large Scale Winds Transfer Heat, Note Air Pressure Zones
Let’s Consider Pressure Variations as a Cause for Winds
Air flows down a pressure gradient, from high (H) to low (L) pressure.
We’ll draw the windfields around these low and high pressure cells. Whoa?
Why do they look like that? Shouldn’t winds blow directly from high to low pressure
centers? (we’ll talk about the Coriolis effect as a cause a bit later)
Global Pattern of Winds on Earth!
Low Pressure
High Pressure
Low Pressure
High Pressure
Low Pressure
Winds around high pressure: clockwise in N. hemisphere and
Counterclockwise in S. hemisphere
Here’s the picture: why do winds blow this way?
Required viewing:
A year of Weather.
Credit: NASA
Note large scale
wind directions and
storm circulation
patterns from N. to
S. Hemisphere.
(animation) Thanks
to Justin D.
Recall the uneven heating of the Earth’s surface
Let’s examine how the Hadley Cell arises
Credit: NASA
Air cools, sinks
Rising air is replaced
Warm air rises
LOW Pressure
30° N
0
30° S
Rising air cools,
which causes
Rain drops to
form!
Air cools, sinks
Rising air is replaced
Warm air rises
HIGH
30° N
LOW Pressure
0
HIGH
30° S
At Earth’s
surface, wind
moves away
from Highs
Pressure and
toward Lows
Air cools, sinks
Divergent
Wind
HIGH
30° N
Convergent
Wind
LOW Pressure
0
Divergent
Wind
HIGH
30° S
At Earth’s
surface, wind
moves away
from Highs
Pressure and
toward Lows
Air cools, sinks
Divergent
Wind
HIGH
30° N
Convergent
Wind
LOW Pressure
0
Divergent
Wind
HIGH
30° S
GLOBAL ATMOSPHERIC CIRCULATION (WINDS)
Temperature gradients create pressure differences which drive winds
Global Pattern of Pressure Cells and Winds on Ea
Low Pressure
High Pressure
Low Pressure
High Pressure
Low Pressure
Ocean's Role in Energy Transfer and Climate Regulation
Ocean Surface Currents
Western Boundary Currents
Gulf Stream, Kuroshio,
Labrador, Kamchatka (Oyashio)
Eastern Boundary Currents
Canary, California
Ocean Surface Currents:
Some Interesting Differences Between Eastern & Western
Boundary Currents
Western Boundary Currents
Gulf Stream, Kuroshio,
Labrador, Kamchatka (Oyashio)
Eastern Boundary Currents
Canary, California
Gulf Stream as an
example of a Western
Boundary Current
East Australian Current &
Gulf Stream are
examples of Western
Boundary Currents
Western boundary
currents are intensified
--transport warm water
to higher latitudes
Surface currents
transport heat
toward poles
Labrador Current
Surface currents
transport heat
toward poles
Example: The Gulf Stream
This is a map of
surface water
temperature
Note these features:
• Sharp boundaries of
currents (1 & 2)
• Eddies
• Warm-core rings (3)
• Cold-core rings (4)
Heat Transfer:
Is that all there is to it?
OK, warm water flows
toward the poles, but How
does heat actually get
transferred??
Two mechanisms:
1) Sensible heat transfer to
atmosphere
2) Latent heat transfer
(remember: evaporationprecipitation?)
Ocean's Role in Energy Transfer and Climate Regulation
Key factors & processes
1) Pattern of solar energy
absorption leads to
temperature gradient
2) Heat transfer drives
winds and ocean
circulation.
3) Sensible heat transfer
(wind, currents) and
latent heat transfer to
the atmosphere
4) Eastern and Western
boundary currents
Why do winds
circulate around
High and Low
pressure
systems?
Gustav