Transcript The Ocean, Atmosphere & Weather

Ocean and the
Atmosphere
Notes for Ocean Planet
Wnek
Layers of the atmosphere
The role of the atmosphere
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The atmosphere influences the
ocean, especially through winddriven and density driven circulation
Wind-driven circulation can cause a
deflection of water off continents
The wind-driven pattern can create
coastal upwelling and downwelling
patterns (discussed later)
Earth’s Rotation
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Coriolis Effect
Ekman Spiral
The Motion of the
earth can be up to
45 degrees to the
right of the wind
direction in the
northern
hemisphere and left
in the southern
hemisphere
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Upwelling
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Movement of water away from land
(coasts) where it is replaced by
colder water (nutrient rich) from
deeper areas
The movement of water away from
the coast is called “divergence”
In the northern hemisphere on the
east coast of continents a southerly
wind causes upwelling…
Courtesy of NOAA 2004
Upwelling Schematic
http://oceanservice.noaa.gov/education/kits/
currents/03coastal4.html
Courtesy of NOAA 2004
The role of the wind
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Unequal heating of the atmosphere
by the land and ocean surfaces
Friction between the moving air and
the ocean surface create surface
currents
Negating the rotation of the earth,
the wind would cause surface
currents to move, thus layers move
below it causing a net movement
Pacific Decadal Oscillation considered a climate
index (Mantua et al. 1997; NOAA 2011)
Increase in carbon dioxide levels between 1860 and 1990. Image from Purves et al.,
Life: The Science of Biology, 4th Edition, by Sinauer Associates (www.sinauer.com) and
WH Freeman (www.whfreeman.com).
Are Ice Cores Accurate?
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It is difficult to believe that a chemically
active gas such as carbon dioxide can
remain unaffected by burial in ice for as
long as 160,000 years. There are
questions whether the carbon dioxide can
diffuse through the snow, react with dust
particles, or form clathrate compounds
under pressure The technique of drilling,
removal and preservation of the ice core is
very difficult, and there are many things
that can go wrong (Jaworski, 1996, 1997).
Findings
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The period since 1972, when the
increase has been linear despite an
increase of over 45% in emissions,
suggests that there are new carbon
sinks being established in the ocean
and in the terrestrial biosphere to
absorb the increases (Gray, 1998).
Sea Level Rise
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Global mean sea level has been
rising at an average rate of 1 to 2
mm/year over the past 100 years,
which is significantly larger than the
rate averaged over the last several
thousand years. Projected increase
from 1990-2100 is anywhere from
0.09-0.88 meters (depending on the
severity of the warming)
Ocean Currents?
Illustration by Jack Cook, Woods Hole Oceanographic Institution
This is now being reconsidered in terms of the
rate of slowing
Coupled ocean-atmospheric models
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Rising carbon dioxide indicate upperocean stratification
Stability will increase & mixing will
decrease the next 50 years
Net primary productivity (NPP) of
microplankton will increase and
megaplankton will decrease (Barber
2007)
The Future
Precipitation is also expected to
increase over the 21st century,
particularly at northern mid-high
latitudes, though the trends may be
more variable in the tropics.
Snow extent and sea-ice are also
projected to decrease further in the
northern hemisphere, and glaciers and
ice-caps are expected to continue to
retreat.
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Weather and the Ocean
Pressure Gradients
Air is constantly moving to seek an equilibrium
between areas of more air molecules (higher
pressure) and those with less (lower pressure).
Wind is nothing more than the movement of air
molecules from one place to the next. The direction
and speed of the wind represents the balance
between three basic forces acting on it: the
pressure gradient, the Coriolis force, and surface
friction.
Pressures are trying to stay in balance.
Pressures are reported in Isobars
Isobars
What is a jet stream?
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It is an area with significant pressure
differences within a 9 km band
It generally moves from west to east
and is more substantial in from 20,000
feet or higher
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Can move in speeds greater than 200
mph
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Can dip down in the winter as a result
of sinking cold air from the north
NOAA.gov
Tropical Systems
Defined as low pressure systems that have a
counterclockwise rotation in the northern hemisphere
& the opposite in the southern hemisphere
The opposite rotation in each hemisphere is due to
the Coriolis Effect
They are all CYCLONES; however they are called
HURRICANES in the western hemisphere and strong
storms are TYPHOONS in the eastern hemisphere
Formed by storms, Intertropical Convergent Zone
areas
Tropical Cyclones
For a cyclone to form, the ocean waters need to
be warm, at least 26°C. Above the warm ocean,
water evaporates and form clouds. If there is low
air pressure where the clouds are formed, it
pulls them in and they begin to rotate.
If a storm achieves wind speeds of 38 miles (61
kilometers) an hour, it becomes known as a
tropical depression.
Hurricanes spin around a low-pressure center
known as the “eye.” Sinking air makes this 20to 30-mile-wide (32- to 48-kilometer-wide) area
notoriously calm. But the eye is surrounded by a
circular “eye wall” that hosts the storm’s
strongest winds and rain.
NASA.gov
http://www.cyclonerita.com/hurricane-irene.html
Scale to determine the strength of tropical cyclones
1 knot = 1.15 miles/hour
Storm Designations
The Saffir-Simpson
Hurricane Wind
Scale is a 1 to 5
categorization
based on the
hurricane's
intensity at the
indicated time.
Where do tropical cyclones come from
and when?
Most hurricanes begin in the Atlantic as a result
of tropical waves that move westward off the
African coast.
Official Hurricane season is June 1 – November
30 each year.
Many early and late Atlantic Ocean Hurricanes
originate in the Gulf of Mexico or Caribbean
Intertropical Convergence Zone
Intertropical Convergence Zone
Tropical Activity as of September 4, 2011 (Weather Underground)
Weather underground. com
Hurricane Irene (NASA 2011)
Hurricane Sandy 2012
Problems Associated with Tropical Cyclones
Winds
Storm Surge
Flooding
Storm Surge Can
Devastate Marinas
Hurricane Irene Storm Surge at New Bourne, NC
Storm Surge in Bayside Long Island
from Hurricane Irene
Pier at Atlantic Beach, NC
Hurricanes: The Most Powerful on Record
(Lowest Pressures)
Ranking
Storm ID
Storm Name
Origin Date
Minimum Central
Pressure (in mb.)
1
1347
WILMA
2005-10-15
882
2
1122
GILBERT
1988-09-08
888
3
615
UNNAMED
1935-08-29
892
4
1342
RITA
2005-09-18
897
5
1045
ALLEN
1980-07-31
899
6
1336
KATRINA
2005-08-23
902
7
934
CAMILLE
1969-08-14
905
8
1234
MITCH
1998-10-22
905
9
1383
DEAN
2007-08-13
907
10
1314
IVAN
2004-09-02
910
11
815
JANET
1955-09-21
914
12
1298
ISABEL
2003-09-06
915
13
1134
HUGO
1989-09-10
918
14
1196
OPAL
1995-09-27
919
15
1097
GLORIA
1985-09-16
920
16
870
HATTIE
1961-10-27
920
17
1241
FLOYD
1999-09-07
921
18
1161
ANDREW
1992-08-16
922
19
917
BEULAH
1967-09-05
923
20
14
UNNAMED
1853-08-30
924
Sandy was 940 mb at landfall, which is lowest north of NC ever!
Nor’easters
Nor’easter
These strong areas of low pressure often
form either in the Gulf of Mexico or off the
East Coast in the Atlantic Ocean. The low will
then either move up the East Coast into New
England and the Atlantic provinces of Canada
or out to sea.
Detailed studies taken from satellite imagery
and other readings suggest that some low
pressure systems associated with nor'easters
may develop tropical storm characteristics
such as an eye in the center of the low.
El Nino
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El Niños are not caused by global
warming.
However, it has been hypothesized
that warmer global sea surface
temperatures can enhance the El
Niño phenomenon, and it is also true
that El Niños have been more
frequent and intense in recent
decades.
La Nina 1998-1999
dnr.sc.gov
El Nino and its impacts on the
Leatherback Sea Turtle
in Costa Rica
All of the pictures and graphics were provided
by Dr. James Spotila, Drexel University and the
Leatherback Trust
Leatherback
Jelly-vore
The turtle all the other biologists wish they could study
Results- counting turtles
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1719 turtles have been tagged in 11
years
448 have returned to nest again
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Annual mortality rates 22%
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22%!!
Leatherbacks in the Pacific
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1980- 91,000 adult females
1995- 6,500 adult females
2000- 3,490 adult females
 East Pacific- 1995- 4638
2000- 1690
2006- 800
Exponential Decline
1504 1474
1400
1200
1000
1000
847
732
800
569
600
421
417
400
246
234
195
200
140
188
126
79
68
54
124
Season
Parque Nacional Marino Las Baulas, Costa Rica
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6
05
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5
04
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4
03
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3
02
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2
01
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1
00
/0
0
99
/9
9
98
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8
97
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7
96
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6
95
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5
94
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4
93
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3
92
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2
91
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1
90
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0
89
/8
9
0
88
Number of nesting turtles
turtles
1600
Climatic variables may play a major
role in influencing return interval and
apparent population size
Beach Profile at Marker #16
Normal Dune elevation has
a berm but with development
the berm is destroyed
4.00
Meters above Mean Sea Level
3.50
3.00
2.50
2.00
1.50
1.00
0.50
53
50
47
43
40
37
33
30
27
23
20
17
13
10
7
3
0
0.00
Distance (m)
Beach Profile at Marker #31
Beach Profile for Marker #1
4.00
3.00
3.50
Meters above Mean Sea Level
3.50
2.50
2.00
1.50
1.00
0.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
Distance (m)
Distance in Meters
70
67
63
60
57
53
50
47
43
40
37
33
30
27
23
20
17
13
10
7
3
0
53
50
47
43
40
37
33
30
27
23
20
17
13
10
7
0.00
3
0
Meters above Mean Sea Level
4.00
Threats
Fishing
Longlines
Gill Nets
Shrimp Nets
Poaching
Eggs
Adults
Loss of Nesting Beaches
No nesting beaches = no turtles
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Longlining for swordfish and tuna is one of the most
significant threats to sea turtles
Longlines stretch as much as 60 miles and have
thousands of baited hooks
~1.4 billion longline hooks in the oceans each year
Graphic: Sea Turtle Restoration Project
The Great BP Oil Spill
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The large strands of sargassum seaweed atop
the ocean are normally noisy with birds and thick
with crustaceans, small fish and sea turtles. But
now this is a silent panorama, heavy with the
smell of oil.
There are no birds. The
seaweed is soaked in
rust-colored crude and
chemical dispersant. It is
devoid of life except for
the occasional juvenile
sea turtle, speckled with
oil and clinging to the
only habitat it knows.
Thick ribbons of oil
spread out through the
sea like the strips in egg
flower soup, gorgeous
and deadly.
Loss of 10 years of sea turtle
conservation- Effects for a generation
Boiling the turtles alive!
References
Barber, R.T. 2007. Picoplankton do some heavy lifting. Science,
February 9: pp. 777-778.
Etheridges, D.M., L.P. Steele, R.L. Langenfelds, R.J. Francey, J.-M
Barnola, V.I. Morgan. 1996. "Natural and anthropogenic changes
in atmospheric CO2 over the last 1000 years from air in Antarctic
ice and firn" J. Geophys. Res. 101 (D2) 4115-4128
Etheridges, D.M., L.P. Steele, R.L. Langenfelds, R.J. Francey, J.-M
Barnola, V.I. Morgan. 1996. "Natural and anthropogenic changes
in atmospheric CO2 over the last 1000 years from air in Antarctic
ice and firn" J. Geophys. Res. 101 (D2) 4115-4128
Gray, V.R., 1998. "The IPCC future projections: are they plausible"
Climate Research 10 155-162
http://palaeo.gly.bris.ac.uk/Palaeofiles/Permian/PALIntro.html
http://www.ncdc.noaa.gov/oa/climate/globalwarming.html#Q11
Jaworowski, Z. 1996 "Reliability of Ice Core Records for Climatic
Projections" in "The Global Warming Debate", (John Emsley, Ed.)
European Science and Environment Forum , London, 95-105.
Jaworowski, Z., 1997. "Ice Core Data Show No Carbon Dioxide
Increase" 21st Century Science and Technology 10 , (1) 42-52