The dominant periodicities are the same as those from astronomical calculations of changes in the...
-
date post
21-Dec-2015 -
Category
Documents
-
view
220 -
download
0
Transcript of The dominant periodicities are the same as those from astronomical calculations of changes in the...
![Page 1: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/1.jpg)
The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.
![Page 2: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/2.jpg)
Our Planet’s Music has Many Beats:
(a) 1 DAY: Day- Night – Day Spins around its axis
(b) 1 Year: Winter – Summer – Winter Orbits the Sun
(c) 23,000 Years: Stronger Summer, Stronger Winter Precession
(d) 40,000 Years: Tilted axis rocks back and forth OBLIQUITY
(e) 100,000 Years: Eccentricity of the orbit varies
MILANKOVITCH CYCLES
SUN
![Page 3: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/3.jpg)
Seasonal Changes in Sunlight as a function of latitude:
ANNUAL Average
PRECESSION redistributes
sunlight in time so that the
the average over a year is
zero
OBLIQUITY redistributes
sunlight latitudinally so that
the average over the globe
is zero.
![Page 4: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/4.jpg)
WARM
COOLING TREND + AMPLIFYING 40K CYCLES
NONLINEAR
40 .. 80 .. 120K
THRESHOLD THRESHOLD ?
40K WORLD
Vt+1 - Vt = a + bt + c(Vt – V*) Obliquity(t)
0 1 2 3 4 5 6
x 106
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3x 10
7
time
tem
perature
temperature versus time
![Page 5: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/5.jpg)
Ice Ages:
19th Century: Evidence for Ice Ages in the northern Hemisphere
Milankovitch: ICE ALBEDO
Sunlight at 65N in July is the controlling factor
Why is precession unimportant? Huybers
What causes the 110K cycle?
There is no 100K cycle! 40K…80K….120K..
Huybers and Wunsch
What caused the huge cycles of the past million years?
What feedbacks other than ice-albedo increased climate sensitivity?
Measurements in low latitudes provide an unexpected answer!!
![Page 6: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/6.jpg)
OBSERVATIONS: Obliquity variations affect mostly high latitudes….glaciers
Precession affects mostly low latitudes …. monsoons
Surprising Recent Observations:
The tropical Pacific responds mainly to Obliquity!
The records for SST are very similar to Ice Volume records
![Page 7: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/7.jpg)
~ 3 Ma Cold Surface Waters Start Appearing in Low Latitudes
![Page 8: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/8.jpg)
March 1998 - El Niño Apparently conditions similar to these persisted up to 3 million years ago
October 1988 - La Niña
![Page 9: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/9.jpg)
Tropical Sea Surface Temperature patterns strongly influence Rainfall patterns and hence the global climate.
Sea Surface Temperatures (Degrees Centigrade)
![Page 10: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/10.jpg)
W E W E
Dep
th
Latitude
Temperature along a section in the mid-Pacific (152W)
El Nino La NinaAdiabatic:
_ _ _ _ _ _ _ __________ El Padre La MadreDiabatic:
_ _ _ _ _ _ _ ______________
1000m
4000m
A shallow thermocline permits two different processes for varying
sea surface temperatures
Diabatic:
_ _ _ _ _ _ _ ______________
Diabatic:
_ _ _ _ _ _ _ ______________
Diabatic:
_ _ _ _ _ _ _ ______________
Diabatic:
_ _ _ _ _ _ _ ______________
Diabatic:
_ _ _ _ _ _ _ ______________
Diabatic:
_ _ _ _ _ _ _ ______________
Diabatic:
_ _ _ _ _ _ _ ______________
Diabatic:
_ _ _ _ _ _ _ ______________
Diabatic:
_ _ _ _ _ _ _ ______________
Diabatic:
_ _ _ _ _ _ _ ______________
![Page 11: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/11.jpg)
To remain cold, the ocean
must have a circulation
![Page 12: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/12.jpg)
An Easterly Wind blowing over a Rotating, Spherical Shell of Fluid maintains a Meridional Overturning Circulation
winds
![Page 13: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/13.jpg)
How the Flux of Heat across the Ocean Surface affects its Subsurface thermal structure.
![Page 14: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/14.jpg)
The Response, the Heat Gain, increases in amplitude as the Period of the forcing increases. Note that there is also a change in the phase of the response.
Response to Imposed Changes in Heat Loss in high latitudes. In the Four Different experiments the amplitude of the forcing remains constant but the period changes from 2 to 5 to 10 to 20 years.
2 years 5 Years
20 Years10 Years
![Page 15: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/15.jpg)
Heat Flux across the Ocean Surface
![Page 16: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/16.jpg)
IN A WARM WORLD: A small oceanic heat loss implies a small oceanic heat gain which requires a deep tropical thermocline.
IN A COLD WORLD ……. A large oceanic heat loss implies a large oceanic heat gain which requires a shallow tropical thermocline.
The Heat Budget determines the Depth of the Oceanic Thermocline
The ocean acts as a low pass filter:
The seasonal cycle in high latitudes can not induce
a seasonal cycle at the equator
![Page 17: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/17.jpg)
UP to 3 Million Years Ago: Drifting continents cause Global Cooling
Shoaling Thermocline
Around 3 Million Years Ago: Glaciers Appear in high northern latitudes
Ice albedo feedback
Cold Surface Water appear in low latitudes
air-sea interactions and stratus cloud feedback
3 Million Years ago onward: Trend in global ice volume
shoaling of the thermocline*
expansion of stratus clouds
oceanic salinity
Amplification of 40K Oscillations
![Page 18: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/18.jpg)
THE ROLE OF SALINITY TEMPERATURE SALINITY
• Salinity introduces an indirect mechanism for interfering with the oceanic heat budget
The MELTING of ICE, and variations in EVAPORATION and RAINFALL can profoundly affect the oceanic circulation, hence
Sea Surface Temperatures and the Global Climate.
1. Salinity and temperature have comparable effects on density.
2. The effects of temperature and salinity are in opposition because of heavy rainfall in cold high latitudes. (This introduces the possibility of singularities.)
3. Boundary conditions for temperature and salinity are different Heat Flux = a(T – T*) …. negative feedback! Salt Flux = b(Evaporation – Precipitation) No negative feedback.
![Page 19: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/19.jpg)
Surface Salinities
![Page 20: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/20.jpg)
The Slow, Deep Thermohaline Circulation
The Shallow, Swift Wind-driven Circulation
Antarctic Circumpolar Current
D = k1/3
D2 = D*2 + /T..
![Page 21: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/21.jpg)
![Page 22: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/22.jpg)
.
![Page 23: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/23.jpg)
Temperature
Along the Equator Looking Down
Numerical Experiments in which the oceanic
surface waters are freshened in high latitudes.
Fedorov JPO
Hea
t T
rans
port
Freshening m/year
![Page 24: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/24.jpg)
1.022
1.024
1.026
1.028
Sur
face
Den
sity
gm
/cm
3
![Page 25: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/25.jpg)
![Page 26: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/26.jpg)
41 K WORLD Nonlinear WorldWarm World
Threshold
Warm World (El Nino?)
Trend + Cycles
![Page 27: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/27.jpg)
Since 3 Ma, feedbacks (glaciers, tropical stratus clouds) caused
Cooling Trends
that led to
Thresholds
followed by
Rapid Warming
followed by
Cooling Trend
Milankovitch forcing (Obliquity) is a pace maker
![Page 28: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/28.jpg)
![Page 29: The dominant periodicities are the same as those from astronomical calculations of changes in the Earth’s orbital parameters.](https://reader036.fdocuments.in/reader036/viewer/2022062516/56649d6b5503460f94a4a6c7/html5/thumbnails/29.jpg)