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TEXAS A&M / Science / Sci 251 / What is autumnal equinox?

What is autumnal equinox?

What is autumnal equinox?


School: Texas A&M University
Department: Science
Course: Oceanography
Professor: Benjamin giese
Term: Fall 2016
Tags: Oceanography, intro to oceanography, and Ocean
Cost: 50
Description: COMPLETED 'OCEANOGRAPHY 251' STUDY GUIDE FOR EXAM 2, FOLLOWING DR. GIESE'S OUTLINE: Includes all outlined/needed information for Chapters 6, 7, and 16.
Uploaded: 10/19/2016
17 Pages 9 Views 16 Unlocks

Oceanography Study Guide Exam 2 Annie Flowers

What is autumnal equinox?





Vocabulary - Definition

[Study Guide Outline Title]


Equilibrium: F = Ma

- If there is no force on the mass, there is no acceleration

• Ex. Heat in = Heat out – perfect example of equilibrium

o [Uneven heating of the earth’s surface – seasons]

▪ Earth’s axis of rotation is tilted 23.5 degrees with  

respect to…

???? Ecliptic: plane traced by Earth’s solar orbit

▪ Seasonal changes and Earth’s rotation cause unequal 

What is the effect of coriolis?

solar heating of Earth’s surface – the largest signal of  

climate change

▪ Tilt is responsible for seasons 

▪ Vernal Equinox – Spring – when Easter occurs, equator  

receives most heating

▪ Summer Solstice – northern hemisphere is pointing  

towards the sun

▪ Autumnal Equinox – Fall – equator receives most  


▪ Winter Solstice – northern hemisphere is pointing away  

from the sun – Also when Earth is closest to the sun,  Don't forget about the age old question of a person who promotes firm police action, swift and severe punishments for criminals, and more laws regulating behavior is identified as a

aka: the Earth-Sun distance-difference doesn’t really  

have to do much in regards to how hot the Earth is  

What shows the total change of the earth’s total energy change at the earth’s surface?

???? Equinox: everywhere on Earth receives 12 hours  

of day, 12 hours of night

o [Heating and Convection in the Earth’s atmosphere]

▪ Distribution of Solar Energy:

???? Concentrated solar radiation is present at low  

latitudes – high angle of incidence (Earth’s curve)

???? Solar radiation more diffused at high latitudes – If you want to learn more check out pdx.edu d2l

low angle of incidence (Earth’s curve) 

▪ Absorption vs. Reflection:

***Very important in regards to ‘Greenhouse’  

argument – bc it’s not as a result of reflection… But as a result of  absorption!! 

• Transmission/Reflection – there is no change in light, there is no  change in heat. We also discuss several other topics like even though it is a freestanding sculpture, sculpture of the lady sennuwy was made to be displayed in what fashion?

• Absorption – the sunlight comes in and it is absorbed and contained o Aka: there is a change – light becomes heat energy

▪ Ex. oceans absorb solar radiation… NOT the  


• *Reflection/absorption of solar energy = relative to the angle of  incidence on a flat sea

“So, the equator is warm and the poles are cold for two reasons…” • A: more intense sunlight at the equator

• A: less reflection at the equator

“The earth is heated by sunlight… So how is it cooled?”

(Remember heat in=heat out!!)

• A: Blackbody radiation – anything that has a temperature emits  radiation

- “Since the Earth has an temperature, it emits radiation, even though the  radiation cannot be seen – as soon as molecules start moving, they create  some regard of heat, they create and release that radiation” Don't forget about the age old question of homology vs homoplasy

• Density variations in the atmosphere:

o Convection cell – rising and sinking airIf you want to learn more check out What is the hindsight bias in psychology?

▪ Warm air rises (bc it’s less dense)

▪ Cool air sinks (bc it’s more dense)

o Differential solar heating is due to different heat capacities of  land and water: If you want to learn more check out hemaphobia

▪ Sea breeze – from ocean to land (during the day)  ???? Cool ocean creates cool air, cool air moves  

towards warm land, transfers as hot air on land,  


???? Possible because of oceans high heat capacity

▪ Land breeze – from land to ocean (during the night) ???? Land cools, creates cool air, cool air moves  

towards warm ocean, transfers as hot air above  

ocean, rises.

o Atmosphere Pressure:

▪ Cool, dense air sinks (bc higher surface pressure)

▪ Warm, moist air rises (bc lower surface pressure)


• [Coriolis Force]

• The Coriolis Effect:

o Deflects path of moving object from viewer’s perspective ▪ Moves to the right in the Northern Hemisphere

▪ Moves to the left in the Southern Hemisphere

???? All as a result of Earth’s rotation 

▪ = 0, at the equator

▪ = Greatest, at poles

▪ change in Earth’s rotating velocity with latitude

???? ex. = 0km/hr at the poles, = 1600km/hr at the  

equator (aka: around 1000 miles per hour)

▪ as the greatest impact on objects that move long  

distances across latitudes

• [Global Bands of Winds]

• Global Atmospheric Circulation:

o High pressure zones = descending air

▪ Subtropical highs – 30 degrees latitude

▪ Polar highs – 90 degrees latitude

▪ “Clear skies”

o Low pressure zones = rising air

▪ Equatorial low – equator

▪ Subpolar lows – 60 degrees latitude

▪ “overcast skies with lots of precipitation”

• Global Wind Belts:

o Trade Winds – from subtropical highs to the equator: ▪ NE Trades in N. Hemisphere

▪ SE Trades in S. Hemisphere

o Prevailing Westerlies – from 30-60 degrees latitude o Polar Easterlies – 60-90 degrees latitude

o Boundaries between wind belts:

▪ Doldrums (“Intertropical Convergence Zone) =  Equator

▪ Horse Latitudes = 30 degrees

▪ Polar Fronts = 60 degrees

• [Weather vs. Climate]

• Weather – conditions of atmosphere at particular time and place • Climate – long-term average of weather

• [Hurricanes]

o About 100 worldwide per year:

Hurricane season = June 1st – November 30th

• Hurricane – Large rotating masses of low pressure that require  ocean water warmer than 25 degrees C, warm-moist air, the  Coriolis Effect

o Result in: strong winds, torrential rain

o Classified by: maximum sustained wind speed

o Other names:

▪ Hurricane – Atlantic

▪ Typhoon – pacific  

▪ Cyclone – other

• Hurricane Origins:

o Low pressure cell

o Winds feed water vapor – latent heat of condensation o Air rises as low pressure deepens

o Storm develops

▪ As hurricanes get stronger and stronger, they begin to  

curve more

???? Tropical depression – winds less than 61km/hr

???? Tropical storm – winds 61-120km/hr

???? Tropical cyclone/hurricane – winds above 120  


• Winds:

o Cyclonic flow – counterclockwise winds around a ‘low,’ in  the Northern Hemisphere, but clockwise around a ‘low,’ in the  Southern Hemisphere 

o Anticyclonic Flow – clockwise winds around a ‘high,’ in the  Northern Hemisphere, but counterclockwise around a ‘high,’  in Southern Hemisphere 

“What cause hurricanes to be so destructive?”

• High winds

• Intense rainfall

• Storm surges – increase in shoreline sea level

o – what kills most people: elevation of water level

(the low pressure pulls up the ocean surface)  



[Evidence of Climate Change]


• Weather – conditions of atmosphere at particular time and place • Climate – long-term average of weather

o (Ocean influences both Earth’s weather and climate patterns!) [Climate System]

• Earth’s climate includes interactions of:

o Atmosphere (without atmosphere, the temperature of the  Earth would be about -17C = “Warm Earth Paradox”)

o Hydrosphere

o Geosphere

o Biosphere

o Cryosphere (where there is ice)

o ^^ all interact with each other in important ways and result  in the long-term affects in the atmosphere – it’s impossible to  understand one component of the climate system without  look at all interactions (also why it’s so hard to develop a  

model bc of all the intricate interactions)

• Climate System – exchanges of energy and moisture between  these^ spheres

• Energy Content Change Graph – shows total change of the  Earth’s total energy change at the Earth’s surface – provides for  understanding of oceans as a part of the climate system

- shows oceans are contributing almost all energy – its ability  to store energy completely overwhelms any other aspect of  the climate system

[Evidence continued]

** Carbon dioxide concentration today: 400 parts per million • Changes from Global Warming:

o Melting glaciers and ice caps

o Shorter winters

o Species distribution shifts

o Global temperature rise – Earth’s surface temp has risen .8C  in the last 140 years

o Sea surface temperature increases

• Changes in the Oceans:

o Increasing ocean temperatures: 

▪ Sea surface risen mostly since 1970

▪ Deep waters showing increases

▪ Arctic Amplification – polar ice melting

???? Loss of more than 2 million sq. km of Arctic sea  

ice in the last decade

• Loss of ice just enhances the warming due  

to lower albedo

• Albedo – how much light is reflected off  

given surface

• With contraction of sea ice, there is less  

reflection, light is then absorbed by the  

water – makes water warmer – warmer

water melts even more ice, results in even  

lower albedo absorbs more heat, contracts  

even more – aka: once triggered, the  

process becomes eminent and rapid

• = ^ ex. of Positive Feedback:

> Feedback Loops – modify atmospheric processes:

• Positive Feedback Loops – enhance initial change

• Negative Feedback Loops – counteract initial change (changes in the oceans cont...)

• Increase in Ocean Acidity: 

o Ocean Acidification – ocean acidity increases as Carbon  Dioxide from the atmosphere and dissolves in ocean water ▪ Acidifies ocean

???? Threatens calcifying organisms:

• Coccolithosphores

• Foraminifers

• Sea urchins

• Corals (bleeching)

• Rising sea level – (already occurring) 

o Main contributors:

▪ Melting of Antarctic ice sheets

▪ Thermal expansion of ocean surface waters

▪ Melting of land glaciers and ice caps

▪ Thermal expansion of deep-ocean waters

o Severely affects areas with gently sloping coastlines

▪ Ex. U.S. Atlantic/Gulf Coasts

[Natural Causes of Climate Change: “Natural Variability”] • Solar Energy Changes:

o variable energy from the sun overtime

▪ ex. luminosity

▪ ex. sunspots

• Variations in Earth’s orbit:

o Milankovitch Theory of Factors:

▪ The eccentricity of Earth’s orbit

▪ The obliquity of Earth’s axis

▪ The precession of Earth’s axis

• Volcanic Eruptions

o Volcanic ejecta may block sunlight

▪ Would need many eruptions in short time period

???? Ex. Tambora in 1815

{Predicted Changes to come:} 

o Earlier, hotter summers

o More sever droughts in some places, flooding in others

o Retreat of mountain glaciers

o Water contamination issues  

o Ecosystem changes and extinctions

[The Greenhouse Mechanism]

• - actually what allows life to exist on Earth, bc without the  Greenhouse Affect Earth would be frozen solid (Warm Earth  Paradox^)

Greenhouse Effect Process:

• visible light from the sun goes through the atmosphere and heats  land/oceans (absorption)

• land/oceans emit ‘microwave’ radiation

• gas molecules in the atmosphere absorb radiation, heating up the  atmosphere

Natural Components:

• Water Vapor

o Most important

o 66-85% of greenhouse effect

• Carbon Dioxide:

o Natural part of atmosphere

o BUT: greatest relative contribution is from human activities  (burning fossil fuels)

> Human-Caused Greenhouse Gases: 

???? Carbon Dioxide: we know CO2 is increasing (the  

average is “monotonically increasing”)  

• Made obvious when looking at the  

Keeling Curve – The record of Carbon  

Dioxide going back to 1957

• “Using Rigid Ice Mass” – we can now drill  

into ice and pull of “core of ice,” and look

for pockets of air and measure the CO2  

Concentration within the ice – some have  

gone back 800,000 years.

???? Methane 

• Second most abundant human-caused  

greenhouse gas

• Great warming power per molecule

• Landfill decompistion

• Cattle

???? Nitrous Oxide, CFC’s, Ozone = other traced gases

Global Engineering – attempts to counteract human-caused climate  change

• Goals include reducing sunlight reaching earth, removing human caused greenhouse gases

“The Ocean’s Role” 

• Ocean as “biological pump”

o Aka: as a “sink” for CO2

o Pumps from surface to deep waters

• Ocean as “thermal sponge”

o Unique thermal properties of water

o Oceans absorb much heat without changing temperature o Oceans still warming

Possibilities for Reducing Greenhouse Gases: 

• Ex. Iron Hypothesis:

o Fertilize the ocean to increase productivity

o Increase phytoplankton, increases CO2 removal from  


o Sequestering excess CO2 in oceans

• Ex. Kyoto Protocol: Failed attempt to create an International  agreement in hopes of limiting Greenhouse Gas Emissions o International agreement

o Voluntarily limit greenhouse gases

▪ Even if gas emission stablilize, Earth will continue to  

warm (“commitment to warming”

o Why it failed:

▪ Impossible to enforce

▪ Unequal contributions can be unfair

???? U.S. signed, but did not ratify Kyoto

Documenting Human-Caused Climate Change: 

• Intergovernmental Panel on Climate Change (‘IPCC’) o Global group of scientists publishing assessments since 1990 o Predict global temperature changes of 1.4-5.8C

o “climate change models can mimic modern conditions only if  human emissions are taken into account.”




Types of Ocean Currents:


• Surface Currents – ocean currents driven by wind, in primarily  horizontal motion

• Deep Currents – ocean currents driven by differences in density  caused by differences in temperature and salinity, in vertical and  horizontal motions

[Thermohaline Circulation]

Thermohaline Circulation – deep ocean circulation driven by temperature  and salinity differences in water

• Slow velocity

o Ex. ‘The Day After Tomorrow’ is NOT realistic – but rather a  very sped up, “overnight” version of process

• Formed in regions where there is sea ice

o When ice forms, sea water becomes salty

o Cold salty water is very dense

o Water sinks to the bottom

▪ Faster sinking = faster circulation

▪ Slower sinking = slower circulation

???? Aka: can regulate climate by regulating sinking

Effects of deep-water circulation: 

• North atlantic = especially sensitive

• Melting glaciers

• Warmer surface waters

[Wind Driven Circulation]

Surface Currents: (cont.)

• Occur above pycnocline 

• Result in frictional drag between wind and ocean

o Factors:

▪ Distribution of continents

▪ Gravity  

▪ Friction

▪ Coriolis Effect 

[Ekman Flow]

Ekman Spiral – describes speed and direction of seawater flow at different  depths

• Surface currents move at an angle to the wind

• Each successive layer moves increasingly to the right in the  Northern Hemisphere (Coriolis Effect) 

Ekman Transport – average movement of seawater under influence of  wind

• 90 degrees to the right of the wind in the Northern Hemisphere • 90 degrees to the left of the wind in the Southern Hemisphere • Upwelling – vertical movement of cold, nutrient-rich water to  surface

o High biological productivity 

▪ Ex. Surface Area of the Oceans:

Open ocean: 80%

Coastal Ocean: 19.5%

Upwelling Areas: .5%

▪ Ex. Productivity of the Oceans:

???? Open Ocean: .5%

???? Coastal Ocean: 50%

???? Upwelling Areas: 49.5%

• Downwelling – vertical movement of surface water downward in  water column

“Diverging Surface Water…”

• Surface waters move away from area, resulting in…

o Equatorial Upwelling

o Coastal Upwelling:

▪ Ex. > Ekman Transport moves surface seawater  


???? Cool, nutrient rich deep water comes up to  

replace displaces surface waters

• Ex. U.S. West Coast

“Converging Surface Water…”

• Surface waters move toward each other, resulting in…

o Water pile up

o Low biological productivity 

o Coastal Downwelling:

▪ Ex. > Ekman Transport moves surface seawater  

toward shore… 

???? Water piles up and moves downward in water  

column, which results in lack of marine life 

[Geostrophic Flow (Gyres)]

Geostrophic Flow – the balance of the Coriolis Effect and gravitational  forces – generated by friction

• Ekman Transports piled up water within subtropical gyres o Surface water flows downhill and to the right

Subtropical Gyres – large, circular loops of moving water centered around  30 degrees latitude, bounded by…

“Four Main Currents that into one another:”

• 1. Equatorial Currents:  

o travel westward along equator

• 2. Western Boundary Currents :

o warm waters

• 3. Northern/Southern Basin Currents: 

o easterly water flowing across ocean basins

• 4. Eastern Boundary Currents:

o cool waters

> 2. Western Boundary Currents: (Cont.) 

• Displaced toward west, due to Earth’s rotation

o Intensified in both hemispheres:

▪ Fast

▪ Narrow

▪ Deep

▪ Warm

???? Coriolis Effect contributes to this^ western  


> 4. Eastern Boundary Currents: (Cont.) 

• Eastern side of ocean basins

o Tend to have opposite properties of Western Boundary  Currents^

▪ Slow

▪ Wide

▪ Shallow

▪ Cold

Antarctic Circumpolar Current: 

• Only current to completely encircle Earth 

• Moves more water than any other current!

o Ex. of Antarctic Circulation…

▪ > Ex. Antarctic Convergence:

???? Cold, dense Antarctic waters converge with  

warmer, less dense sub-antarctic waters

• Northernmost boundary of Antarctic Ocean

▪ > Ex. East Wind Drift:

???? Creates surface divergence with opposite flowing  

Antarctic Circumpolar Current

• Polar Easterlies

▪ > Ex. Antarctic Divergence:

???? “Abundant marine life”

[“Gyres continued…”]

• Gyres or “loops” can cause loss of water volume, generating… o Warm-Core Rings – warm water trapped in a continuous  loop (aka: ring) surrounded by cool water

▪ Ex. Sargasso Sea

o Or: Cold-Core Rings – cold water trapped in a continuous loop (aka: ring) surrounded by warmer water

▪ Result in unique biological populations 

[“El Nino” - ENSO]

ENSO – “El Nino Southern Oscillation”

• “El Nino Warm Phase:” 

o Walker Cell Circulation (“normal circulation”) is disrupted o High pressure in eastern Pacific weakens

o > Weaker trade winds

o Warm pool migrates eastward

o Thermocline deeper in eastern Pacific

o Downwelling 

o Lower biological productivity

• “La Nina Cool Phase:” 

o Increased pressure difference across equatorial Pacific

o > Stronger trade winds

o Stronger upwelling in eastern Pacific

o Shallower thermocline

o Cooler than normal seawater

o Higher biological productivity

Occurrence of ‘ENSO’ Events: 

• ^El Nino Warm Phase occurs about every 2-10 years

• Highly irregular

• Phases usually last 12-18 months

• 10000-year sediment = record of events

Predicting El Nino Events: 

• Tropical Ocean-Global Atmosphere – ‘TOGA’ program  established in 1985 that monitored equatorial South Pacific through  a system of buoys

• Tropical Atmosphere and Ocean – ‘TOA’ project that continues  to monitor and research ENSO

o ** ENSO events are still not fully understood and can  result in flooding, drought, erosion, fires, tropical  

storms, and harmful effects on marine life.



10/19/16 4:06 PM

10/19/16 4:06 PM

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