Some people who take this course have already taken Geography 1013/100/103. However neither course is a prerequisite for the other.
- We spend a bit more time on Chapter 1 in Geography 1013/100/103.
- This week’s notes begin with a summary of Chapter 1 in the text: a brief introduction to physical geography.
* Note that you may be using one of two editions of Geosystems: for convenience I will use abbreviations:
– if you have Geosystems, 4th Canadian edition 2016, I will use the abbreviation: 4CE. Note an updated version of this textbook is available. Any differences in the updated version will be addressed as required.
– if you have Geosystems, 3rd Canadian edition 2013, I will use the abbreviation: 3CE
I. INTRODUCTION to Physical Geography (a summary of Chapter 1)
1. Background to the course
This course is an introduction to“physical geography” or “earth and atmospheric sciences.” Physical geography includes:
- the physical structure of the earth and atmosphere, and
- natural processes that shape the surface of the earth and atmosphere.
- the distribution of living organisms within the earth/atmosphere system
a. The study of the physical structure of the earth and the processes that shape the earth is called geomorphology
- (“geo” = earth; “morph” = form/shape; “ology” = study of).
- This is the focus of GEOG 1013/102/100: rocks, glaciers, rivers, erosion, landslides, earthquakes, volcanoes, etc.
b. The study of the atmospheric structure and processes includes two parts
i. climatology – the study of climate and long-term atmospheric conditions: for example, tropical versus arctic climates
ii. meteorology – the study of weather and day-to-day atmospheric conditions: for example, hurricanes, tornadoes, high pressure, dew point, etc..
- These are components of GEOG 1023/101/102.
c. The study of the distribution of living organisms is called biogeography. This is also studied in GEOG 1023/102/101
These sciences are all aspects of a broader discipline called “geography.” “Geography” literally means “description of the earth” (from the Greek words: “geos” – earth, and “grapho” – write).
As soon as you start recognizing that things are different in different locations – whether it’s noting that there is a creek here and not over there, or that there is a house over there and not here – you are studying geography! When you walk/cycle/drive from one place to another, you are doing geography! Geography seeks to describe and explain the differences that occur in different places.
- Those differences can be naturally occurring (hills, soils, trees, weather, climate)
- Those differences can be human (towns, roads, political boundaries, industries, ethnic groups)
Geography, along with history, philosophy, and religion, is one of the oldest disciplines of study. It first developed with the early Greeks who were concerned about the nature of the universe and the origin of things.
- For example: Herodotus 484-425 BC), historian of the Persian Wars, spent much time discussing the lands, peoples, economies and cultures of the Persian Empire in order to explain the causes and progression of the wars.
- Strabo (64 BC – 20 AD) defined geography as the attempt to “describe the known parts of the inhabited word … to write the assessment of the countries of the wood (and) to treat the differences between countries. “
- measured the earth
- devised the first longitude/latitude grid
- drew sophisticated maps
- described known territories physically, socially and culturally
- tried to explain climatic and cultural variations
- described river systems
- discussed cycles of erosion and deposition
- discussed the dangers of deforestation
- emphasised that humans are active participants in a cultural – physical partnership
Geography has been described as the “mother of all sciences” because from it have sprung: meteorology (weather), climatology (climate), geomorphology (landforms), geology (rocks and minerals), environmental studies, soil science, sociology, economics, urban studies, political science, cultural anthropology, etc. These disciplines tend to look at specific aspects of the world in isolation from other influences and forces. But the real world is not like that. Economic activity happens in a real world context. Soils exist within a complex matrix of climate, weather, geology, biology, and human activity.
The Earth is a complicated place! Human activity and natural processes are intimately inter-related. Geographers try to look at things holistically (as a complex, interconnected whole). Geographers try to see the Earth as a complete entity: an interacting set of physical, chemical and biological systems that also interact with human behaviour, economics, and political processes to create the physical and social landscape we experience.
For instance, human activity dramatically impacts the physical environment:
- Human decisions to build coal-fired electricity generating plants will impact the local region where the plant is built (environmentally, socially, and economically), will require coal to be mined and transported in other regions (environmental, social, and economic implications), and will impact other lakes, forests, and grasslands by producing airborne and water-borne pollution. The choice to produce electricity by burning coal also has implications on the development (or NON-development) of other energy possibilities such as hydro-power, wind-power, etc.
The physical landscape influences human behaviour:
- Human settlement patterns are directly related to physical realities such as the location of mountains, rivers, and lakes, and global patterns of weather and climate. You don’t see major cities located in the high Arctic, in major mountain ranges, in the middle of the Pacific Ocean, or in the middle of hot deserts!
Today geographers consider (among other things):
- nature of the physical environment and human interactions with it
- patterns, causes and possibilities of human settlement, economic, social and political activity
It is important to note that those who study the earth and atmospheric sciences do so recognising that their field of study is intimately interconnected with other areas of research, including social sciences like sociology, economics, anthropology, political science, and human geography.
In most major universities, geography departments offer degree programs in either the arts or sciences:
- you can do a B.A. in geography (emphasizing the human side – cultural studies, economic location, urban planning, etc.). This is usually called “human geography.” It is often subdivided into urban geography, cultural geography, historical geography, and economic geography. These graduates often go into urban planning, architecture, economic development (especially in the Third World), education, community services, social services, missions, and other people-related careers.
- Or, you can do a B.Sc. in geography (emphasizing the natural science side – geomorphology, meteorology, climatology, biogeography, etc.). This is either called “physical geography” or “earth and atmospheric sciences.” Most universities offer “environmental studies” majors which combine several aspects of physical geography. These graduates often work in environmental services, parks, government and private industry, education, and overseas in development and missions.
In either case, the interconnectedness between all of the disciplines is recognized. Human geographers do consider the influence of natural processes. And physical geographers account for human influences upon natural processes.
3. Why bother ?
Are these courses relevant? Why bother study these processes at all?
To try to communicate some of my enthusiasm and passion for geography, earth and atmospheric sciences (as a pastor!) I want to suggest that these courses are critical components of your educational experience for several reasons:
a. It’s practical! We live in the real world of rocks, hills, seasons, thunderstorms, cities, highways, and countries which physical geography studies! You experience this “stuff” as you walk in the woods or feel the westerly wind! You will find that you look at your everyday world differently because of this course.
b. As you take these courses you will discover why your local topography (the shape of the land – hills, rivers, lakes, etc.) is the way it is! And you will understand the processes that continue to shape it. You will know where to drill a well and drill for oil. You will know where it is safer to dump your garbage and build drainage field (and where it is definitely not safe to do so!). You can make smarter real estate choices! Hey … as a parent, I’m even able to help my kids figure out how best to dam a stream!
c. You will begin to understand the natural processes that determine your climate. And you will begin to explore the debate on climatic change (global warming, the greenhouse effect) and how that will affect your life. Are you from a farm background? What are the global climatic trends going to mean for you? What do they mean for the most vulnerable people in the world?
d. You will begin to understand weather patterns that influence your region – you will know the tell-tale signs of thunderstorms and tornadoes … and the signs of a peaceful summer day! You will know what to wear in the morning! It may save you a soaking next summer when you’re out fishing on the lake!
e. You will discover practical ways to be a more environmentally conscientious person!
f. You will learn things! You will know why the sky is blue! You will know why mountain lakes are turquoise! You will know why Greenland is not really green and heating costs in Iceland (and Medicine Hat, Alberta) are among the lowest in the world!
g. You will be able to make wise choices.
- You will know the best part of town to buy real estate (yes, it’s true!)
- You will begin to appreciate how decisions you make – about everything from what you buy to how you spend your spare time – can impact your environment for good, or for bad.
h. The Greeks were right! Study of the earth/atmosphere are the fundamental sciences upon which all others – biology, chemistry, physics, etc. – are built. If you do go on to study other sciences, you will have an excellent foundation! If you end up in missions anywhere in the developing world, earth and atmospheric sciences issues (for instance: soil erosion, clean drinking water, proper sanitation, soil fertility, and severe weather prediction), are among the most critical needs. This course will give you a great beginning to be able to give some practical help and knowledge to people most in need in developing countries.
i. You will grow spiritually! In Scripture, God is Creator of the earth, atmosphere, and the entire physical universe. As we study about the earth and atmosphere, we are studying about God! The study of God is theology (Greek, “theos” = God). This course is really a study in theology because we are studying what God has made! Rather a different way of looking at it, eh? (Try to remember that as you’re studying for the mid-term!)
Johannes Kepler (1571-1630), an astronomer, studied planetary motion, optics, and mathematics (we have him to thank for calculus!); he wrote that his pursuit of the natural sciences was “thinking God’s thoughts after Him.” Kepler was a faithful Christian, who saw his scientific research as a spiritual journey to better understand the Creator through His creation. In this course, as we study God’s creation, we are also exploring “God’s thoughts;” understanding something of the mind of the Creator by beginning to understand His amazing creation!
Sir Isaac Newton (1642-1727) – physicist, mathematician, and astronomer – wrote, “This most beautiful system of the sun, planets, and comets could only proceed from the counsel and dominion of an intelligent and powerful Being. And if the fixed stars are the centres of other like systems, these, being formed by the like wise counsel, must be all subject to the dominion of One … This Being governs all things, not as the soul of the world, but as Lord over all.” (Newton, commenting on the amazing complexity and intricacy of creation, is also reported to have said: “In the absence of any other proof, the thumb alone would convince me of God’s existence.”)
Carl Linnaeus (1707-1778), the botanist who created the “scientific names” for species (e.g. the American Robin is turdus migratorius … yes, it really is!), believed that God created in orderly fashion and part of our role as humans is to discover that order. Then we can make wise choices.
We can certainly learn the most about God through the book of God’s Word, the Bible. But we can also learn much about God by studying the book of God’s works, His creation. Through the study and care of His creation we can develop a closer relationship with God Himself.
As you study this course, TRY to keep in mind that the mountains, rivers, glaciers, and other landforms we study — that the processes of weathering, erosion, etc — are all created by God! As we study them, we study God’s handiwork! We are walking through His art gallery! And we are learning about the amazing processes by which God sustains and continues to actively shape His world. We are studying God’s world!
That’s why I, as a pastor, and also passionate about earth and atmospheric sciences! My faith in God and my enjoyment of the natural world that God created go hand-in-hand! As I learn more about the wonder of God’s world, my wonder at the glory of God grows! I worship God better as I develop a deeper appreciation of His incredible work in creation!
Now on to Chapter 2 …
In the beginning God created the heavens and the earth. The earth was formless and empty, and darkness covered the deep waters. And the Spirit of God was hovering over the surface of the waters.
Then God said, “Let there be light,” and there was light. And God saw that the light was good. Then he separated the light from the darkness. God called the light “day” and the darkness “night.”
And evening passed and morning came, marking the first day.
Then God said, “Let there be a space between the waters, to separate the waters of the heavens from the waters of the earth.” And that is what happened. God made this space to separate the waters of the earth from the waters of the heavens. God called the space “sky.”
And evening passed and morning came, marking the second day.
Then God said, “Let the waters beneath the sky flow together into one place, so dry ground may appear.” And that is what happened. God called the dry ground “land” and the waters “seas.” And God saw that it was good. Then God said, “Let the land sprout with vegetation—every sort of seed-bearing plant, and trees that grow seed-bearing fruit. These seeds will then produce the kinds of plants and trees from which they came.” And that is what happened. The land produced vegetation—all sorts of seed-bearing plants, and trees with seed-bearing fruit. Their seeds produced plants and trees of the same kind. And God saw that it was good.
And evening passed and morning came, marking the third day.
Then God said, “Let lights appear in the sky to separate the day from the night. Let them be signs to mark the seasons, days, and years. Let these lights in the sky shine down on the earth.” And that is what happened. God made two great lights—the larger one to govern the day, and the smaller one to govern the night. He also made the stars. God set these lights in the sky to light the earth, to govern the day and night, and to separate the light from the darkness. And God saw that it was good.
And evening passed and morning came, marking the fourth day.
Genesis 1:1-19 (NLT)
There is an introductory video here: http://youtu.be/aIVHXtWMLzE
A. The Solar System, Sun, and Earth
Read page 44 in the text – the introductory section on “The Solar System, Sun, and Earth.” This section simply sets the context of the earth in the universe. Hopefully this is common knowledge. I’ll assume you know most of it. You will not be tested on this. Isn’t it exciting to think about how awesome the God who created this must be!
Begin studying on page 45 4CE (p.44 3CE) “Solar Energy: from Sun to Earth.”
1. Solar Energy
All the earth’s natural systems require energy in order to function. The primary source of energy that fuels the Earth’s natural systems is the sun.
The sun produces radiant energy and solar wind through the process of nuclear fusion.
- Fusion refers to the process by which hydrogen atoms, under intense pressure and high temperatures, are forced together to produce helium atoms and energy. This process is the process by which the sun creates energy — which reaches Earth and makes life possible!
For cool, current solar images, click here.
2. Solar Wind
One by-product of solar nuclear fusion is a cloud of electrically charged particles
- electrically charged particles are called ions.
This cloud, called the solar wind, travels over 2,000,000 km/h, taking 3 days to reach Earth.
This solar wind is not constant. It appears to be strongest during periods of increased sunspot activity (why? we can only speculate). There is an average 11 year cycle from maximum to minimum sunspot activity, although there is much variation! Thus there is also much variation in the solar wind, although it, too, follows an approximate 11 year cycle. For more on the solar cycle, see this link.
The solar wind, combined with other “stuff” from Earth-asteroids encounters, to meteor showers, to solar flares, is referred to as “Space Weather” …
When these ions interact with the earth’s magnetic field (or magnetosphere), they are deflected toward the north or south poles.
Some of the effects of these interactions between solar wind ions and the earth’s magnetic field include:
a. Auroras: solar radiation ionizes (passes on electrical charges to) atoms and molecules in the atmosphere, 80-500 km above polar regions. The atmospheric molecules then become electrically charge particles (ions). These atmospheric ions reradiate the electric-magnetic energy as light (they appear to glow). These are:
- the aurora borealis (or Northern Lights) and
- the aurora australis (or Southern Lights).
There are many excellent aurora sites (complete with photos and videos) online … check out:
- University of California Aurora Page
- Michigan Tech Aurora Page
- BBC – Future – Science & Environment – Northern Lights: More than just a pretty light show
- BBC News: How solar storms create the Northern Lights
- cool video: Northern lights: spectacular footage captured in Iceland – video | Travel | guardian.co.uk
b. Weather: Solar wind/sunspot activity appears to affect weather on Earth (although no one knows why).
- Periods of increased sunspot/solar wind activity are strongly correlated with wetter conditions in mid-latitude regions of the world (like Canada, the United States, and Europe).
- Periods of decreased sunspot/solar wind activity correlate with drier/drought conditions in mid-latitude regions of the world (like Canada, the United States, and Europe).
3. Radiant Energy
Every object (including the sun and the Earth) emits radiant energy (provided its temperature is above absolute zero, -273°C).
Radiant energy is emitted in a variety of wavelengths, only a small range of which is visible to the human eye as visible light.
- The range of radiant energy is referred to as the electromagnetic spectrum. See Figure 2.5, “A portion of the electromagnetic spectrum…” p.48 4CE (p.46 3CE).
Radiant energy from the sun is composed of:
- 8% gamma, X-, and ultraviolet wavelengths
- 47% visible light wavelengths
- 45% infrared wavelengths
See Figure 2.6, “Solar and terrestrial energy distribution by wavelength,” p.48 4CE (p.47 3CE)
There are some principles to this electromagnetic radiation:
- at low temperatures, radiation is low intensity and long wave.
- at high temperatures, radiation is high intensity and short wave.
- the amount of solar radiation received diminishes with distance from the sun (Pluto receives less solar energy than Mercury)
- some radiation is able to penetrate matter (x-rays); some is absorbed (transferred from radiant energy to thermal/heat energy); some is reflected.
- some radiation may be scattered as it strikes gas molecules, water droplets, ice crystals, and pollutants in the atmosphere.
The sun emits mostly short wave radiation, which we see as visible light (much of the sun’s energy is emitted in the visible light spectrum, relatively short wave lengths).
The earth emits mostly long wave radiation, which we cannot actually see (much of the earth’s radiated energy is in the infrared portion of the electromagnetic spectrum, relatively long wavelengths).
B. Energy at the Top of the Atmosphere
The top of the Earth’s atmosphere is called the thermopause. This is located approximately 480 km above the Earth’s surface.
At the thermopause, Earth intercepts only a minute fraction (one two billionth) of the energy which the sun emits.
The energy the Earth does intercept is referred to as incoming solar radiation or insolation (Not to be confused with insulation … the pink fiberglass stuff in the walls and attic of your home!).
NOTE: InsOlation is incoming solar radiation!
InsUlation is the pink fiberglass stuff in your attic!
The average amount of insolation received at the thermopause is 1372 W/m2 (watts per square meter). This average value is called the solar constant (also called irradiance … you don’t need to know this term, but if you run across it, it means the same as “solar constant”). Generally, this figure is constant over time. But it may vary, annually, by several watts). These variations may, potentially, influence global climates.
As much as 50% of this insolation received at the thermopause is lost as it makes its way through the atmosphere, before it reaches the Earth’s surface. It may be lost as some is:
- reflected back to space,
- absorbed by clouds or atmospheric particles, or
- refracted and scattered in the atmosphere itself.
Because the earth is approximately spherical, different points on the surface receive insolation at different angles (See Figure 2.8, “Insolation receipts and Earth’s curved surface,” p.50 4CE (p.48 3CE). Notice:
- At the point on the surface closest to the sun, insolation is most concentrated and travels through the least atmosphere (least loss of energy) – thus maximum insolation is received at the surface at the point closes to the sun. (in Figure 2.8, the Equator receives the most insolation)
- At points on the surface further from the sun, energy is more diffuse and travels through a lot of atmosphere (more loss of energy) – thus, less insolation is received at the surface further from the sun (in Figure 2.9, the poles receive the least insolation).
Because the earth is tilted on its axis, the same point on the surface is not always closes to the sun!
- On March 21 and September 21, the equator is the closest, the poles are furthest.
- On June 21, the Tropic of Cancer (23½° North latitude) is the closest, the South Pole is furthest.
- On December 21, the Tropic of Capricorn (23½ ° South latitude) is closest, the North Pole is furthest.
Thus the daily insolation received at the top of the atmosphere varies.
- Study Figure 2.9, “Daily insolation received …” p.50 4CE (p.48, 3CE):
This is graph of insolation at every point on the Earth throughout the year.
- Note latitude is graphed on vertical axis (the sides) and months of the year are graphed along the horizontal axis (bottom).
- The lines on the map indicate insolation.
Consider March 21 (Dotted line – Vernal equinox):
- The sun is directly over the Equator.
- Maximum insolation (400+ W/m2) occurs over the equator.
- Insolation decreases symmetrically toward the poles.
Consider June 21 (Summer solstice):
- The sun is directly over the Topic of Cancer.
- The South Pole receives 0 insolation (because of the tilt of the earth it has 24 hours of darkness).
- The North Pole actually receives a bit more insolation (550 W/m2) than the Tropic because it receives insolation 24 hours per day! However the insolation is more intense at the Tropic.
Consider September 21 (Autumnal equinox):
- The sun is directly over the Equator.
- Maximum insolation (400+ W/m2) occurs over the equator.
- Insolation decreases symmetrically toward the poles.
- This is the same as March 21.
Consider December 21 (Winter solstice):
- The sun is directly over the Tropic of Capricorn.
- The North Pole receives 0 insolation (because of the tilt of the earth it has 24 hours of darkness).
- The South Pole actually receives a bit more insolation (550 W/m2) than the Tropic because it receives insolation 24 hours per day! However the insolation is more intense at the Tropic.
- This is the exact opposite of June 21.
C. Seasonal Variation
The Earth revolves around the sun – this takes 365.24 days … we call it one year! It is significant to note that the Earth’s orbit is not perfectly spherical – the Earth is a bit closer to the sun during our (Northern Hemisphere) winter than our summer. (To ponder: what might the implications for Northern Hemisphere climates be if we were further during our winter and closer in summer? What would our summers be like? What would our winters be like?)
The Earth rotates on its axis — takes approximately 24 hours. This is responsible for tides. This is also responsible for the sun’s apparent east-west movement and our cycle of day and night. If the Earth didn’t rotate at all, our day/night cycle would be 365.24 days long, too! For an awesome view of the earth, showing the current position of day and night, click here.
See Figure 2.12, “Earth’s revolution and rotation” p.53 4CE (p.51 3CE)
Understand these two concepts!
The Earth is tilted on its axis 23.5°. That’s why our day/night length varies and why insolation varies during the year (See Figure 2.13, “The plane of the Earth’s orbit …” p.54 4CE (p.52 3CE)).
The sun is constant — earth moves! But it appears to us as if the sun moves! So we speak of the sun’s altitude (it’s apparent angle above the horizon).
- See Figure 2.3 p.57 4CE (p. 56 3CE), “Seasonal observations …” To understand the seasons, click here.
Day length is one effect of seasonality.
- Study Figure 2.2 p.57 4CE (p.53 3CE) “Annual march of the seasons” .
The summer solstice (June 21) and winter solstice (December 21) are times when the sun’s declination (position over the earth’s surface) is furthest north (23.5° N. latitude, the Tropic of Cancer) and furthest south (23.5° S. latitude, the Tropic of Capricorn). This is when the days are longest or shortest.
- During the summer solstice, the northern hemisphere receives maximum insolation. The earth’s axis is aligned so that the northern hemisphere is closest to the sun. The sun is directly over the Tropic of Cancer (23½° N). Find this on Figure 2.2 p.57 4CE (p.53 3CE), “Annual march …”
- Regions north of the Arctic Circle (66.5° N latitude) receive 24 hours of daylight. The southern hemisphere receives minimum insolation (regions south of the Antarctic Circle, 66.5° S latitude) receive no insolation – the sun never rises!
- The opposite is true in the winter solstice. Find this on Figure 2.2 p.57 4CE (p.53 3CE), “Annual march …” The earth’s axis is aligned so that the southern hemisphere is closest to the sun. The sun is directly over the Tropic of Capricorn (23½° S).
- Regions south of the Antarctic Circle (66.5° S latitude) receive 24 hours of daylight. The northern hemisphere receives minimum insolation (regions north of the Arctic Circle, 66.5° N latitude) receive no insolation – the sun never rises!
The Vernal (or Spring) equinox and the Autumnal (or September) equinox occur on March 20/21 and September 21-23 when the sun is directly over the Equator. All locations on the earth receive exactly 12 hours of daylight and 12 hours of darkness. The earth’s axis is “straight up and down (as in Figure 2.8 “Insolation receipts …” p.50 4CE)
Dawn is the period of diffused light before the sun actually rises.
Twilight is the period of diffused light after the sun has set. During these periods the sun’s rays may be reflected or refracted within the atmosphere so we see sunlight even when the sun itself is below the horizon.
The lengths of dawn and twilight are functions of latitude (because of the amount of atmosphere the insolation passes through):
- At the equator, the sun’s rays pass through little of the sun’s atmosphere – causing a short dawn/twilight – approximately 30-45 minutes.
- At our latitude, insolation passes through considerable atmosphere – causing a longer longer dawn/twilight – up to 2.5 hours.
- The poles receive up to 7 weeks of dawn/twilight – because the sun has to travel through so much atmosphere! – they should receive 6 months of darkness; they actually only receive about 2.5 months.
D. Terrestrial (Earth) Radiation
The earth re-radiates much of the insolation from the sun. It also creates a small amount of energy of its own – the core of the earth is very hot (2600°C); some of this heat reaches the surface as volcanoes, hot springs, etc. However most terrestrial (Earth) radiation is a re-radiation of solar energy
The earth radiates energy in several ways:
- Some is reflected or scattered in the atmosphere (by clouds, gas molecules and pollution) and some is reflected from the surface directly back to space.
- Some is absorbed by the atmosphere/surface, changed into thermal energy, and re-radiated at longer wavelengths (mostly infrared)
- See Figure 2.6 “Solar and terrestrial energy distribution …” p.48 4CE (p.47 3CE). Note the orange line representing Earth’s infrared emission to space.
- See Figure 2.7 “Earth’s energy budget simplified” p.49 4CE (p.47 3CE). Note that Solar input tends to be shorter wavelengths (visible, shortwave infrared), while Earth’s output tends to be longer wavelengths (thermal infrared – heat energy).
- This reradiated thermal infrared (heat) energy is often reabsorbed in the atmosphere – it is trapped – this makes our atmosphere warm enough to live in.
E. Energy Transfers
Energy cannot be destroyed, but can be transformed and transferred (This is called the first law of thermodynamics).
Within the earth-atmosphere system this implies that the insolation cannot be lost, but may be redistributed or transferred by a variety of processes. This is critical! Remember that for much of the year two regions on the earth (north and south of the Arctic/Antarctic Circles) receive no insolation at all! If no heat was transferred to these regions, the temperature would drop to intolerable levels!
At the global scale, thermal energy (heat) is transferred to different regions by:
- warm air masses (50% of energy flow). Air masses from more temperate regions carry heat to the poles.
- atmospheric moisture (20%). Moisture in the atmosphere carries latent heat (to be discussed later), that results in a transfer of heat energy poleward.
- warm ocean currents (30%). Surface ocean currents tend to flow from the tropics toward the poles. Thus heat absorbed water in tropical regions is carried poleward.
- See Figures 6.18, p.165 4CE (p.155 3CE) “Major ocean currents” and 6.20 “Deep ocean thermohaline circulation” p.168 4CE (p.159 3CE).
Thus polar regions are “warmer” (believe it or not!) than might be expected during winter months, even when they receive no insolation! Were it not for the poleward flow of energy by air masses, moisture and currents, the poles would be MUCH COLDER during their winters, because they receive absolutely no direct solar radiation for several weeks/months each year.
This is also responsible for continentality – coastal areas tend to be warmer than inland areas at the same latitude.
Coastal areas receive the heating benefit of all three factors. Inland areas receive diminished effects of warm air masses and atmospheric moisture. Ocean currents have negligible effects, except as related to the other two (as in El Niño).
- Thus Vancouver is much warmer (and wetter) in the winter than Regina (although they are at approximately the same latitude. Vancouver receives warming from warm air masses, atmospheric moisture and ocean currents. However Regina does not receive these benefits.
To review …
Check out the resources at www.masteringgeography.com.
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Scripture quotations marked (NLT) are taken from the Holy Bible, New Living Translation, copyright © 1996. Used by permission of Tyndale House Publishers, Inc., Wheaton, Illinois 60189. All rights reserved