Youth Science – The Water Planet Lesson 3 – Climate
This is a word we have heard many times over the last decades.
Climate change, increased wildfires, more hurricane landfalls, Mississippi River flooding, warmest months on record, and more.
For some, these are controversially linked, for others they are following the climate model’s science has been working over the last few decades. But what is climate? How does it work? And what role does the ocean play in controlling all of this?
First let’s differentiate climate from weather. Weather is atmospheric conditions that occur over a short period of time, say 30 hours. Climate is longer, say 30 years. When we talk about the weather, we talk about whether we will need to bring a jacket or raincoat to school. With climate we talk about the fact we live in a warm humid part of the country, and that is not going to change tomorrow – or next year. With climate we know that the southeastern United States is warm and humid. There tends to be a lot of rainfall, Pensacola being one of the highest areas with about 60 inches of rain each year. The southwestern United States is different. It is warm yes, but it is not humid, and rainfall is scarce – some areas may receive less than 10 inches in one year. Because of the humidity and rainfall difference, in the southeast we find forest and swamps – in the southwest deserts and chapparals. And, of course, the wildlife difference is noticeable as well – alligators and catfish in the southeast, roadrunners and tarantulas in the southwest. Yes, the climate is different – but why?
There are a couple things we will need to expand on to better understand the climatic differences we find in our country – and yes, the northwest is very different from the northwest as well.
You might recall in The Water Planet Lesson 1 we discussed the polarity of the water molecule and this made water the “universal solvent”. The polarity allows water to dissolve lots of compounds like salt, metals, and even rock (even given enough time). But we failed to mention in that lesson that because water is polar and acts like a magnet, it is attracted to other water molecules as well. When you place a lot of water molecules together, they literally bond together. It would be like placing a lot of magnets in a bag together, they would all connect to each other. The bonds holding water molecules together are known as hydrogen bonds. They are not very strong, moving water around is enough energy to break them apart, but they are bonded together none the less. These bonds make it harder for increased air temperatures to warm the water. If you place one cup of sand on a hot plate, a cup of water on a hot plate, place a thermometer in each, turn both hot plates to high, you will notice the sand warms faster. This is because the energy from the hot plate with water must first break the hydrogen bonds holding water together before the water can begin to absorb the heat.
We notice this in our local waterways. Right now, mid/late October – the air is beginning to cool. As we enter November, we find our selves wearing jackets more often. However, we can still swim in the Gulf of Mexico comfortably – it’s when we get out that it gets cold. In the spring it is the opposite. We have just finished a cold winter. Air temps have been cold enough we have needed to wear jackets, and sometimes gloves, and then spring comes. The air warms and we run and jump into the Gulf only to find it is still cold. Because of this we say water has high heat capacity. It holds on to heat longer than air and soil, and it takes longer to warm it up (and cool it down). This is important in why the country’s climates are different.
Next is where and how the sun’s rays hit the earth. Of course, the world is round – 360°. If you draw a line from top to bottom you have the geographic north and south pole. If you draw one side to side (across the middle) you have the equator.
And we know that the planet is tilted at 23.5°.
And we know that it remains in this orientation as it spends the year revolving around the sun. We understand that the most direct rays of the sun strike the earth at the equator – and that is where you find the warmest temperatures on the planet.
But as it revolves around, the direct angle of the sun’s rays are not always directly on the equator (see illustration above). We have labeled the equator as 0° Latitude. As you move north towards the north pole. The angle being formed increases.
Here you can see the change in latitudes from 0° (equator) to 90°N (north pole) – the same happens when looking south – 0° (equator) to 90°S (south pole). Remember that the earth (and hence the equatorial line) is actually tilted at 23.5°. The sun’s rays hitting will be directly on the equator. But as the planet revolves around the sun, those direct rays move off of the point of the equator and drift south. However, they do not move any further south than 23.5°S. They reach 23.5°S on December 21 – the winter solstice. For those in the southern hemisphere – this is the longest day of the year. For us in the northern hemisphere – the shortest.
As we continue around the sun – beginning on December 22 – the direct rays begin to move back towards the equator – reaching it on March 21 – the spring equinox. It is called the equinox because when the rays are directly on the equator the length of the day is “equal” – 12 hours of sunlight, 12 hours of darkness.
The earth continues to revolve around the sun and on March 22 the direct rays are now slightly north of the equator. They will reach 23.5°N on June 21 – the summer solstice – our longest day of the year, and the shortest for the southern hemisphere.
We continue to revolve on June 22 and will again reach the equinox on September 21 – the fall equinox, equal daylight and darkness, and the process continues, as it has been for millions of years.
This area of the earth between 23.5°N-S where the sun’s rays hit directly is known as the tropics, and we have an image in our minds of what the tropics are like. Warm, sometimes hot, palm trees, jungles and rainforest. And it is. But some portions of the tropics are not like this at all. Some portions are warm, dry, massive deserts with little noticeable life. This is not our image of the tropics, but it can be.
Why such a difference? More to come.
Between 23.5°N-S and 60°N-S is the temperate zone. This region of the planet is between the tropics and the poles. It experiences weather and climate influences from both. There are warm-hot summers and cool-cold winters. They have a true spring and fall season. As fall comes (and the earths orientation to the sun changes) cold air from the polar region reaches further south meeting the warm tropical air from the south. These collisions of air masses create great exchanges of heat and energy and form storms that you do not find in either the tropics or the polar regions. Tornados, hurricanes, nor’easters are storms the temperate region deals with each year.
Between 60°N-S and 90°N-S is the polar region. Like the tropics, we have an image of what this part of our planet is like. Cold, barren, ice, penguins, and polar bears. A place we really do not want to live – but some people do! It is the land of the “mid-night sun” because in summer, the sun never sets here. The poles in the summer are pointing directly at the sun and it never goes below the horizon. It only lasts a couple of months, but it is a really neat phenomenon.
Pensacola is lying at 30°N and much of the Florida peninsula is below that. This is only 6.5° north of the tropic line of 23.5°. each degree latitude is about 60 miles so this would make us 390 miles north of the tropics. The Upper Florida Keys begin at 25°N and Key West is at 24.5°N. This places Key West just 60 miles north of the tropics.
Think of Key West and compare this to Pensacola…
Do you think of Key West as being more tropical than Pensacola? Most would say, very much so. Due to this climate change between the two cities there are very different plants and animals living there. Key West is known for coral reefs, green iguanas, and tropical palms. Pensacola is more temperate with colder winters, pine trees, and sandy beaches. We can actually see a change in Florida’s climate as you drive down the panhandle and then begin to head south. As soon as you cross the Suwannee River the landscape and biology changes. Florida is referred to as sub-tropic, and you can see why. We are not technically in the tropics, but close. Florida’s climate is very different than Georgia’s or Tennessee’s, who are more temperate. Then continue north to Michigan and New York – very different, but not polar! You will need to travel to northern Canada before you begin the experience the polar climate.
So, we now understand our position on the planet and how this effects our climate. But what about that question we had at the beginning… why are some places in the tropics wetter and more forested and others drier and desert like?
Let’s look again at Pensacola – Latitude 30°N. Hot in the summer… very hot sometimes. Lots of rain – 60” or more. Forested with pine and oak. Lots of rivers and bays. A great variety of wildlife like mammals, reptiles, and birds. Hurricanes are common and tornados do happen. Humidity is high, you are going to sweat if you live here. Biting insects are common.
Then there is San Diego California and Tijuana Mexico – 32°N. Hot in the summer also… sometimes very hot. Very little rain – about 12” each year. It is a more desert like environment with cactus, mesquite and Joshua trees and roadrunners being found. Hurricanes and tornados are not common here. Humidity is very low; people do not sweat there as they do here.
Basically, the same latitude – same position on the planet – but two different climates. What’s up?
The ocean plays a part here.
We know that 70% of the surface of the planet is covered by water – 90% of that are the oceans. We know that water is a polar molecule and that as the direct rays of the sun hit the tropical oceans it warms this water up – albeit slowly. We know that the mean ocean temperatures in the tropics are in the 80°F range, and we would expect as you move north away from the tropics, the ocean would cool – reaching near freezing in the polar seas – and they do. But the water in the ocean is not sitting still, it is moving.
The world is rotating once every 24 hours. We are rotating towards the east. We know the sun rises earlier in Jacksonville than it does here in Pensacola – and the sun will rise 2 hours after us in San Diego. Think of it as a bus driving down a highway. Jacksonville is in the front seat and will see the sun first. Pensacola is in the second row and San Diego is in the fourth row. As this “bus” drives into the Atlantic Ocean the water will hit the front windshield and flow over the bus, moving from Jacksonville to Pensacola and eventually to San Diego. So, in a way, the water is moving from the east to the west. If you test this idea in the ocean to see if it is true (using the scientific process and repeat this test as many times as time and money will allow) you will see that buoys dropped at ocean near Africa do in fact flow across the ocean to the United States. These are the large ocean currents known to the early sailors (see lessons in Nature of Science) and charted. They do exist.
The water along the equator is within the tropics and receiving direct rays from the sun. Like tropic continents and islands, it is warmer here. The tropical oceans are very warm. This warm water flows westward carry heat with it. When water reaches the United States, it is forced northward out of the tropics and into the temperate region – where it is colder. But, because the water is polar and the ocean holds on to heat longer than air does, the warm ocean water (holding its heat) flows north much further than the tropical air – and this warm water flows along the coast of the temperate United States. Off of Miami you would expect a tropical climate and warm ocean – and you would have it. As you reach Jacksonville you would expect a colder climate and cooler ocean. Colder yes, the ocean cooler… not so much – the “Gulf Stream” is still warm (remember water holds heat longer). Off of North Carolina (where it snows sometimes) the Gulf Stream is still very warm. This current eventually flows off of North Carolina towards Europe and passes the island of Bermuda on the way.
Bermuda… what comes to mind when you think of the island of Bermuda?
Many think of tropical plants, coral reefs, and men in Bermuda shorts. Pretty close to correct. But the latitude of Bermuda is 32° N – it is due east of Charleston SC. It has palms, remnant patches of mangroves, and coral reefs. But at this latitude you would not expect this – the ocean temperature is the reason why you have it.
Eventually the ocean current cycles back to Europe. This is how the ancient sailors navigated the trip. Leaving Europe, you would head south and pick up the ocean currents heading to the equator. From there you would ride those currents across the equator, through the Caribbean Sea to the new world in Virginia. The return trip home would put you in the Gulf Stream heading north and eventually back to Europe. Across the north portion of this loop the sea would eventually lose its heat and the temperatures would drop. But they were still warmer than the surrounding the sea when they reached Ireland. Southern Ireland is at latitude 51°N – almost past the 60°N mark for entering the sub polar region – and, except for the higher elevations in the mountains (another factor in determining climate), it does not snow here. However, just across the Irish Sea in England, it snows a lot. This climatic phenomena is due to the ocean currents bringing warm water to their coastline and impacting their climate.
As the ocean currents head south passing Ireland and Europe heading towards Africa it becomes cooler. The temperatures of these colder ocean currents drop from the 70-80°F we see along the United States to 50-60°F range. Here large kelp forest grow (they love colder water) and corals are very rare. And this colder water also reduces the humidity in the coastal air – rainfall decreases – and deserts form. In the northern reaches of this zone there is what we call the “Mediterranean Climate”. It is not warm enough for deserts, but it is much drier. Sparce vegetation, maybe cactus, think of southern Spain, Morocco, and coastal Italy. Further south is the Sahara, the desert we were talking about. The ocean currents eventually reach the equator and circle back across the ocean to the United States warming in the tropics once again. And this heat/water/climate continues year after year after year. As long as we keep turning and the surface remains water.
Now, San Diego…
The Pacific currents slide from California across the ocean warming and holding heat as they go. On the other side they reach Polynesia – and we all have a picture what this looks like. Islands, palms, tropical animals, coral reefs – paradise. From here the currents, like the Atlantic, flow north carrying heat with it to higher latitudes but maintaining a subtropical climate – such as Okinawa and southern Japan. Eventually the currents slide from Korea across the Pacific passing the Aleutian Island near Alaska to Canada, where much of the heat is lost. The current then heads south towards California. At this point the current is cold and the air humidity is low. Seattle is known for its rain due to the warm mass coming off the United States meeting the cold ocean current. Little further south are the giant redwoods and coastal fog. Then the arid “Mediterranean” climate of southern California (similar to Spain and Morocco). A little further south – we head again across the equator and warm up. And so it goes.
With inland areas, such as Kansas and Texas, the ocean currents do impact their climate, but other factors do as well – such as mountain ranges. There is MUCH more to understanding the worlds climate beyond this – but this gives the student an idea of how the oceans play a role. Oh, by the way… the southern hemisphere is “playing the same game”.
What about climate change?
That will be the focus of Lesson 4
- World Map
There are two ways to do this activity. One would be to use the ocean current map you developed in The Nature of Science Lesson 1. The other would be to look at or create a new map. You will need to know where the major ocean currents are – how they rotate across the planet and know whether they are cold or warm currents. Again, you did this in The Nature of Science Lesson 1. Look along the shorelines of continents with colder ocean currents – such as the western side of South America. What would you expect the climate of Peru, Chile, and Ecuador to be like? The Galapagos Islands are 500 miles west of Ecuador at latitude 0°S – (the equator). Based on its location and the ocean currents near it – what would you expect the climate there to be like?
What about eastern Australia – where Sydney and Brisbane are located – as is the great barrier reef. What would the climate here be like?
What about western Australia?
- Heating sand and water
If you have the supplies at home, test that idea of water polarity. Place one cup of water outside with a thermometer first thing in the morning. Place a second cup right next to it with sand and a thermometer. In this experimental design can you account for experimental constants? (only thing different between the two cups is the material within them). Check the temperature every 15 minutes until noon. Record each time you check. Now graph the results. When graphing the independent variable always goes on the x-axis, and the dependent on the y-axis. Remember that the dependent variable “depends” on the independent. So, in this case which is the dependent variable? Graph both of these and compare the rate of heating. They may both reach the same temperature by noon, but which reaches it faster? How is this connected to what was taught in this lesson.
To make it more scientific – run replicates of each, maybe 5 cups of water and 5 cups of sand (if you have the supplies to do this). Remember, the more replicates the better.
We just experienced a hurricane – one of the climate phenomena that occurs in this part of the country. If you can, take the little ones out to observe hurricane damage. Maybe some erosion, a damaged house or dock, downed trees. Take pictures and when back home look at them all to discuss the power of these storms. Help the little ones understand that, because of where we live, this will happen again and that we need to be ready for each one. Maybe they will have some good ideas of how to be more ready next time. 😊