The change in temperatures over the course of the year. Click image to enlarge. Images from 1987 via NOAA's GLOBE Earth System Poster.
The continents heat up faster than the oceans, and they cool down faster too. You can see this quite clearly in the animation above: notice how cold North America gets in the winter compared to the North Atlantic. It’s why London has an average January low temperature of 2˚C while Winnepeg’s is closer to -20˚C, even though they’re at almost the same latitude. There are a few reasons for the land-ocean cooling differences, and they all have to do with how heat is absorbed and transported.
(1) Specific Heat Capacity. Water has a higher heat capacity than land. So it takes more heat to raise the temperature of one gram of water by one degree than it does to raise the temperature of land. 1 calorie of solar energy (any type of energy really) will warm one gram of water by 1 degree Celcius, while the same calorie would raise the temperature of a gram of granite by more than 5 degrees C. The Engineering Toolbox has specific heat capacities of common materials.
(2) Transparency. The heat absorbed by the ocean is spread out over a greater volume because the oceans are transparent (to some degree). Since light can penetrate the surface of the water the heat from the sun is dispersed over a greater depth.
(3) Evaporation. The oceans loose a lot of heat from evaporation. In the evaporative heat loss experiment, While there is some evaporation from wet soils and transpiration by plants, the land does not have anywhere near as much available moisture to cool it down.
(4) Currents. Not only do the oceans absorb heat over a greater depth, but they can also move that energy around with their currents. The solar energy absorbed at the equator gets transported towards the poles, while the colder polar water gets transported the other way. Currents help average out ocean temperatures.
The mascot Kergolus superimposed on the islands of Kerguelen. Mascot by Mathieu Valleton and posted on Frank Jacobs' blog Strange Maps.
In response to the submission from a reader, Frank Jacobs has a wonderfully detailed post on the Southern Ocean island of Kerguelen. The island has a French scientific outpost but no permanent population.
Looking at the satellite image, with the marked contrast between the glacial snowfields and the green lowlands, the mascot fairly jumps out at you.
Paths of hurricanes in 2010. The North Atlantic hurricane season was the 3rd most active on record. Visualization from NOAA's excellent Historical Hurricane Tracks interactive map. Forest fires in the Amazon. Image from NASA.
Jeff Masters has an impressively detailed post laying out the argument that 2010, with its record setting snowstorms, droughts, heatwaves, flooding, hurricanes, etc, had the most extreme weather since 1816, the year without a summer.
Looking back through the 1800s, which was a very cool period, I can’t find any years that had more exceptional global extremes in weather than 2010, until I reach 1816. That was the year of the devastating “Year Without a Summer”–caused by the massive climate-altering 1815 eruption of Indonesia’s Mt. Tambora, the largest volcanic eruption since at least 536 A.D. It is quite possible that 2010 was the most extreme weather year globally since 1816.
In 1900 fish stocks in the North Atlantic looked like this:
Biomass of Popularly Eaten Fish in 1900. Design: David McCandless // Map render Gregor Aisch. Source: Hundred year decline of North Atlantic predatory fishes, V.Christensen et al., 2003. From Information is Beautiful , via the Guardian.
IN the year 2000, fish stocks looked like this:
Biomass of Popularly Eaten Fish in 2000. Design: David McCandless // Map render Gregor Aisch. Source: Hundred year decline of North Atlantic predatory fishes, V.Christensen et al., 2003. From Information is Beautiful , via the Guardian.
There are more data and visualizations on the European Ocean2012.eu site.
The Fund for Peace has been doing a lot of thinking about what it takes for a country to be considered peaceful, and what it takes for a state to fail. For the last seven years they’ve been putting together maps of the world with an index of how stable different countries are.
Finland - the most sustainable state, at least according to the Failed State Index.
While it’s pretty in-depth and makes for rather sobering reading, it’s worth taking a look at the criteria they’ve come up with to determine a country’s stability. It may be useful to include some of this information in the cycle where we focus on peace.
Amount of refugees and internally displaced peoples (refugees are people who’ve crossed international borders). Both leaving or entering refugees can undermine stability.
Historical Injustice – communities can have an understandably hard time forgetting the past, just look at Isreal/Palestine.
Brain Drain – when countries start to fail, the first to leave are the ones who can afford to. Yet these intellectuals and professionals, with their college degree are vital for creating a stable and prosperous country.
Inequality – especially when driven by active discrimination (wealth inequality is something to watch out for).
Economic decline – pushes trade into the black market and increases criminality and corruption.
Illegitimacy of the state – if people don’t believe the people in government have everyone in the country’s best interests at heart, and are only looking out for themselves and their friends, then there’s probably going to be trouble.
Public Services go kaput – It’s a really bad sign when the government can meet people’s basic needs – like picking up the garbage.
The Rule of Law goes kaput – when you’re ruled by the caprice of men, and your rights under the law are not respected, you may begin to consider and agitate for other options for government.
Personal Armies – forces that are tied to individual leaders, like private militias or super-secret police for example, are very damaging to a country’s cohesion.
Fighting elites – healthy countries need robust arguments in their political class – think checks and balances – but it can go too far and lead to things like extreme nationalism and ethnic cleansing.
Invasion – both overt invasion and covert meddling in the affairs of a country are unhealthy for that state’s stability.
It’s also very nice that you can download their index data as a MS Excel spreadsheet, which you can let students analyze to answer their own research questions. For example, I was wondering what was the difference between the best, the worst and the USA, so I plotted this graph.
Comparing the best (Finland), worst (Somalia) and the USA using the Fund for Peace's Failed State Indicies.
The USA is much closer to Finland than Somalia, thank goodness, but should probably watch out for that Uneven Development (wealth inequality).
I think something like this would make a good experiential exercise for the science of geography.
To the left, a long, narrow, lightly-wooded island. Skeletal trees, dying on the upwind end; drowned by the attrition of the waves. To the right, a narrow, eager, urban strip. Hotels and casinos, pressing against the water’s edge; vying for access to the white sand beaches and gentle waters of the sound. Such different places on either side, yet the one on the right is the reason we’ve come to the one on the left. We’re here as part of our Adventure Trip to pick up any artificial debris that’s managed to float across the sound and collect and contaminate the quiet, isolated beaches of the island.
We’d gotten on a pontoon at the research lab right after breakfast, so the early adolescents were still a little groggy. Our vessel’s captain asked a question about team mascots which promptly woke up approximately 63.64% of the class, and served as a topic of conversation for the twenty or so minutes it took to get to the drop-off point on the west-north-western end of Deer Island.
Shrimp boat caught in the act of deploying its nets.
Mostly unobserved by my busy students were the half dozen shrimp boats casting their nets in the sound. Long, spider-like, almost robotic arms spread out from the vessel to lower the nets. It’s quite an impressive sight. Commercial shrimping is a major industry all along the Gulf coast.
The island itself is long and thin, wedge shaped, no more than a couple hundred meters at its widest at the eastern end, but thinning to less than 100 meters to the west. Although wider, almost all the trees seem to have died on the eastern end. Then there is a gap and the trees are mostly alive. Looking at the satellite image, you can see a clear channel cutting through the island. From the image, I’d guess the channel is tidal, with water moving back and forth, filling and draining the sound with each cycle of the tides. The sediment deposited in the quieter waters of the sound (to the north) seem to be forming a small, white-sand delta; the equivalent deposits on the south are probably washed away by the longshore current pretty quickly since that shore is exposed to the wind and waves.
Deer Island is not an active barrier island: twelve kilometers to the south, Horn and Ship Islands do that job today. However, given the shape of Deer Island, it may have once been a barrier when the coastline was further inland. This is all part of the coastal plains deltas, which includes the Mississippi Delta and smaller rivers. These rivers transport sediment from the mountains inland and deposit them in the ocean, gradually building out the land. As the deltas build out, the barrier islands also push out to accommodate them.
Scrambling for dry land. Note the rich, black mud.
The pontoon pulled up on a broad, sandy beach then retreated to deeper waters where the fishing is better. The white sand beach we landed on was an artifice, just like the East Beach Drive beach we’d walked the day before. Our first steps betrayed the secret. Breaking through a thin cover of sand, we sank knee-deep into a rich black mud that’s the natural sediment in a quiet waterway like the sound.
Our guide, on the other hand, seemed to have a preternatural ability to avoid sinking into the mud, or even getting her feet wet, or even touching the water.
Stephanie, our guide, carefully takes her first few steps off the boat. (no photoshopping was involved in the creation of this image).
A groin strains to hold back the longshore drift. It is, as always, only partially successful.
It was about 1.5 kilometers from the Research Lab to the estuary where we spent our first morning sampling (overview of the trip is here).
Elevated beach house.
Walking along the beach to get there, we could see the beach houses to the right of us, across the narrow road of East Beach Drive, standing tall on columns to keep them above the reach of the storms. According to Stephanie, our guide, the storm surge from Hurricane Katrina in 2005, reached awfully close to the tops of the columns. The research lab, which is not elevated, lost an entire building to that hurricane. Indeed, much of the coast is still recovering from Katrina’s damage.
The white sandy beach, on the other hand, looked beautiful, which was a bit odd. After all, how did it survive the storm? Furthermore, when you think about it, this beach is located behind a string of barrier islands, which protect the coast from the full force of the waves coming out of the Gulf of Mexico, so how come there is enough wave energy to maintain a sandy beach. The relatively calm waters should allow finer grained sediment, like clay and silt, to settle out, and this area really should be a marsh. The answer, it seems, is that this is an artificial beach. Every few years, thousands of tons of sand are dumped along the coast to “replenish” the beachs.
Without beach replenishment the beaches would revert to salt marshes like this one.
This coastline really should be a tidal marsh, like the one we found when we got to the estuary. These Gulf-coast salt-marshes are fronted by a relatively short version of smooth cordgrass (spartina alterniflora), backed up by the taller, and more common black needlerush (Juncus roemerianus Scheele) .
Longshore Drift
Now, if this is a low-energy environment that allows silt and clay can settle out of the water column, where does the sand go so that it has to be replenished every so often? It is gradually moved along the coast by longshore drift.
Longshore drift moves sand along the coast in the direction of the wind. Image via the USGS.
Waves hit the beach at an angle. As they break, the turbulent swash pushes sand up the beach at the same angle as the movement of the waves. As the wave retreats, the backwash, drawn by gravity, pulls sand perpendicularly down towards the water. The net effect, is that sand gradually moves down the coastline with each swash and backwash of the waves.
Since dumping tons of sand is expensive, engineers try other things to prevent the sand from running off down the beach. Someone, a very long time ago, had the great idea to build a wall sticking out from the beach to impede the sand in its unwanted migration. This type of wall is called a groin (or sometimes a groyne in polite company), and it does stop the sand. In fact, the sand builds up on the upwind side of the groin. Unfortunately, it does not stop the longshore drift on the downwind side, and that results in the erosion of a bay on that side.
A groin impedes longshore drift. Note that the waves approach the beach at an oblique angle.
Pufferfish
Beaches are also great places to find random things washing up. We lucked upon an unusually large pufferfish (family: tetraodontidae). It was quite puffed up. It was also quite dead.
Pufferfish.
Pufferfish are famous for being extremely poisonous. According to the National Geographic page on pufferfish, their tetrodotoxin over a thousand times more poisonous than cyanide, and there is no known antidote.
