Oceanography (Great Courses) DVD Review

Oceanography: Exploring Earth’s Final Wilderness

It’s been almost 50 years since I took an oceanography course, so I ordered this course as a refresher. It was a refresher all right, and not just of what I remembered of oceanography — this course covers everything from the history of the Earth to modern-day pollution. As one of my old colleagues at the Geophysical Institute says, “It’s not Planet Earth, it’s planet Cloud-Ocean.”  And this course was a marvelous refresher of the whole of geophysics, core to tropopause, and some biology with the whole thing straightforward enough to be understandable to almost anyone.

It started out conventionally enough, with an overview of the history of oceanic exploration. But many of the observations of the ocean basins demanded explanation. Why did the mid-Atlantic ridge exist, for instance? The Challenger Deep? For that matter, why were island arcs so often paralleled by trenches and home to volcanoes and earthquakes? What were the magnetic stripes discovered during World War II? How was it that the sea floor, which should have been receiving sediments from the continents throughout geologic history, had astonishingly young bedrock when drills began to penetrate those sediments? Some of these questions were touched on 50 years ago, some were hastily swept under the rug, and some (such as the puzzlingly young age of the seafloor bedrock) had not even been discovered yet.

These questions eventually led to the theory of plate tectonics, and several lectures on these DVDs are devoted to explaining this theory and how it came about. But that’s a small part of the first two discs in this set of six.

The physics and chemistry of water take up several lectures. Waves, rogue waves, tsunamis, and tides are covered, along with some of the physics of water. For something so familiar (oxygen and hydrogen are two of the most common reactive elements in the universe) water has some astonishing properties. Not only does it have an extraordinarily high heat capacity and is it very nearly the universal solvent, it is one of the few compounds in which the solid phase is less dense than the liquid. In other words, ice floats! We’re so used to this we don’t even think about it, but the world would be very different if ice sank, as most solids do in their own melts.

Life in the seas is interesting in itself and also critical to feeding our global population. Food webs, plankton, jellyfish, fish, marine mammals and birds and whales all get their moments of exposure, along with fish farming.

Then the course moves on to coasts: estuaries, deltas, beaches and sea cliffs. Life is here, too, from sea grasses and mangroves to coral reefs.

The lectures then cover storms, the deep ocean circulation, and the effects of climate change and pollution.

As a meteorologist I would of course like to have seen more on the role of the oceans in influencing weather. Not only are the oceans the great flywheel of climate, and their slow response one of the problems in climate modeling, they provide much of the water vapor that transports energy around the globe. Still, 36 half hour lectures can’t cover everything. Professor Tobin certainly tried, though, and for a single course succeeded brilliantly.

Plate Tectonics Index

Here are the links to posts on Plate Tectonics. I have more in mind on this subject.

Plate Tectonics Index

Plate Tectonics Part I 7/1/11
Plate Tectonics Part II 7/8/11
Plate Tectonics Part III 8/5/11

January Wasn’t Warm in Alaska!

A warm January? Not in Alaska! Borrow, at the northernmost tip of the state, was only 7°F below normal, but the western and central parts of the state fared far worse: 22°F below normal at Nome, in the far west, 24°F below normal in Bethel in the southwest, a mere 14.5° below normal at Anchorage in the south, even 4°F below normal at Annette, in the far southeast.

Fairbanks, the area where I live, was 19°F below normal, for the fifth coldest January in a record that goes back over 100 years, and the coldest January since 1971. Snowfall was extremely heavy on the south coast, but lacking inland.

I remember 1971, as does anyone who lived through it. We had 100” of snowfall before the end of 1970, and the roads were well coated with ice. That was the Christmas my father visited from Kansas, and I still remember picking him up at the airport very late in the evening of December 23. The temperature was 36 above and it was raining. My father couldn’t understand why I was driving only about 5 miles an hour on a straight, level road that simply looked wet from the rain. I made sure there was no traffic in sight before I tapped the accelerator to show him why. It was a light tap, and I was able to let the fishtail correct itself, but there’s a lot of difference between wet pavement and wet ice.

By the time my father left, at the beginning of January, the temperature was 36 below and dropping fast at the start of the coldest January in the Fairbanks record. Waist-deep snow with an icy crust from the rain did not help!

But why was Alaska so cold this year when much of the rest of the country was warm?

The sun shines more directly and longer at the equator than at the poles, especially in winter. The air is radiating energy to space, so if there were no movement of air, the poles would get colder and colder while latitudes nearer the equator would get warmer and warmer. Since the earth rotates, direct flow of cold air south and warm air north forces a west-to-east current of air, the jet stream, which always has warmer air to its right side (in the northern hemisphere) and cold air to its left.

But this is an unstable situation – the cold air keeps getting colder and the warm air keeps getting warmer until the simple west to east flow breaks into waves which carry colder air south and warmer air north, though at different longitudes. In one extreme case (rare this winter) warm air from Hawaii flows north over Alaska, the so-called pineapple express, and the air turns back south over Northwestern Canada and continues south to produce the Siberian express. When this happens, temperatures in Fairbanks can be warmer than those in Miami.

The jet stream not only moves air, it steers storms. So storm tracks frequently follow the jet stream.

This January the jet stream in the western hemisphere didn’t have much in the way of waves. The cold air stayed north, while the warm air stayed south. The upper winds over Alaska mostly came from Siberia or the northernmost Pacific. Things are changing, though. Not quite as much as I might like, but probably a bit too much for those of you enjoying unseasonably balmy weather. For the jet stream forecasts, look here. The different colored lines are different forecast models. Where they cluster close together, the forecast is likely to be accurate; where they spread apart there is a lot of uncertainty. Next week? It might even warm up here, but there’s a lot of spread in the forecasts, so I’m not counting on it.

Index of Science Posts

Here are links to all of the posts I would count as science, including those that explain how I use science in my science fiction. This list will be updated as new science posts are added. (Note that some posts listed under “Health” or “Technology” may also be of interest.)

The Science Behind Homecoming 4/2/10
Why do we have Weather? 4/24/10
Precession – Astronomy and Milankovitch 5/6/15
The Four Horsemen of the Apocalypse 6/12/10
Why Planets Have Seasons 6/24/10
Full of Sound and Fury (Fireworks) 7/3/10
Tricycles are not Bicycles 8/8/10
Planet Building 8/15/10 – 10/24/10
Racemization 9/2/10
Equinoxes and Daylight Savings 9/23/10
Horse Color Genetics 10/31/10 – 5/8/11
R’il’nai, Humans and Crossbreds: Life Span 12/11/10
Conservation Laws of Energy and Teleportation 12/20/10
Winter Solstice 12/22/10
Mass into Energy 12/24/11
Momentum and Teleportation 1/1/11
Snowflakes 1/7/11
Ice Fog: Ground Level Contrails 1/25/11
The Planets of Tourist Trap: Eversummer 3/6/11
Earthquakes, Tsunamis and Volcanoes 3/13/11
Why 12-Hour Days Already? 3/19/11
Ice Sculpture: Ice and Sun 3/26/11
More on Ice Melting 3/27/11
Why Temperatures Remembered Don’t Match the Record 4/5/11
When It’s Springtime in Alaska 4/8/11
Twilight 4/12/11
How High the Moon? 4/15/11
Breakup 4/16/11
The Cambrian Explosion 4/22/11
How Did We Learn to Walk? 4/29/11
Back to the Water 5/6/11
Where did the First Plants Come from? 5/13/11
The Geophysical Institute 5/15/11
Alaskan Mosquitoes 5/19/11
Colored-Leaf Geraniums 5/20/11
Early History of the Geophysical Institute 5/22/11
The Fairbanks Flood of 1967 5/29/11
Before Computers 6/5/11
Ice Ages and Alaska 6/17/11
Cumulus Clouds and Cloud Streets 6/24/11
Plate Tectonics Part I 7/1/11
Plate Tectonics Part II 7/8/11
Plate Tectonics Part III 8/5/11
Frost Hollows 8/19/11
Be Careful What You Ask For 8/27/11
Autumn Colors 9/10/11
Thermometers in Fairbanks 9/17/11
Junk Mail and Plants 9/20/11
The Chimney Sweep 9/22/11
Lights, Batteries, Temperatures? 9/24/11
How Dry I Am 10/15/11
Keeping Windows Dry 10/22/11
Snowflakes 10/29/11
The Alaskan Mesozoic 11/1/11
Mesozoic Alaska Part 2 8/11/11
Alaskan Mesozoic 3 11/15/11
Death of Blue Babe 11/17/11
Nightlength Sensitivity in Houseplants 12/10/11
Our Sense of Smell 12/17/11
What Time of Day is Warmest? 12/31/11
Alaska Winter Weather: Cordova and Nome 1/14/12
Inversions and Smokestacks 1/28/12
January Wasn’t Warm in Alaska 2/4/12
Fog, Fog, Fog 2/11/12
Oceanography DVD Review 2/14/12
Snow Festoons 2/18/12
Disturbance Hardening of Snow 3/24/12
Cold-Packed Snow and White Ice 3/31/12
Tornadoes and Climate Change 4/7/12
Breakup Season 4/14/12
Ice Jam Floods 4/21/12
Calories and Weight 5/5/12
Battery Woes 5/12/12

What Time of Day is it Warmest?

What’s the most likely time of day for the daily maximum temperature?

Actually, it depends on a lot of things, including how clouds build up over the course of the day. But would you be likely to guess midnight?

In Fairbanks, Alaska at this time of year the likeliest time of day for the temperature to reach its warmest (or coldest) is midnight. Why?

There are a lot of temperature cycles. The seasonal cycle is obvious — warm in summer, cold in winter. Likewise the diurnal cycle: warmest when the sun is heating the ground; coldest when it is not. There is also an irregular cycle of several days or more, when large-scale winds blow first from the north and then from the south, bringing cold or warm air.

A figure from my thesis, showing how the hour-by-hour temperature (middle line) changed over the time period from Nov 24 through Dec 1.

In mid-Alaska in winter, the daily cycle is very weak. If you take the average temperature for a particular hour of the day, there is a slight warming a little after solar noon, but it is only a degree or two. A single day between about December 1 and January 12 rarely has a discernible temperature rise in the daytime. I actually checked this back when I was preparing my M.S. thesis on ice fog, and determined that during this time period the temperature changes were controlled almost entirely by thermal radiation, with sudden warming when clouds or warm air aloft came in and abrupt cooling when the sky cleared or cold air arrived. Not too surprising, as the sun this time of year is never more than 3 ½ ° above the horizon.

That leaves the seasonal cycle, which is slow, and the irregular variations due to clouds and warm or cold air advection, which can be very large – 100°F over a period of 3 to 4 days, in the extreme. Daily maximum and minimum temperatures are primarily controlled by these longer variations rather than by the very slight solar heating around midday.

Suppose it is warming up, as was happening around November 30 in the graph. The daily minimum for November 30 was at midnight at the beginning of the day. The daily maximum was also at midnight, but at the end of the day. This maximum was also the minimum for the next day, December 1. The opposite would be true if there were a cooling trend. It all happens because maximum and minimum daily temperatures are defined for a 24-hour period from midnight to midnight.

In most places this affects only the minimum, which tends to be just before dawn. In wintertime Fairbanks the effect is enough to completely decouple the daily maximum and minimum temperatures from the solar cycle.

Why an Index?

With 550 posts as of today, I’ve started to have problems remembering what I’ve already put on here. This is particularly a problem with posting existing content such as poems, short pieces from the Summer Arts Festival, or science explanations originally written for the Alaska Science Forum. I can’t remember which books or DVDs I’ve posted reviews on. It also is starting to be a problem when I want to link to a previous post and can’t remember when it was put up or what the title was. And there are posts on this blog that have permanent information, like the series on planet building and the one on horse color genetics, or the book and DVD reviews. I want to make it easier for my readers as well as myself to find things.

I made a start some time ago by adding an index page, which can be accessed from the menu at the top of any page. Right now, the only links are to index pages on my author site. This takes you out of the site and sometimes back in, which is rather clumsy. The index list is also incomplete.

I’m going to start posting an occasional entry which is strictly an index of past posts on a particular topic. These posts will be linked from the index page, and will link forward to the individual blog posts. As it takes a while to find all the posts that belong together, this will be a slow process—probably extending over the next few months. The first in this series, on DVD reviews, is already queued for January 3. Others will follow, most on Thursdays.

I probably won’t be indexing every post. Some, like those early posts which were simply glossary entries for my books, are on the author site and really belong there. Others, like the regular Monday updates on North Pole weather starting in November 2010, can be found easily enough just by using the calendar on the site. But I hope that by the time I have finished this, older posts of interest will be easier to find.

The Alaskan Mesozoic

The OLLI classes are on again, and my favorite teachers are back – this time, with a course on the Alaskan Mesozoic.

What’s that? Well, the Mesozoic is the “Middle period” of multicellular life on earth, lasting roughly from 250 million years ago to 65 million years ago. It is probably better known as the age of dinosaurs, although many of the animals of the time often looked on as dinosaurs – weren’t. And the fossils of many of these animals are indeed found in Alaska – which has led to a new look at dinosaurs.

I missed the first class of the series, on the paleogeography of Alaska, but a good deal of it was put together at the Geophysical Institute, where I used to work. I already knew that the mountain ranges that make up most of Alaska were originally island chains, carried into the state on the moving Pacific and Arctic plates and crushed against it. The north slope was actually at a higher latitude than today during the Mesozoic, and while the world (and Alaska) were a good deal warmer then, the sun was still below the horizon 24 hours a day in midwinter. Plants cannot grow without sunlight, herbivores would have a lean time of it in winter, and carnivores need herbivores to survive. It is difficult to imagine cold-blooded reptiles managing this (there are no crocodiles or snakes in mainland Alaska today) so the discovery of dinosaurs, but not fossil crocodiles, at these high latitudes has forced some reconsideration of their cold-bloodedness.

So what are dinosaurs? That was the Saturday lecture.

First, they are diapsids. That means they have two holes (other than those for eyes, nostrils and ears) in their skulls. In contrast we mammals have one on each side and are called synapsids, and turtles have none and are called anapsids. Don’t think you have one? It’s behind your cheekbone, and your jaw muscle passes through it. Feel above your cheekbone and clench your jaw, and you can feel the muscle. Well, dinosaurs, crocodiles, lizards and birds have two such holes.

In order to be a dinosaur, however, something else is required. Diapsids (think reptiles) started out sprawling. At some point some brought their hind legs under themselves – somewhat earlier than we mammals learned the trick – and began to use their forelegs as grasping hands. The first dinosaur probably looked like a large (but not too large) featherless (we think) bird.

And dinosaurs, as defined by being diapsids with upright rear legs and three-toed grasping forelegs, include birds. Furthermore, discoveries over the last ten to fifteen years have made it clear that many perfectly good, classic dinosaurs had feathers. After all, feathers make excellent insulation, as demonstrated by the down parka I wear.

So far, we’ve learned also that some creatures often lumped with dinosaurs are in fact not dinosaurs. The sail-backs often included with dinosaurs, for instance, are in fact synapsids and are our own distant relatives. Pterosaurs and marine reptiles, though flourishing at the same time as dinosaurs, were not dinosaurs, though they were diapsids.

I know there were marine reptiles in Alaska, but I’ll be fascinated to hear about pterosaurs in our long, dark winters. Did they live here, even in the summer? Did their wings allow them to migrate?

Next week we’ll focus on plants, but the final week is scheduled to cover the marine reptiles and pterosaurs. If you can’t wait, there is some information on a PBS NOVA program.

(P.S. That’s a Pterosaur skull that Pat Druckenmiller is holding.)

The Place Where You Go to Listen

©Sue Ann Bowling

The music of the spheres–
A trite phrase, and one with little meaning
Since universal gravitation replaced crystalline spheres
And first man
And then the sun
And then a point in the center of the galaxy
And then everywhere and nowhere became our center.
We drift, uncentered.

But here
The music of the sun, the moon
The deep rumblings of the moving plates of the earth
The colors of our world–now gold below, blue above–
Make up a different music of the spheres.
Monotonous at first.  The heart of earth
Beats slowly by the beating of our hearts.
But change does come, bacteria
Gave way to jellyfish,
And dinosaurs to man.

These notes change slowly, night to day,
Season to season, the cycles of the sun.
Here we are centered once again.

What’s this about? There is a room at the UAF museum in which the rhythms of the earth — seismic tremors, sun, stars, aurorae – are expressed as musical tones and colors on the wall. This poem was inspired by that room.

Plate Tectonics Part III

The next “a-hah!” moment for me in understanding geophysics came in 1965 with a paper by J. Tuzo Wilson, “A new class of faults and their bearing on continental drift.” At the time it seemed a light had gone off in my head, even though by then I was deeply enmeshed in ice fog studies.

The red lines are spreading centers; the blue line is a transform fault which has its origin in the offset between portions of the spreading center. The part of the transform fault between the offset segments is active; the plates are sliding past each other. The parts to either side are "fossil"--although the offsets are still visible, there is no movement.

Up to that point, it was assumed that if a feature—such as a stream, a mountain range, or a magnetic stripe—was displaced by a fault, it was evidence that they had once been continuous, and movement along the fault had separated them. This paper suggested the existence of a new kind of fault, now called a transform fault, where the apparent displacement was due to an offset in a spreading center. Spreading centers were themselves new, though grabens (places where the crust on either side was moving apart, resulting in a downdropped block in the middle) had previously been recognized.

Suddenly the apparent faults in the Pacific Ocean floor, faults that stopped at the coast, made sense. The rocks on either side of the transform fault did not move relative to each other. The only motion was between the offsets on the spreading center.

We now know that plates are bounded by three kinds of faults:

Spreading centers, where plates move apart,

Converging boundaries, where plates collide,

Transform boundaries, which often connect the two, and allow plates to slide past each other.

The familiar faults such as the San Andreas are the active portions of transform faults, but the offset magnetic stripes in the Pacific are generally the “fossil” parts of transform faults. Looked at this way, the “end” of an active fault makes sense: it is where the transform fault joins another type of fault to make part of a plate boundary.

The full plate tectonics hypothesis had not yet been fully formulated, but the essential pieces had been found.

Plate Tectonics: Part II

My next step in understanding geophysics came when my father took me along to a lecture. At that point I was somewhat immunized against continental drift by the professor at Harvard, in spite of my unanswered questions. Since the topic of the talk was something to do with continental drift, I was prepared to be quite critical. Remember this was in the early ‘60’s, before the idea of plate tectonics. The notion that sea floor was the youngest, not the oldest, crust on Earth had not even entered anyone’s mind, and the lack of traces of the continents plowing through the sea floor seemed definitive.

That lecture totally changed my attitude.

The lecture was about paleomagnetism, the fact that when lava cools, it retains the signature of the terrestrial magnetic field present at the time. The horizontal part of the field gives the direction to the north pole; the vertical part gives how far the pole is from the site — the latitude. There were complications – sometimes two lava flows close enough in time and space that they should have pointed to the same pole had exactly opposite directions. But if the north and south poles were considered interchangeable it was found that rocks of the same age on the same continent pointed to a consistent pole location at any given time in the past.

(Why the magnetic signature seemed to reverse at times was a mystery at the time and is still not totally understood, though it now known to be a reversal of the magnetic field rather than a reversal of the magnetism of the rocks.)

The next step was to produce what are called apparent polar wander curves: plots of how the pole moved through time as seen from the site of the lava flow. Again, it was found that these curves were quite consistent for a given continent. (There are exceptions, but I’ll get to them in a later post.)

But the curves for different continents were quite different.

In particular, if the curves for north America, Africa and Europe were compared, and the continents were assumed to move in such a way that they “saw” the same pole, those continents must have been snuggled together back in the late Triassic.

I walked into that lecture convinced that the apparent fit of the continents (and the geology) of the continents across the Atlantic was a coincidence, and that Wegener’s continental drift hypothesis was wrong. Certainly his mechanisms were; there was no evidence that continents had ever plowed through seafloor. But I walked out convinced that while Wegener’s hypothesis was wrong in detail, the continents had indeed moved.

But how?

Formally, I shifted my studies for the next few years to ice fog. Informally, I kept trying to make sense of  solid-earth geophysics. Could there be some sort of underground erosion going on? What about those faults with hundreds of miles of displacement that disappeared when they reached continents?

Luckily, the major journal of my field was the Journal of Geophysical Research, so I was able to follow the steps people were making in the gradual emergence of plate tectonics. More of that later – but in the order I remember finding out, rather than in the order the discoveries were made.