I'll be off-net in June. Not that I couldn't connect if I decided to, but I'll be travelling and I believe in enjoying the places I go to. Blogging, I can do anywhere. Walking up Notre Dame and the Great Wall of China, on the other hand, are special and deserve attention. So I'm back in July, perhaps with pictures on the blog.
When I do get back, I'll be putting up several notes in response to Dave's thoughtful questions (comment on my ocean introduction note) regarding climate. Several, because he has several different questions, and I think they warrant individual consideration and discussion from ... well, at least him and me. If we can get additional considered views, or questions from folks who'd like to know more, that'll be good. If you already have contributions to make, go ahead; I'll see them when I get back. Just be prepared that it'll be a month before they show up.
Happy trails!
30 May 2008
06 May 2008
Introduction to the Oceans
Just a quick look at who they are and what they're made of. The fact that I do polar work leads to me taking a somewhat different accounting of the 'who' side than low and mid-latitude oceanographers tend to. So, for me, the oceans are: Pacific, Atlantic, Indian, Southern, Arctic. The Southern and Arctic oceans are not infrequently neglected. The Arctic can reasonably be called a sea rather than an ocean; that is, it is a body of water that has limited inflow and outflow (the Bering Strait on the Pacific side and Fram Strait on the Atlantic side).
The Southern ocean truly is oceanic rather than sea-like. We polar types consider it separate from the other oceans because of the Antarctic Circumpolar Current. South of this, the Southern Ocean waters are mixed pretty well with each other and are not much like the waters to the north. North of there, the other oceans have greatly limited transport with the Southern Ocean. Currents tend to flow from one of the other three to another of the others, rather than in to the Southern Ocean. Since the Antarctic Circumpolar Current, like all currents, is a dynamic feature, it moves. This means that the boundary location and size of the Southern Ocean (and, conversely, the Pacific, Atlantic, and Indian) fluctuates somewhat in time.
The elements in the ocean, as for most geophysical systems, are mostly a fairly select subset of the periodic table. Although there are over 110 elements known now, only 8 account for most of the ocean. If we take a kilogram of sea water (1000 grams, remember), then there are about:
858 grams Oxygen (O)
107 grams Hydrogen (H)
10.3 g Sodium (Na)
19.5 g Chlorine (Cl)
1.3 g Magnesium (Mg)
0.9 g Sulphur (S)
0.4 g Potassium (K)
0.4 g Calcium (Ca)
Aside: Sodium and Potassium's chemical symbol comes from their Latin names 'Natrium', and 'Kalium', respectively. Their symbols do make sense, at least if you know the right second language.
So, 8 elements, 8 symbols to remember out of the 110+, and you've got well over 99% of the ocean's content. Even better is that the composition of the ocean varies by very little throughout, at least for the major elements. Very scarce elements, like Iron (Fe -- Ferrum) do vary substantially, but they're so rare this doesn't affect the ocean's dynamics.
If we think instead of molecules, the main components are water (H2O), table salt (NaCl), additional salts (KCl, CaCl), and Magnesium Sulphate (MgSO4, epsom salts). Of these, water is the overwhelming majority. Table salt is most of the rest. Viewed in terms of its bulk composition, the ocean is fairly simple. But if we think about living things in the sea, it gets complicated very quickly. Living things depend on elements and chemicals which are very scarce.
The oceans, all together (and however we name them), occupy about 70% of the surface of the earth. This is one reason oceanographers take an interest -- it is most of the surface of our planet. (Calling it 'Earth' is poor naming, we feel. It should be 'Water', or 'Oceania' or something like that.) The average depth of the ocean is about 3730 meters (about 12,200 feet), farther below sea level than almost all land areas are above sea level (land averages about 800 meters, 2600 feet, above sea level; by the time you get to 12,000 feet above sea level, you're on the side of a good mountain).
Later, we'll get more detailed about the ocean. But here's a start on names.
The Southern ocean truly is oceanic rather than sea-like. We polar types consider it separate from the other oceans because of the Antarctic Circumpolar Current. South of this, the Southern Ocean waters are mixed pretty well with each other and are not much like the waters to the north. North of there, the other oceans have greatly limited transport with the Southern Ocean. Currents tend to flow from one of the other three to another of the others, rather than in to the Southern Ocean. Since the Antarctic Circumpolar Current, like all currents, is a dynamic feature, it moves. This means that the boundary location and size of the Southern Ocean (and, conversely, the Pacific, Atlantic, and Indian) fluctuates somewhat in time.
The elements in the ocean, as for most geophysical systems, are mostly a fairly select subset of the periodic table. Although there are over 110 elements known now, only 8 account for most of the ocean. If we take a kilogram of sea water (1000 grams, remember), then there are about:
858 grams Oxygen (O)
107 grams Hydrogen (H)
10.3 g Sodium (Na)
19.5 g Chlorine (Cl)
1.3 g Magnesium (Mg)
0.9 g Sulphur (S)
0.4 g Potassium (K)
0.4 g Calcium (Ca)
Aside: Sodium and Potassium's chemical symbol comes from their Latin names 'Natrium', and 'Kalium', respectively. Their symbols do make sense, at least if you know the right second language.
So, 8 elements, 8 symbols to remember out of the 110+, and you've got well over 99% of the ocean's content. Even better is that the composition of the ocean varies by very little throughout, at least for the major elements. Very scarce elements, like Iron (Fe -- Ferrum) do vary substantially, but they're so rare this doesn't affect the ocean's dynamics.
If we think instead of molecules, the main components are water (H2O), table salt (NaCl), additional salts (KCl, CaCl), and Magnesium Sulphate (MgSO4, epsom salts). Of these, water is the overwhelming majority. Table salt is most of the rest. Viewed in terms of its bulk composition, the ocean is fairly simple. But if we think about living things in the sea, it gets complicated very quickly. Living things depend on elements and chemicals which are very scarce.
The oceans, all together (and however we name them), occupy about 70% of the surface of the earth. This is one reason oceanographers take an interest -- it is most of the surface of our planet. (Calling it 'Earth' is poor naming, we feel. It should be 'Water', or 'Oceania' or something like that.) The average depth of the ocean is about 3730 meters (about 12,200 feet), farther below sea level than almost all land areas are above sea level (land averages about 800 meters, 2600 feet, above sea level; by the time you get to 12,000 feet above sea level, you're on the side of a good mountain).
Later, we'll get more detailed about the ocean. But here's a start on names.
21 April 2008
Math, Science, and Engineering, oh my
Since I've studied all three, and appreciate all three, it always surprises me when people try to claim that they're not different. Usually this is a math or engineering person trying to say their area is science. This is, well, just wrong, I think.
One area of confusion is that each is a matter of what you're doing at a given time. One can easily have a job which carries one label, but be doing on of the other things. My job title, for instance, says that I'm a scientist, but much of what I actually do is what I consider engineering. No problem to my psyche as I respect engineering. The only question then is whether I can do good engineering. Conversely, some with a job title of engineer may at times be doing science. What matters to me is not the title, but what one does.
The main divider between the three, as I see it, is how do you decide that you're right (or, have done good math, science, or engineering). In mathematics, you work within a rigorous framework and prove that you are correct (that a theorem you or somebody else proposed is either true or false). You might have made an error in your proof, and the decision on that is made by other mathematicians.
Science and engineering both appeal to nature, rather than scientists and engineers. The scientists compare the predictions of their theory to the observations. If they're close enough, then the theory is considered good enough. It isn't proven. Next year we might have more and better observations, and the theory might not agree well enough any more. A different side is, scientists can think of highly idealized systems (frictionless surfaces, massless strings, point masses, ...) which don't actually exist in nature. If the predictions are close enough, however, then the science is good.
Engineering, does appeal to nature (did the bridge hold up?), but has very limited degrees to which it can simplify its systems (real bridge beams vary in their properties, while ideal ones don't, and the difference can crash the bridge). The more significant distinction from science goes back to the matter of how you decide you've done good engineering. Engineering, I take it, is the application of a knowledge of science to achieve a useful end. But who decides useful? Somebody, somewhere, writing the checks to support the project. It would be very easy to
build a several mile long bridge, for instance, if your budget were unlimited and so were the time for construction. But for real engineering, you have serious limits on time and money. How do you build a bridge fast enough and cheap enough, while still carrying the required load? That's an engineering challenge.
20 April 2008
No running in thunderstorms
Blogging instead of running right now. I run through almost all weather, including rain, snow, sleet, -10 F temperature, -30 F wind chill, temperatures over 100 F, etc. The one type of weather I won't run in is thunderstorms. It isn't strong now, but I'm still hearing occasional thunder.
Thunder means lightning, and lightning is bad for my health. Plus, I can't outrun lightning.
Thunder means lightning, and lightning is bad for my health. Plus, I can't outrun lightning.
11 April 2008
Sorts of ice age
In addition to there being types of ice, there are types of ice age. Again this seems odd, but again the differences become important if we try to understand the climate. Depending on which of the three types of ice age we're concerned with, the answer to the question 'Are we in an ice age now?' is either no, we've been in one for 2.5 million years, or we've been in one for about 35 million years.
The first type of ice age is probably the most familiar. It really is asking 'Is there a whole lot of ice in the northern hemisphere?'. A little more specifically, it is about how much ice mass there is. While the area of snow cover and sea ice cover can be large, we don't think of that as being an ice age for this type. The ice age for this is when most of Canada and the northern USA are under 1-2 miles (1-4 km) of ice. The last time we were in that sort of ice age was about 15,000 years ago, give or take. Certainly we were done with it by about 7,000 years ago. Call this ice age type 'ice burying Chicago'.
The next sort is the 'ice burying Greenland' ice age. We've been in that condition continually since about 2.5 million years ago. Greenland is larger than Texas or France, so counts for having some significant size. The question here is 'Is there substantial ice anywhere in the northern hemisphere?' Before about 2.5 million years ago, back to over about 250 million years ago, the answer was no.
Those two types of ice age are biased towards an interest in the northern hemisphere. Since I, and most of the world's people, live in the northern hemisphere, I'm not entirely opposed to the bias. But, since I also am concerned about ice and ice sheets in their own right, let's consider the more general question for ice age 'Is there substantial ice anywhere on the planet?'
The answer to this is yes, and has been so for about 35 million years. Antarctica, sitting down on and around the South Pole, has had substantial ice since about then.
Now it isn't the case that we always have lots of ice somewhere on the earth. Prior to that 35 million years ago, you'd have to go back more than another 200 million years to find an ice age by the third definition. Over the history of the earth, it appears that ice ages are an unusual condition for the earth. Most of the time (over 80% in fact), the earth doesn't have any significant ice. Obviously to see it this way, we have to be taking a very long view of the earth's history.
For thinking about current climate, then, we want to be careful about what sort of ice age we're talking about. Some people refer to us 'still coming out of the ice age'. They're wrong for all three sorts of ice age. We were done coming out of the last 'bury Chicago' sort of ice age 7,000 years ago. And we're still in the other two sorts. If they were to end, sea level would rise by about 7 meters (about 20 feet) for the 'ice in the northern hemisphere' ice age, or about 70 meters (over 200 feet) for 'ice in the world' ice age. Since some hundreds of millions of people live less than 20 feet above sea level, I'd rather not come out of even just the northern hemisphere sort of ice age any time soon.
The first type of ice age is probably the most familiar. It really is asking 'Is there a whole lot of ice in the northern hemisphere?'. A little more specifically, it is about how much ice mass there is. While the area of snow cover and sea ice cover can be large, we don't think of that as being an ice age for this type. The ice age for this is when most of Canada and the northern USA are under 1-2 miles (1-4 km) of ice. The last time we were in that sort of ice age was about 15,000 years ago, give or take. Certainly we were done with it by about 7,000 years ago. Call this ice age type 'ice burying Chicago'.
The next sort is the 'ice burying Greenland' ice age. We've been in that condition continually since about 2.5 million years ago. Greenland is larger than Texas or France, so counts for having some significant size. The question here is 'Is there substantial ice anywhere in the northern hemisphere?' Before about 2.5 million years ago, back to over about 250 million years ago, the answer was no.
Those two types of ice age are biased towards an interest in the northern hemisphere. Since I, and most of the world's people, live in the northern hemisphere, I'm not entirely opposed to the bias. But, since I also am concerned about ice and ice sheets in their own right, let's consider the more general question for ice age 'Is there substantial ice anywhere on the planet?'
The answer to this is yes, and has been so for about 35 million years. Antarctica, sitting down on and around the South Pole, has had substantial ice since about then.
Now it isn't the case that we always have lots of ice somewhere on the earth. Prior to that 35 million years ago, you'd have to go back more than another 200 million years to find an ice age by the third definition. Over the history of the earth, it appears that ice ages are an unusual condition for the earth. Most of the time (over 80% in fact), the earth doesn't have any significant ice. Obviously to see it this way, we have to be taking a very long view of the earth's history.
For thinking about current climate, then, we want to be careful about what sort of ice age we're talking about. Some people refer to us 'still coming out of the ice age'. They're wrong for all three sorts of ice age. We were done coming out of the last 'bury Chicago' sort of ice age 7,000 years ago. And we're still in the other two sorts. If they were to end, sea level would rise by about 7 meters (about 20 feet) for the 'ice in the northern hemisphere' ice age, or about 70 meters (over 200 feet) for 'ice in the world' ice age. Since some hundreds of millions of people live less than 20 feet above sea level, I'd rather not come out of even just the northern hemisphere sort of ice age any time soon.
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