Beneath the Surface

The World Turned Upside Down

By Farwell Forrest
farwell@paddling.net

October 19, 2004

You don't often hear a paddler shouting "Dive!" to her partner. That's to be expected. Canoeists and kayakers are creatures of the air, operating along the fluid interface between the worlds of wind and water. Even the submariners among us seldom venture deeper than six feet beneath the surface. But that doesn't mean we don't wonder what lies under our keels, does it? I do. As I paddle across the wind-rippled surface of an Adirondack lake on a blustery autumn morning, a kingfisher rattles in the distance, and a yearling buck drinks warily in the shallows. Nothing else is going on. Or is it? I can't escape the feeling that something big is happening — and that it's happening somewhere very close. But where? And what going on?

My curiosity about the unknown country beneath the surface of the water began when I was a boy. Long before I could afford a canoe — the boats I built with orange crates and scrap lumber salvaged from the city dump seldom lasted long — I owned a snorkel, a cheap diving mask, and a pair of swim-fins. On sultry summer days, I'd grab my fins, hop on my bike, and ride to a disused reservoir just outside the city limits. There I'd crawl through a gap in the chain-link fence and spend an hour or two seeing what I could see.

That usually wasn't much, to be honest. The reservoir was so choked with silt and algae that I was lucky if I could glimpse my hand in front of my face once I was underwater. This led to some unpleasant moments, including a nightmarish encounter with a drowned barbed-wire fence. Not all surprises were so unwelcome, however. After long weeks of hot, humid weather, the water near the reservoir's surface was nearly as warm as the air — almost too warm to cool a boy still sweating from a 15-mile bike ride. So I'd swim out beyond the tepid shallows and then dive as deep as my lungs would let me. Ten feet. Fifteen feet. Twenty feet. My eardrums protested painfully, but the water was still as warm as syrup. And then, somewhere between twenty and thirty feet down, a miracle occurred. In less time than it took me to swim one stroke, the temperature dropped twenty degrees or more. Now I was swimming in water that was cold enough to make me shiver. The instant relief from the enervating heat of an eastern summer was wonderful, and I stayed down as long as could. It wasn't very long, of course — a minute or two at most. That didn't matter. Each second was delightful. Only when my racing pulse reminded me that I was an air-breathing mammal would I jackknife my oxygen-starved body around and head for the surface, back into the heat of the day.

The sudden transition from warm water to cold puzzled me at the time, but I was content to let it remain a mystery. I didn't think about it again until many years later, when I was a thirty-year-old student on a limnology field trip to an Adirondack lake — the same lake, as it happens, to which I've returned today, more than twenty years later still, to watch a deer drinking and to listen to the rattle of a kingfisher. And just what is limnology? Simply another name for the systematic study of inland waters. It's a comparatively new science. The word was coined in the last years of the nineteenth century by F. A. Forel, a Swiss professor whose work on Lake Geneva earned him the title "father of limnology." Some would dispute this. Henry David Thoreau's meticulous record of Walden Pond is arguably the pioneering text in the field, even if Thoreau didn't feel the need to elevate his observations to the status of a new science, let alone publish them in a professional journal. Not that such quibbles are important. Limnologists were continuing to debate the history and scope of their discipline in the late 1970s, and for all I know they're at it even now.

In any event, my fellow students and I were blissfully unaware of these sterile academic squabbles. Away from the confines of the lecture hall at last, we got ready for our first practical exercise in limnology. And though I didn't yet know it, I was preparing to revisit the almost-forgotten mystery from my youth. The experiment didn't go well at first. As a boy, I'd gone swimming to escape the stultifying heat of the city. Now, as a superannuated college student, I'd come to limnology for much the same reason: to escape from the lifeless, stultifying abstractions of economics, if only for a few hours. This time around, though, my escape attempt nearly failed. The biologist who taught our class was the sort of tedious time-server who sometimes settles out in small state colleges, far more interested in his part-time job as coach of the women's volleyball team than in his classroom duties. (Only later, when I met the biologist's wife, did I begin to understand why.) So I and the other students were left largely on our own, to learn the subject as best we could. We did what we thought best. We headed for the water.

What happened next? I dropped a weighted temperature probe over the side of the leaky aluminum rowboat that did duty as the college research vessel. Then I lowered the probe slowly down into the water on a knotted line, watching the needle on the thermometer and calling out temperatures at one-meter intervals. My partner in the boat recorded these readings, plotting a rough graph of temperature against depth on a pad of squared paper. At first, his hastily-sketched line was nearly vertical. Water temperature was almost constant. Suddenly, though, the line jogged to the left. In the space of two meters, water temperature dropped 10 degrees Celsius, nearly 20 degrees Fahrenheit. That was when I remembered my childhood trips to the reservoir outside the city. And even though I was sitting in a rowboat on a warm, late-summer afternoon, I began to shiver.

That evening, I opened my textbook to try to make sense of what we'd seen. I soon learned that we'd found the thermocline, the interface between warm surface water and the much colder water of the Adirondack lake's depths. The sudden transition from warm to cold is characteristic of many lakes in temperate regions, particularly in summer months. Surface waters are warmed by the sun, and warm water is less dense than cold. As one hot day follows another, each a little hotter than the last, the lake slowly stratifies. The water in the lightless depths retains its winter chill, while sun-warmed water floats above it. And a sharply-defined transition zone — the thermocline — divides the two.

Nor is temperature the only thing to change with depth. The water below the thermocline is dark as well as cold. No light, no photosynthesis. No photosynthesis, no oxygen. The result? The lake's deeper waters are both cold and oxygen-poor. Above the thermocline, all is warmth and light and life. Below, there is only the chilly stillness of the tomb. This isn't just empty rhetoric. The inhabitants of the upper, sun-warmed waters, from plankton to pike, sooner or later suffer the fate of all living things. The newly dead then sink downward into the chill depths. Once there, they decompose, further depleting the already diminished oxygen reserves, while at the same time enriching water and sediment with nutrients derived from their bodies. Over time, the upper and lower worlds diverge. The upper waters are oxygen-rich but nutrient-poor. The depths, oxygen-poor but nutrient-rich. The upper world starves. The lower world suffocates. Yet there is little exchange between the two. Little, that is, beyond the gentle rain of the dead, augmented by the waste products of the living. This rain falls steadily from the world of light into the lower realm, a tomb in fact as well as fancy: dark, still, and silent — and stocked with the treasures of the dead.

Now summer draws to a close. Shorter days and cooler temperatures allow the water near the surface of the lake to cool, and as it cools, it sinks. The stable, ordered world of summer — warm, light water on top; heavy, cool water below — begins to break down. It's a revolution of sorts, hurried along by the brisk northerly winds that drive the first masses of cold air south from the subarctic. And when autumnal storms kick up big waves on the lakes, deep vertical eddies form, breaching the thermocline barrier again and again and putting an end to the surface water's splendid isolation. The fall overturn is under way. The mixing of waters has begun, and a new chapter in the life of the northern lakes is about to open.

Overturn. Upheaval. A new order. These words strike a chord with most of us Americans, don't they? Our national folklore is rich in revolutionary images. In fact, I've often heard it said that a British marching band played a melancholy air entitled "The World Turned Upside Down" when Lord Cornwallis surrendered to General Washington. It's a wonderful tale, to be sure, rich in dramatic irony. And the defeat of the British army at Yorktown did signal a revolutionary change in the established order of things, as well as being a harbinger of even greater upsets to come. But historians — a rather sour lot, on the whole, with little appreciation for a good story — insist on pooh-poohing the whole idea. Few of them would suggest that the scarlet-coated fifers played a jolly tune, of course. The British had little reason to celebrate. But no one took enough notice of whatever it was they played to write it down. It could have been almost anything.

So much for history. A revolution of a very different kind is going on beneath my boat, even as I paddle out across this choppy Adirondack lake. An ordered, stable underwater world is experiencing a great, unseen cataclysm. Two long-separated realms — a kingdom of light and warmth and life, on the one hand, and a chilly tomb, richly endowed with the treasures of the dead, on the other — are now being forced together. Each gives something up, and each gains by the exchange. The warm water surrenders some of its oxygen; the cold, some of its treasure of nutrients. A great equalizing has begun, just in time for the long sleep of winter.

If that doesn't warrant playing "The World Turned Upside Down," I don't know what does. But let's not score it as a melancholy dirge. A lively tune is far better suited to the day. This is one revolution that leaves no defeated enemy in its wake, makes no grieving widows or orphaned children. This revolution brings new life to northern waters.

And that is something to celebrate.

Copyright © 2004 by Verloren Hoop Productions. All rights reserved.