Seven-Tenths (2 page)

They are a blank to most people, these bald oceans, much as they appear on a globe. As such they have their own coherence as two-dimensional representations of
not-land
. ‘The sea’ survives elsewhere in piecemeal images, scattered pictures which never link up. They include beach scenes from summer holidays, an aunt being seasick, storms, sunken treasure, pirates, monsters of the deep. … ‘The sea’ as a reservoir of private imagery and public myth remains on the one hand without limits, on the other banally circumscribed. Yet it haunts us. We are full of its beauty, of that strange power it gives off which echoes through our racial history and fills our language with its metaphors. The salt which is in seawater is in our blood and tears and sweat. The lungs of an infant
in utero
can be seen rhythmically breathing as it inhales and expels amniotic fluid, even as its oxygen supply comes from the mother’s bloodstream via the umbilicus. Each of us has breathed warm saline for days on end and survived. The lungs themselves derive from fused pharyngeal pouches, and branchial clefts (‘gill slits’) still form temporarily in all chordate embryos, including humans, reminding us that something which became
Homo
did crawl up a beach many millions of years ago. The satisfaction for certain people of walking back down a beach and into the sea is akin to that of a long-postponed homecoming.

Too late, though. We have lost our place and no longer know how to return. It is never quite enough, the ecstasy of splashing or the torpid floating while a fine slick of tanning oil spreads its iridescent pollution around us. Too much knowledge, too much strangeness slips by. Maybe we should approach the whole thing through science. Marine biology will tell us about the phytoplankton in their gemlike flakes, trigonometry will reveal where we are. The business
of orientation on the blank and shifting waters of the open sea, of establishing a fixed
point de repère
which is not a landmark, is central not merely to navigation but to various sciences coming under the general heading of oceanography. (The very word suggests a difficulty, the writing down of an ocean.) Until a certain moment in history there must have been a conceptual impossibility in the idea of a sea chart without a coastline on it, implying as it logically would the drawing of lines and boundaries – albeit notional ones – on a fluid surface. Being boatless and lost in mid-ocean at noon in the tropics at least makes vivid certain problems which have faced all navigators and cartographers, with the sun directly overhead and the seabed far out of sight a mile below. The panic of a careless swimmer keen to avoid joining his ancestors thus makes a good starting point as he twirls despairingly round and round like a demented compass needle in search of any bearing, any point of reference, any direction other than down.

The swimmer wanted to know many things. Gazing straight down beyond his parsnip-white feet into the purple depths he wanted to know not just what was down there but how it might be mapped. How did one make an accurate chart of the seven-tenths of the Earth’s crust hidden from sight? Since he had always wanted to know such things he wondered why he had never become a marine scientist. This was imponderable so he inverted the question and speculated about what it is that makes a scientist choose his particular field of study. This swimmer, who is almost as obsessed with the idea of the sea as with its actuality, wondered if oceanographers necessarily shared his own obsession, and if so, to what effect. Did they love to go delving into the sea? Was it scientifically useful to be imaginatively caught up in the deeps?

Such speculations bring me in due time (early December 1990) to Pier 40 of Honolulu Port and aboard the R/V
Farnella
, a British-registered research vessel. The
Farnella
is under charter to the United States Geological Survey, which is using her to map the seabed contained by the US 200-mile Exclusive Economic Zone. It seems curious that this grand national task should be carried out using a
system developed in Surrey and mounted aboard a converted Hull trawler. Some years ago the ship’s refrigerators were taken out and her forward hold filled with huge spools of cable for towing instruments. The stern hold is now largely given over to a spacious air-conditioned laboratory humming with bays of computers, sonographs, plotters and assorted electronic gear. When we leave Honolulu we have aboard fourteen crew, thirteen scientists (American and British) and myself, my capacity officially listed as ‘Fly on wall’.

We spend the first two days at sea simply reaching the area of the survey, which is that surrounding Johnston Island. At this moment Johnston Island is a high-risk, high-security area since this is the atoll where the US is destroying its stocks of nerve-gas shells and other chemical weapons from bases in Germany. Several of the scientists had put ashore there briefly on a previous trip. ‘Can’t land if you’ve got a beard,’ said one, ‘or even a couple of days’ growth. Your gas mask mightn’t be airtight.’ ‘Don’t worry,’ said another. ‘We’ll be over a hundred miles away most of the time and with any luck upwind.’

I wander the ship, stare at the ocean rolling past, meet the Captain. ‘He’s temporary,’ a crew member tells me. ‘Wicked sense of humour.’ A dapper man, he had distinguished himself during the last Cod War of 1975 by deliberately ramming an Icelandic trawler. Otherwise, his sense of humour seems not greatly in evidence. Ah, but a previous captain, now, he’d been gross in all sorts of ways. ‘Pig fat, he was. Also, I remember up on the bridge, you’d never know when, sort of absentminded-like he’d take out his teeth to scratch the eczema on his legs, the top plate usually, and you’d see this dust like cornflour come puffing out of his trousers. Then he’d slippem back innagain.’ The sea has always been kind to eccentrics, and indeed the
Farnella
’s crew give off a feeling of dourly amiable tolerance, even towards scientists and flies on walls.

The main piece of equipment for bathymetry aboard, and the chief tool of the entire USGS programme, is GLORIA: Geological Long Range Inclined Asdic (‘asdic’ being the British equivalent of the American ‘sonar’). Since seawater is four and a half times better than air at conducting sound, some kind of sonar system remains
the most effective way of mapping a seabed which may be anything up to 11 kilometres below the surface. The very earliest sonars were simple echo rangers. The sinking of the
Titanic
in 1912 had made finding some sort of defence against icebergs an urgent matter, but it was actually World War I – and specifically the development of submarine warfare – which encouraged sonar technology and in so doing gave the biggest boost to modern oceanography.
*
One offshoot of military research was an efficient echo sounder for cable laying.

In 1854 Lieutenant Matthew Fontaine Maury of the US Depot of Charts and Instruments had published a profile of the Atlantic seabed, his
Bathymetrical
Map of the North Atlantic Basin with
Contour Lines Drawn in at 1,000, 2,000, 3,000 and 4,000 Fathoms.
This was based on only a couple of hundred deep soundings achieved with a weighted line, and its imposing title suggested a survey rather more thorough than it actually was. Nevertheless, it interested a good many people, among them a rich industrialist, Cyrus W. Field. Field had long dreamed of linking America with Europe by telegraphy. The seabed between Newfoundland and Ireland was, according to Maury’s survey, mostly plateau. Suddenly, the romantic notion of voices emerging from the deep took on real commercial possibility. In 1856 the Atlantic Telegraph Company was founded and two years later it laid the first transatlantic cable. Unfortunately, Maury’s ‘plateau’ turned out to include over 1,000 miles of fracture zone: the spine, in fact, of the Earth’s largest mountain range, the mid-Atlantic Ridge. This runs for 7,000 miles with peaks rising two and a half miles above the seabed. Within three months the cable had broken. Under the continued pressure of the Company’s commercial determination, though, Maury’s team were inspired to develop better sounding devices and bathygraphy. The result was a permanent telegraph link, finally laid in 1866. Yet even the best sounding techniques using plummets and lines had great limitations (see Chapter 6). At least another half-century was to elapse before the novel alternative of sonar was devised.

In 1922 a historic moment in cartography and oceanography occurred when the USS
Stewart
used a Navy Sonic Depth Finder to draw a continuous profile across the bed of the Atlantic, 68 years after Maury had published his map. But whereas Maury’s had involved large amounts of guesswork, the
Stewart
’s involved none, aside from certain problems of interpretation. Otherwise the soundings were fast, accurate and simple to take. The principle of sonar is straightforward. A pulse of sound is bounced off the sea floor and received by the vessel which sent it. Having made small allowances for such things as the speed of the vessel, it is a matter of the simplest arithmetic: divide the time elapsed by two and multiply the result by 4,800, which gives the depth in feet, 4,800 feet per second being the mean speed of sound in water. (The layman is astonished only that, with a principle as thoroughly understood and long turned to practical use, it should have taken so long to develop radar, that apparently magical World War II conceptual breakthrough. Since then, with a good deal of technical wizardry but zero intellectual daring, radio pulses and even laser beams have been bounced off the Moon, ranging it to a matter of a few centimetres.)

There are, however, certain difficulties to this kind of bathymetric depth sounding. One can be intuited from the phrase ‘mean speed of sound in water’, since in practice the speed of sound in seawater varies. It travels faster, for instance, if the temperature, pressure or salinity increase. This is to leave aside for the moment all the difficulties in interpreting the returning signals, which may be severely affected by shoals of fish and other powerful sources of scattering. A further drawback is that a series of pulses focused vertically downwards beneath a ship’s keel will give only a series of depths. In order to build up a contour map of how the sea floor actually looks a ship using this method would have to make a laborious succession of very closely spaced passes. Otherwise, only a narrow cross-section of the seabed being traversed is possible.

A way around this difficulty was pioneered at the Institute of Oceanographic Sciences in Surrey. Instead of using vertical echo sounding, they developed a sidescan sonar in which the sound pulses are emitted sideways in two slanting fans, one on either side
of the ship and at right angles to its course. The outer edges of these fans brush irregularities on the seabed as far away as 30 kilometres. The returning echoes, since they do not come merely from a single point directly beneath the vessel’s keel, are complex and take skill and experience to interpret. Yet the profile which emerges from the plotters provides by far the clearest imagery yet possible of a continuous swathe of seabed, certainly on a cost-effective scale. GLORIA’s efficiency is striking. In good conditions and with the ship travelling at 8 or more knots it can reveal a strip of seabed 60 kilometres wide. In twenty-four hours this amounts to mapping more than 20,000 km2, or an area the size of Wales.

This cruise in the
Farnella
is one of a series at the end of a great project on the part of the US to map the 200-mile EEZ around all 19,924 km of its coastline. The EEZ of the continental US has already been mapped, including Alaska and the Aleutian Islands. Now
Farnella
is working away at the Hawaiian Chain. As the scientists aboard keep telling me, only the GLORIA system could have covered such an area, and even that has taken ten years.

Such things are explained as the ship bounces and judders through seasonal Pacific rollers on her way to the survey area. On and off a tropic sun blazes the sea to a luminous indigo across which flying fish skip and glide. In the intermittent bursts of sunlight there is a stampede of scientists up on to the deck where they grill themselves on towels, redolent of coconut oil. December! Hawaii! Field trips sometimes throw in for free the costly ingredients of other people’s holidays. They are watched by two boobies clumsily slithering on the button atop the radar mast while a small albatross flies elegant, mournful rings around
Farnella
. On successive days of watching I never once saw it move its wings, only soar and tilt in any direction and at any speed into the headlong breeze while keeping pace with the ship. It looked as though it knew by heart a map of the ocean’s surface, a map no man will ever make.

Time was spent checking the various instruments which were soon to be lowered into the sea and towed behind us. First of all GLORIA itself: a large yellow torpedo lined inside with banks of transponders precisely angled to give the correct fan-shaped pulse.
It sits in a hydraulic cradle directly over the ship’s stern. From time to time technicians climb up to tighten a nut and pat it protectively. Even without its cable it is worth nearly half a million pounds. There is spare cable but only one GLORIA aboard. ‘We don’t even like to think about that,’ is the response to the obvious ‘What if?’

Amidships, two little ‘fish’ like fat yellow bombs wait on wooden trestles. These are the 10 kilohertz and 3.5 kilohertz sonars. The first will act more or less like an old-fashioned depth sounder to give the distance to the seabed immediately beneath us. The second will send pulses up to 400 metres into the ocean floor to provide some idea of the underlying geology. It is explained that its readout, taken by itself, would be fairly meaningless since in physics, as elsewhere, one cannot get something for nothing and the deeper penetration gained by using a higher frequency is at the expense of detail and spread. But taken in conjunction with information coming from other instruments this data will be usefully corroborative.

Over the starboard stern will go the air gun. This is a heavy pot of machined steel, something like the body of a pneumatic drill and similar in principle. Connected to a high-pressure air hose it will ‘fire’ itself every ten seconds with a loud detonation and send sound waves capable of penetrating up to 1 kilometre into the ocean floor. This is the oceanographer’s equivalent of seismologists’ ‘thumper trucks’ which used to drive around the deserts of the Middle East, dropping huge blocks of concrete and listening for signs of oil-bearing strata. The air gun is a safer and simpler alternative to throwing overboard dynamite charges at timed intervals. Its echoes are received on a hydrophone ‘streamer’, hundreds of metres of transparent plastic tube filled with bundles of multicoloured sensor wires and light oil. The streamer may be towed well over a kilometre behind the ship and is of all the equipment the most susceptible to damage. (At the end of the cruise when the streamer is wound aboard there is a section leaking oil with a broken shark’s tooth embedded in the gash.)