than half a metre.
Macleod pulled the stick back to its default alignment.
“A freefall spin followed by a perfect recovery.” He grinned at Jack, who well remembered their ROV dogfights when they had trained together at the IMU deep-sea equipment facility off Bermuda.
“ROVs have been used extensively by scientific teams for a couple of decades now,” Macleod explained. “But over the last few years the technology has become increasingly refined. For exploratory survey we use AUVs, autonomous operated vehicles, which have multitask sensor packages including video and side-scan sonar. Once a target is identified we deploy direct-control ROVs. The IMU Mark 7 we’re operating here is not much larger than a briefcase, small enough to penetrate a sub-sea vent.”
“You can turn one of these babies on a dime,” Costas added. “And the Doppler radio-pulse control means it can go fifteen nautical miles horizontally or straight down to the deepest abyss.”
“Nearly there,” Macleod interrupted. “Activating floodlights.”
He depressed the joystick, flipping several switches on the console panel as he did so. Suddenly the screen came to life, the inky blackness replaced by a brilliant shimmer of speckles.
“Silt,” Macleod explained. “Our lights reflecting off particles disturbed in the water.”
They began to make out something more substantial, a shadowy background which gradually came into clearer view. It was the sea floor, a bleak, featureless expanse of grey. Macleod switched on the ROV’s terrain- contour radar which showed the seabed sloping down on a 30-degree gradient from the south.
“Depth 148 metres.”
A strange tower-like structure suddenly hove into view and Macleod halted the ROV a few metres away.
“Another of Costas’ ingenious contraptions. A remote-operated excavator, capable of drilling cores a hundred metres below the seabed or airlifting huge volumes of sediment.” With his free hand Macleod reached into a box beside his seat. “And this is what we found just below the sea floor.”
He passed Katya a shiny black object the size of his fist. She weighed it in her hand and cast a quizzical look.
“A beach pebble?”
“Worn smooth on the seashore. All along this gradient we’ve found evidence of an ancient coastline, one hundred and fifty metres deep and ten nautical miles from shore. Even more astonishing is its date. It’s one of the most remarkable discoveries we’ve ever made.”
Macleod punched in a set of GPS co-ordinates and the image on the screen began to move, the floodlit sea floor showing little change as the ROV kept to the same depth contour.
“I’ve put it on autopilot. Fifteen minutes to target.”
Katya handed back the blackened beach pebble. “Could this be associated with the Messinian salinity crisis?”
“We certainly would have put it before the arrival of humans — or rather, hominids — in this region two million years ago.”
“But?”
“But we would have been wrong. Wildly wrong. Submerged shorelines are hardly unusual in our line of work but this one’s big news. Follow me and I’ll show you.”
Macleod downloaded a computer-generated isometric map of the Black Sea and the Bosporus.
“The relationship between the Mediterranean and the Black Sea is a kind of microcosm of the Atlantic and the Mediterranean,” he explained. “The Bosporus is only about one hundred metres deep. Any lowering of the Mediterranean below that depth and it becomes a land bridge, cutting off the Black Sea. These were the conditions that allowed the first hominids in Europe to cross over from Asia.” He moved the cursor to highlight three river systems leading into the sea.
“When the Bosporus was a land bridge, evaporation caused the Black Sea to lower, just like the Mediterranean in the salinity crisis. But the Black Sea was replenished by river inflow, from the Danube, the Dnieper and the Don. A median was reached where the rate of evaporation equalled the rate of inflow, and from then on the change was in salinity, with the Black Sea eventually becoming a vast freshwater lake.”
He punched a key and the computer began to simulate the events he had been describing, showing the Bosporus becoming dry and the Black Sea lowering to a point about 150 metres below present sea level and 50 metres below the floor of the Bosporus, where its level was maintained by inflow from the rivers.
He swivelled round and looked at the others.
“Now for the surprise. This is not an image from the early Pleistocene, from the depths of the Ice Age. What you’re looking at is the Black Sea less than ten thousand years ago.”
Katya looked dumbfounded. “You mean
Macleod nodded vigorously. “The most recent glaciation peaked about twenty thousand years ago. We believe the Black Sea was cut off some time before that and had already dropped to the hundred and fifty metre contour. Our beach was the seashore for the next twelve thousand years.”
“Then what happened?”
“It recapitulates the Messinian salinity crisis. The glaciers melt, the Mediterranean rises, water cascades over the Bosporus. The immediate cause may have been a retreat phase some seven thousand years ago in the West Antarctic Ice Sheet. We believe it took only a year for the Black Sea to reach its present level. At full flow almost twenty cubic kilometres poured in daily, resulting in a rise of up to forty centimetres a day or two to three metres a week.”
Jack pointed at the lower part of the map. “Could you give us a close-up of this?”
“Certainly.” Macleod tapped a sequence and the screen zoomed in on the coast of northern Turkey. The isometric terrain mapper continued to depict the topography of the land before the inundation.
Jack edged forward as he spoke. “We’re currently eleven nautical miles off the north coast of Turkey, say eighteen kilometres, and the depth of the sea below us is about one hundred and fifty metres. A constant gradient to the present seashore would mean a rise of about ten metres for every kilometre and a half inland, say a ratio of one to one hundred and fifty. That’s a pretty shallow slope, hardly noticeable. If the sea rose as quickly as you indicate, then we’re looking at three or four hundred metres being flooded inland every week, say fifty metres a day.”
“Or even more,” Macleod said. “Before the inundation, much of what lies beneath us was only a few metres above sea level, with a sharper gradient close to the present shoreline as you begin to ascend the Anatolian Plateau. Within weeks huge areas would have been swamped.”
Jack looked at the map in silence for a few moments. “We’re talking about the early Neolithic, the first period of farming,” he mused. “What would conditions have been like here?”
Macleod beamed. “I’ve had our palaeoclimatologists working overtime on that one. They’ve run a series of simulations with all possible variables to reconstruct the environment between the end of the Pleistocene and the inundation.”
“And?”
“They believe this was the most fertile region in the entire Near East.”
Katya let out a low whistle. “It could be an entirely new tapestry of human history. A strip of coast twenty kilometres wide, hundreds of kilometres long, in one of the key areas for the development of civilization. And never before explored by archaeologists.”
Macleod was twitching with excitement. “And now the reason you’re here. It’s time to return to the ROV monitor.”
The seabed was now more undulating, with occasional rocky outcrops and furrowed depressions where there had once been ravines and river valleys. The depth gauge showed the ROV was over the submerged land surface, some fifteen metres shallower and a kilometre inland from the ancient shoreline. The GPS co-ordinates were beginning to converge with the target figures programmed in by Macleod.
“The Black Sea should be an archaeologists’ paradise,” Jack said. “The upper hundred metres are low in salt, a relic of the freshwater lake and a result of river inflow. Marine borers such as the shipworm
“But it’s a biologist’s nightmare,” Macleod countered. “Below a hundred metres it’s poisoned with hydrogen sulphide, a result of the chemical alteration of seawater as bacteria use it to digest the huge quantities of organic
