The Sea Around Us (27 page)

But these bland climatic conditions begin to deteriorate in the thirteenth century. The Eskimos began to make troublesome raids, perhaps because their northern sealing grounds were frozen over and they were hungry. They attacked the western settlement near the present Ameralik Fiord, and when an official mission went out from the eastern colony about 1342, not a single colonist could be found—only a few cattle remained. The eastern settlement was wiped out some time after 1418 and the houses and churches destroyed by fire. Perhaps the fate of the Greenland colonies was in part due to the fact that ships from Iceland and Europe were finding it increasingly difficult to reach Greenland, and the colonists had to be left to their own resources.

The climatic rigors experienced in Greenland in the thirteenth and fourteenth centuries were felt also in Europe in a series of unusual events and extraordinary catastrophes. The seacoast of Holland was devastated by storm floods. Old Icelandic records say that, in the winters by the early 1300's, packs of wolves crossed on the ice from Norway to Denmark. The entire Baltic froze over, forming a bridge of solid ice between Sweden and the Danish islands. Pedestrians and carriages crossed the frozen sea and hostelries were put up on the ice to accommodate them. The freezing of the Baltic seems to have shifted the course of storms originating in the low-pressure belt south of Iceland. In southern Europe, as a result, there were unusual storms, crop failures, famine, and distress. Icelandic literature abounds in tales of volcanic eruptions and other violent natural catastrophes that occurred during the fourteenth century.

What of the previous era of cold and storms, which should have occurred about the third or fourth century B.C., according too the tidal theory? There are shadowy hints in early literature and folklore. The dark and brooding poetry of the Edda deals with a great catastrophe, the Fimbul-winter or Götterdämmerung, when frost and snow ruled the world for generations. When Pytheas journeyed to the seas north of Iceland in 330 B.C., he spoke of the
mare pigrum,
a sluggish, congealed sea. Early history contains striking suggestions that the restless movements of the tribes of northern Europe—the southward migrations of the ‘barbarians' who shook the power of Rome—coincided with periods of storms, floods, and other climatic catastrophes that forced their migrations. Large-scale inundations of the sea destroyed the homelands of the Teutons and Cimbrians in Jutland and sent them southward into Gaul. Tradition among the Druids said that their ancestors had been expelled from their lands on the far side of the Rhine by enemy tribes and by ‘a great invasion of the ocean.' And about the year 700 B.C. the trade routes for amber, found on the coasts of the North Sea, were suddenly shifted to the east. The old route came down along the Elbe, the Weser, and the Danube, through the Brenner Pass to Italy. The new route followed the Vistula, suggesting that the source of supply was then the Baltic. Perhaps storm floods had destroyed the earlier amber districts, as they invaded these same regions eighteen centuries later.

All these ancient records of climatic variations seemed to Pettersson an indication that cyclic changes in the oceanic circulation and in the conditions of the Atlantic had occurred. ‘No geologic alteration that could influence the climate has occurred for the past six or seven centuries,' he wrote. The very nature of these phenomena—floods, inundations, ice blockades—suggested to him a dislocation of the oceanic circulation. Applying the discoveries in his laboratory on Gulmarfiord, he believed that the climatic changes were brought about as the tide-induced submarine waves disturbed the deep waters of polar seas. Although tidal movements are often weak at the surface of these seas, they set up strong pulsations at the submarine boundaries, where there is a layer of comparatively fresh, cold water lying upon a layer of salty, warmer water. In the years or the centuries of strong tidal forces, unusual quantities of warm Atlantic water press into the Arctic Sea at deep levels, moving in under the ice. Then thousands of square miles of ice that normally remain solidly frozen undergo partial thawing and break up. Drift ice, in extraordinary volume, enters the Labrador Current and is carried southward into the Atlantic. This changes the pattern of surface circulation, which is so intimately related to the winds, the rainfall, and the air temperatures. For the drift ice then attacks the Gulf Stream south of Newfoundland and sends it on a more easterly course, deflecting the streams of warm surface water that usually bring a softening effect to the climate of Greenland, Iceland, Spitsbergen, and northern Europe. The position of the low-pressure belt south of Iceland is also shifted, with further direct effect on European climate.

Although the really catastrophic disturbances of the polar regime come only every eighteen centuries, according to Pettersson, there are also rhythmically occurring periods that fall at varying intervals—for example, every 9, 18, or 36 years. These correspond to other tidal cycles. They produce climatic variations of shorter period and of less drastic nature.

The year 1903, for instance, was memorable for its outbursts of polar ice in the Arctic and for the repercussions on Scandinavian fisheries. There was ‘a general failure of cod, herring, and other fish along the coast from Finmarken and Lofoten to the Skagerrak and Kattegat. The greater part of the Barents Sea was covered with pack ice up to May, the ice border approaching closer to the Murman and Finmarken coasts than ever before. Herds of arctic seals visited these coasts, and some species of the arctic whitefish extended their migrations to the Christiana Fiord and even entered into the Baltic.' This outbreak of ice came in a year when earth, moon, and sun were in a relative position that gives a secondary maximum of the tide-producing forces. The similar constellation of 1912 was another great ice year in the Labrador Current—a year that brought the disaster of the
Titantic.

Now in our own lifetime we are witnessing a startling alteration of climate, and it is intriguing to apply Otto Pettersson's ideas as a possible explanation. It is now established beyond question that a definite change in the arctic climate set in about 1900, that it became astonishingly marked about 1930, and that it is now spreading into sub-arctic and temperate regions. The frigid top of the world is very clearly warming up.

The trend toward a milder climate in the Arctic is perhaps most strikingly apparent in the greater ease of navigation in the North Atlantic and the Arctic Sea. In 1932, for example, the
Knipowitsch
sailed around Franz Josef Land for the first time in the history of arctic voyaging. And three years later the Russian ice-breaker
Sadko
went from the northern tip of Novaya Zemlya to a point north of Severnaya Zemlya (Northern Land) and thence to 82° 41' north latitude—the northernmost point ever reached by a ship under its own power.

In 1940 the whole northern coast of Europe and Asia was remarkably free from ice during the summer months, and more than 100 vessels engaged in trade via the arctic routes. In 1942 a vessel unloaded supplies at the west Greenland port of Upernivik (latitude 72° 43' N) during Christmas week ‘in almost complete winter darkness.' During the 'forties the season for shipping coal from West Spitsbergen ports lengthened to seven months, compared with three at the beginning of the century. The season when pack ice lies about Iceland became shorter by about two months that it was a century ago. Drift ice in the Russian sector of the Arctic Sea decreased by a million square kilometers between 1924 and 1944, and in the Laptev Sea two islands of fossil ice melted away completely, their position being marked by submarine shoals.

Activities in the nonhuman world also reflect the warming of the Arctic—the changed habits and migrations of many fishes, birds, land mammals, and whales.

Many new birds are appearing in far northern lands for the first time in our records. The long list of southern visitors—birds never reported in Greenland before 1920—includes the American velvet scoter, the greater yellowlegs, American avocet, black-browed albatross, northern cliff swallow, ovenbird, common crossbill, Baltimore oriole, and Canada warbler. Some high-arctic forms, which thrive in cold climates, have shown their distaste for the warmer temperatures by visiting Greenland in sharply decreasing numbers. Such abstainers include the northern horned lark, the grey plover, and the pectoral sandpiper. Iceland, too, has had an extraordinary number of boreal and even subtropical avian visitors since 1935, coming from both America and Europe. Wood warblers, skylarks, and Siberian rubythroats, scarlet grosbeaks, pipits, and thrushes now provide exciting fare for Icelandic bird watchers.

When the cod first appeared in Angmagssalik in Greenland in 1912, it was a new and strange fish to the Eskimos and Danes. Within their memory it had never before appeared on the east coast of the island. But they began to catch it, and by the 1930's it supported so substantial a fishery in the area that the natives had become dependent upon it for food. They were also using its oil as fuel for their lamps and to heat their houses.

On the west coast of Greenland, too, the cod was a rarity at the turn of the century, although there was a small fishery, taking about 500 tons a year, at a few places on the southwest coast. About 1919 the cod began to move north along the west Greenland coast and to become more abundant. The center of the fishery has moved 300 miles farther north, and the catch is now about 15,000 tons a year.

Other fishes seldom or never before reported in Greenland have appeared there. The coalfish or green cod is a European fish so foreign to Greenland waters that when two of them were caught in 1831 they were promptly preserved in salt and sent to the Co-penhagen Zoological Museum. But since 1924 this fish has often been found among the cod shoals. The haddock, cusk, and ling, unknown in Greenland waters until about 1930, are now taken regularly. Iceland, too, has strange visitors—warmth-loving southern fishes, like the basking shark, the grotesque sunfish, the six-gilled shark, the swordfish, and the horse mackerel. Some of these same species have penetrated into the Barents and White seas and along the Murman coast.

As the chill of the northern waters has abated and the fish have moved poleward, the fisheries around Iceland have expanded enormously, and it has become profitable for trawlers to push on to Bear Island, Spitsbergen, and the Barents Sea. These waters now yield perhaps two billion pounds of cod a year—the largest catch of a single species by any fishery in the world. But its existence is tenuous. If the cycle turns, the waters begin to chill, and the ice floes creep southward again, there is nothing man can do that will preserve the arctic fisheries.

But for the present, the evidence that the top of the world is growing warmer is to be found on every hand. The recession of the northern glaciers is going on at such a rate that many smaller ones have already disappeared. If the present rate of melting continues others will soon follow them.

The melting away of the snowfields in the Opdal Mountains in Norway has exposed wooden-shafted arrows of a type used about A.D. 400 to 500. This suggests that the snow cover in this region must now be less than it has been at any time within the past 1400 to 1500 years.

The glaciologist Hans Ahlmann reports that most Norwegian glaciers ‘are living only on their own mass without receiving any annual fresh supply of snow'; that in the Alps there has been a general retreat and shrinkage of glaciers during the last decades, which became ‘catastrophic' in the summer of 1947; and that all glaciers around the Northern Atlantic coasts are shrinking. The most rapid recession of all is occurring in Alaska, where the Muir Glacier receded about 10½ kilometers in 12 years.

At present the vast antarctic glaciers are an enigma; no one can say whether they also are melting away, or at what rate. But reports from other parts of the world show that the northern glaciers are not the only ones that are receding. The glaciers of several East African high volcanoes have been diminishing since they were first studied in the 1800's—very rapidly since 1920—and there is glacial shrinkage in the Andes and also in the high mountains of central Asia.

The milder arctic and sub-arctic climate seems already to have resulted in longer growing seasons and better crops. The cultivation of oats has improved in Iceland. In Norway good seed years are now the rule rather than the exception, and even in northern Scandinavia the trees have spread rapidly above their former timber lines, and both pine and spruce are making a quicker annual growth than they have for some time.

The countries where the most striking changes are taking place are those whose climate is most directly under the control of the North Atlantic currents. Greenland, Iceland, Spitsbergen, and all of northern Europe, as we have seen, experience heat and cold, drought and flood in accordance with the varying strength and warmth of the eastward and northward-moving currents of the Atlantic. Oceanographers who have been studying the matter during the 1940's have discovered many significant changes in the temperature and distribution of great masses of ocean water. Apparently the branch of the Gulf Stream that flows past Spitsbergen has so increased in volume that it now brings in a great body of warm water. Surface waters of the North Atlantic show rising temperatures; so do the deeper layers around Iceland and Spitsbergen. Sea temperatures in the North Sea and along the coast of Norway have been growing warmer since the 1920's.

Unquestionably, there are other agents at work in bringing about the climatic changes in the Arctic and sub-Arctic regions. For one thing, it is almost certainly true that we are still in the warming-up stage following the last Pleistocene glaciation—that the world's climate, over the next thousands of years, will grow considerably warmer before beginning a downward swing into another Ice Age. But what we are experiencing now is perhaps a climatic change of shorter duration, measurable only in decades or centuries. Some scientists say that there must have been a small increase in solar activity, changing the patterns of air circulation and causing the southerly winds to blow more frequently in Scandinavia and Spitsbergen; changes in ocean currents, according to this view, are secondary effects of the shift of prevailing winds.