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by Diamond, Jared

  First, because the Greenland Norse were literate and were visited by literate Icelanders and Norwegians, it would have been nice for those of us interested today in the Greenland Vikings’ fate if they had bothered to leave some accounts of Greenland’s weather then. Unfortunately for us, they didn’t. For Iceland, though, we have many accounts of weather in different years—including mentions of cold weather, rainfall, and sea ice—from incidental comments in diaries, letters, annals, and reports. That information about the climate in Iceland is of some use for understanding the climate in Greenland, because a cold decade in Iceland tends to be cold in Greenland as well, though the agreement isn’t perfect. We are on more secure ground in interpreting the significance for Greenland of comments about sea ice around Iceland, because that was the ice that made it difficult to sail to Greenland from Iceland or Norway.

  Our second source of information about past Greenland climates consists of pollen samples from sediment cores drilled into Greenland lakes and bogs by palynologists, the scientists who study pollen and whose insights into the vegetational history of Easter Island and the Maya area we already encountered (Chapters 2 and 5). Drilling down into the mud at the bottom of a lake or bog may not strike the rest of us as exciting, but it’s nirvana for a palynologist, because the deeper mud layers were deposited longer ago in the past. Radiocarbon dating of organic materials in a mud sample establishes when that particular layer of mud settled out. Pollen grains from different plant species look different under the microscope, so that the pollen grains in your (you the palynologist’s) mud sample tell you what plants were growing near your lake or bog and were releasing pollen that fell into it in that year. As past climates became colder in Greenland, palynologists find pollen shifting from that of warmth-demanding trees to that of cold-tolerant grasses and sedges. But that same shift in pollen may also mean that the Norse were cutting down trees, and palynologists have found other ways to distinguish those two interpretations of declining tree pollen.

  Finally, by far our most detailed information about Greenland climates in the past comes from ice cores. In Greenland’s cold and intermittently wet climate, trees are small, grow only locally, and their timber deteriorates quickly, so we don’t have for Greenland the logs with beautifully preserved tree rings that have enabled archaeologists to reconstruct year-to-year climate changes in the dry U.S. southwestern deserts inhabited by the Anasazi. Instead of tree rings, Greenland archaeologists have the good fortune of being able to study ice rings—or, actually, ice layers. Snow that falls each year on Greenland’s ice cap becomes compressed by the weight of later years of snow into ice. The oxygen in the water that constitutes snow or ice consists of three different isotopes, i.e., three different types of oxygen atoms differing just in atomic weight because of different numbers of uncharged neutrons in the oxygen nucleus. The overwhelmingly prevalent form of natural oxygen (99.8% of the total) is the isotope oxygen-16 (meaning oxygen of atomic weight 16), but there is also a small proportion (0.2%) of oxygen-18, and an even smaller amount of oxygen-17. All three of those isotopes are stable, not radioactive, but they can still be distinguished by an instrument called a mass spectrometer. The warmer the temperature at which snow forms, the higher is the proportion of oxygen-18 in the snow’s oxygen. Hence each year’s summer snow is higher in its proportion of oxygen-18 than the same year’s winter snow. For the same reason, snow oxygen-18 in a given month of a warm year is higher than in the same month of a cold year.

  Thus, as you drill down through the Greenland ice cap (something that Greenland-ice-cap-drilling scientists have now done down to a depth of almost two miles) and measure the oxygen-18 proportion as a function of depth, you see the oxygen-18 proportion wiggling up and down as you bore through one year’s summer ice into the preceding winter’s ice and then into the preceding summer’s ice, because of the predictable seasonal changes in temperature. You also find oxygen-18 values to differ among different summers or different winters, because of unpredictable year-to-year fluctuations in temperature. Hence the Greenland ice core yields information similar to what archaeologists studying the Anasazi deduce from tree rings: it tells us each year’s summer temperature and each year’s winter temperature, and as a bonus the thickness of the ice layer between consecutive summers (or between consecutive winters) tells us the amount of precipitation that fell during that year.

  There is one other feature of weather about which we can learn from ice cores, but not from tree rings, and that is storminess. Storm winds pick up salt spray from the ocean around Greenland, may blow it far inland over the ice cap, and drop there some of the spray frozen as snow, including the sodium ions in seawater. Onto the ice cap, storm winds also blow atmospheric dust, which originates far away in dry dusty areas of the continents, and that dust is high in calcium ions. Snow formed from pure water lacks those two ions. When one finds high concentrations of sodium and calcium in an ice layer of the ice cap, it may mean that that was a stormy year.

  In short, we can reconstruct past Greenland climates from Icelandic records, pollen, and ice cores, and the latter let us reconstruct climate on a year-to-year basis. What have we thereby learned?

  As expected, we’ve learned that the climate warmed up after the end of the last Ice Age around 14,000 years ago; the fjords of Greenland became merely “cool,” not “bitterly cold,” and they developed low forests. But Greenland’s climate hasn’t remained boringly steady for the last 14,000 years: it has gotten colder for some periods, then reverted to being milder again. Those climate fluctuations were important to the settling of Greenland by Native American peoples before the Norse. While the Arctic has few prey species—notably reindeer, seals, whales, and fish—those few species are often abundant. But if the usual prey species dies out or moves away, there may be no alternative prey for hunters to fall back on, as they can at lower latitudes where species are so diverse. Hence the history of the Arctic, including that of Greenland, is a history of people arriving, occupying large areas for many centuries, and then declining or disappearing or having to change their lifestyle over large areas when climate changes bring changes in prey abundance.

  Such consequences of climate changes for native hunters have been observed firsthand in Greenland during the 20th century. A warming of sea temperatures early in that century caused seals almost to disappear from southern Greenland. Good seal hunting returned when the weather got cooler again. Then, when the weather got very cold between 1959 and 1974, populations of migratory seal species plummeted because of all the sea ice, and total sea catches by native Greenland seal hunters declined, but the Greenlanders avoided starvation by concentrating on ringed seals, a species that remained common because it makes holes in the ice through which to breathe. Similar climate fluctuations with consequent changes in prey abundance may have contributed to the first settlement by Native Americans around 2500 B.C., their decline or disappearance around 1500 B.C., their subsequent return, their decline again, and then their complete abandonment of southern Greenland some time before the Norse arrived around A.D. 980. Hence the Norse settlers initially encountered no Native Americans, though they did find ruins left by former populations. Unfortunately for the Norse, the warm climate at the time of their arrival was simultaneously allowing the Inuit people (alias Eskimos) to expand quickly eastwards from Bering Strait across the Canadian Arctic, because the ice that had permanently closed the channels between northern Canadian islands during cold centuries began to melt in the summer, permitting bowhead whales, the mainstay of Inuit subsistence, to penetrate those Canadian Arctic waterways. That climate change allowed the Inuit to enter northwestern Greenland from Canada around A.D. 1200—with big consequences for the Norse.

  Between A.D. 800 and 1300, ice cores tell us that the climate in Greenland was relatively mild, similar to Greenland’s weather today or even slightly warmer. Those mild centuries are termed the Medieval Warm Period. Thus, the Norse reached Greenland during a period good for growing hay and pasturin
g animals—good by the standards of Greenland’s average climate over the last 14,000 years. Around 1300, though, the climate in the North Atlantic began to get cooler and more variable from year to year, ushering in a cold period termed the Little Ice Age that lasted into the 1800s. By around 1420, the Little Ice Age was in full swing, and the increased summer drift ice between Greenland, Iceland, and Norway ended ship communication between the Greenland Norse and the outside world. Those cold conditions were tolerable or even beneficial for the Inuit, who could hunt ringed seals, but were bad news for the Norse, who depended on growing hay. As we shall see, the onset of the Little Ice Age was a factor behind the demise of the Greenland Norse. But the climate shift from the Medieval Warm Period to the Little Ice Age was complex, and not a simple matter that “it got steadily colder and killed off the Norse.” There had been sprinklings of cold periods before 1300 that the Norse survived, and sprinklings of warm periods after A.D. 1400 that failed to save them. Above all, there remains the nagging question: why didn’t the Norse learn to cope with the Little Ice Age’s cold weather by watching how the Inuit were meeting the same challenges?

  To complete our consideration of Greenland’s environment, let’s mention its native plants and animals. The best-developed vegetation is confined to areas of mild climate sheltered from salt spray in the long inner fjords of the Western and Eastern Settlements on Greenland’s southwest coast. There, vegetation in areas not grazed by livestock varies by location. At higher elevations where it is cold, and in the outer fjords near the sea where plant growth is inhibited by cold, fog, and salt spray, the vegetation is dominated by sedges, which are shorter than grasses and have lower nutritional value to grazing animals. Sedges can grow in these poor locations because they are more resistant to drying out than are grasses, and they can thus establish themselves in gravel containing little water-retaining soil. Inland in areas protected from salt spray, the steep slopes and cold windy sites near glaciers are virtually bare rock without vegetation. Less hostile inland sites mostly support a heath vegetation of dwarf shrubs. The best inland sites—i.e., ones at low elevation, with good soil, protected from the wind, well watered, and with a south-facing exposure that lets them receive much sunlight—carry an open woodland of dwarf birch and willows with some junipers and alders, mostly less than 16 feet tall, in the very best sites with birches up to 30 feet tall.

  In areas grazed today by sheep and horses, the vegetation presents a different picture, and would have in Norse times as well (Plate 17). Moist meadows on gentle slopes, such as those around Gardar and Brattahlid, have lush grass up to one foot high, with many flowers. Patches of dwarf willow and birch grazed down by sheep reach only a foot-and-a-half in height. Drier, more sloping and exposed fields carry grasses or dwarf willow up to only a few inches high. Only where grazing sheep and horses have been excluded, such as within the perimeter fence around Narsarsuaq Airport, did I see dwarf willows and birches up to seven feet tall, stunted by cold wind coming off a nearby glacier.

  As for Greenland’s wild animals, the ones potentially most important to the Norse and Inuit were land and sea mammals and birds, fish, and marine invertebrates. Greenland’s sole native large terrestrial herbivore in the former Norse areas (i.e., not considering the musk ox in the far north) is the caribou, which Lapps and other native peoples of the Eurasian continent domesticated as reindeer but which the Norse and Inuit never did. Polar bears and wolves were virtually confined in Greenland to areas north of the Norse settlements. Smaller game animals included hares, foxes, land birds (of which the largest were grouse relatives called ptarmigans), freshwater birds (the largest being swans and geese), and seabirds (especially eider ducks and auks, a.k.a. alcids). The most important marine mammals were seals of six different species, differing in significance to the Norse and Inuit, related to differences in their distribution and behavior that I shall explain below. The largest of these six species is the walrus. Various species of whales occur along the coast, and were successfully hunted by the Inuit but not by the Norse. Fish abounded in rivers, lakes, and oceans, while shrimp and mussels were the most valuable edible marine invertebrates.

  According to sagas and medieval histories, around the year 980 a hot-blooded Norwegian known as Erik the Red was charged with murder and forced to leave for Iceland, where he soon killed a few more people and was chased out to another part of Iceland. Having ended up, there too, in a quarrel and killed still more people, he was this time exiled entirely from Iceland for three years beginning around 982.

  Erik remembered that, many decades earlier, one Gunnbjörn Ulfsson had been blown westwards far off course while sailing for Iceland and had spotted some barren small islands, which we now know lay just off Greenland’s southeast coast. Those islands had been revisited around 978 by Erik’s distant relative Snaebjörn Galti, who of course got into a quarrel of his own there with his shipmates and was duly murdered. Erik sailed for those islands to try his luck, spent the next three years exploring much of the Greenland coast, and discovered good pastureland inside the deep fjords. On his return to Iceland he lost yet another fight, impelling him to lead a fleet of 25 ships to settle the newly explored land that he shrewdly named Greenland. News brought back to Iceland of the fine homesteads available for the asking in Greenland motivated three more fleets of settlers to sail from Iceland during the next decade. As a result, by A.D. 1000 virtually all the land suitable for farms in both Western and Eastern Settlements had been occupied, yielding an eventual total Norse population estimated at around 5,000: about 1,000 people at Western Settlement, 4,000 at Eastern Settlement.

  From their settlements the Norse undertook explorations and annual hunting trips northwards along the west coast, far north of the Arctic Circle. One of those trips may have gotten as far north as latitude 79° N only 700 miles from the North Pole, where numerous Norse artifacts including pieces of chain mail armor, a carpenter’s plane, and ships’ rivets were discovered in an Inuit archaeological site. More certain evidence of northwards exploration is a cairn at latitude 73° N containing a runestone (a stone with writing in the Norse runic alphabet), which states that Erling Sighvatsson, Bjarni Thordarson, and Eindridi Oddson erected that cairn on the Saturday before Minor Rogation Day (April 25), probably in some year around 1300.

  Greenland Norse subsistence was based on a combination of pastoralism (growing domestic livestock) and hunting wild animals for meat. After Erik the Red brought livestock with him from Iceland, the Greenland Norse proceeded to develop a dependence on additional wild food to a degree much greater than in Norway and Iceland, whose milder climate permitted people to obtain most of their food requirements from pastoralism and (in Norway) gardening alone.

  Greenland’s settlers started out with aspirations based on the mix of livestock maintained by prosperous Norwegian chiefs: lots of cows and pigs, fewer sheep and still fewer goats, plus some horses, ducks, and geese. As gauged by counts of animal bones identified in radiocarbon-dated Greenland garbage middens from different centuries of Norse occupation, it quickly turned out that that ideal mix was not well suited to Greenland’s colder conditions. Barnyard ducks and geese dropped out immediately, perhaps even on the voyage to Greenland: there is no archaeological evidence of their ever having been kept there. Although pigs found abundant nuts to eat in Norway’s forests, and although Vikings prized pork above all other meats, pigs proved terribly destructive and unprofitable in lightly wooded Greenland, where they rooted up the fragile vegetation and soil. Within a short time they were reduced to low numbers or virtually eliminated. Archaeological finds of packsaddles and sledges show that horses were kept as work animals, but there was a Christian religious ban against eating them, so their bones rarely ended up in the garbage. Cows required far more effort than sheep or goats to rear in Greenland’s climate, because they could find grass in pastures only during the three snow-free summer months. For the rest of the year they had to be kept indoors in barns and fed on hay and other fodder whose acqu
isition became the main summer chore of Greenland farmers. The Greenlanders might have been better off to discard their labor-intensive cows, whose numbers did become reduced through the centuries, but they were too prized as status symbols to be eliminated entirely.

  Instead, the staple food-producing animals in Greenland became hardy breeds of sheep and goats much better adapted to cold climates than were the cattle. They had the additional advantage that, unlike cows, they can dig down under snow to find grass for themselves in the winter. In Greenland today, sheep can be kept outdoors for nine months per year (three times as long as cows) and have to be brought into shelter and fed for only the three months of heaviest snow cover. Numbers of sheep plus goats started off barely equal to cow numbers at early Greenland sites, and then rose with time to as many as eight sheep or goats for every cow. As between sheep and goats, Icelanders kept six or more of the former for every one of the latter, and that was also the ratio at the best Greenland farms during early years of settlement, but relative numbers shifted with time until goat numbers rivaled those of sheep. That’s because goats but not sheep can digest the tough twigs, shrubs, and dwarf trees prevalent in poor Greenland pastures. Thus, while the Norse arrived in Greenland with a preference for cows over sheep over goats, the suitability of those animals under Greenland conditions was in the opposite sequence. Most farms (especially those in the more northerly and hence more marginal Western Settlement) had to content themselves eventually with more of the despised goats and few of the honored cows; only the most productive Eastern Settlement farms succeeded in indulging their cow preference and goat scorn.