Stefán Ólafsson of the Icelandic Archaeological Institute and Céline Dupont Hébert of Laval University, Quebec City, are the crew chiefs of a team of archaeologists with the unglamorous job of excavating a garbage dump at Hjalmarvik, an ancient farm on the northeastern coast of Iceland. Their approximately 9-by-12-foot excavation trench sits just outside what was a sod-walled farmhouse that may date back to the years shortly after 871, when Iceland was first settled by groups of Vikings from Norway. Today, the remains of the house are no more than a flat spot on the ground overlooking a small bay a few hundred yards to the west. The excavation of the garbage dump, or midden, is revealing a detailed record of life at the farm and provides clues to how its residents handled the severe challenges the island faced during an extended period of climatic disruption.

      The walls of the trench are striped with orange peat ash, probably discarded when the hearth inside the house was cleaned. Although the crew has uncovered interesting whalebone carvings—some decorated with images and others that were used as gaming pieces—the most common items found in the trench are the discarded bones of the animals eaten by Hjalmarvik’s residents. Laboratory analysis of the bones has not yet begun, but at first glance it looks like most of the food they were eating came from the surrounding ocean..

      “We are seeing a lot of seal and a lot of fish bones, also some sheep and a little bit of cow,” says Hébert, pointing to small chunks of bone. A large bone that may have come from a beached whale sticks out of the north wall of the trench. There are also pockets of oyster, clam, and periwinkle shells. Hébert says that until recently Icelanders ate shellfish only under dire circumstances, preferring to use it as bait for fishing.

      Near the top of the trench’s east wall, Ólafsson points out a gray stipe of volcanic ash that came from the 1477 eruption of a volcanic fissure named Veidivötn. This layer provides an easy way to date the latest part of the midden. The ash shows that the site was occupied throughout a period when Icelanders faced one of the greatest challenges to their survival—the Little Ice Age. Currently, an international group of archaeologists is excavating sites across the country in an effort to understand how Icelanders adapted to the colder climate. The project at Hjalmarvik and another excavation at a fishing station in the west called Gufuskálar are revealing how Icelanders changed the way they produced food so that they could survive what turned out to be centuries of long, cold winters.

      In 1258, somewhere near the equator, a massive volcano erupted, ultimately lowering global temperatures. According to a study coauthored by Penn State University climatologist Michael Mann, average temperatures in the years after the eruption dropped between 3.6 and 4.5 degrees, or about half as much as temperatures had dropped at the peak of the last major ice age, between

18,000 and 12,000 years ago. A group of scientists at the Institute of Arctic and Alpine Research in Colorado have identified the chain of events that followed the eruption, which they believe led to the long-term climate change of the Little Ice Age.

      The chain of events began when volcanoes threw chemical compounds called sulfates into the atmosphere. According to Gifford Miller, the institute’s associate director and a professor of geology at the University of Colorado Boulder, the process continued as sulfates reflected sunlight back into space. The resulting lack of sunlight not only dropped the temperature in the atmosphere, it made the surface waters of the ocean colder. The colder ocean produced more sea ice, which spread out from the polar ice caps, cooling waters closer to the equator. In addition, the white surface of the ice reflected sunlight, fu ther dropping temperatures. Miller says that although the sulfates would have fallen out of the atmosphere within two to four years, ocean temperatures would have taken 20 or 30 years to rebound. Sulfate levels in ice cores taken from glaciers in Greenland and Iceland show that additional eruptions at volcanoes in the tropics took place in 1268, 1275, and 1285, reinforcing the cooling effect. Because the effects of a changing climate are not felt evenly across the globe, the Little Ice Age began and ended at different times in different places. According to Miller, it started around 1258 in Iceland and lasted until about 1900.

      Even by the standards of a nation on the edge of the Arctic Circle, Hjalmarvik is a cold place. The warm water that comes up from the Caribbean andkeeps southern Iceland relativelywarm doesn’t reach this area. Here, the cold water of the Arctic Ocean dominates the climate. On a sunny day in mid-June, the temperature was about 50 degrees, while it was about 10 degrees warmer in the capital city of Reykjavik.

      Hjalmarvik seems to have been just one property within a much larger estate called Svalbard, which covered about 58 square miles of land. Most of Svalbard’s wealth came from growing grass to feed its herds of livestock, primarily cattle and sheep. No single farm could have made use of such a large amount of land, so smaller subordinate farms and workstations were built throughout the property to take advantage of pastures and other resources that were far from the main farm. To date, archaeologists have identified 17 of these. James Woollett, also of Laval University, is one of the project leaders looking at sites within Svalbard’s property, including Hjalmarvik, to understand how the farm functioned as a whole and how it changed over time.

      The relationship between Hjalmarvik and Svalbard is not entirely clear. The people at Hjalmarvik may have been independent farmers who gave a percentage of what they produced to Svalbard, or they may have been essentially slave laborers—people working only for food and shelter and forbidden by law to marry. In either case, Svalbard’s owner was in a position to allocate labor to herding livestock, fishing, and seal hunting. Once the Little Ice Age began, the farmers were faced with shorter growing seasons, which meant that they had to reduce the size of their herds. The colder climate forced the people living at Svalbard to change how they were producing their food.

      In 1988 Woollett was part of a team that excavated the midden at Svalbard. What that dig, as well as excavations at other sites on Svalbard’s property, revealed is that the people at the farm ate mostly mutton, beef, and a little pork in the middle of the thirteenth century, before the climate got colder. Woollett believes that the farmers at Svalbard figured out an ingenious strategy to adapt to the colder and less predictable climate as the Little Ice Age set in.

      During the coldest winters, sea ice would have covered the bays at Svalbard. This usually meant a short summer with little time to grow grass to feed sheep, but the ice also brought a food resource with it—seals. According to Woollett, the excavations around Svalbard reveal that after the Little Ice Age began, the amount of seal and fish bone in the middens dramatically increases, demonstrating that these animals were an important part of the diet. The people of Svalbard could also rely on getting a certain amount of food by fishing and by butchering beached whales.

      At the same time, the farmers at Svalbard changed their herding strategy. The farm would have kept a few cows for dairying and a few horses for transportation, but almost all of the animals raised at Svalbard were sheep. According to Woollett, this was a good approach because sheep are hardier and require less fodder than pigs and cattle. The pastures in northeastern Iceland aren’t as productive as those in continental Europe, so the strategy at Svalbard seems to have been to raise a relatively small number of sheep on a large amount of land. “The land is pretty crappy, but there is a lot of it,” says Woollett, adding, “they’re not producing what you want to eat if you are an elite [i.e., beef], but it is a predictable and durable system.” A similar system persisted for centuries. Even after farmers began to use tractors in the early to mid-twentieth century and were making money from tourists who wanted to fish in their rivers, sheep herding remained the agricultural focus of the area’s farms.

      Climate was not the only factor affecting the Icelanders’ survival. Even after the Little Ice Age had set in, the country was becoming more connected to Europe through trade as word spread about Iceland’s rich fishing grounds. Along the coast, then, as now, the warm-water Irminger Current and the cold-water East Greenland Current meet, causing nutrients from the deep ocean to rise closer to the surface, where fish feed. The water temperature and relatively shallow continental shelf around western Iceland also make it a perfect area for cod spawning. Fishing had started as a way for farmers to feed their families and trade with their neighbors, but, ultimately, it transformed into the lucrative international trade in dried cod. Historical documents record that by 1410 English ships were coming to Iceland both to buy dried cod and to fish these waters. The English were soon followed by traders from across Europe, including members of the Hanseatic League, an association of mostly German merchants who controlled much of the trade in northern Europe.

Evidence of the cod trade comes from the site of Gufuskálar at the end of the Snaefelsnes peninsula in western Iceland. There, Lilja Pálsdóttir of the Icelandic Archaeological Institute is leading a project to uncover the remains of an enormous fish-processing site. Walking along the shoreline, Pálsdóttir points out a few places where grooves were worn into the rock from years of having boat keels dragged over them. After hauling their boats on shore, fishermen would unload their catch and take the fish to be cleaned at workstations just off the rocky shoreline. The fish were gutted and their heads and part of their spines removed. The discarded bones of hundreds of years of activity now form a midden about three feet thick that extends for nearly a mile along the beach, testifying to the number of cod that were caught here. The fish would then have been taken back down to the beach, where they were washed and laid flat to dry on tables made of stacked lava rocks. After the fish were dried, they were piled inside a group of small huts, also made of lava rock, that sit a few hundred yards from the beach, to await transport. In 2009, when she first surveyed the drying huts, Pálsdóttir identified 154 of them, and takes them to be another indicator of how vast the fishing enterprise was and the impact it had on Iceland’s economy. “The cod trade changed the focus from inland farming to fishing,” says Pálsdóttir. Gufuskálar was on one of many tracts of land owned by the Catholic Church, and it is likely, according to Pálsdóttir, that the fishermen were providing their catch to the Church as rent for the pastureland where they grazed their sheep. In exchange for the fish, the Icelanders received some of the essential goods that they had trouble producing themselves—iron, grain, and lumber—as well as luxury goods from Europe, Pálsdóttir thinks. Cod, then, had become an important linchpin in Iceland’s economic survival. In 1450, a volcano called Kuwae erupted in the South Pacific, again cooling the climate. Within 50 years, Kuwae was followed by three eruptions at other, so-far-unknown, locations, which compounded the cooling effect. In addition, 1450 happened to be the beginning point of a 90-yearlong period of low solar activity called the Spörer Minimum. This combination of events led to one of the coldest phases of the Little Ice Age.. During periods when the climate was too cold for grass to grow and sheep were dying off, marine fish