Tuesday 23 June 2020

Viking History Is Melting Away in Greenland

One of the archaeological sites included in the study is located at Kangeq in the archipelago outside of Nuuk in West Greenland. Credit: Jørgen Hollesen National Museum of Denmark

Lining the fjords of Greenland are remnants of Viking-era Norse outposts that flourished for less than 500 years before they were mysteriously abandoned. And now this lost culture is experiencing a second disappearance, triggered by climate change.

Of all the archaeological sites in Greenland, Norse settlements are at the most risk of rotting away as the Arctic warms, according to new research published Thursday in Scientific Reports. The study estimates that up to 70 percent of the organic material in these sites could decay by 2100.

What stands to be lost is a unique record of remarkably preserved material: hair, textiles, human and animal bones, woods, hides, leathers. As the soil warms up and the number of frost-free days increases, microbes attack these fragile organics, leaving only rot behind. The changes are already happening near Greenland’s capital city of Nuuk, says lead study author Jørgen Hollesen, a senior researcher at the National Museum of Denmark. “Here we have some sites where we know that they found a lot of artifacts, a lot of bones, 40 years ago—but today we don’t see that much left,” he says. “There were bones at some point, but now it’s just this fine-grained mush.”

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Sunday 21 June 2020

History in Ice

(Dr. Nicole Spaulding, Climate Change Institute, University of Maine)
Colle Gnifetti glacier, Switzerland

Lead pollution levels from the Middle Ages preserved in an ice core taken from Colle Gnifetti glacier in the Swiss Alps reflect political upheaval in England, some 500 miles away, a multidisciplinary research team has found. In addition to studying archaeological data and tax records, the researchers used lasers to measure how lead levels in the core changed from year to year. They observed a major spike in lead pollution during the reign of the English Angevin kings—Henry II, Richard I, and John—between 1154 and 1216, when economic growth led to an increase in silver and lead production from British mines. Lead particles from the extraction and smelting processes were carried southeast by weather patterns, and traces of the metal were trapped in Swiss glaciers.

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Saturday 13 June 2020

Tree-ring analysis has solved many historical mysteries

Tree rings are now considered to be one of the most revealing of all climatic indicators. Getty Images

Depopulation, pandemics, the rise and fall of empires — all can be explained by dendrochronology, according to Valerie Trouet

History is only as good as its sources. It is limited largely to what has survived of written records, and in prehistory to random fragments unearthed by archaeologists and paleontologists. Climate history is no different. As the effects of global warming accelerate, it becomes ever more urgent to reassemble what we can of the atmospheric conditions of the past to gather evidence from wherever it may be.

Glacial ice cores are one place, with their frozen snapshots of long-ago air and traces of ash and pollen and greenhouse gases such as carbon dioxide or methane. Other climate proxies include the annual accretion of stalagmites, the growth of corals and the incremental layers of bone in the ears of fish. But in recent decades, tree rings have emerged as one of the most precise and revealing of all paleoclimatic indicators.

Each growing season, a tree adds an outer layer of cambium to its core of dead wood. How much is added is a function of thermal and pluvial conditions. The exact width of the ring and its microscopic structure give a very clear picture of the weather during a period of a few warm months, like a postcard from a distant summer.

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