Archive for the ‘paleoclimate’ Category

Thousands of years ago, a warm Arctic made mid-latitudes drier

March 28th, 2019
The Arctic is the fastest-warming region of the planet.

Enlarge / The Arctic is the fastest-warming region of the planet. (credit: NASA)

The thing about a global climate change is that it isn’t as simple as shifting the temperatures everywhere by a set number of degrees. The temperature change isn’t uniform around the globe, and these regional differences can drive considerable knock-on effects on weather patterns.

The Arctic, for example, will warm more than the equatorial region. For our current global warming venture, there will be consequences of this fact beyond the Arctic itself. One juicy hypothesis is that the greater Arctic warming affects the behavior of the polar jet stream, driving significant changes on extreme weather patterns in the mid-latitudes. This idea is the subject of ongoing research, as well as genuine scientific debate and uncertainty.

Lessons from the past

One way to study patterns like this is to look to past climate changes. That’s what a team led by Northern Arizona University’s Cody Routson did, compiling paleoclimate records of rainfall in the Northern Hemisphere over the last 10,000 years.

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Posted in climate change, paleoclimate, science | Comments (0)

Huge, previously unknown impact crater found beneath Greenland’s ice

November 18th, 2018
Huge, previously unknown impact crater found beneath Greenland’s ice

Enlarge (credit: Natural History Museum of Denmark et al.)

You might not think of giant impact craters as being particularly subtle or in any way capable of hiding from us. If so, you’ll be surprised by the discovery, announced this week, of a 31-kilometer- (19-mile-) wide crater we didn’t know existed.

Let’s get the important questions out of the way—no, the crater isn’t home to a Godzilla or some Lovecraftian horror. It’s filled with ice. And that’s how it escaped our notice for so long.

The crater lies beneath Hiawatha Glacier in northwestern Greenland. One of the tools researchers use to monitor the shrinking of the Greenland Ice Sheet is airborne radar surveys. The resulting high-resolution data shows the shape of the ice sheet’s surface, some of its internal layering, and even the bedrock below. In this case, it revealed a suspiciously circular depression in the ice near the glacier’s edge.

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Posted in Greenland, Impact crater, paleoclimate, science, Younger Dryas | Comments (0)

Neanderthal teeth reveal lead exposure and difficult winters

October 31st, 2018
Neanderthal teeth reveal lead exposure and difficult winters


A new study of oxygen isotope ratios and heavy metals in the tooth enamel of Neanderthals who lived and died 250,000 years ago in southeast France suggests that they endured colder winters and more pronounced differences between seasons than the region’s modern residents. The two Neanderthals in the study also experienced lead exposure during their early years, making them the earliest known instances of this exposure.

Enduring harsh winters

Tooth enamel forms in thin layers, and those layers record the chemical traces of a person’s early life—from climate to nutrition to chemical exposures—a little like tree rings on a much smaller scale. Archaeologist Tanya Smith of Griffith University and her colleagues examined microscopic samples of tooth enamel from two Neanderthal children from the Payre site in southeastern France. The teeth were radiocarbon dated to around 250,000 years ago, and the set of samples recorded about three years of life.

One important clue to past environments is oxygen, which comes from the water a person drank or the plants they ate. The ratio of the oxygen-18 isotope to oxygen-16 depends on temperature, precipitation, and evaporation. Generally, higher ratios of oxygen-18 indicate warmer, drier conditions with more evaporation.

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Posted in Archaeology, biological archaeology, isotope analysis, Neanderthals, paleoanthropology, paleoclimate, science, teeth | Comments (0)

Archaeologists find 300,000-year-old stone tools in Saudi Arabia

October 29th, 2018
Archaeologists find 300,000-year-old stone tools in Saudi Arabia

Enlarge (credit: Roberts et al. 2018)

Stone tools unearthed in Saudi Arabia’s inhospitable Nefud Desert indicate that members of our genus Homo had ventured beyond the familiar borders of Africa and the Levant sometime between 300,000 and 500,000 years ago. And according to climate data captured in the bones of animals found at the site, the environment they moved into may not have been that different from the one they left behind in East Africa. That may help anthropologists better understand the role of environment—and the ability to adapt to challenging new landscapes—in shaping human evolution and global expansion.

The things they left behind

Archaeologist Patrick Roberts of the Max Planck Institute for the Science of Human History and his colleagues recently discovered a handful of stone tools in a sandy layer of soil beneath the dry traces of a shallow Pleistocene lake at Ti’s al Ghadah, in the Nefud Desert of northern Saudi Arabia. The soil layer dated to between 300,000 and 500,000 years ago, and it also contained fossilized remains of grazing animals, water birds, and predators like hyena and jaguar. Many of the bones seem to bear the marks of butchering by tool-wielding hominins.

Archaeologists had found other fossils at the site with possible cut marks, but, without stone tools, it’s difficult to determine if a notch in a fossil rib was put there by a human hand and not another predator or natural process. The tools—six sharp brown chert flakes and a scraper—make a much clearer case. Roberts and his colleagues say they’re the oldest radiometrically dated hominin artifacts in the Arabian Peninsula, edging out the previous contender by 100,000 years.

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Posted in anthropology, arabian peninsula, Archaeology, fossil record, homo erectus, human ancestors, human migration, out of africa, paleoanthropology, paleoclimate, paleoecology, Saudi Arabia, science, Stable isotope, stone tools | Comments (0)