Smeltende mongolsk is afslører skrøbelige artefakter, der giver fingerpeg om, hvordan tidligere mennesker levede

I verdens høje bjergområder, livet har brug for is. Fra Rockies til Himalaya, gletsjere og andre ophobninger af sne og is fortsætter hele året. Findes ofte på skyggefulde skråninger beskyttet mod solen, disse ispletter forvandler golde toppe til biologiske hot spots.

Som arkæolog, Jeg værdsætter disse sne- og ispletter for det sjældne kig, de kan give tilbage i tiden gennem tågen fra alpine forhistorie. Når folk mister genstande i isen, ispletter fungerer som naturlige dybfrysere. I tusinder af år, de kan gemme øjebliksbilleder af kulturen, daglig liv, teknologi og adfærd hos de mennesker, der skabte disse artefakter.

Frossen arv smelter fra bjergis på hver halvkugle. Som det gør det, små grupper af arkæologer kæmper for at samle den nødvendige finansiering og bemanding for at identificere, genvinde og studere disse genstande, før de er væk.

Sammen med en gruppe forskere fra University of Colorado, Mongoliets nationalmuseum og partnere fra hele verden, Jeg arbejder på at identificere, analysere og bevare gamle materialer, der dukker op fra isen i de græsklædte stepper i Mongoliet, hvor sådanne opdagelser har en enorm indflydelse på, hvordan videnskabsmænd forstår fortiden.

Livet ved iskanten

I de varme sommermåneder, unikke planter trives ved de godt vandede kanter af ispletter. Store dyr som rensdyr, elg, får og endda bisoner søger isen for at køle af eller flygte fra insekter.

Fordi ispletter er forudsigelige kilder til disse planter og dyr, samt ferskvand, de er vigtige for nærliggende menneskers underhold næsten overalt, hvor de findes. I Mongoliets tørre stepper, smeltevand fra bjergis føder sommergræsgange, og tamrensdyr opsøger isen på nogenlunde samme måde som deres vilde modstykker. Klimaopvarmning til side, iskanter fungerer som magneter for mennesker - og depoter af de materialer, de efterlader.

Det er ikke kun deres biologiske og kulturelle betydning, der gør ispletter til vigtige redskaber til at forstå fortiden. De håndgribelige genstande lavet og brugt af tidlige jægere eller hyrder i mange bjergrige områder blev konstrueret af bløde, organiske materialer. Disse skrøbelige genstande overlever sjældent erosion, vejr og udsættelse for de alvorlige elementer, der er almindelige i alpine områder. Hvis det kasseres eller tabes i isen, selvom, genstande, der ellers ville nedbrydes, kan bevares i århundreder under dybfrysningsforhold.

Men høje bjerge oplever ekstremt vejr og er ofte langt fra bycentre, hvor moderne forskere er koncentreret. Af disse grunde, betydelige bidrag fra bjergbeboere til den menneskelige historie er nogle gange udeladt af den arkæologiske optegnelse.

For eksempel, i Mongoliet, de høje bjerge i Altai var vært for regionens ældste pastorale samfund. Men disse kulturer kendes kun gennem en lille håndfuld begravelser og ruinerne af et par vindblæste stenbygninger.

Flere artefakter smelter ud af isen

En af vores opdagelser var et fint vævet stykke dyrehårreb fra en smeltende bjergtop-isplet i det vestlige Mongoliet. Ved undersøgelse, we spotted it lying among the rocks exposed at the edge of the retreating ice. The artifact, which may have been part of a bridle or harness, appeared as though it might have been dropped in the ice the just day before—our guides even recognized the technique of traditional manufacture. Imidlertid, scientific radiocarbon dating revealed that the artifact is actually more than 1, 500 years old.

Objects like these provide rare clues about daily life among the ancient herders of western Mongolia. Their excellent preservation allows us to perform advanced analyses back in the lab to reconstruct the materials and choices of the early herding cultures that eventually gave rise to pan-Eurasian empires like the Xiongnu and the Great Mongol Empire.

For eksempel, scanning electron microscopy allowed to us to pinpoint that camel hair was chosen as a fiber for making this rope bridle, while collagen preserved within ancient sinew revealed that deer tissue was used to haft a Bronze Age arrowhead to its shaft.

Sometimes, the objects that emerge end up overturning some of archaeologists' most basic assumptions about the past. People in the region have long been classified as herding societies, but my colleagues and I found that Mongolian glaciers and ice patches also contained hunting artifacts, like spears and arrows, and skeletal remains of big game animals like argali sheep spanning a period of more than three millennia. These finds demonstrate that big game hunting on mountain ice has been an essential part of pastoral subsistence and culture in the Altai Mountains for thousands of years.

But the clock is ticking. The summer of 2021 is shaping up to be one of the hottest ever recorded, as scorching summer temperatures fry the rainforests of the Pacific Northwest and wildfires ravage the Siberian Arctic. The impact of escalating temperatures is particularly severe in the world's cold regions.

In the area my colleagues and I study in western Mongolia, satellite photos show that more than 40% of the surface cover of ice has been lost over the past three decades. After each artifact is exposed by the melting ice, it may have only a limited window of time for recovery by scientists before it is damaged, degraded or lost because of the combination of freezing, thawing, weather and glacial activity that can affect previously frozen artifacts.

Because of the scale of modern climate change, it's difficult to quantify how much material is being lost. Many of the high mountains of Central and South Asia have never been systematically surveyed for melting artifacts. Ud over, many international projects have been unable to proceed since summer 2019 because of the COVID-19 pandemic—which has also prompted reductions, pay cuts and even complete closures of archaeology departments at leading universities.

Revealed by warming, providing climate clues

Ice patch artifacts are irreplaceable scientific datasets that can also help researchers characterize ancient responses to climate change and understand how modern warming may affect today's world.

In addition to human-made artifacts left behind in the snow, ice patches also preserve "ecofacts"—natural materials that trace important ecological changes, like shifting tree lines or changing animal habitats. By collecting and interpreting these datasets along with artifacts from the ice, scientists can gather insights into how people adapted to significant ecological changes in the past, and maybe expand the toolkit for facing the 21st-century climate crisis.

I mellemtiden the plant, animal and human communities that depend on dwindling ice patches are also imperiled. In northern Mongolia, my work shows that summer ice loss is harming the health of domestic reindeer. Local herders worry about the impact of ice loss on pasture viability. Melting ice also converges with other environmental changes:In western Mongolia, animal populations have dramatically dwindled because of poaching and poorly regulated tourism hunting.

As soaring heat exposes artifacts that provide insights into ancient climate resilience and other important scientific data, the ice loss itself is reducing humanity's resilience for the years ahead.

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