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From memory alloys now to the fragile historical record left by prehistoric societies. In some places, what little we know about those who came before us is being threatened by climate change.
As NPR's Elizabeth Shogren reports, archeologists are racing to learn about people who lived in the Arctic thousands of years ago, before the traces of their lives disappear forever.
ELIZABETH SHOGREN, BYLINE: Portland State University archeologist Shelby Anderson is fascinated by the ancient people who lived along the coast of what is now Northwestern Alaska. They hunted whales and seals and were connected by trade routes with people as far away as Northeast Asia. Frigid temperatures preserved lots of clues of their lives: tools, houses and even animal skins. But climate change is hastening their disappearance.
SHELBY ANDERSON: It's literally taking them away out into the ocean where I can't find them.
SHOGREN: When the sea ice connects to the shore, it protects the land from big waves and flooding. Because of global warming the ice connects about two weeks later in the autumn, than it did a decade ago. This leaves the coast vulnerable during the time of year when the worst storms usually come. There's also a larger area of water that is free of ice in the summer and early fall, which translates into bigger waves and storm surges. These forces exacerbate natural erosion on this coast.
Anderson has searched stretches of the coast for settlements that her colleagues documented 20 years ago, only to conclude that they've completely washed away. She also sees the damage in real time when she's in Alaska doing field work.
ANDERSON: Sites that I've been walking past, you know, for months, I'll see them lose five feet in one storm.
SHOGREN: There's another threat. Many areas that used to be permanently frozen are melting. Permafrost preserved plant material, leather and even whole people, which archeologists don't find in non-frozen environments.
ANDERSON: So something that survived for thousands of years, once it's exposed to the elements, quickly decomposes. And so, you know, there's less that we can learn from those objects.
SHOGREN: Like, say, an ivory carving that depicts the parkas and boots people wore thousands of years ago.
The permafrost also protected the shoreline. Exposed bluffs erode much faster than the ice covered ones did. All of this is agonizing for Anderson.
ANDERSON: And if these sites are gone, there's going to be nothing left to study. And I feel worried about it.
SHOGREN: Anderson knows she can't stop the forces of nature that are wiping away these archeological treasures. But she's determined to document as much as she can before it's gone. What she needs is better forecasts of which sections of the coast are likely to erode first.
ANDERSON: It's thousands and thousands of acres of uninvestigated land. I need to know, like, which specific area of the coast should I focus on.
SHOGREN: There could be some help on the way. The National Park Service owns the coastal land where Anderson works. It recently hired paleo-climatologist Maria Caffrey to calculate the risk national parks face from sea level rise and storm surges.
MARIA CAFFREY: We will be able to see where there are areas that are really exceptionally vulnerable to sea level rise.
SHOGREN: Caffrey hopes to finish forecasts for 105 coastal parks by 2016. She can make the best predictions when she has lots of historic data. She gets it from devices called tide gauges which can be used to measure sea level. The only tide gauge along the Northwestern Alaskan coast didn't record the data she needs.
CAFFREY: There's still a lot of question marks about what could happen with sea level in that particular area.
SHOGREN: Still, Caffrey hopes she can make good predictions. She found some data from Russian tide gauges and plans to use a temporary tide gauge on the Alaskan shore, before she makes her forecasts.
Elizabeth Shogren. NPR news. Transcript provided by NPR, Copyright NPR.