Illuminating the Past to Guide the Future

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On a humid August morning in south-central Alaska, a group of scientists hiked for four miles along a horse trail armed with rifles and an order to make as much noise as possible.

Their goal? Deter wandering grizzly and black bears.

“Field work can really keep you on your toes,” said Miriam Jones, one of the daring scientists, especially in a location as remote as the Kenai Peninsula. Jones and her team set off on this trek almost 13 years ago to extract a 5-meter long tube of squishy peat from sprawling wetlands. This was no ordinary mud. It contained approximately 14,500 years of information on past climates, including wet and dry periods of time.

With information from Alaskan mud and various other sites across North America, scientists from the U.S. Geological Survey and partners released a comprehensive study to improve our understanding of past climates and help fine-tune climate models for the future.

Understanding hidden records

Researchers extracting a peat core from a Kenai Peninsula peatland
Researchers extracting a peat core from a Kenai Peninsula peatland to study the climate and vegetation history over the last 14,500 years. Credit: Miriam Jones, USGS(Public domain.)

Artifacts of hurricanes and droughts are preserved in mud and other natural materials in the form of proxies like pollen, plant fossils and isotopes.

Understanding when past floods and dry spells occurred helps scientists reconstruct the natural climate system thousands of years ago. “We can look to the past to see what drives wet and dry patterns,” said Jessica Rodysill, the study’s lead author and a scientist with the U.S. Geological Survey.

The study gathers information from 73 different sites across North America. Each site holds information stretching back 2,000 years. Rodysill and her coauthors, including Jones, also a USGS scientist, found that generally, when temperatures warmed, the continent became drier. However, specific regions could deviate from the general trend depending on ocean temperatures and atmospheric pressure changes, which influence how air flows across the continent.

Understanding past climate requires precise data from many locations to capture these regional variations and show how they fit into a larger narrative.

Looking to the future

Although the study encompasses many parts of the continent, it also elucidates current gaps. For instance, the central and southeastern regions of the United States, central Canada and northern Mexico lack high resolution paleoclimate data that would otherwise have gone into this study.

Reconstructing ancient climates reveals extreme weather events as well as more moderate ones. Pinpointing when climate changed over time can help us better understand how and why environments reacted. Understanding the past will help us more accurately predict and prepare for the future.