http://stream.publicbroadcasting.net/production/mp3/knau/local-knau-966983.mp3
Flagstaff, AZ – Earth Notes: Valles Caldera Climate Study
As concerns mount about the world's and the region's climate, scientists have found a time machine in New Mexico that helps them better understand the past.
At the Valles Caldera National Preserve west of Los Alamos, researchers from Northern Arizona University and other institutions have been studying sediments laid down long ago in a now-dry lakebed. They have extracted a plug of materials from as deep as 260 feet underground.
Close examination of these chemical, plant, and pollen remains provides a detailed record of what the area was like between 360,000 and 550,000 years ago. This regional picture of ancient climates is a rarity, since most cores studied for such purposes have come from beneath the ocean or Antarctica.
The researchers found that the climate of the Valles Caldera region shifted dramatically in the past. Some periods show evidence that the summer monsoon failed for many hundreds of years at a stretch, leading to what the team calls "mega-droughts" lasting for centuries. During these periods even drought-tolerant grasses decreased dramatically.
The sediment core shows regular shifts between such warm, dry conditions and cool, wet conditions that prevailed during ice ages as glaciers moved south. It suggests that overall temperatures, and the strength of the summer monsoon, may be a critical factor in determining what vegetation dominates the area.
And the researchers say that today's higher global temperatures may be leading to similar conditions including long-term drought that would alter not only plant communities, but also how people live in the area.
-Richard Mahler