This supports the idea that temperature cycles in the region of 60 years are very likely a common feature of Earth’s climate.
Deploying a new technique for the first time in the region, geoscientists at the University of Massachusetts Amherst have reconstructed the longest and highest-resolution climate record for the Northeastern United States, which reveals previously undetected past temperature cycles and extends the record 900 years into the past, well beyond the previous early date of 1850, reports Phys.org.
First author Daniel Miller, with Helen Habicht and Benjamin Keisling, conducted this study as part of their doctoral programs with advisors geosciences professors Raymond Bradley and Isla Castañeda.
As Miller explains, they used a relatively new quantitative method based on the presence of chemical compounds known as branched glycerol dialkyl glycerol tetra ethers (branched GDGTs) found in lakes, soils, rivers and peat bogs around the world. The compounds can provide an independent terrestrial paleo-thermometer that accurately assesses past temperature variability.
Miller says, “This is the first effort using these compounds to reconstruct temperature in the Northeast, and the first one at this resolution.” He and colleagues were able to collect a total of 136 samples spanning the 900-year time span, many more than would be available with more traditional methods and from other locations that typically yield just one sample per 30-100 years.
In their results, Miller says, “We see essentially cooling throughout most of the record until the 1900s, which matches other paleo-records for North America. We see the Medieval Warm Period in the early part and the Little Ice Age in the 1800s.”
An unexpected observation was 10, 50-to-60-year temperature cycles not seen before in records from Northeast U.S., he adds, “a new finding and surprising. We’re trying to figure out what causes that. It may be caused by changes in the North Atlantic Oscillation or some other atmospheric patterns. We’ll be looking further into it.”
via Tallbloke’s Talkshop
January 13, 2019 at 11:03AM