Paleoclimate changes in the Pacific Northwest over the past 36,000Â years from clumped isotope measurements and model analysis

We use clumped isotope (Lambda(47)) thermometry and carbonate delta O-18 measurements of glacial and deglacial pedogenic carbonates from the Palouse Loess to provide constraints on hydroclimate changes in the Pacific Northwest. We also employ analysis of climate model simulations to help us further provide constraints on the hydroclimate changes in the Pacific Northwest.

The coldest clumped isotope soil temperatures T( Delta(47)) (13.5 +/- 1.9(degrees)C to 17.1 1.7(degrees)C) occurred similar to 34,000-23,000 years ago. Using a soil-to-air temperature transfer function, we estimate Last Glacial Maximum (LGM) mean annual air temperatures of similar to-5.5(degrees)C and warmest average monthly temperatures (i.e., mean summer air temperatures) of similar to 4.4 degrees C. These data indicate a regional warming of 16.4 +/- 2.6(degrees)C from the LGM to the modern temperatures of 10.9(degrees)C, which was about 2.5-3 times the global average.