NOAA/WDS Paleoclimatology - Trout Lake, Yukon 14,400 Year Midge-Inferred July Temperature

STUDY NOTES: Fossil midge larval data and inferred mean July air temperature, plus pollen data and Loss-on-Ignition data from Trout Lake, northern Yukon covering the past 14,400 years. Trout Lake, Yukon: 68.828°N, 138.75°W, 150m elevation, ~9m water depth.
ABSTRACT SUPPLIED BY ORIGINATOR: Two cores from Trout Lake, northern Yukon, yielded quantitative estimates of summer air temperatures using fossil midge larvae. Warming began around 14,400 cal yr BP, with inferred mean July air temperatures reaching values warmer than present by 12,800 cal yr BP. A 1°C cooling from 12,200 to 11,200 cal yr BP closely corresponds with the Younger Dryas chronozone. A broad temperature maximum occurred between 10,800 and 9,800 cal yr BP, with mean July air temperature about 2.2 °C warmer than present. This represents an early Holocene thermal maximum and coincides with increased organic content of the sediment. Both the shallow- and deep-water cores show similar temperature trends for their overlapping periods. The inferred rise in mean July air temperature at 14,200 cal yr BP coincides with a shift in vegetation from an herb- to shrub-dominated landscape. In contrast, the increase in Alnus pollen at 6,400 cal yr BP does not coincide with a change in temperature, but may be a response to a rise in precipitation.