Impact of millennial-scale Holocene climate variability on eastern North American terrestrial ecosystems: pollen-based climatic reconstruction

摘要

We present paleoclimatic evidence for a series of Holocene millennial-scale cool intervals in eastern North America that occurred every ～1400 years and lasted ～300-500 years, based on pollen data from Chesapeake Bay in the mid-Atlantic region of the United States. The cool events are indicated by significant decreases in pine pollen, which we interpret as representing decreases in January temperatures of between 0.2° and 2℃. These temperature decreases include excursions during the Little Ice Age (～1300-1600 AD) and the 8 ka cold event. The timing of the pine minima is correlated with a series of quasi-periodic cold intervals documented by various proxies in Greenland, North Atlantic, and Alaskan cores and with solar minima interpreted from cosmogenic isotope records. These events may represent changes in circumpolar vortex size and configuration in response to intervals of decreased solar activity, which altered jet stream patterns to enhance meridional circulation over eastern North America.