Deglacial to middle Holocene (16,600 to 6000 calendar years BP) climate change in the northeastern United States inferred from multi-proxy stable isotope data, Seneca Lake, New York

摘要

Climate change in the northeastern United States has been inferred for the last deglaciation to middle Holocene (~16,600 to 6000 calendar years ago) using multi-proxy data (total organic matter, total carbonate content, δ~(18)O calcite and δ~(13)C calcite) from a 5 m long sediment core from Seneca Lake, New York. Much of the regional postglacial warming occurred during the well-known Bolling and Allerod warm periods (～14.5 to 13.0 ka), but climate amelioration in the northeastern United States preceded that in Greenland by ~2000 years. An Oldest Dryas climate event (～15.1 to 14.7 ka) is recognized in Seneca Lake as is a brief Older Dryas (～14.1 ka) cold event. This latter cold event correlates with the regional expansion of glacial Lake Iroquois and global meltwater pulse IA. An increase in winter precipitation and a shorter growing season likely characterized the northeastern United States at this time. The Intra-Allerod Cold Period (～13.2 ka) is also evident supporting an “Amphi-Atlantic Oscillation” at this time. The well-known Younger Dryas cold interval occurred in the northeastern United States between 12.9 and 11.6 ka, consistent with ice core data from Greenland. In the Seneca Lake record, however, the Younger Dryas appears as an asymmetric event characterized by an abrupt, high-amplitude beginning followed by a more gradual recovery. Compared to European records, the Younger Dryas in the northeastern United States was a relatively low-amplitude event. The largest amplitude and longest duration anomaly in the Seneca Lake record occurs after the Younger Dryas, between ~11.6 and 10.3 ka. This “post-Younger Dryas climate interval” represents the last deglacial climate event prior to the start of the Holocene in the northeastern United States, but has not been recognized in Greenland or Europe. The early to middle Holocene in the northeastern United States was characterized by low-amplitude climate variability. A general warming trend during the Holocene Hypsithermal peaked at ～9 ka coincident with maximum summer insolation controlled by orbital parameters. Millennial- to century-scale variability is also evident in the Holocene Seneca Lake record, including the well-known 8.2 ka cold event (as well as events at ～7.1 and 6.6 ka). Hemispherical cooling during the Holocene Neoglacial in the northeastern United States began ～5.5 ka in response to decreasing summer insolation.