Regional atmospheric circulation change in the North Pacific during the Holocene inferred from lacustrine carbonate oxygen isotopes, Yukon Territory, Canada

Analyses of sediment cores from Jellybean Lake, a small, evaporation-insensitive groundwater-fed lake, provide a record of changes in North Pacific atmospheric circulation for the last ̈7500 yr at 5to 30-yr resolution. Isotope hydrology data from the southern Yukon indicate that the oxygen isotope composition of water from Jellybean Lake reflects the composition of mean-annual precipitation, y18Op. Recent changes in the yO of Jellybean sedimentary calcite (yOca) correspond to changes in the North Pacific Index (NPI), a measure of the intensity and position of the Aleutian Low (AL) pressure system. This suggests that y18Op variability was related to the degree of fractionation during moisture transport from the Gulf of Alaska across the St. Elias Mountains and that Holocene shifts were controlled by the intensity and position of the AL. Following this model, between ̈7500 and 4500 cal yr B.P., long-term trends suggest a predominantly weaker and/or westward AL. Between ̈4500 and 3000 cal yr B.P. the AL shifted eastward or intensified before shifting westward or weakening between ̈3000 and 2000 cal yr B.P. Rapid shifts eastward and/or intensification occurred ̈1200 and 300 cal yr B.P. Holocene changes in North Pacific atmospheric circulation inferred from Jellybean Lake oxygen isotopes correspond with late Holocene glacial advances in the St. Elias Mountains, changes in North Pacific salmon abundance, and shifts in atmospheric circulation over the Beaufort Sea. D 2005 University of Washington. All rights reserved.