A 267 YEAR RECONSTRUCTION OF SPRING LAKE ERIE LEVELS BASED ON NORTH PACIFIC TREE RING SERIES

The Pacific North American teleconnection pattern (PNA) is an index of atmospheric circulation that links climate in the North Pacific with the Midwestern United States. Previous comparisons show significant relationships between the PNA and precipitation and streamflow in Ohio. Tree ring series in the North Pacific reflect the ocean-atmosphere system and have been used to reconstruct surface air temperatures, sea surface temperatures and climate indices of Pacific decadal variability. These tree-ring series are also highly correlated with hydrometeorological records in the Midwest, such as Lake Erie levels. Eighteen tree ring chronologies from the Gulf of Alaska region are all significantly correlated with spring lake levels as recorded by NOAA since 1918. A well-verified model using principal component regression analysis was constructed based on a subset of four ring-width series from coastal sites in southern Alaska. The tree-ring based model explains 53% of the variation in recorded Lake Erie levels for a common 70 year period (1918-1987). Reconstructed Lake Erie levels span 267 years, extending the observational record back 197 years. According to this reconstruction during the mid 1700's and mid 1800's spring lake levels were as high as levels of recent decades. Relatively low stands occurred during the late 1700's and early 1900's. The variability in the lake levels over this time period is multidecadal in scale. Further verification based on observational records is currently in progress.

Negative phases of the PNA are associated with cold intervals in the North Pacific, which are linked to cooler and wetter winters in the Lake Erie basin. These conditions result in reduced lake evaporation with more continuous ice cover coupled with higher precipitation that together may explain the past higher spring lake levels.