Inter-comparison of Ice Core δ(18O) and Precipitation Records from Sites in Canada and Greenland over the last 3500 years and over the last few Centuries in detail using EOF Techniques.
Oxygen -18 records for the Polar sites in Canada and Greenland are compared over the last 3500 years on a 50 yr average basis. The common spatial covariance is found using EOF (Empirical Orthogonal Functions) techniques that identify two main spatial modes that occur with nearly the same frequency. Together these two Eigenvectors explain 50% of the variance in the detrended O-18 records.
One year averages of absolutely dated O-18 and precipitation records for the most recent few centuries from Greenland and Canada are compared and stacked by region, to reduce noise levels. The stacked records are then compared to met-station temperature and precipitation data in Greenland, Iceland and Canada. When the ice core δ and met-station temperature series are normalized and their common Eigenvectors found, a remarkable 50 % of the variance is explained by the first vector with the δ and temperature sites being in phase. The second vector segregates the δ ice core sites from the met-stations.
The advantage of regional stacking of ice core δ records is discussed as a means of reducing noise. The stacked records and the first influence coefficient of their first Eigenvector contain a very strong temperature signal, but still 50% of the variance is not explained by temperature.
KeywordsEmpirical Orthogonal Function Camp Century Influence Coefficient Average Time Series Eigenvector Component
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