CLIMATE RESPONSE OF YELLOW-CEDAR ON EXCURSION RIDGE, GLACIER BAY, ALASKA: A PRELIMINARY ANALYSIS OF PRE- AND POST LITTLE ICE AGE CLIMATE SIGNALS

The Alaska yellow-cedar, Callitropsis nootkatensis (D. Don) Örsted, is in the midst of a century-long decline, coinciding with the end of the Little Ice Age, circa A.D. 1880. This decline appears to have not yet affected yellow-cedar stands around Glacier Bay, southeast Alaska. The longevity of the species is conducive to the creation of long-term chronologies of a half millennium or more.

A preliminary ring-width chronology of thirty-four cores from seventeen yellow-cedar that spans 439 years, from 1538-2006 was created, showing a strong common signal with a 0.518 series intercorrelation. The chronology was then standardized using a conservative 150-year cubic smoothing spline and the standard chronology was then compared to various local climate data. Of particular interest were two distinct response trends when compared with the extensive Sitka Magnetic Observatory records. These records are among the longest continuous recorded climate record in North America, starting in 1828 and ending in 1989. In the Russian, pre-LIA data, the Cedar responded positively to warmer winter temperatures. Comparison with the post-LIA indicated the trees responded negatively to warmer spring and December. Warmer winter temperatures in the Gulf of Alaska correlate strongly with higher snowfall in the coastal areas, and available snowpack is vital to the survival of shallow-rooted trees such as the yellow-cedar. Decreases in winter snowpack and frost damage to roots has been implicated in the decline of yellow cedar in Southeast Alaska. This correlation between winter temperatures, precipitation and the relative effect on cedar survival merits further investigation.

Ongoing work includes the development of a second cedar site from the Glacier Bay region as well as the expansion of the current site’s chronology. These chronologies will continue to be assessed for indications of cedar decline and potential for climate reconstruction.