And That’s a Wrap!

I am so thrilled and sad that this program is over. I had such a great time creating bonds, learning about dendrochronology, and just living the island life in general. The REU symposium is tomorrow and I am so nervous and so excited to finally wrap up my project. My abstract is as follows:

In the northeastern Pacific Ocean, sea surface temperatures have shifted from warm to cool phases in 20-30-year cycles over the course of the instrumental record (1900-present) (Mantua et al, 1997). This pattern of Pacific Decadal Variability was originally described as the Pacific Decadal Oscillation (PDO), defined as the dominant pattern of sea surface temperatures in the North Pacific (Mantua et al. 1997). The PDO significantly affects ecosystem functioning in marine and terrestrial systems with implications for human societies.

We aimed to develop a new reconstruction of Pacific Decadal variability using all available tree-ring data in the International Tree Ring Data Bank (ITRDB)—one that includes the global trend in warming temperatures, collectively identified by Johnstone and Mantua in 2014 as the Arc pattern.

Research began with collating available chronologies from the International Tree Ring Data Bank. Then, raw measurement data available on the ITRDB were used to construct chronologies. Afterwards, all chronologies were compared to the Arc pattern using a regression analysis in SAS. Significant chronologies were screened for crossdating accuracy via COFECHA.

Later, all significant chronologies that are properly crossdated will be recreated and detrended using raw measurement data. These chronologies will then be averaged together in order to create a comprehensive look at patterns in pacific decadal variability.

At the moment, we have a preliminary reconstruction that indicates many areas of interest. First of all, the periodicity of the Arc pattern appears not to be 20-30 years as previously thought, but instead around 50 years. Additionally, there are no regime shifts in the 1800s, further evidence for a periodicity of 50 years. Lastly, sea surface temperature is at its record high in the twenty-first century.


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