Stable isotopic and trace metal analyses of two Porites Lobata colonies - Oahu, Hawaii: implications for past seasonal variation and sea surface temperatures and anthropogenic effects on the reef environment
Date of Award
Master of Science (MS)
Corals from the western and equatorial Pacific Ocean have been extensively studied for the purposes of generating paleoclimate reconstructions spanning the last several hundred years. However, in the central subtropical North Pacific, there are currently few published coral records extending beyond 10 to 20 years. The hermatypic coral species Porites lobata and Porites lutea have proven to be useful indicators of paleoclimate and past sea surface conditions at other locations. Here I have analyzed two Porites lobata coral cores collected from colonies from opposite sides of Oahu, Hawaii to assess their utility for developing multi-decadal length climatic reconstructions in this region.
The two coral records are from Punalu'u Beach (157.881607°W, 21.576752°N) and Waikiki Beach (157.881607° W, 21.576752° N) and presented here are isotopic (δ18O and δ13C) and trace metal data (Sr/Ca, Pb, and other metals) from these two corals. An absolute increase in sea surface temperatures of 1°C over the last 40 years is clear in the instrumental SST data, along with a clear bias towards the times of maximum SST during a negative phase of the Pacific Decadal Oscillation (PDO). Lead (Pb) concentration for one of the corals also coincides with the change in the PDO seen in 1976, with Pb concentrations decreasing from ~4-6ppm to between 0.5-1ppm. However, I infer this decline in concentration is more probably due to the elimination of lead in gasoline. Other trace metal data trends show increased concentrations of specific metals during times of known Kona storm events. Presented here is the longest sub-annual resolution paleoclimate record derived from Hawaiian corals along with a comprehensive analysis of their usefulness as a paleoclimate and environmental change indicator.
MacDonald, Jonathan, "Stable isotopic and trace metal analyses of two Porites Lobata colonies - Oahu, Hawaii: implications for past seasonal variation and sea surface temperatures and anthropogenic effects on the reef environment" (2004). Geology Theses and Dissertations. 54.