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Description:
Title:
Intercolony δ18O and Sr/Ca variability among Porites spp. corals at Palmyra Atoll: Toward more robust coral‐based estimates of climate
Author(s):
Sayani, Hussein R.
Cobb, Kim M.
DeLong, Kristine
Hitt, Nicholas T.
Druffel, Ellen R. M.
Dates of Publication:
2019
Abstract:
Quantitative estimates of natural climate variability are required to detect anthropogenic climate trends in the tropical Pacific; however, instrumental records from this region are too short and scarce. Coral oxygen isotopic (δ18O) and strontium to calcium (Sr/Ca) records are often used to extend instrumental observations; however, differences in the mean Sr/Ca and δ18O values of Porites spp. colonies from the same reef can introduce large uncertainties in coral‐based climate reconstructions. To quantify intercolony variability at Palmyra Atoll, we generate monthly resolved Sr/Ca and δ18O time series from five Porites spp. colonies that grew between 1980 and 2010. Monthly to interannual variability in Sr/Ca and δ18O is well‐reproduced among different colonies; however, we document intercolony offsets in mean Sr/Ca of ±0.09 mmol/mol (1σ) or ~1 °C, and in mean δ18O of ±0.12‰ (1σ) or ~0.1 °C. The sensitivity of each proxy to climate also varies across colonies, with Sr/Ca‐SST slopes ranging from −0.06 to −0.1 mmol mol−1 °C−1 and δ18O‐SST slopes ranging from −0.25 to −0.35‰ °C−1. Intercolony variability in both coral Sr/Ca and δ18O reduces the reproducibility of coral‐based δ18Osw reconstructions across overlapping colonies. Accounting for both intercolony variability and slope error suggests that SST reconstructions using Sr/Ca from a single Palmyra coral have an uncertainty of ±1.3 °C (1σ); however, replicating Sr/Ca records across multiple colonies can greatly reduce this uncertainty. A composite Sr/Ca record built using five modern cores, for example, offers a reduced error of ±0.6 °C (1σ) in mean SST reconstructions, ~2.5 times smaller than errors associated with reconstructions from single corals.
Keywords:
Geochemistry and Petrology
Geophysics
Local Corporate Name:
OAR (Oceanic and Atmospheric Research)
CoRIS (Coral Reef Information System)
Format:
PDF
Type of Resource:
Journal Article
Note:
Quantitative estimates of natural climate variability are required to detect anthropogenic climate trends in the tropical Pacific; however, instrumental records from this region are too short and scarce. Coral oxygen isotopic (δ18O) and strontium to calcium (Sr/Ca) records are often used to extend instrumental observations; however, differences in the mean Sr/Ca and δ18O values of Porites spp. colonies from the same reef can introduce large uncertainties in coral‐based climate reconstructions. To quantify intercolony variability at Palmyra Atoll, we generate monthly resolved Sr/Ca and δ18O time series from five Porites spp. colonies that grew between 1980 and 2010. Monthly to interannual variability in Sr/Ca and δ18O is well‐reproduced among different colonies; however, we document intercolony offsets in mean Sr/Ca of ±0.09 mmol/mol (1σ) or ~1 °C, and in mean δ18O of ±0.12‰ (1σ) or ~0.1 °C. The sensitivity of each proxy to climate also varies across colonies, with Sr/Ca‐SST slopes ranging from −0.06 to −0.1 mmol mol−1 °C−1 and δ18O‐SST slopes ranging from −0.25 to −0.35‰ °C−1. Intercolony variability in both coral Sr/Ca and δ18O reduces the reproducibility of coral‐based δ18Osw reconstructions across overlapping colonies. Accounting for both intercolony variability and slope error suggests that SST reconstructions using Sr/Ca from a single Palmyra coral have an uncertainty of ±1.3 °C (1σ); however, replicating Sr/Ca records across multiple colonies can greatly reduce this uncertainty. A composite Sr/Ca record built using five modern cores, for example, offers a reduced error of ±0.6 °C (1σ) in mean SST reconstructions, ~2.5 times smaller than errors associated with reconstructions from single corals.
Grant no. NA11OAR4310165
URL:
DOI:
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