Coral Sr‐U thermometry

DeCarlo, Thomas M.; Gaetani, G. A.; Cohen, Anne L.; Foster, Gavin L.; Alpert, Alice E.; Stewart, Joseph

doi:10.1002/2015pa002908

Cited by 49 publications

(85 citation statements)

References 69 publications

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“…Repeated measurements of an in-house secondary coral standard indicate an external precision of ±0.035 mmol/mol (1σ, n=173, 0.4% relative) for Sr/Ca and 0.02 µmol/mol for U/Ca (1σ, n=173, 0.019% relative) and the ICPMS was stable throughout our study. We have previously measured the Sr/Ca and U/Ca values of three aliquots of JCp-1 powder as 8.870 ± 0.028 mmol/mol and 1.23 ± 0.01 µmol/mol [Alpert et al, 2016] which is within uncertainty of the mean, and within the range of precision, reported from JCp-1 analyses conducted in 21 different laboratories .…”

Section: Temporal Reconstructionsupporting

confidence: 60%

“…They derived an expression relating Sr-U to temperature with an uncertainty of 0.5˚C. DeCarlo et al [2016] tested the theoretical basis of Sr-U using the boron isotope (δ 11 B) proxy for pH in the calcifying fluid. They confirmed that δ 11 B and U/Ca in several corals with differing Sr/Ca is consistent with vital effects on Sr/Ca due to calcifying fluid .…”

Section: Coral Paleoceanographymentioning

confidence: 99%

“…In situ logged temperatures are available for Jarvis Island, Palmyra, Palau, Pacora Island and the Red Sea sites [Pineda et al, 2009;Cantin et al, 2010;Barkley et al, 2015;Alpert et al, 2016]. At other sites, logger data were available but discontinuous or not covering the same time period as the coral records.…”

Section: Temperature Data For the Calibrationmentioning

confidence: 99%

“…However, accessing that information has been compromised by uncertainties associated with the application of single element-ratio coral thermometers, including Sr/Ca. A new approach, Sr-U, combines Sr/Ca and U/Ca to constrain the influence of Rayleigh fractionation on the temperature dependence of Sr/Ca [DeCarlo et al, 2016]. Here, we build on the initial Pacific Porites Sr-U calibration to include multiple Atlantic and Pacific coral genera spanning a temperature range of 23.2-30.1 ˚C, and show that Sr-U is strongly correlated with average temperature over which coral growth occurs (R=-0.96, P<0.01, n=19).…”

Section: Introductionmentioning

confidence: 99%

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Little Ice Age climate in the Western Tropical Atlantic inferred from coral geochemical proxies

Alpert¹

2016

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Paleoclimate archives place the short instrumental record of climate variability in a longer temporal context and allow better understanding of the rate, nature and extent by which anthropogenic warming will impact natural and human systems. The ocean is a key component of the climate system and records of past ocean variability are thus essential for characterizing natural variability and quantifying climate sensitivity to radiative forcing. Coral skeletons are high-resolution archives of tropical sea surface temperatures (SSTs), but inconsistencies call the accuracy of existing coral proxy records into question.In this thesis, I first quantify the errors associated with the traditional coral thermometer, Sr/Ca, by comparing in situ logged SST with Sr/Ca-derived SST in four corals on the same reef. I show that intercolony disparities in mean Sr/Ca, amplitude of variability, and trend are not due to differences in water temperature, but rather to "vital effects" that result in a ± 2 C uncertainty on reconstructed SST.I then expand, refine, and test a new paleothermometer, Sr-U, across multiple coral species and through time. I show that Sr-U captures spatial SST variability with an uncertainty of ± 0.6 C. When applied to two corals outside of the calibration, Sr-U accurately captures the mean SST and the 20 th century trend in the Western Tropical Atlantic.Finally, I apply Sr-U to a coral from the Little Ice Age (LIA) to address uncertainties in the magnitude of western tropical Atlantic cooling during a 95-year period spanning 1465-1560. Results suggest the region was 1.1 C±0.6°C cooler than the 1958-1988 mean, but within error of early 20 th century SST at this site. Critically, several periods of warmth, equivalent to the 1958-1988 mean, occurred during a solar minimum that is widely believed to have been a cool period of the LIA. My results indicate that Sr/Ca exaggerates the actual cooling by almost 3 °C. My record demonstrates the value of Sr-U and highlights the need for continuous accurate SST records to better constrain the amplitude, drivers, and mechanisms of LIA tropical climate change.

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Section: Temporal Reconstructionsupporting

confidence: 60%

Section: Coral Paleoceanographymentioning

confidence: 99%

Section: Temperature Data For the Calibrationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Little Ice Age climate in the Western Tropical Atlantic inferred from coral geochemical proxies

Alpert¹

2016

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“…In recent years, boron systematics (including δ 11 B and B/Ca) have become one of the most commonly applied proxies for the carbonate chemistry of coral calcifying fluid (cf) (Hönisch et al, 2004;Trotter et al, 2011;McCulloch et al, 2012bMcCulloch et al, , a, 2017Allison et al, 2014;DeCarlo et al, 2016;Stewart et al, 2016;Comeau et al, 2017;Wu et al, 2017;D'Olivo and McCulloch, 2017;Kubota et al, 2017;Ross et al, 2017;Schoepf et al, 2017). The sensitivity of boron isotopes to seawater pH arises from the borate versus boric acid speciation being pH-dependent and the isotopic fractionation between these species being constant 15 (Klochko et al, 2006).…”

mentioning

confidence: 99%

Reviews and syntheses: Revisiting the boron systematics of aragonite and their application to coral calcification

DeCarlo¹,

Holcomb²,

McCulloch³

2018

Preprint

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has not yet been a comprehensive analysis that considers both experimental datasets and explores the implications for interpreting coral skeletons. Here, we evaluate four potential K D formulations: three previously presented in the literature and one newly developed. We assess how well each formulation reconstructs the known fluid carbonate chemistry from the abiogenic experiments, and we evaluate the implications for deriving the carbonate chemistry of coral calcifying fluid. Three of the K D formulations performed similarly when applied to abiogenic aragonites precipitated from 10 seawater and to coral skeletons. Critically, we find that some uncertainty remains in understanding the mechanism of boron elemental partitioning between aragonite and seawater, and addressing this question should be a target of additional abiogenic precipitation experiments. Despite this, boron systematics can already be applied to quantify the coral calcifying fluid carbonate system, although uncertainties associated with the proxy system should be carefully considered for each application. Finally, we present a user-friendly computer code that calculates coral calcifying fluid carbonate chemistry, including propagation of 15 uncertainties, given inputs of boron systematics measured in coral skeleton.

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Twentieth century warming of the tropical Atlantic captured by Sr‐U paleothermometry

et al. 2017

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Coral skeletons are valuable archives of past ocean conditions. However, interpretation of coral paleotemperature records is confounded by uncertainties associated with single‐element ratio thermometers, including Sr/Ca. A new approach, Sr‐U, uses U/Ca to constrain the influence of Rayleigh fractionation on Sr/Ca. Here we build on the initial Pacific Porites Sr‐U calibration to include multiple Atlantic and Pacific coral genera from multiple coral reef locations spanning a temperature range of 23.15–30.12°C. Accounting for the wintertime growth cessation of one Bermuda coral, we show that Sr‐U is strongly correlated with the average water temperature at each location (r2 = 0.91, P < 0.001, n = 19). We applied the multispecies spatial calibration between Sr‐U and temperature to reconstruct a 96 year long temperature record at Mona Island, Puerto Rico, using a coral not included in the calibration. Average Sr‐U derived temperature for the period 1900–1996 is within 0.12°C of the average instrumental temperature at this site and captures the twentieth century warming trend of 0.06°C per decade. Sr‐U also captures the timing of multiyear variability but with higher amplitude than implied by the instrumental data. Mean Sr‐U temperatures and patterns of multiyear variability were replicated in a second coral in the same grid box. Conversely, Sr/Ca records from the same two corals were inconsistent with each other and failed to capture absolute sea temperatures, timing of multiyear variability, or the twentieth century warming trend. Our results suggest that coral Sr‐U paleothermometry is a promising new tool for reconstruction of past ocean temperatures.

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Coral Sr‐U thermometry

Cited by 49 publications

References 69 publications

Little Ice Age climate in the Western Tropical Atlantic inferred from coral geochemical proxies

Little Ice Age climate in the Western Tropical Atlantic inferred from coral geochemical proxies

Reviews and syntheses: Revisiting the boron systematics of aragonite and their application to coral calcification

Twentieth century warming of the tropical Atlantic captured by Sr‐U paleothermometry

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