BayClump: Bayesian Calibration and Temperature Reconstructions for Clumped Isotope Thermometry

AbstractUnderstanding the Earth’s climate system during past periods of high atmospheric CO2 is crucial for forecasting climate change under anthropogenically-elevated CO2. The Mesozoic Era is believed to have coincided with a long-term Greenhouse climate, and many of our temperature reconstructions come from stable isotopes of marine biotic calcite, in particular from belemnites, an extinct group of molluscs with carbonate hard-parts. Yet, temperatures reconstructed from the oxygen isotope composition of belemnites are consistently colder than those derived from other temperature proxies, leading to large uncertainties around Mesozoic sea temperatures. Here we apply clumped isotope palaeothermometry to two distinct carbonate phases from exceptionally well-preserved belemnites in order to constrain their living habitat, and improve temperature reconstructions based on stable oxygen isotopes. We show that belemnites precipitated both aragonite and calcite in warm, open ocean surface waters, and demonstrate how previous low estimates of belemnite calcification temperatures has led to widespread underestimation of Mesozoic sea temperatures by ca. 12 °C, raising estimates of some of the lowest temperature estimates for the Jurassic period to values which approach modern mid-latitude sea surface temperatures. Our findings enable accurate recalculation of global Mesozoic belemnite temperatures, and will thus improve our understanding of Greenhouse climate dynamics.

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Belemnites, clumped isotopes and oxygen fractionation

10.5194/egusphere-egu2020-260 ◽

2020 ◽

Author(s):

Madeleine Vickers ◽

Stefano Bernasconi ◽

Clemens Ullmann ◽

Stephen Hesselbo ◽

Gregory Price ◽

...

Keyword(s):

Oxygen Isotope ◽

Isotope Fractionation ◽

Clumped Isotopes ◽

Fractionation Factor ◽

Oxygen Isotope Fractionation ◽

Temperature Reconstructions ◽

Life Habits ◽

Stable Oxygen ◽

Clumped Isotope ◽

Low Precipitation

Belemnite calcite has been used extensively for Jurassic and Cretaceous stable oxygen isotope temperature reconstructions since the 1950s. However, with the advent of clumped isotope thermometry, a consistent offset between reconstructed &#948;18O temperatures vs &#916;47 temperatures from the same belemnites has been observed. We investigate the causes of this offset by analyzing samples from the aragonitic phragmacone and calcitic rostrum from the same Cylindroteuthis belemnites, along with other aragonitic benthos, from the Callovian-aged Christian Malford Lagerst&#228;tte, U.K. Our new clumped isotope data suggest that the water-calcite 18O-fractionation factor in belemnite calcite was larger than that of the commonly used &#948;18O thermometry equations (e.g. Kim and O&#8217;Neil, 1997), and which is currently observed in other marine calcifiers. Our reconstructions suggest that the oxygen isotope fractionation is compatible with that observed in slow-forming abiotic calcites (e.g. Coplen, 2007) and in rapidly precipitating Travertines (Kele et al. 2015). The application of more established &#948;18O thermometry equations (Kim and O&#8217;Neil, 1997) to belemnite calcite for temperature reconstructions has resulted in a consistent underestimation of belemnite calcification temperatures, which has led to erroneous conclusions about belemnite life habits, and underestimation of global temperatures during these greenhouse times. We therefore advocate the use of calcite equations based on low precipitation rate experiments (e.g. Coplen, 2007; Kele et al., 2015) for belemnite rostra temperature reconstructions.

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First absolute seasonal temperature estimates for greenhouse climate from clumped isotopes in bivalve shells

10.21203/rs.3.rs-128320/v1 ◽

2021 ◽

Author(s):

Niels de Winter ◽

Inigo Müller ◽

Ilja Kocken ◽

Nicolas Thibault ◽

Clemens Ullmann ◽

...

Keyword(s):

Seasonal Variability ◽

Climate Model ◽

Sea Water ◽

Isotope Composition ◽

Seasonal Temperature ◽

Deep Time ◽

Temperature Reconstructions ◽

Climate Model Simulations ◽

Clumped Isotope ◽

Bivalve Shells

Abstract Seasonal variability in sea surface temperatures plays a fundamental role in climate dynamics and species distribution. As such, it is essential to better understand seasonal variability in climates of the past. Previous reconstructions of seasonality in deep time are poorly constrained, relying on controversial assumptions such as estimates of seawater composition and neglect seasonal bias. This work presents the first absolute seasonal temperature reconstructions based on clumped isotope measurements in bivalve shells which, critically, do not rely on these assumptions. Our new approach reconstructs highly precise higher mid-latitude (~50°N) monthly temperatures from individual oyster and rudist shells of the Campanian (78 million years ago) greenhouse period (15—27 °C seasonal range). Our analysis demonstrates that seasonal bias and previous assumptions about sea water oxygen isotope composition can lead to highly inaccurate temperature reconstructions, distorting our understanding of the behavior of greenhouse climates and our ability to model them. Our results agree with fully coupled climate model simulations showing greenhouse climates outside the tropics were warmer and more seasonal than previously thought.

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First absolute seasonal temperature estimates for greenhouse climate from clumped isotopes in bivalve shells

10.21203/rs.3.rs-39203/v1 ◽

2020 ◽

Author(s):

Niels de Winter ◽

Inigo Müller ◽

Ilja Kocken ◽

Nicolas Thibault ◽

Clemens Vinzenz Ullmann ◽

...

Keyword(s):

Seasonal Variability ◽

Climate Model ◽

Sea Water ◽

Isotope Composition ◽

Seasonal Temperature ◽

Deep Time ◽

Temperature Reconstructions ◽

Climate Model Simulations ◽

Clumped Isotope ◽

Bivalve Shells

Abstract The seasonal variability of sea surface temperatures plays a fundamental role in climate dynamics and species distribution. As such, it is essential to better understand seasonal variability in warm climates of the past. Previous reconstructions of seasonality in deep time are relatively unconstrained, relying on unsupported assumptions such as estimates of seawater composition and negligible seasonal bias. This work presents the first absolute seasonal temperature reconstructions based on clumped isotope measurements in bivalve shells which, critically, do not rely on these assumptions. Our new approach reconstructs highly precise mid-latitude (~50°N) monthly temperatures from individual oyster and rudist shells of the Campanian (78 million years ago) greenhouse period (15—27 °C seasonal range). Our analysis demonstrates that seasonal bias and previous assumptions about sea water oxygen isotope composition can lead to highly inaccurate temperature reconstructions, distorting our understanding of the behavior of greenhouse climates and our ability to model them. Our results agree remarkably well with fully coupled climate model simulations showing greenhouse climates outside the tropics were warmer with higher seasonality than previously thought.

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Advances in high-resolution paleoclimate reconstructions using growth experiments, age modelling and clumped isotope analyses

10.5194/egusphere-egu21-6120 ◽

2021 ◽

Author(s):

Niels de Winter ◽

Rob Witbaard ◽

Inigo Müller ◽

Ilja Kocken ◽

Tobias Agterhuis ◽

...

Keyword(s):

High Resolution ◽

Trace Element ◽

Shell Growth ◽

Seasonal Temperature ◽

Human Scale ◽

Temperature Reconstructions ◽

Shell Chemistry ◽

Clumped Isotope ◽

Isotope Analyses ◽

Bivalve Shells

Geochemical records from incremental carbonate archives, such as fossil mollusk shells, contain information on climate and environmental change at the resolution of days to decades (e.g. Sch&#246;ne and Gillikin, 2013; Ivany, 2012). These high-resolution paleoclimate data, providing snapshots of past climate change on a human scale, complement more conventional reconstructions on a geological timescale of thousands to millions of years. Recent innovations in geochemical techniques such as high-resolution trace element and clumped isotope analyses provide the unique potential to improve the accuracy and resolution of these high-resolution climate reconstructions in the near future (see e.g. de Winter et al., 2020a; b; Caldarescu et al., 2021). However, to be able to make the most out of these new techniques requires a more detailed understanding of the timing and mechanisms of mollusk shell growth as well as the relationship between environment and shell chemistry on daily to weekly timescales.The UNBIAS (UNravelling BIvAlve Shell chemistry) project combines investigations on lab-grown modern bivalve shells with reconstructions based on fossil shell material from past greenhouse periods in an attempt to improve our understanding of short-term temperature variability in warm climates. Samples from cultured shells labeled with a novel trace element spiking method are used to calibrate accurate temperature reconstructions from bivalve shells using the state-of-the-art clumped isotope method. As a result, we present a temperature calibration of clumped isotope measurements on aragonitic shell carbonates. New statistical routines are developed to accurately date microsamples within shells relative to the seasonal cycle (ShellChron; de Winter, 2020) and to strategically combine these microsamples for seasonal reconstructions of temperature and salinity from fossil shells (seasonalclumped, de Winter et al., 2020c; de Winter, 2021). We present the first results of this integrated seasonal reconstruction approach on fossil bivalve shells from the Pliocene Warm Period and Late Cretaceous greenhouse of northwestern Europe as well as an outlook on future plans within the UNBIAS project.&#160;ReferencesCaldarescu, D. E. et al. Geochimica et Cosmochimica Acta 294, 174&#8211;191 (2021).de Winter, N. J. ShellChron v0.2.8: Builds Chronologies from Oxygen Isotope Profiles in Shells. (2020).de Winter, N. J. seasonalclumped v0.3.2: Toolbox for Seasonal Temperature Reconstructions using Clumped Isotope Analyses. (2021).de Winter, N. J. et al. Paleoceanography and Paleoclimatology 35, e2019PA003723 (2020a).de Winter, N. J. et al. Nature Communications in Earth and Environment (in review; 2020b) doi:10.21203/rs.3.rs-39203/v2.de Winter, N., Agterhuis, T. & Ziegler, M. Climate of the Past Discussions 1&#8211;52 (2020c) doi:https://doi.org/10.5194/cp-2020-118.Ivany, L. C. The Paleontological Society Papers 18, 133&#8211;166 (2012).Sch&#246;ne, B. R. & Gillikin, D. P. Palaeogeography, Palaeoclimatology, Palaeoecology 373, 1&#8211;5 (2013).

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First absolute seasonal temperature estimates for greenhouse climate from clumped isotopes in bivalve shells

10.21203/rs.3.rs-39203/v2 ◽

2020 ◽

Author(s):

Niels de Winter ◽

Inigo Müller ◽

Ilja Kocken ◽

Nicolas Thibault ◽

Clemens Vinzenz Ullmann ◽

...

Keyword(s):

Seasonal Variability ◽

Climate Model ◽

Sea Water ◽

Isotope Composition ◽

Seasonal Temperature ◽

Deep Time ◽

Temperature Reconstructions ◽

Climate Model Simulations ◽

Clumped Isotope ◽

Bivalve Shells

Abstract The seasonal variability of sea surface temperatures plays a fundamental role in climate dynamics and species distribution. As such, it is essential to better understand seasonal variability in warm climates of the past. Previous reconstructions of seasonality in deep time are relatively unconstrained, relying on unsupported assumptions such as estimates of seawater composition and negligible seasonal bias. This work presents the first absolute seasonal temperature reconstructions based on clumped isotope measurements in bivalve shells which, critically, do not rely on these assumptions. Our new approach reconstructs highly precise mid-latitude (~50°N) monthly temperatures from individual oyster and rudist shells of the Campanian (78 million years ago) greenhouse period (15—27 °C seasonal range). Our analysis demonstrates that seasonal bias and previous assumptions about sea water oxygen isotope composition can lead to highly inaccurate temperature reconstructions, distorting our understanding of the behavior of greenhouse climates and our ability to model them. Our results agree remarkably well with fully coupled climate model simulations showing greenhouse climates outside the tropics were warmer with higher seasonality than previously thought.

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Extreme deep-sea warmth supports high climate sensitivity in the early Eocene hothouse

10.31223/x5nc9h ◽

2021 ◽

Author(s):

Tobias Agterhuis ◽

Martin Ziegler ◽

Lucas Lourens

Keyword(s):

Climate Sensitivity ◽

Deep Sea ◽

Isotope Composition ◽

Ph Effect ◽

Deep Ocean ◽

Early Eocene ◽

Sea Temperature ◽

Temperature Reconstructions ◽

Hyperthermal Events ◽

Clumped Isotope

The early Eocene (56–48 Ma) hothouse experienced the highest CO2 levels of the Cenozoic, as well as the occurrence of multiple transient global warming events, so-called hyperthermals. The deep ocean constitutes a stable and vast heat reservoir in the climate system, and hence compromises a robust setting to estimate past global mean temperatures. However, available deep-sea temperature reconstructions rely on uncertain assumptions of non-thermal influences. Here, we apply for the first time the carbonate clumped isotope paleothermometer (Δ47), a proxy not governed by these uncertainties, on early Eocene benthic foraminifera to evaluate South Atlantic deep-sea temperatures across two hyperthermal events (ETM2 and H2; ~54 Ma). In comparison to the conventional δ18O-based estimates, our new temperature reconstructions indicate two and a half degrees warmer deep water conditions, i.e. 13.2±1.9 °C (95% Confidence Interval) for background state, and average deep-sea warming of 3.3±2.9 °C (95% CI) during these hyperthermal events. These findings imply a reassessment of the assumed isotope composition of the ancient seawater and of a potential pH effect on foraminiferal oxygen isotopes. On a broad scale, our Δ47-based overall warmer deep-sea temperatures provide new evidence for high climate sensitivity during the early Eocene hothouse.

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