publications

2026

1. PALO

   Biomarker Constraints on Indo-Pacific Warm Pool Temperature During the Late Pleistocene: The Role of Orbital Forcing

   Trang T Tran, Jessica E Tierney, Ann Holbourn, and Ronnakrit Rattanasriampaipong

   Paleoceanography and Paleoclimatology, 2026

   Abs DOI

   Abstract The Indo-Pacific Warm Pool (IPWP) exerts a major influence on global atmospheric circulation, yet the drivers of late Pleistocene IPWP sea surface temperature (SST) variability remain debated. To evaluate how IPWP temperature responds to different climate forcings, we present new SST records spanning the past 650 kyr based on three independent proxies? {\text{TEX}}_{86}, {\mathrm{U}}_{37}^{{K}^{\prime }}, and Mg/Ca?from International Ocean Discovery Program Site U1482, located off northwestern Australia at the southernmost margin of the IPWP. Core top samples suggest that {\mathrm{U}}_{37}^{{K}^{\prime }} and Mg/Ca are biased toward austral summer, while {\text{TEX}}_{86} is elevated under low-nutrient conditions. Down-core, all proxies exhibit coherent glacial?interglacial SST variations of ?5 {}^{∘}C, although {\text{TEX}}_{86} is affected by nutrient stress during interglacials. The {\mathrm{U}}_{37}^{{K}^{\prime }} record shows relatively warm conditions during Marine Isotope Stage 6 compared to other glacial intervals, but this is not observed in the {\text{TEX}}_{86} or Mg/Ca records. Total alkenone concentration, reflecting paleo-productivity, indicate enhanced productivity during glacial intervals and reduced productivity during interglacials. The SST proxy records are in phase with greenhouse gas and ice volume in the 100 and 41 kyr orbital bands, emphasizing tropical-high latitude climate coupling, while local precession forcing impacts seasonal SSTs. Productivity variations track both glacial-interglacial cycles and precession-driven changes in wind-driven upwelling and surface current intensity in the Indo-Pacific. Our regional synthesis highlights sea-level and shelf exposure as key drivers of IPWP SST patterns, with a more pronounced precession influence at the southern IPWP margin. Our findings demonstrate that both glacial-interglacial cycles and precession govern SST and productivity variations in the IPWP.

2025

1. BG

   Reviews and syntheses: Best practices for the application of marine GDGTs as proxy for paleotemperatures: sampling, processing, analyses, interpretation, and archiving protocols

   Peter K. Bijl, Kasia K. Śliwińska, Bella Duncan, Arnaud Huguet, Sebastian Naeher, and 19 more authors

   Biogeosciences, 2025

   Abs DOI

   Abstract. Marine glycerol dialkyl glycerol tetraethers (GDGTs) are used in various proxies (such as TEX86) to reconstruct past ocean temperatures. Over 20 years of improvements in GDGT sample processing, analytical techniques, data interpretation and our understanding of proxy functioning have led to the collective development of a set of best practices in all these areas. Further, the importance of Open Science in research has increased the emphasis on the systematic documentation of data generation, reporting and archiving processes for optimal reusability of data. In this paper, we provide protocols and best practices for obtaining, interpreting and presenting GDGT data (with a focus on marine GDGTs), from sampling to data archiving. The purpose of this paper is to optimize inter-laboratory comparability of GDGT data, and to ensure published data follows modern open access principles.

2. GRL

   A nutrient effect on the TEX₈₆ paleotemperature proxy

   Ronnakrit Rattanasriampaipong, Jessica E. Tierney, Jordan T. Abell, and Lauren D. Gilmore

   Geophysical Research Letters, 2025

   Abs DOI PDF

   The TEX₈₆ paleotemperature proxy is widely used to reconstruct ocean surface temperatures over the past 100 million years. However, archaeal culture experiments show that nutrient stress elevates TEX₈₆ values by increasing glycerol dialkyl glycerol tetraether (GDGT) cyclization. Here, we demonstrate that this “nutrient effect" is also recorded in sedimentary GDGTs. Using an expanded core-top database, we find a significant negative correlation between TEX₈₆ and nitrate concentrations (ρ= -0.31; P<.001) once the thermal effect is removed. There are stronger correlations (ρ-0.73 to -0.91; P<.001) in regions with steep nitrate gradients. Comparisons between TEX₈₆ and U^K’₃₇-based reconstructions from the Arabian Sea and Tasman Sea suggest that nutrient stress influenced GDGT distributions during glacial-interglacial cycles. Our findings underscore the need to account for nutrient effects when applying TEX₈₆ paleothermometry.

2022

1. Sci. Data

   The PhanSST global database of Phanerozoic sea surface temperature proxy data

   Emily J. Judd, Jessica E. Tierney, Brian T. Huber, Scott L. Wing, Daniel J. Lunt, and 21 more authors

   Scientific Data, 2022

   Abs DOI PDF

   Paleotemperature proxy data form the cornerstone of paleoclimate research and are integral to understanding the evolution of the Earth system across the Phanerozoic Eon. Here, we present PhanSST, a database containing over 150,000 data points from five proxy systems that can be used to estimate past sea surface temperature. The geochemical data have a near-global spatial distribution and temporally span most of the Phanerozoic. Each proxy value is associated with consistent and queryable metadata fields, including information about the location, age, and taxonomy of the organism from which the data derive. To promote transparency and reproducibility, we include all available published data, regardless of interpreted preservation state or vital effects. However, we also provide expert-assigned diagenetic assessments, ecological and environmental flags, and other proxy-specific fields, which facilitate informed and responsible reuse of the database. The data are quality control checked and the foraminiferal taxonomy has been updated. PhanSST will serve as a valuable resource to the paleoclimate community and has myriad applications, including evolutionary, geochemical, diagenetic, and proxy calibration studies.

2. PNAS

   Archaeal lipids trace ecology and evolution of marine ammonia-oxidizing archaea

   Ronnakrit Rattanasriampaipong, Yi Ge Zhang, Ann Pearson, Brian P Hedlund, and Shuang Zhang

   Proceedings of the National Academy of Sciences, 2022

   Abs DOI Bib PDF

   Archaeal membrane lipids are widely used for paleotemperature reconstructions, yet these molecular fossils also bear rich information about ecology and evolution of marine ammonia-oxidizing archaea (AOA). Here we identified ‘thermal’ and ‘non-thermal’ behaviors of archaeal glycerol dialkyl glycerol tetraethers (GDGTs) by comparing the GDGT-based temperature index (TEX₈₆) to the ratio of GDGTs with two and three cyclopentane rings (GDGT-2/GDGT-3). Thermal-dependent biosynthesis should increase TEX₈₆ and decrease GDGT-2/GDGT-3 when the ambient temperature increases. This presumed temperature-dependent (PTD) trend is observed in GDGTs derived from cultures of thermophilic and mesophilic AOA. The distribution of GDGTs in suspended particulate matter (SPM) and sediments collected from above the pycnocline— ‘shallow-water’ samples—also follows the PTD trend. These similar GDGT distributions between AOA cultures and shallow-water environmental samples reflect ‘shallow’ ecotypes of marine AOA. While there are currently no cultures of ‘deep’ AOA clades, GDGTs derived from ‘deep-water’ SPM and marine sediment samples exhibit non-thermal behavior deviating from the PTD trend. The presence of ‘deep’ AOA increases the GDGT-2/GDGT-3 ratio and distorts the temperature-controlled correlation between GDGT-2/GDGT-3 and TEX₈₆. We used Gaussian Mixture Models to statistically characterize these diagnostic patterns of modern AOA ecology from paleo-GDGT records to infer the evolution of marine AOA from the Mid-Mesozoic to the present. Long-term GDGT-2/GDGT-3 trends suggest the suppression of today’s ‘deep-water’ marine AOA during the Mesozoic–early Cenozoic greenhouse climates. Our analysis provides insights into the evolutionary timeline and the expansion of AOA niches associated with major oceanographic and climate changes.

   @article{rattanasriampaipong2022pnas,
     title = {Archaeal lipids trace ecology and evolution of marine ammonia-oxidizing archaea},
     author = {Rattanasriampaipong, Ronnakrit and Zhang, Yi Ge and Pearson, Ann and Hedlund, Brian P and Zhang, Shuang},
     journal = {Proceedings of the National Academy of Sciences},
     volume = {119},
     number = {31},
     pages = {e2123193119},
     year = {2022},
     publisher = {Proceedings of the National Academy of Sciences},
     doi = {10.1073/pnas.2123193119},
     dimensions = {true},
     url = {https://doi.org/10.1073/pnas.2123193119},
   }

2025

1. Archaeal tetraether lipids as tracers for past marine environmental change

   Felix J Elling, Gordon N Inglis, Nina Davtian, Sarah Hurley, Bernhard David Naafs, and 35 more authors

   ESS Open Archive, 2025

   DOI

2024

1. Methylation index of Overly Branched tetraether lipids (MOB): a proxy for deep ocean (de)oxygenation?

   Ronnakrit Rattanasriampaipong, Yi Ge Zhang, Olawale Alo, Xiaolei Liu, Yang Zhang, and 4 more authors

   preprint, 2024

   DOI