Skip to content

The impact of alkenone degradation on UK'37 paleothermometry: a model-derived assessment

Research output: Contribution to journalArticle

Original languageEnglish
Pages (from-to)648
Number of pages672
JournalPaleoceanography
Volume32
Issue number6
DOIs
DateAccepted/In press - 15 May 2017
DatePublished (current) - 28 Jun 2017

Abstract

The UK'37 proxy for past sea surface temperature (SST) is based on the unsaturation ratio of C37 alkenones. It is considered a diagenetically robust proxy, but biases have been invoked because the index can be altered by preferential degradation of the C37:3 alkenone, resulting in higher reconstructed SST. However, alkenone degradation rate constants are poorly constrained, making it difficult to evaluate the plausibility of such a bias. Therefore, we quantitatively assessed the effect of: (1) different alkenone degradation rate constants; (2) differential degradation factors between di- and tri-unsaturated C37 alkenones; (3) and initial UK'37 values on the UK'37 paleothermometer for two depositional environments (shelf and upper-slope), by means of a Reaction-Transport Model (RTM). RTM results reveal that preferential degradation of C37:3 can potentially alter the original signal of the UK'37 paleothermometer, but SST biases (ΔSST) are largely within UK'37 calibration error (ΔSST < 1.5 ºC) assuming realistic model parameters. The magnitude of ΔSST is largely determined by the degradation rate constant, but it also increases with higher differential degradation factors. Additionally, initial UK'37 values exert a non-linear influence on the extent of potential SST bias, with mid-range values (0.4 < UK'37 < 0.6) being most sensitive. The most significant changes occur in the shallowest sediment layers and are attenuated with burial time/depth. Scenarios where ΔSST > 1.5 ºC are associated with marked downcore decreases in alkenone concentration. Consequently, we caution against the interpretation of U_37^K' indices when extensive degradation results in very low alkenone concentrations (< 5 ng g-1).

    Research areas

  • Sea surface temperatures, Reaction-transport model, Paleoceanography, Paleoclimate, UK'37 paleothermometer, preferential degradation

Download statistics

No data available

Documents

Documents

  • Full-text PDF (accepted author manuscript)

    Rights statement: This is the author accepted manuscript (AAM). The final published version (version of record) is available online via Wiley at http://onlinelibrary.wiley.com/doi/10.1002/2016PA003043/full . Please refer to any applicable terms of use of the publisher.

    Accepted author manuscript, 2 MB, PDF document

    Licence: Unspecified

DOI

View research connections

Related faculties, schools or groups