alkenone; sea surface temperature; proxies; climate; carbon cycle
AusinBlanca, SarntheinMichael, HaghipourNegar (2021), Glacial-to-deglacial reservoir and ventilation ages at the southwest Iberian continental margin, in Quaternary Science Reviews
, 255, 106818.
Ausín Blanca, Hodell David A., Cutmore Anna, Eglinton Timothy I. (2020), The impact of abrupt deglacial climate variability on productivity and upwelling on the southwestern Iberian margin, in Quaternary Science Reviews
, 230, 106139-106139.
Ausín Blanca, Magill Clayton, Haghipour Negar, Fernández Álvaro, Wacker Lukas, Hodell David, Baumann Karl-Heinz, Eglinton Timothy I. (2019), (In)coherent multiproxy signals in marine sediments: Implications for high-resolution paleoclimate reconstruction, in Earth and Planetary Science Letters
, 515, 38-46.
Ausín Blanca, Haghipour Negar, Wacker Lukas, Voelker Antje H. L., Hodell David, Magill Clayton, Looser Nathan, Bernasconi Stefano M., Eglinton Timothy I. (2019), Radiocarbon Age Offsets Between Two Surface Dwelling Planktonic Foraminifera Species During Abrupt Climate Events in the SW Iberian Margin, in Paleoceanography and Paleoclimatology
, 34(1), 63-78.
Since the discovery of alkenones in 1986 [Brassell et al., 1986], these organic biomarkers have become one of the most applied and well-established paleoclimate proxies, allowing estimation of sea surface temperature (SST) and pCO2 variations in most oceanographic settings. We know now that much of the organic matter (OM) preserved in marine sediments is physically associated with mineral surfaces by sorption. Specifically, OM tends to concentrate within fine grain-size fractions (i.e. clay (<2 µm) and fine silt (2-10 µm)), which have higher surface area. Considering that mineral particles might behave in a cohesive or in a sortable manner depending on their size, alkenone-mineral associations and the governing hydrodynamic conditions may determine the transport pathways of alkenones. Consequently, we hypothesize that hydrodynamically-driven sediment sorting processes might introduce biases in autochthonous climate signal, compromising the spatial and temporal reliability of the derived proxy records. Similarly, we expect hydrodynamic processes to exert significant control on the transport pathways of other proxy-bearing particles represented in the finer-grained sediment fractions (< 63 µm) (e.g. nannofossils), which are more prone to resuspension than those represented in coarser-grained sediment fractions (> 63 µm) (e.g. microfossils). In the proposed investigation, we aim to determine alkenone-grain size-14C age interrelationships in surface sediments retrieved from diverse environmental settings: Bermuda Risa, Santa Barbara Basin, Namibian Margin, NW African Margin, and SW Iberian Margin. These different regions are strategic benchmark areas for high-temporal-resolution paleoclimate investigations where pre-existing evidence suggests temporal de-coupling of proxy records due to lateral transport. We aim to assess possible spatial and temporal offsets by specific radiocarbon dating of the alkenones contained within each grain-size fraction and identify the plausible factors that cause them. We also aim to evaluate possible asynchronous signals between alkenones, coccoliths, and planktonic foraminifera by means of radiocarbon dating of each of these sedimentary components. Complementary geochemical and sedimentological analyses will be performed to constrain OM distribution and provenance, and associated lateral sediment transport processes. We then plan to apply derived information and our novel measurement strategy to a sediment core retrieved from the so-called Shackleton Sites in the SW Iberian Margin in order to assess the role of hydrodynamic processes impact on the paleotemperatures estimated from proxies residing in different grain size fractions. In this way, we will develop the first proxy-specific radiocarbon chronology for a sediment core. Since the Shackleton Sites represent one of the few regions in the world where direct correlation of ice-marine-terrestrial signals are feasible, constraining the provenance and temporal fidelity of proxy records is of crucial importance. Given the importance attached to molecular fossils as proxies for the study of past climate variations, and the attention focused on these strategic regions, this investigation is expected to expand horizons in the field of paleoceanography and deepen our understanding of paleoceanographic records.