Resolving sea ice dynamics in the north-western Ross Sea during the last 2.6 ka: From seasonal to millennial timescales

• Published in: Quaternary Science Reviews
• Main Authors: Tesi, T, Belt, S T, Gariboldi, Karen, Muschitiello, F, Smik, Lukas, Finocchiaro, F, Giglio, F., Colizza, Ester, Gazzurra, G, Giordano, Patrizia, Morigi, C., Capotondi, L., Nogarotto, Alessio, Koseoglu, Devrim, Di Roberto, Alessio, Gallerani, A, Langone, L.
• Other Authors: Istituto di Scienze Polari - Consiglio Nazionale delle Ricerche ISP-CNR, Via P. Gobetti 101, 40129, Bologna, Italy, Biogeochemistry Research Centre, School of Geography, Earth and Environmental Sciences, University of Plymouth, Drake Circus, Plymouth, Devon, PL4 8AA, UK, Dipartimento di Scienze della Terra, Universit a di Pisa, Via Santa Maria, 53, 56126, Pisa, Italy, Department of Geography, University of Cambridge, Cambridge, CB2 3EN, UK, Dipartimento di Matematica e Geoscienze, Universit a di Trieste, Via E. Weiss 2, 34127, Trieste, Italy, Istituto di Scienze Marine - Consiglio Nazionale delle Ricerche ISMAR-CNR, Via P. Gobetti 101, 40129, Bologna, Italy, Campus Scientifico, Universit a Ca’ Foscari Venezia, Via Torino 155, 30172, Venezia, Mestre, Italy, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione Pisa, Pisa, Italia
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2020
• Subjects: Ross Sea; Fast ice; Laminated sediments; IPSO25; Sea ice; Sea ice dynamics in the north-western Ross Sea; Edisto; Edisto Inlet
• Online Access: http://hdl.handle.net/2122/14124; https://doi.org/10.1016/j.quascirev.2020.106299

Time-series analyses of satellite images reveal that sea ice extent in the Ross Sea has experienced significant changes over the last 40 years, likely triggered by large-scale atmospheric anomalies. However, resolving how sea ice in the Ross Sea has changed over longer timeframes has until now remained more elusive. Here we used a laminated sediment piston core (14.6 m) collected from the Edisto inlet (Western Ross Sea) to reconstruct fast ice dynamics over the last 2.6 ka. Our goal was to first understand the climate expression of selected well-defined sediment laminae and then use these characteristics for reconstructing past sea ice behaviour across the whole sedimentary sequence. We used the recently established sea ice diatom biomarker proxy IPSO25 in combination with diatom census counts and bulk analyses. Analyses performed on a suite of discrete laminae revealed statistically significant differences between dark and light laminae reflecting different depositional conditions. Based on their respective biogeochemical fingerprints, we infer that dark laminae accumulated during sea ice thaws in early summer. Under these conditions, laminae contain relatively high concentrations of IPSO25 and display an enriched d13C composition for the bulk organic matter (OM). While diatom assemblages in dark laminae are relatively homogenous, as the thaw continues later in the summer, Corethron pennatum becomes the dominant diatom species, resulting in the formation of light laminae characterized by low IPSO25 concentrations. Since C. pennatum can migrate vertically through the water column to uptake nutrients and avoid competition in oligotrophic waters, its high concentration likely reflects stratified and ice-free surface waters typical of late summer. Down-core trends show that the correlation between sediment brightness and geochemical fingerprint (i.e., IPSO25 and d13C) holds throughout the record. Based on the knowledge gained at lamina level, our down-core high-resolution reconstruction shows that the summer fast ...