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

QUATERNARY SCIENCE REVIEWS

卷:237

Article

Tesi, T.¹  Belt, S. T.²  Gariboldi, K.³  Muschitiello, F.⁴  Smik, L.²  Finocchiaro, F.⁵  Giglio, F.¹  Colizza, E.⁵  Gazzurra, G.³  Giordano, P.¹  Morigi, C.^3,6  Capotondi, L.⁷  Nogarotto, A.⁸  Koseoglu, D.²  Di Roberto, A.⁹  Gallerani, A.⁷  Langone, L.¹ 

[1] Consiglio Nazl Ric ISP CNR, Ist Sci Polari, Via P Gobetti 101, I-40129 Bologna, Italy

[2] Univ Plymouth, Biogeochem Res Ctr, Sch Geog Earth & Environm Sci, Plymouth PL4 8AA, Devon, England

[3] Univ Pisa, Dipartimento Sci Terra, Via Santa Maria 53, I-56126 Pisa, Italy

[4] Univ Cambridge, Dept Geog, Cambridge CB2 3EN, England

[5] Univ Trieste, Dipartimento Matemat & Geosci, Via E Weiss 2, I-34127 Trieste, Italy

[6] Geol Survey Denmark & Greenland GEUS, Oster Voldgade 10, DK-1350 Copenhagen, Denmark

[7] Consiglio Nazl Ric ISMAR CNR, Ist Sci Marine, Via P Gobetti 101, I-40129 Bologna, Italy

[8] Univ Ca Foscari Venezia, Campus Sci,Via Torino 155, I-30172 Venice, Mestre, Italy

[9] Ist Nazl Geofis & Vulcanol INGV, Sez Pisa, Via Faggiola 32, I-56126 Pisa, Italy

关键词: Ross sea;    Fast ice;    Laminated sediments;    IPSO25;    Sea ice;   

DOI  :  10.1016/j.quascirev.2020.106299

来源: Elsevier

【 摘 要 】

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 delta C-13 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 delta C-13) holds throughout the record. Based on the knowledge gained at lamina level, our down-core high-resolution reconstruction shows that the summer fast ice coverage changed dramatically during the late Holocene. Specifically, we conclude that the Edisto inlet experienced regular early summer opening between 2.6 ka, and ca. 0.7 ka, after which, coastal fast ice persisted during summer months and ice-free conditions became less frequent. Comparison with previous regional ice core data suggests that the sudden cooling recorded over the Victoria Land Coast region since 0.7 ka might potentially explain our observation of persistent summer fast ice in the Western Ross Sea. Our study has shown that multi-proxy data derived from laminated sediments can provide hitherto unknown detail regarding past summer sea ice dynamics in coastal Antarctic regions. (C) 2020 Elsevier Ltd. All rights reserved.

【 授权许可】

Free