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Detailing the Little Ice Age on the Swedish west coast: a multi-proxy study of a sediment record from Gullmar Fjord

Konferensbidrag (offentliggjort, men ej förlagsutgivet)
Författare Irina Polovodova
Helena L. Filipsson
Rex Harland
Kjell Nordberg
Publicerad i Marchant, M . & Hromic, T. (eds . ) 201 4 . Internation al Symposium on Foraminifera Forams 2014, Chile, 19 – 24 January 2014 , Abstract Volume . Grzybowski Foundation Special Publication, 20 , 124 pp.
Sidor 38-39
ISBN 978-83-88927-35-5
Publiceringsår 2014
Publicerad vid Institutionen för geovetenskaper
Sidor 38-39
Språk en
Länkar gf.tmsoc.org/Documents/Marchant+Hro...
Ämnesord climate change, stable isotopes, benthic foraminifera, dinocysts, marine sediment archive
Ämneskategorier Geovetenskap och miljövetenskap

Sammanfattning

Gullmar Fjord, on the west coast of Sweden, represents a high-resolution environmental archive due to high sedimentation rates, low bioturbation and negligible tidal activity. In this study we attempt to detail the climatic and environmental changes in NE Europe during the last millennium by using a ca. 8-m long well dated sediment record from the deep fjord basin. According to the 14C-datings, the record includes the period of the late Holocene characterised by anomalously cold summers and well known as the Little Ice Age (LIA). Using a high-resolution stratigraphy of benthic foraminifera and dinoflagellate cysts along with lithology, bulk sediment geochemistry and foraminiferal δ13C we identify the timing of the cold period, reconstruct its various phases, and discuss the land-sea interactions occurring in the study area during that time. The onset of the LIA is indicated at ~1350 A.D by an increase in abundances of cold-water foraminifer Adercotryma glomerata and the cryophilic dinoflagellate cyst Islandinium cf. cezare. The first phase of the LIA was characterised by a stormy climate and higher productivity, as suggested by a foraminiferal assemblage of Nonionella iridea and Cassidulina laevigata. The hypothesis of higher productivity is supported by the isotopic and the dinoflagellate cyst records, which show a shift towards more negative δ13C values, and a marked increase in the microreticulate cysts of Gymnodinium nolleri at the onset of the LIA. The dinoflagellate species G. nolleri becomes relict towards the LIA termination and could be also associated with lower surface water temperatures at that time. It is likely that due to land use changes in the second part of the LIA there was an increased input of terrestrial organic matter to the fjord, which is indicated by lighter δ13C values and an increase of detritivorous and omnivorous foraminiferal species such as Textularia earlandi and Eggerelloides scaber. The climate deterioration during the climax of the LIA (1675-1704 A.D.) may have driven a decline in primary productivity, as suggested by the increase of agglutinated foraminiferal species, the presence of Hyalinea balthica, and a decline of N. iridea during that time.

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