The Little Ice Age: evidence from a sediment record in Gullmar Fjord, Swedish west coast

Abstract

We discuss the climatic and environmental changes during the last millennium in NE Europe based on a ca. 8-m long high-resolved and well-dated marine sediment record from the deepest basin of Gullmar Fjord (SW Sweden). According to the ²¹⁰Pb- and 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 benthic foraminiferal stratigraphy, lithology, bulk sediment geochemistry and stable carbon isotopes we reconstruct various phases of the cold period, identify its timing in the study area and discuss the land–sea interactions occurring during that time. The onset of the LIA is indicated by an increase in cold-water foraminiferal species <i>Adercotryma glomerata</i> at ~ 1350 AD The first phase of the LIA was characterised by a stormy climate and higher productivity, which is indicated by a foraminiferal unit of <i>Nonionella iridea</i> and <i>Cassidulina laevigata</i>. Maximum abundances of <i>N. iridea</i> probably mirror a short and abrupt warming event at ~ 1600 AD. 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 &delta;¹³C values and an increase of detritivorous and omnivorous species such as <i>Textularia earlandi</i> and <i>Eggerelloides scaber</i>. The climate deterioration during the climax of the LIA (1675–1704 AD), as suggested by the increase of agglutinated species, presence of <i>Hyalinea balthica</i>, and a decline of <i>N. iridea</i> may have driven the decline in primary productivity during this time period

Tracing winter temperatures over the last two millennia using a NE Atlantic coastal record

“…For the Gullmar Fjord a general cooling during the LIA has been previously suggested based on increased abundances of 30 cryophilic dinocysts (Harland et al, 2013) and benthic foraminifer Adercotryma glomerata, which prefers bottom water temperatures < 4°C (Polovodova Asteman et al, 2013). This agrees rather well with the data presented herein, which show Clim.…”

“…The age model for GA113-2Aa and 9004 has been previously published in Filipsson and Nordberg (2010) with further revisions by Polovodova et al (2011) andPolovodova Asteman et al (2013). Eleven intact marine bivalve shells were recovered in life position from the core 9004 and were subject to the AMS 14 C analysis ( Fig.…”

“…AMS 14 C dates obtained for the gravity core 9004 and calibrated calendar ages. All dates presented in Nordberg (2010) andPolovodova Asteman et al (2013) were re-calibrated using Calib 7. 10 (Stuiver et al 2017), the Marine13 calibration dataset (Reimer et al, 2013), and ∆R = 100 ± 50.…”

The interplay between the surface and bottom water environment within the Benguela Upwelling System over the last 70 ka

“…Other species within this assemblage such as N . iridea also consume fresh organic matter [ Polovodova Asteman et al , ] but cannot tolerate such low oxygen conditions to the same extent. High relative abundance of E .…”

Mg/Ca and Mn/Ca ratios in benthic foraminifera: the potential to reconstruct past variations in temperature and hypoxia in shelf regions

“…Zillén and Conley (2010) show that, especially during the last two millennia, phases of hypoxia such as during the early medieval expansion (700-1300 AD) seem to correlate with major changes in population and land use in Scandinavia instead of correlating with natural climate variations. Some of the fjords of southwest Sweden, e.g., the Gullmar Fjord off the Skagerrak, have been studied extensively, especially with respect to changes in hydrography, eutrophication, and oxygen status (Gustafsson and Nordberg, 1999, 2000Eriksson et al, 2002;Nordberg, 2004a, b, 2010;Filipsson et al, 2004;Erlandsson et al, 2006;Polovodova et al, 2011;Polovodova Asteman et al, 2013). Due to their relatively small area, fjords provide ideal settings for monitoring changes in water mass conditions.…”