Climate and environment in southwest Sweden 15.5–11.3 cal. ka BP

Abstract

Lake sedimentary records that allow documentation of the distinct climatic and environmental shifts during the early part of the Last Termination are scarce for northern Europe. This multi-proxy study of the sediments of Attek€ opsmosse, southwest Sweden, therefore fills an important gap and provides detailed information regarding past hydroclimatic conditions and local environmental responses to climatic shifts. Lake infilling started c. 15.5 cal. ka BP, but low aquatic productivity, cold summer lake water temperatures, unstable catchments, and scarce herb and shrub vegetation prevailed until c. 14.7-14.5 cal. ka BP. Inflow of warmer air masses and higher July air temperatures favoured a rise in aquatic productivity and lake water summer temperatures, and the establishment of a diverse herb, shrub and dwarf shrub vegetation, which also included tree birch c. 14.5 cal. ka BP. Freshening of the moisture source region c. 13.7-13.6 cal. ka BP does not seem to have had a large impact on the ancient lake and its catchment, as lake aquatic productivity increased further and lake water summer temperatures and minimum mean July air temperatures remained around 12-14°C. In contrast, further freshening of the moisture source region c. 13 cal. ka BP triggered a decrease in lake productivity, drier conditions and lower lake water summer temperatures. Macroscopic finds of tree Betula and Pinus sylvestris at 13-12.8 cal. ka BP demonstrate the presence of these trees in the lake's catchment. The transition into the Holocene (11.6-11.5 cal. ka BP) is marked by a change in chironomid assemblages and by a rise in lake water summer temperatures and aquatic productivity. These changes were followed by the re-establishment of a diverse aquatic and terrestrial vegetation, including tree birch and Pinus sylvestris at 11.4 cal. ka BP.

Lake Sedimentary DNA Research on Past Terrestrial and Aquatic Biodiversity: Overview and Recommendations

“…Study sites-The study sites are listed in Table A6. Southern Sweden Lake ~15,000 [285] DNA extraction-Three extractions protocols were conducted on seven sediment samples in duplicate; see Figure A5 for the extraction schemes. All extractions were performed from ca 0.25 g of sediments.…”

On the timing of retreat of the Loch Lomond (‘Younger Dryas’) Readvance icefield in the SW Scottish Highlands and its wider significance

“…Ice growth also continued after the onset of the Holocene in some parts of Svalbard (Farnsworth et al, 2018). Furthermore, independent palaeoclimatic studies based on a range of palaeobiological data indicate that cold conditions persisted in western Norway until ~11.5 cal 14 C ka BP (Gulliksen et al, 1998), in Denmark tundra vegetation prevailed beyond the start of the Holocene (Bennike and Mortensen, 2018) and temperatures in SW Sweden remained cold until around 11.56 cal 14 C ka BP, and were most severe during the later part of GS-1 (Wohlfarth et al, 2018). Therefore, evidence is increasingly pointing to cold conditions having prevailed throughout parts of NW Europe until or beyond the start of the Holocene, and the new evidence we have presented for the SW Scottish icefield fits this scenario.…”

Amino acid racemization in Quaternary foraminifera from the Yermak Plateau, Arctic Ocean

“…The cold surface layer is dominated by the polar foraminifer N. pachyderma, which has highest abundances in the top 200 m (Carstens and Wefer, 1992;Carstens et al, 1997;Pados and Spielhagen, 2014;Greco et al, 2019). Cassidulina neoteretis is one of the dominant benthic species in sediments from the Yermak Plateau (Bergsten, 1994;Wollenburg and Mackensen, 1998;Wollenburg et al, 2004), and its abundance is often associated with the presence of Atlantic water (Polyak and Solheim, 1994;Ślubowska et al, 2005).…”