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Tracing Holocene temperatures and human impact in a Greenlandic Lake: Novel insights from hyperspectral imaging and lipid biomarkers
Get PDFGlobal warming particularly impacts terrestrial and aquatic ecosystems in the Arctic. To constrain the sensitivity of Arctic lakes and make meaningful predictions about future change under global warming, we need to examine their response to previous warm phases. Lake sediments from Greenland's deglaciated area offer valuable archives to investigate past climate variability and associated lake changes. Here, we applied hyperspectral imaging and lipid biomarker thermometry to a Holocene-length sediment record from Lake 578 in the Eastern Settlement of the Norse (61.08 • N, 45.62 • W;~155 m a.s.l) to investigate local temperature, productivity, and anoxia histories. We calibrated branched glycerol dialkyl glycerol tet-raethers (brGDGTs) with summer mean water temperatures (SMWT) using a previously published site-specific calibration and analyzed pigment fluxes based on hyperspectral imaging. Notably, the anoxia reconstructions were corroborated with two independent proxies (GDGT-0/Crenarchaeol and bacterio pheophytins). We investigated the lake's environmental history and identified periods of significant change by employing generalized additive models (GAMs). Our results reveal significant transitions in Lake 578 driven both by natural climate shifts and anthropogenic impacts. During the early Holocene, low SMWT and productivity coupled with high anoxia suggest strong sea-sonality and prolonged inverted thermal stratification, possibly enhanced by extended ice cover. The mid-Holocene showed higher SMWT and productivity along with low anoxia, indicating a dimictic lake system. The early Holocene temperature rise lagged that of to the Northern Hemisphere, but closely followed the Atlantic-Fennoscandian stack. The Holocene Thermal Maximum (7.5-4.5 cal ka BP) aligns with other regional reconstructions. After 3 cal ka BP, we observed a Neoglacial cooling characterized by increased anoxia and reduced temperatures due to enhanced stratification. At around 1.0 cal ka BP, Lake 578 saw a surge in productivity and anoxia, which we attribute to land use and lake damming by the Norse. Despite a post-Norse decline in productivity and disappearance of anoxia, the lake never reverted to its pre-Norse state, with modern sheep farming further intensifying productivity in recent decades. While early Holocene anoxia resulted from natural cold temperature stratification, anoxia during the Norse period was anthropogenically induced. This research underscores the value of integrating lipid biomarkers with hyperspectral imaging for detailed reconstructions of changes within Arctic lakes. It provides crucial insights for anticipating the ecologic and climatic resilience of Arctic lakes to ongoing global warming and anthropogenic influence
Uligheder, sårbarhed og robuste lokale hverdagsløsninger:en undersøgelse af danske almene beboeres affaldshåndtering
No full textA sixteenth century bridal jewel, a gift from Queen Dorothea of Denmark to the town-hall of Copenhagen
No full textIn 1557, the Danish Queen Dorothea, wife of King Christian III, gave a large bridal jewel of gilt-silver with stones, enamel andpearls to the city of Copenhagen for daughters of mayors and councillors to borrow for their wedding celebrations at the town-hall.The jewel, created to be used either as a brooch or a pendant, is made of multiple components. The central pelican has a tailthat had, at some stage, been extended to hold a setting with an enamelled shield plaque featuring the year 1557, the year ofthe gift, and also the coat-of-arms of Sachsen-Lauenburg, belonging to Dorothea and her ancestors.In 1986 the Museum of Copenhagen gained funding for scientific analysis of individual parts of the piece. Analysis of the backpanel and the scroll-work of its framing proved it to be of fine silver but other parts of the jewel are of lesser quality. This study of thebridal jewel found it to be composed of components of different materials and different standards of workmanship. It is proposedthat these components were brought together, probably in 1557, and that the frame and back-panel could have originated from asmall pax/reliquary. The other parts may be reused from items in the queen’s jewellery box or outdated costume jewellery.This paper presents the historical background to the creation of this jewel, as several issues seem relevant to the royal couple’ssituation and interests: Christian had come to power after a civil war, forcing the entire state to convert from Catholicismto Lutheranism. He and Dorothea had for several years to ‘make ends meet’ and present an exemplary Lutheran face whilemaintaining royal dignity. Dorothea is known to have re-used parts of her coronation crown in a hat ornament for her husband, soit would not be surprising that she re-used other items to create this jewel
Good and Bad Nature:Slum clearance and metabolic poverty in mid-twentieth century Copenhagen
No full textKøge 2. A Clinker-built Shipwreck from the Medieval Harbour of Køge, Zealand, Denmark
No full textThe development of a new cityscape in the old industrial harbourknown as ‘Sønder Havn’ in Køge in eastern Zealand ledin the summer of 2018 to the finding of a clinker-built shipwreck.The ship had been built in the 1520s, exclusively fromoak, and had undergone a reinforcement in the stem some tenyears after the initial building phase, hereby adding an extraouter layer of clinker planks and five riders on top of the floortimbers. The extensive dendrochronological analysis showedthat the planks had been felled in the eastern Baltic area,while the floor timbers and the keel of the vessel were fromsomewhere in the vicinity of the Rhine’s mouth. Of the ship,only the parts below the waterline were preserved, partly dueto the groundwater level but probably equally due to salvagingshortly after wrecking.The development of a new cityscape in the old industrial harbourknown as ‘Sønder Havn’ in Køge in eastern Zealand ledin the summer of 2018 to the finding of a clinker-built shipwreck.The ship had been built in the 1520s, exclusively fromoak, and had undergone a reinforcement in the stem some tenyears after the initial building phase, hereby adding an extraouter layer of clinker planks and five riders on top of the floortimbers. The extensive dendrochronological analysis showedthat the planks had been felled in the eastern Baltic area,while the floor timbers and the keel of the vessel were fromsomewhere in the vicinity of the Rhine’s mouth. Of the ship,only the parts below the waterline were preserved, partly dueto the groundwater level but probably equally due to salvagingshortly after wrecking
Blå er det hemmelighedsfuldes farve
No full textDe mange forskellige blå pigmenter, som kunstmalere har anvendt gennem historien, er varieret over tid og er derfor væsentlige at afdække for at bestemme et maleris tidsperiode. Preussisk blå er for eksempel en markør for malerier produceret efter 1706, hvor den for første gang blev produceret i Berlin og straks blev enormt populær, da den var billig og havde en fremragende dækevne
