English
norskBlar i forfatter "Sørensen, Steffen Aagaard"
Viser treff 1-13 av 13
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Benthic foraminiferal growth seasons implied from Mg/Ca-temperature correlations for three Arctic species
(Peer reviewed; Journal article; Tidsskriftsartikkel, 2016-11-22)Core-top sediment samples from Kongsfjorden, Svalbard, and adjacent fjord and shelf areas were collected in order to investigate a potential relationship between Mg/Ca-ratios of Arctic benthic foraminifera and the ambient bottom water temperatures (BWT). The area is influenced by large seasonal variation in factors such as light and temperature, which is further strengthened by oceanographic shifts, ... -
Environmental baselines and reconstruction of Atlantic Water inflow in Bjørnøyrenna, SW Barents Sea, since 1800 CE
(Journal article; Tidsskriftartikkel, 2017-10-28)Metal concentrations, sediment properties and benthic foraminiferal assemblages were investigated in sediment cores in the SW Barents Sea, to reconstruct environmental baselines and natural variability of Atlantic Water inflow since 1800 CE. Metal concentrations correspond to no effect levels and do not influence the foraminifera. Increased Hg and Pb was linked to inflow of Atlantic Water. The data ... -
Evidence for influx of Atlantic water masses to the Labrador Sea during the Last Glacial Maximum
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-03-21)The Last Glacial Maximum (LGM, 23–19,000 year BP) designates a period of extensive glacial extent and very cold conditions on the Northern Hemisphere. The strength of ocean circulation during this period has been highly debated. Based on investigations of two marine sediment cores from the Davis Strait (1033 m water depth) and the northern Labrador Sea (2381 m), we demonstrate a significant influx ... -
Identifying past petroleum exploration related drill cutting releases and influences on the marine environment and benthic foraminiferal communities, Goliat Field, SW Barents Sea, Norway
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-01)The present multiproxy investigation of marine sediment cores aims at: 1) Identifying dispersion of petroleum exploration related drill cutting releases within the Goliat Field, Barents Sea in 2006/07 and 2) Assessing past and present influence of drill cuttings on the marine environment. The cores were recovered 5, 30, 60, 125 and 250 m from the drill site in the eastward downstream direction.<p> ... -
Instance Segmentation of Microscopic Foraminifera
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-07-16)Foraminifera are single-celled marine organisms that construct shells that remain as fossils in the marine sediments. Classifying and counting these fossils are important in paleo-oceanographic and -climatological research. However, the identification and counting process has been performed manually since the 1800s and is laborious and time-consuming. In this work, we present a deep learning-based ... -
Late Glacial – Holocene climate variability and sedimentary environments on northern continental shelves Zonal and meridional Atlantic Water advection
(Doctoral thesis; Doktorgradsavhandling, 2011-03-22)The overall objective for this PhD-study was to further advance the understanding of the oceanographic variability and development in the Nordic Seas during the Late Glacial and the Holocene and towards the present. The focus is specifically on the poleward Atlantic Water advection along the continental margins of Norway, into the SW Barents Sea and along the West Spitsbergen slope. Four high ... -
A Late Glacial–Early Holocene multiproxy record from the eastern Fram Strait, Polar North Atlantic
(Journal article; Tidsskriftartikkel; Peer reviewed, 2014) -
A late-Holocene multi-proxy record from the northern Norwegian margin: Temperature and salinity variability
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-11-01)To elucidate the natural variability of Atlantic and Coastal water, a late-Holocene multi-proxy analysis is performed on a marine sediment core from the northern Norwegian margin. This includes planktic foraminiferal fauna and their preservation indicators, stable isotopes (δ18Oc, δ13C), sub-surface temperature (SSTMg/Ca) and salinity (SSS) records based on paired Mg/Ca and δ18Oc measurements of ... -
Reconstruction of Atlantic Water variability during the Holocene in the western Barents Sea
(Journal article; Tidsskriftartikkel; Peer reviewed, 2014-01-10)The gravity core JM09-KA11-GC from 345m water depth on the western Barents Sea margin was investigated for down-core distribution patterns of benthic Foraminifera, stable isotopes, and sedimentological parameters in order to reconstruct the flow of Atlantic water during the Holocene. The core site is located below the Atlantic water masses flowing into the Arctic Ocean and close to the Arctic front. ... -
Semi-quantitative reconstruction of early to late Holocene spring and summer sea ice conditions in the northern Barents Sea
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-06-07)Semi-quantitative estimates of early to late Holocene spring sea ice concentration (SpSIC) andoccurrence of summer sea ice for the northern Barents Sea have been obtained by analysing the biomarkers IP<sub>25</sub>,brassicasterol and a tri-unsaturated highly branched isoprenoid lipid in a Holocene marine sediment core.Sub-surface water mass variations were derived from planktic foraminiferal assemblages ... -
Spreading of drill cuttings and sediment recovery of three exploration wells of different ages, SW Barents Sea, Norway
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-14)Five stations (≤250 m from the well heads) from three exploration wells of different ages from the SW Barents Sea were studied to investigate the spreading of drill cuttings and sediment quality. Two of the wells were drilled before the restriction of use of oil-based drilling fluids (1993). Elevated concentrations of Ba were found in sediments near all the wells with the highest concentrations ... -
Sub sea surface temperatures in the Polar North Atlantic during the Holocene: Planktic foraminiferal Mg/Ca temperature reconstructions
(Journal article; Tidsskriftartikkel; Peer reviewed, 2013)Holocene sea surface temperatures in the eastern Fram Strait are reconstructed based on Mg/Ca ratios measured on the planktic foraminifer Neogloboquadrina pachyderma (sin). The reconstructed sub sea surface temperatures (sSSTMg/Ca) fluctuate markedly during the earliest Holocene at ~11.7 and 10.5 kyr BP. This is probably in response to the varying presence of sea-ice and deglacial meltwater. Between ... -
Towards detection and classification of microscopic foraminifera using transfer learning
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-06)<p>Foraminifera are single-celled marine organisms, which may have a planktic or benthic lifestyle. During their life cycle they construct shells consisting of one or more chambers, and these shells remain as fossils in marine sediments. Classifying and counting these fossils have become an important tool in e.g. oceanography and climatology. <p>Currently the process of identifying and counting ...
