Sökning: "δ18O"

Visar resultat 1 - 5 av 23 avhandlingar innehållade ordet δ18O.

1. 1. Testing palaeomagnetic and 14C based geochronological methods in the Baltic Sea

   Författare :Bryan Lougheed; Kvartärgeologi; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Baltic Sea; coastal; geochronology; palaeomagnetic secular variation; PSV; radiocarbon; 14C; reservoir age; R t ; ΔR; salinity; δ18O; geomagnetic field; Holocene; deglacial; Fennoscandia.;

   Sammanfattning : The Baltic Sea is a continental shelf sea that is influenced by both river runoff and marine water. The two water masses are vertically stratified in the Baltic Sea, resulting in a positive, estuarine circulation system, which has undergone changes in the past due to isostatic uplift of the Baltic basin. LÄS MER

3. 2. Late Holocene humidity variability in central Sweden

   Författare :Sofia Andersson; Stefan Wastegård; Gunhild Rosqvist; Kristian Schoning; Frank Chambers; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; humidity change; stable isotopes; Chara spp; Pisidium spp; testate amoebae assemblages; humification; C N ratio; late Holocene; central Sweden; Quaternary geology; Kvartärgeologi; kvartärgeologi; Quarternary Geology;

   Sammanfattning : The aim of this thesis was to reconstruct humidity variability in central Sweden during the late Holocene. A multi-proxy approach was used to infer humidity changes as recorded in a lake and a mire. Age-models were constructed based on radiocarbon dating and the Askja-1875 tephra. LÄS MER

4. 3. Holocene climate and environmental change in high latitudes as recorded by stable isotopes in peat deposits

   Författare :Päivi Kaislahti Tillman; Steffen Holzkämper; Stefan Wastegård; Peter Kuhry; Thomas W. D. Edwards; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; stable isotopes; Holocene; subarctic; climate; Sphagnum fuscum; kvartärgeologi; Quarternary Geology;

   Sammanfattning : In this thesis, stable carbon and oxygen isotopes in α-cellulose isolated from Sphagnum fuscum moss remains were used as climate proxies. The main focus was to implement the methods in records from high latitude peatlands in the Northern Hemisphere (west-central Canada and north-eastern European Russia), reconstruct palaeoclimate of the studied regions during the Holocene, and evaluate the compatibility of results with other proxy records, especially tree-ring isotope time-series. LÄS MER

5. 4. Nitrate stable isotopes and major ions in snow and ice from Svalbard

   Författare :Carmen Paulina Vega Riquelme; V. A. Pohjola; R. Pettersson; E. Isaksson; C. E. Bøggild; Kumiko Goto-Azuma; Uppsala universitet; []
   Nyckelord :nitrate stable isotopes; nitrate; NOx proxies; ice cores; percolation; ion relocation; Svalbard; stabila isotoper av nitrat; nitrat; indikator för kväveoxider; iskärnor; perkolation; joniska omlokalisering; Svalbard; Earth Science with specialization in Physical Geography; Geovetenskap med inriktning mot naturgeografi;

   Sammanfattning : Increasing atmospheric reactive nitrogen (Nr), as consequence of human activities, has generated accumulation of nitrate (NO3-) in Arctic regions. The Arctic has fragile nitrogen limited ecosystems that can be altered by increases of dry or wet deposition of Nr. LÄS MER

7. 5. Climate in the eastern Mediterranean during the Holocene and beyond – A Peloponnesian perspective

   Författare :Martin Finné; Karin Holmgren; Hanna S. Sundqvist; Georgia Destouni; Neil Roberts; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Stable isotopes; U-Th dating; stalagmites; climate variability; flooding history; eastern Mediterranean; southern Greece; Holocene; Pleistocene; Physical Geography; naturgeografi;

   Sammanfattning : This thesis contributes increased knowledge about climate variability during the late Quaternary in the eastern Mediterranean. Results from a paleoclimate review reveal that regional wetter conditions from 6000 to 5400 years BP were replaced by a less wet period from 5400 to 4600 years BP and to fully arid conditions around 4600 years BP. LÄS MER