Sökning: "varves"

Visar resultat 1 - 5 av 7 avhandlingar innehållade ordet varves.

1. 1. Investigations of temporal changes in climate and the geomagnetic field via high-resolution radiocarbon dating

   Författare :Anette Mellström; Kvartärgeologi; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; wiggle-matching; Radiocarbon dating; 14C; 2800 cal BP; climate change; solar activity; palaeomagnetism; lake sediments; varves; post-depositional remanent magnetisation; PDRM; lock-in; peat deposits; Sweden;

   Sammanfattning : Geological archives have shown periods of abrupt climate change in the relatively stable Holocene epoch (last ca. 11 700 years). One of these periods was around 2800 cal BP. Several records, mainly from Europe, reveal a shift towards wetter, cooler and windier conditions. LÄS MER

3. 2. Holocene development of Lake Lögurinn and Eyjabakkajökull : a multi-proxy approach

   Författare :Johan Striberger; Kvartärgeologi; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Iceland; the Holocene; lake sediments; varves; glacial meltwater variability; surge periodicity; palaeoclimate;

   Sammanfattning : The North Atlantic region has experienced significant climate fluctuations during the Holocene. It has been shown that these fluctuations affected the terrestrial environment in Iceland, including its glaciers and ice caps. LÄS MER

4. 3. Varved lake sediments and diagenetic processes

   Författare :Veronika Gälman; Ingemar Renberg; Daniel Conley; Umeå universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Varved annually laminated lake sediment; diagenesis; varve appearance; iron; sulfur; chemical speciation; iron cycling; carbon; nitrogen; stabile isotopes; δ13C; δ15N; Earth sciences; Geovetenskap;

   Sammanfattning : Varved (annually laminated) sediments are of great interest for inference of past environmental conditions, as they provide dated records with high time resolution. After deposition, the sediment varves are affected by diagenesis; i.e., chemical, physical and biological changes that occur within the sediment. LÄS MER

5. 4. Climatic signals and frequencies in the Swedish Time Scale, River Ångermanälven, Central Sweden

   Författare :Mikkel Sander; Kvartärgeologi; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; marklära; kartografi; klimatologi; pedology; cartography; climatology; Fysisk geografi; geomorfologi; geomorphology; Physical geography; winter precipitation; climate change; central Sweden; last 2000 year; discharge; varve;

   Sammanfattning : Any future climate variation forced by human activities will be superimposed on the background of natural climate variation. Therefore, before interpreting the present climate and addressing future climate scenarios some knowledge of past climate is necessary. LÄS MER

7. 5. Functional clustering methods and marital fertility modelling

   Författare :Per Arnqvist; Sara Sjöstedt de Luna; Leif Nilsson; Helle Sørensen; Umeå universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; censoring; Coale-Trussell model; EM-algorithm; functional data analysis; functional clustering; marital fertility; normal approximation; Poisson process; varved lake sediments; warping; Mathematical Statistics; matematisk statistik;

   Sammanfattning : This thesis consists of two parts.The first part considers further development of a model used for marital fertility, the Coale-Trussell's fertility model, which is based on age-specific fertility rates. A new model is suggested using individual fertility data and a waiting time after pregnancies. LÄS MER