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Testing the hypothesis of a link between Earth’s magnetic field and climate change : a case study from southern Sweden focusing on the 1st millennium BC

Ning, Wenxin (2011) In Dissertations in Geology at Lund University
Department of Geology
Abstract
It is commonly believed that long-term (10 to 1000 kyr) and short-term (10 to 1000 years) climatic changes on Earth can be interpreted by periodic variations in Earth’s orbit around the Sun and variations in solar irradiance, respectively. In recent years, geomagnetic field changes have been suggested as a potential driver of climate change. However, a link between these two factors is not straightforward. A relationship between geomagnetic field changes and climate is still debatable. To test the hypothesis of a link between past changes in the geomagnetic field and climate, reliable reconstructions of paleoclimate and paleogeomagnetic field are needed. In this study, high resolution palaeomagnetic and palaeoecological records obtained... (More)
It is commonly believed that long-term (10 to 1000 kyr) and short-term (10 to 1000 years) climatic changes on Earth can be interpreted by periodic variations in Earth’s orbit around the Sun and variations in solar irradiance, respectively. In recent years, geomagnetic field changes have been suggested as a potential driver of climate change. However, a link between these two factors is not straightforward. A relationship between geomagnetic field changes and climate is still debatable. To test the hypothesis of a link between past changes in the geomagnetic field and climate, reliable reconstructions of paleoclimate and paleogeomagnetic field are needed. In this study, high resolution palaeomagnetic and palaeoecological records obtained from varved sediments in Lake Gyltigesjön, southern Sweden, with an emphasis on the 1st millennium BC, are directly compared to test the hypothesis. The 1st millennium BC is one of the most interesting periods of geomagnetic variation during the Holocene, which is characterized in palaeomagnetic records by high magnetic field intensity and relatively abrupt geomagnetic pole movement. Through measurements of magnetic hysteresis parameters and First Order Reversal Curves (FORCs), sediments from Gyltigesjön are believed to contain abundant single domain (SD) magnetite grains, which are an excellent source of paleomagnetic field reconstructions. In order to reconstruct paleoclimate conditions during the 1st millennium BC, pollen analysis, measurements of varve thickness, loss on ignition (LOI), total organic carbon (TOC), ration of C/N, grey scale and magnetic parameters were conducted. The main conclusion is that no evidence of a link between geomagnetic field and climate change can be found in southern Sweden during the study period. Early human activity, however, could have masked the palaeoclimatic significance of the proxies used. (Less)
Abstract (Swedish)
Under senare år har förändringar i det jordmagnetiska fältet föreslagits som en möjlig drivkraft för klimatförändringar. Det finns dock inget enkelt samband mellan dessa två faktorer. Ett samband mellan förändringar i det jordmagnetiska fältet och klimatet är fortfarande omdebatterat. För att testa hypotesen om ett samband mellan tidigare förändringar i det jordmagnetiska fältet och klimatet behövs tillförlitliga rekonstruktioner av det gångna klimatet och jordmagnetiska fältet. I denna studie har högupplösta paleomagnetiska och paleoekologiska arkiv från varviga sediment i Gyltigesjön i södra Sverige direkt jämförts för att testa hypotesen, med betoning på det första årtusendet f.Kr. Det första årtusendet f.Kr. är en av de mest... (More)
Under senare år har förändringar i det jordmagnetiska fältet föreslagits som en möjlig drivkraft för klimatförändringar. Det finns dock inget enkelt samband mellan dessa två faktorer. Ett samband mellan förändringar i det jordmagnetiska fältet och klimatet är fortfarande omdebatterat. För att testa hypotesen om ett samband mellan tidigare förändringar i det jordmagnetiska fältet och klimatet behövs tillförlitliga rekonstruktioner av det gångna klimatet och jordmagnetiska fältet. I denna studie har högupplösta paleomagnetiska och paleoekologiska arkiv från varviga sediment i Gyltigesjön i södra Sverige direkt jämförts för att testa hypotesen, med betoning på det första årtusendet f.Kr. Det första årtusendet f.Kr. är en av de mest intressanta perioderna för jordmagnetiska variationer under Holocen, vilket i paleomagnetiska arkiv kännetecknas av en hög jordmagnetisk intensitet och en relativt abrupt jordmagnetisk polrörelse. Genom mätningar av parametrar för magnetisk hysteres och “First Order Reversal Curves” (FORCs) antas sedimenten i Gyltigesjön innehålla rikligt med magnetitkorn av enda domän (SD) vilket är en utmärkt källa vid rekonstruktioner av det jordmagnetiska fältet. För att rekonstruera de paleoklimatiska förhållandena under det första årtusendet f.Kr. utfördes: pollenanalys, mätningar av varvtjocklek, glödförlust (LOI), totalt kol (TC), förhållande mellan kol och kväve (C/N), gråskala och mätningar av magnetiska parametrar. Den huvudsakliga slutsatsen är att det inte hittats något bevis för ett samband mellan jordens magnetfält och klimatförändringar i södra Sverige under den studerade perioden. Tidig mänsklig aktivitet kan dock ha påverkat betydelsen av de klimatproxies som har använts. (Less)
Please use this url to cite or link to this publication:
author
Ning, Wenxin
supervisor
organization
alternative title
Samband mellan jordens magnetfält och klimatet? : en fallstudie i södra Sverige med fokus på första årtusendet f.Kr.
year
type
H2 - Master's Degree (Two Years)
subject
keywords
paleomagnetism, varve, lake sediment, southern Sweden, climate reconstruction, human impact, sjösediment, södra Sverige, klimatåteruppbyggnad, mänsklig påverkan
publication/series
Dissertations in Geology at Lund University
report number
290
language
English
id
2278604
date added to LUP
2013-01-09 14:13:35
date last changed
2013-01-09 14:13:35
@misc{2278604,
  abstract     = {It is commonly believed that long-term (10 to 1000 kyr) and short-term (10 to 1000 years) climatic changes on Earth can be interpreted by periodic variations in Earth’s orbit around the Sun and variations in solar irradiance, respectively. In recent years, geomagnetic field changes have been suggested as a potential driver of climate change. However, a link between these two factors is not straightforward. A relationship between geomagnetic field changes and climate is still debatable. To test the hypothesis of a link between past changes in the geomagnetic field and climate, reliable reconstructions of paleoclimate and paleogeomagnetic field are needed. In this study, high resolution palaeomagnetic and palaeoecological records obtained from varved sediments in Lake Gyltigesjön, southern Sweden, with an emphasis on the 1st millennium BC, are directly compared to test the hypothesis. The 1st millennium BC is one of the most interesting periods of geomagnetic variation during the Holocene, which is characterized in palaeomagnetic records by high magnetic field intensity and relatively abrupt geomagnetic pole movement. Through measurements of magnetic hysteresis parameters and First Order Reversal Curves (FORCs), sediments from Gyltigesjön are believed to contain abundant single domain (SD) magnetite grains, which are an excellent source of paleomagnetic field reconstructions. In order to reconstruct paleoclimate conditions during the 1st millennium BC, pollen analysis, measurements of varve thickness, loss on ignition (LOI), total organic carbon (TOC), ration of C/N, grey scale and magnetic parameters were conducted. The main conclusion is that no evidence of a link between geomagnetic field and climate change can be found in southern Sweden during the study period. Early human activity, however, could have masked the palaeoclimatic significance of the proxies used.},
  author       = {Ning, Wenxin},
  keyword      = {paleomagnetism,varve,lake sediment,southern Sweden,climate reconstruction,human impact,sjösediment,södra Sverige,klimatåteruppbyggnad,mänsklig påverkan},
  language     = {eng},
  note         = {Student Paper},
  series       = {Dissertations in Geology at Lund University},
  title        = {Testing the hypothesis of a link between Earth’s magnetic field and climate change : a case study from southern Sweden focusing on the 1st millennium BC},
  year         = {2011},
}