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Cosmogenic radionuclides in environmental archives – A paleo-perspective on space climate and a synchronizing tool for climate records

Mekhaldi, Florian LU (2018)
Abstract (Swedish)
Solen är den primära källan för jordens klimatsystem, som driver den atmosfäriska och oceana cirkulationen. Förutom att solens varierande instrålning påverkan jordens klimat, så bestämmer instrålningen även den atmosfäriska produktionen av kosmogena partiklar (t. ex. 10Be, 14C, 36Cl) som sedan lagras i diverse klimatarkiv på jorden. Förändringar i solinstrålningen över tid kan därför undersökas och mätas från till exempel isborrkärnor, årsringar från träd och sjösediment. Solen kan också uppvisa ett mer kaotiskt beteende genom utbrott av ljus, plasma och magnetfält, så kallade solstormar, där partiklar kan accelereras och träffa jordklotet. Dessa partiklar kan skada astronauter, satelliter och annan... (More)
Solen är den primära källan för jordens klimatsystem, som driver den atmosfäriska och oceana cirkulationen. Förutom att solens varierande instrålning påverkan jordens klimat, så bestämmer instrålningen även den atmosfäriska produktionen av kosmogena partiklar (t. ex. 10Be, 14C, 36Cl) som sedan lagras i diverse klimatarkiv på jorden. Förändringar i solinstrålningen över tid kan därför undersökas och mätas från till exempel isborrkärnor, årsringar från träd och sjösediment. Solen kan också uppvisa ett mer kaotiskt beteende genom utbrott av ljus, plasma och magnetfält, så kallade solstormar, där partiklar kan accelereras och träffa jordklotet. Dessa partiklar kan skada astronauter, satelliter och annan rymdteknik samt teknologi på marken. Vid extrema utbrott kan även flygsäkerheten hotas. Samtidigt, när dessa partiklar träffar atmosfären ökar produktionen av kosmogena partiklar.
Avhandlingen har två övergripande mål. Dels att grundligt undersöka potentialen i att använda 10Be, 14C och 36Cl för att hitta dåtida extrema solstormar. Dels så kommer den gemensamma produktionssignalen hos 10Be och 14C att användas för att synkronisera klimatarkiv från olika regioner för att kunna undersöka tidpunkten för fluktuationer i klimatet under de senaste 11 000 åren.
Två stora ökningar av kosmisk strålning, daterade till AD 774/5 och AD 993/4, visar sig härstamma från extrema solstormar som träffade jorden och lämnade tydliga spår i produktionen av 14C i årsringar från träd över hela jorden, samt av 10Be och 36Cl från isborrkärnor från Grönland och Antarktis. Energispektrat och flödet av partiklar under dessa solstormar visar på att de var en magnitud kraftigare än de solstormar som har observerats under rymderan. Vi visar även att den relativa skillnaden i energiproduktionen mellan 10Be och 36Cl kan användas för att ta fram energispektrat. En tredje extrem solstorm tros ha träffat jorden år 2610 BP. De två eventen 774/5 och 993/4 har också undersökts för att testa, och slutligen förkasta, hypotesen att nitrat från isborrkärnor kan länkas till solstormar.
Två högupplösta 36Cl-mätserier från isborrkärnor som sträcker sig över flera hundra år presenteras och visar att flera ökningar av 36Cl möjligen kan kopplas till solenergipartiklar, varav en ökning är samtida med en geomagnetisk storm i september 1909. Mätserierna visar inga förhöjda 36Cl-värden under Carrington-eventet 1859. Ett teoretiskt experiment föreslår att det är möjligt att stora solstormar med ett stort inflöde av lågenergipartiklar kan leda till väsentligt högre värden av 36Cl, men inte av 10Be, i isborrkärnor.
Slutligen visar vi att förändringar i halten av kosmogena partiklar orsakade av långsamma förändringar i solaktivitet kan användas för att synkronisera mätserier från sjösediment i Europa med isborrkärnor från Grönland. Undersökningarna av båda mätserier över samma tidsavsnitt tyder på att klimatförändringar som har observerats på Grönland och i västra Europa kan, åtminstone delvis, tillskrivas solaktivitet.
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Abstract

The Sun is the primary source for Earth’s climate system.
Its fluctuations in irradiance are also known to have an impact on climate. In
addition, changes in solar activity modulate the atmospheric production rates
of cosmogenic radionuclides (e.g. 10Be, 14C, 36Cl)
that all eventually deposit to different environmental archives. The signal of
the changing solar activity through time can thus be retrieved and measured
from these archives, such as ice cores, tree rings, or lake sediments. The Sun can
also display a more chaotic behavior by erupting flashes of light, plasma and
magnetic fields whereby energetic particles can be accelerated, and ... (More)

The Sun is the primary source for Earth’s climate system.
Its fluctuations in irradiance are also known to have an impact on climate. In
addition, changes in solar activity modulate the atmospheric production rates
of cosmogenic radionuclides (e.g. 10Be, 14C, 36Cl)
that all eventually deposit to different environmental archives. The signal of
the changing solar activity through time can thus be retrieved and measured
from these archives, such as ice cores, tree rings, or lake sediments. The Sun can
also display a more chaotic behavior by erupting flashes of light, plasma and
magnetic fields whereby energetic particles can be accelerated, and sometimes
hit Earth. These all can damage our spacecraft technologies, harm astronauts,
and also affect transformer, electric, and electronic infrastructures on the
ground. In the case of extreme events, they may also pose a challenge to
air-travel safety. At the same time, when solar energetic particles enter the
atmosphere, they can enhance the production rate of cosmogenic radionuclides.



The objectives of this thesis are twofold. First, the
potential of using 10Be, 14C, and 36Cl as
tracers of extreme solar storms is explored in depth. Second, the common
production signal of 10Be and 14C caused by the longer term
changes in solar activity is used to synchronize climate records from different
environmental archives from different regions in order to assess the relative timing
of a prominent climate oscillation, over 11,000 years before present.



Two large signatures of cosmic-ray increase date to AD 774/5
and AD 993/4 are conclusively attributed to extreme solar energetic particle
events that have hit Earth and left a clear imprint on the production rates of 14C
as measured in tree rings all around the world, and of 10Be and 36Cl
in ice cores from Greenland and Antarctica. The inferred energy spectrum and flux
of particles of these events indicate that they were an order of magnitude
stronger than any solar high-energy event observed during the space era. To
infer the energy spectrum of ancient events, it is shown that the relative
differences in the energy dependency of the production rates of 10Be
and 36Cl by solar particles can be used. An additional, and
similarly extreme, solar storm is also suggested to have hit Earth 2,610 years BP.
The events from AD 774/5 and AD 993/4 are further explored to test, and
thereafter reject, the hypothesis that nitrate enhancements in ice cores can be
reliably linked to the occurrence of solar storms or to assess their magnitude.
Two high resolution and continuous records of ice-core 36Cl
concentration spanning the past several centuries are also presented. They show
several increases in 36Cl possibly linked to solar energetic
particle events including one that is coeval with the geomagnetic storm of
September 1909 CE. These records also show that there is no enhancement in 36Cl
production rate following the Carrington event of 1859 CE. A theoretical
experiment also proposes that it is possible that major solar storms with a
large flux of lower energy particles could lead to a significant increase in
ice-core 36Cl concentrations but not in 10Be. Finally, it
is shown that wiggles in cosmogenic radionuclides caused by longer-term changes
in solar activity can be used to synchronize lake sediment records from Europe
to Greenland ice cores. The investigation of both archives on the same
time-scale suggests that the climate oscillations observed in Greenland, and
subsequently in Western Europe could be attributed, in part, to solar forcing. 

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Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Ass. Professor Knudsen, Mats Faurschou, Aarhus University, Danmark
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Comogenic radionuclides, 10Be, 36Cl, Solar energetic particles, Solar storms, Paleoclimate, Time-scales, Solar activity
edition
Lundqua Theses
pages
121 pages
publisher
Lunds universitet
defense location
Sal Pangea, Geocentrum II, Sölvegatan 12, Lund
defense date
2019-01-18 13:15
ISBN
978-91-87847-44-8
978-91-87847-45-5
language
English
LU publication?
yes
id
b6cc5cfd-ae78-4990-9b38-b121bfaf99d5
date added to LUP
2018-12-14 17:15:28
date last changed
2018-12-17 16:45:38
@phdthesis{b6cc5cfd-ae78-4990-9b38-b121bfaf99d5,
  abstract     = {<p class="MsoNormal">The Sun is the primary source for Earth’s climate system.<br>
Its fluctuations in irradiance are also known to have an impact on climate. In<br>
addition, changes in solar activity modulate the atmospheric production rates<br>
of cosmogenic radionuclides (e.g. <sup>10</sup>Be, <sup>14</sup>C, <sup>36</sup>Cl)<br>
that all eventually deposit to different environmental archives. The signal of<br>
the changing solar activity through time can thus be retrieved and measured<br>
from these archives, such as ice cores, tree rings, or lake sediments. The Sun can<br>
also display a more chaotic behavior by erupting flashes of light, plasma and<br>
magnetic fields whereby energetic particles can be accelerated, and sometimes<br>
hit Earth. These all can damage our spacecraft technologies, harm astronauts,<br>
and also affect transformer, electric, and electronic infrastructures on the<br>
ground. In the case of extreme events, they may also pose a challenge to<br>
air-travel safety. At the same time, when solar energetic particles enter the<br>
atmosphere, they can enhance the production rate of cosmogenic radionuclides.</p><br>
<br>
<p class="MsoNormal">The objectives of this thesis are twofold. First, the<br>
potential of using <sup>10</sup>Be, <sup>14</sup>C, and <sup>36</sup>Cl as<br>
tracers of extreme solar storms is explored in depth. Second, the common<br>
production signal of <sup>10</sup>Be and <sup>14</sup>C caused by the longer term<br>
changes in solar activity is used to synchronize climate records from different<br>
environmental archives from different regions in order to assess the relative timing<br>
of a prominent climate oscillation, over 11,000 years before present. </p><br>
<br>
<p class="MsoNormal">Two large signatures of cosmic-ray increase date to AD 774/5<br>
and AD 993/4 are conclusively attributed to extreme solar energetic particle<br>
events that have hit Earth and left a clear imprint on the production rates of <sup>14</sup>C<br>
as measured in tree rings all around the world, and of <sup>10</sup>Be and <sup>36</sup>Cl<br>
in ice cores from Greenland and Antarctica. The inferred energy spectrum and flux<br>
of particles of these events indicate that they were an order of magnitude<br>
stronger than any solar high-energy event observed during the space era. To<br>
infer the energy spectrum of ancient events, it is shown that the relative<br>
differences in the energy dependency of the production rates of <sup>10</sup>Be<br>
and <sup>36</sup>Cl by solar particles can be used. An additional, and<br>
similarly extreme, solar storm is also suggested to have hit Earth 2,610 years BP.<br>
The events from AD 774/5 and AD 993/4 are further explored to test, and<br>
thereafter reject, the hypothesis that nitrate enhancements in ice cores can be<br>
reliably linked to the occurrence of solar storms or to assess their magnitude.<br>
Two high resolution and continuous records of ice-core <sup>36</sup>Cl<br>
concentration spanning the past several centuries are also presented. They show<br>
several increases in <sup>36</sup>Cl possibly linked to solar energetic<br>
particle events including one that is coeval with the geomagnetic storm of<br>
September 1909 CE. These records also show that there is no enhancement in <sup>36</sup>Cl<br>
production rate following the Carrington event of 1859 CE. A theoretical<br>
experiment also proposes that it is possible that major solar storms with a<br>
large flux of lower energy particles could lead to a significant increase in<br>
ice-core <sup>36</sup>Cl concentrations but not in <sup>10</sup>Be. Finally, it<br>
is shown that wiggles in cosmogenic radionuclides caused by longer-term changes<br>
in solar activity can be used to synchronize lake sediment records from Europe<br>
to Greenland ice cores. The investigation of both archives on the same<br>
time-scale suggests that the climate oscillations observed in Greenland, and<br>
subsequently in Western Europe could be attributed, in part, to solar forcing. </p>},
  author       = {Mekhaldi, Florian},
  isbn         = {978-91-87847-44-8},
  keyword      = {Comogenic radionuclides,10Be,36Cl,Solar energetic particles,Solar storms,Paleoclimate,Time-scales,Solar activity},
  language     = {eng},
  pages        = {121},
  publisher    = {Lunds universitet},
  school       = {Lund University},
  title        = {Cosmogenic radionuclides in environmental archives – A paleo-perspective on space climate and a synchronizing tool for climate records},
  year         = {2018},
}