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Table of contents
CHAPTER I. INTRODUCTION
I.1. General context
I.2. The global carbon cycle
I.2.1. Coupling between C-cycle – climate: greenhouse effect
I.2.2. Description of global C-cycle
I.3. CO2 evolution in different past time scales
I.3.1. Beyond ice cores
I.3.2. Ice core studies
I.4. Stable carbon isotopes – a climatic tool
I.4.1. Introduction on the notion of isotopes
I.4.2. δ notion – application on C – δ13C definition
I.4.3. Isotopic fractionation
I.4.4. Previous studies using carbon isotopes to constrain the global C cycle
I.5. CO2 and δ13CO2: combined reconstruction from ice cores
I.5.1. Significance in measuring δ13CO2 in ice cores
I.5.2. State of the art
I.6. Scope of this study
CHAPTER II. THE ICE CORE ARCHIVE
II.1. Introduction
II.1.1. Interest in studying polar ice cores
II.1.2. Ice cores of interest during this PhD
II.2. Gas trapping in the ice
II.2.1. Densification process
II.2.2. Gas transport within the firn column
II.3. Physical processes affecting gases occluded in ice
II.3.1. Gravitational separation of gases and isotopes
II.3.2. Thermal diffusion
II.3.3. Diffusion along a concentration gradient
II.3.4. Bubble close-off processes
II.3.5. Clathrate formation and decomposition
II.4. Chemical processes affecting gas composition in ice
II.4.1. Greenland observations
II.4.2. In situ reactions of organic compounds (mainly oxidations)
II.4.3. In situ reactions of inorganic carbonate, CaCO3, followed by reactions under acidic environment
II.5. Extension of physical processes on gas age calculation challenge
II.6. Conclusions
CHAPTER III. METHODS AND INSTRUMENTATION
III.1. Introduction
III.1.1. Analytical challenges related to quantified isotopic measurements
III.2. Overview of gas extraction methods on ice samples
III.2.1. Wet extraction or melt-refreezing method
III.2.2. Dry extraction method
III.2.3. Extraction by sublimation
III.2.4. Intercomparison of the analytical system between 3 European laboratories (EPICA Consortium)
III.3. General concept and layout of the experimental procedure
III.3.1. Overall
III.3.2. sample preparation
III.3.3. air extraction
III.3.4. gas transfer
III.3.5. analysis of (i) CO2; (ii) its stable isotopes
III.4. Description of the analytical procedure
III.4.1. preparative steps before analysis
III.4.2. Strictly time-dependent procedure
III.4.3. Protocol changes through time (2006 vs. 2007-8)
III.5. Corrections applied
III.5.1. Corrections by the IRMS software
III.5.2. Other corrections
III.6. Procedure validation with blank tests and reference gas standards
III.6.1. Laboratory calendar
III.6.2. Results from standard gases
III.6.3. Results from blank measurements
III.7. Analytical observations on ice core measurements
III.7.1. CO2 and isotopic ratio trends with expansion
III.7.2. Reproducibility on numerous replicates of Vostok ice core
III.7.3. Extraction efficiency – bubble against clathrate ice
III.8. Conclusion
CHAPTER IV. TERMINATION I
IV.1. Introduction
IV.2. State of the art
IV.2.1. Reasons for studying this transition in EDC core
IV.2.2. Rapid climate changes presentation
IV.2.3. Paleoceanographic proxies used to interpret the data
IV.3. CO2 and δ13CO2 results over TI from the EDC core
IV.3.1. Laboratory brief calendar
IV.3.2. Main draft
IV.3.3. Supplementary material
IV.4. Discussion – On the causes of CO2 deglacial evolution
IV.4.1. Sea Surface Temperature
IV.4.2. Sea level
IV.4.3. Sea ice extent
IV.4.4. Ocean circulation
IV.4.5. Wind speed
IV.4.6. Coral reef hypothesis
IV.4.7. Carbonate compensation
IV.4.8. Rain ratio change
IV.4.9. Fe fertilization hypothesis
IV.4.10. Role of terrestrial biosphere
IV.4.11. Synopsis
IV.5. Additional “young” points to our dataset
IV.6. Synchronization issues
IV.7. Comparison with unpublished δ13CO2 data
IV.7.1. UBern
IV.7.2. AWI
IV.8. Conclusion
CHAPTER V. TERMINATION II
V.1. Introduction
V.2. State of the art
V.2.1. Why studying TII period on EDC ice core
V.2.2. Main abrupt climatic changes during TII
V.2.3. Absence of proxies from N.H. ice cores
V.3. Results
V.3.1. Laboratory brief calendar
V.3.2. Data processing
V.3.3. CO2 and δ13CO2 time evolution
V.4. Comparisons with other TII data in ice
V.4.1. Deuterium
V.4.2. Vostok CO2
V.4.3. CH4
V.4.4. Deuterium excess
V.4.5. nss-Ca+2 and Fe fluxes in EDC core
V.4.6. ss-Na+ flux in EDC core
V.4.7. paleo-oceanographic data over TII
V.5. Comparison between TI and TII
V.5.1. Amplitude of variations
V.5.2. δ13C depletion
V.5.3. Phase differences
V.5.4. Existence of a seesaw pattern
V.6. Sequence of events during TII
V.7. Clathrated ice and TII results
V.8. Conclusion
CHAPTER VI. CONCLUSIONS
VI.1. Technical conclusions
VI.2. Summary of the new key dataset
VI.3. Conclusions on the carbon cycle / climate interactions
VI.4. Perspectives
REFERENCES
APPENDICES
