Dendroclimatology using stable isotopes from subfossil tree-rings

• Main Author: Pauly, M.
• Format: Doctoral or Postdoctoral Thesis
• Language: unknown
• Published: Freie Universität 2022
• Subjects: Greenland; New Zealand; Greenland ice core; ice core; NGRIP; North Atlantic
• Online Access: https://gfzpublic.gfz-potsdam.de/pubman/item/item_5011160

The overall goal of this PhD dissertation is to develop multi-centennial stable isotope chronologies in annual rings of subfossil pine trees (Pinus sylvestris) from sites in (1) Switzerland (Binz) and (2) the southern French Alps (barbers), as well as (3) decadal records from subfossil New Zealand kauri trees (Agathis australis). After establishing these three chronologies, this dissertation explored the following objectives: (1) detect any potential climatic signal contained within the developed δ18O and δ13C records,(2) identify any probable diagenetic biases impacting the inter- and intra- tree stable isotope correlations (e.g. wood decay), (3) develop a technique to estimate sourcewater δ18O (precipitation) from dual stable isotope models, and (4) reconstruct high frequency climate variability across the Late Glacial. The oldest chronology was developed from 27 Swiss subfossil pine trees, covering ~14,050 – 12,795 cal BP; described in the Chapter 6 paper. The tree-ring δ18O record was compared to ice core del18O (NGRIP) to investigate whether Greenland Stadial “events”, which are often discernible in European lake records, are also recorded in the Swiss plateau during the summer growing season. Two examples of δ18Otree extreme depletions did parallel known North Atlantic ‘cool periods’ (GI-1c, GS-1), while another LG oscillation (GI-1b) is not clearly expressed in δ18Otree. The trees tended to record events more cohesively (higher population signal) during extreme δ18Otreedepletions in relatively wet conditions (high precipitation amount); likely due to the lack of stomata in influence on stable isotope fractionation in high humidity. Generally, this record was able to capture North Atlantic climate oscillations, but to a lesser degree than Greenland ice core δ18O, suggesting the “events” may be less extreme in the summer season. The GS-1 (Younger Dryas) cold reversal recorded in the Swiss pine trees was also documented in 7 pine trees from the southern French alps, as described in the Chapter 7 paper. A ...