Tree-ring widths represent the most commonly used proxy to reconstruct the
climate of the last millennium at high resolution, thanks to their large-scale
availability. The approach often relies on a relationship between tree-ring width
series and climate estimated on the basis of a linear regression. The underlying
linearity and stationarity assumptions may be inadequate. Dendroclimatic
process-based models may be able to overcome some of the limitations of the
statistical approach. In this thesis, we have included for the first time a
dendroclimatic process-based model, MAIDEN, into a data assimilation procedure
in order to improve large-scale climate reconstructions. We have first developed
a protocol to calibrate and apply MAIDEN to potentially any sites with tree-ring
width data in the extratropical region. We have shown that MAIDEN can be
applied at global scale with a good performance and that clear benefits
associated with its level of complexity make it an appealing candidate for
paleoclimate reconstructions. Subsequently, the MAIDEN model has been
successfully incorporated into a data assimilation procedure as a proxysystem
modelto robustly compare the outputs of an Earth system model with tree-ring
width observations. The procedure has been tested to reconstruct the climate
variability in the Southern Hemisphere over the last four centuries with
encouraging results. Even though additional analysis are needed to fully take
advantage of the new development, important steps have been made to
demonstrate that using MAIDEN as a proxysystemmodelis a promising way to
improve the large-scale climate reconstructions with data assimilation.

The public defense will take place in the form of a video conference

Meeting ID: 832 7968 0125
Passcode: 117239