final_program_abstracts[1]

11 IMSC Session Program
Assimilation of low-resolution paleo-proxies for spatial
reconstruction of North American summertime climatology
Tuesday - Poster Session 10
Alicia R. Karspeck, Caspar Ammann and Doug Nychka
National Center for Atmospheric Research, USA
Unlike high-resolution paleo-proxies that might provide information about the
annually resolved climate, low-resolution proxies, such as pollen assemblages,
provide information on decadal-scale climate variability. Ideally, reconstructions
would use both high- and low-resolution proxies to create reconstructions with
corresponding multi-scale uncertainty estimates.
Toward this goal, we focus here on the question of how best to assimilate pollen ratios
representative of 30-yr average summertime temperatures into a spatial reconstruction
of North American surface temperatures. Using an 1150 yr integration of the NCAR
Community Climate System Model (CCSM), we form a prior distribution of the
seasonal climatology (a variable that is not typically a probabilistic quantity).
Although point-proxies of 30 yr means can tell us very little about the instantaneous
annual state, we explore here what they may be able to provide in terms of
adjustments to the temporally evolving seasonal climatology.
Second, we form a statistical autocorrelation model that will allow us to predict how
innovations at discrete time points impact temporally distant state variables. A
realistic network of proxy locations is used to condition the posterior distribution. We
operate within a standard Bayesian framework in which we are able to generate both
the expected value and uncertainties associated with the reconstruction.
Abstracts 116