An approach for constraining mantle viscosities through assimilation of palaeo sea level data into a glacial isostatic adjustment model

[摘要] Glacial isostatic adjustment is largely governed by the rheologicalproperties of the Earth's mantle. Large mass redistributions in theocean–cryosphere system and the subsequent response of theviscoelastic Earth have led to dramatic sea level changes in thepast. This process is ongoing, and in order to understand and predictcurrent and future sea level changes, the knowledge of mantleproperties such as viscosity is essential. In this study, we present amethod to obtain estimates of mantle viscosities by the assimilation ofrelative sea level rates of change into a viscoelastic model of thelithosphere and mantle. We set up a particle filter with probabilisticresampling. In an identical twin experiment, we show that mantleviscosities can be recovered in a glacial isostatic adjustment modelof a simple three-layer Earth structure consisting of an elasticlithosphere and two mantle layers of different viscosity. Weinvestigate the ensemble behaviour on different parameters in the following three set-ups: (1) global observations data set since last glacial maximumwith different ensemble initialisations and observation uncertainties,(2) regional observations from Fennoscandia or Laurentide/Greenlandonly, and (3) limiting the observation period to 10 ka until thepresent. We show that the recovery is successful in all cases if thetarget parameter values are properly sampled by the initial ensembleprobability distribution. This even includes cases in which the targetviscosity values are located far in the tail of the initial ensembleprobability distribution. Experiments show that the method issuccessful if enough near-field observations are available. This makesit work best for a period after substantial deglaciation until the presentwhen the number of sea level indicators is relatively high.

[学科分类] 自动化工程