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Construction of late Pleistocene ice history model that is consistent with Composite Rheology and 3D material property variations

u3003328 - Posted on 12 November 2015

Project Description: 

In our research, the response of the solid earth and its oceans to the glaciation and deglaciation events since the last Ice Age is modeled numerically. This response of the Earth is called the Glacial Isostatic Adjustment (or GIA) process and numerical modeling of such process is very important both practically and academically (see ‘significance’ below). Previous models of the GIA process assume that the flow law or relation between stress and strain in the mantle is linear and that material properties of the earth only vary in the radial direction. However, creep experiments on mantle rocks shows that the flow law in the mantle is likely to be nonlinear. Also, seismic tomography shows that earth material properties vary strongly in the lateral direction. What is special in our model is that material properties are allowed to vary both in the radial and lateral directions as described by seismic tomography. Also a combination of both linear and nonlinear creep is implemented in our model (i.e. Composite Rheology). The ABAQUS finite element software package is used in this study. Our finite element model has spatial resolution at the surface of 1x1 degree grid covering the whole mantle with more than 20 layers. This result in a finite element model of at least 1.3 million finite elements. Thus such computation requires high performance computer with at least 6.4 GB of RAM to run and 200 GB of storage for the results of each job.

Researcher name: 
Prof. Patrick Wu
Researcher position: 
Professor
Researcher department: 
Department of Earth Sciences
Researcher email: 
ppwu@hku.hk
Research Project Details
Project Duration: 
09/2014 to 08/2018
Project Significance: 
The objectives of this work is to construct thickness history models of the huge ice sheets with the correct mantle flow law that can explain all the geologic and geodetic observations of GIA (e.g. global sealevel data, 3D crustal motion as observed by GPS, gravity changes, earth rotation & satellite measurements, postglacial faults & intraplate seismicity data) simultaneously. The results of this study has important applications: the ice sheet history model constructed can be used for climate simulation and leads to better understanding of climate change in the past, present and future. It also allows us to better understand the source of global sea level change and monitor global warming. Understanding of GIA induced sea level change is important to coastal engineering and impact the large human population that lives near the coast. It also affects the adoption of a dynamic geodetic height reference system, which is required in positioning and in engineering construction projects. Study of GIA also leads to better knowledge of the viscosity or flow law of the earth. Knowledge of the viscosity is crucial in understanding plate tectonics and how the structure of our planet has evolved in the past, present and future.