![Strong and safe communities Strong and safe communities](/web/20061103054634im_/http://www.gsc.nrcan.gc.ca/esst_images/2002iscom_e.jpeg) Natural Resources Canada > Earth Sciences Sector > Priorities > Strong and safe communities > Geodynamics
Geodynamics Ice sheet modelling
Computer models of the advance and retreat of the
past great ice sheets can be built that incorporate the Earth's response
to the changing load. Postglacial rebound models integrate disparate observations
related to the last glaciation including geological observations of ice
sheet extent,thickness, and retreat history as well as uplift and tilting
of former ocean and lake shorelines. Modern geodetic observations of crustal
motion andsurface gravity change give new constraints which are just now
beginning to be included.
Because these models include a somewhat realistic Earth response, they
can be used to give numerical predictions of the crustal response in regions
where observations are lacking. For example, postglacial rebound models
have largely been constrained by relative sea level observations (from
Carbon14 dating of features related to former sea level, such as raised
beaches), which are only found at former ocean shorelines.However, a model
built on relative sea level observations can be used to predict the crustal
response in other regions. The predictions can then becompared to other
kinds of observations, such as GPS or absolute gravity.
These models can also give numerical estimates of quantities for which
there are few, if any, direct observations, such as the crustal stress
andstrain changes due to glacial loading and unloading. Estimates of these
stress and strain changes can help significantly with studies of earthquake
processes.
Although our efforts concentrate on reconstructing the North American
ice sheets, ice sheet models are necessarily global in scope. This is
because relative sea level observations remain key to these reconstructions.
They are sensitive to the total amount of water in the oceans, which in
turn depends on the net mass increase or decrease of all the ice sheets.
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