Post-glacial rebound

However, through the processes of ocean siphoning and continental levering, the effects of post-glacial rebound on sea level are felt globally far from the locations of current and former ice sheets.

The enormous weight of this ice caused the surface of the Earth's crust to deform and warp downward, forcing the viscoelastic mantle material to flow away from the loaded region.

At the end of each glacial period when the glaciers retreated, the removal of this weight led to slow (and still ongoing) uplift or rebound of the land and the return flow of mantle material back under the deglaciated area.

The total uplift from the end of deglaciation depends on the local ice load and could be several hundred metres near the centre of rebound.

Unfortunately, that term gives the wrong impression that isostatic equilibrium is somehow reached, so by appending "adjustment" at the end, the motion of restoration is emphasized.

It also gives insight into past ice sheet history, which is important to glaciology, paleoclimate, and changes in global sea level.

Erratic boulders, U-shaped valleys, drumlins, eskers, kettle lakes, bedrock striations are among the common signatures of the Ice Age.

Other pronounced effects can be seen on the island of Öland, Sweden, which has little topographic relief due to the presence of the very level Stora Alvaret.

The rising land has caused the Iron Age settlement area to recede from the Baltic Sea, making the present day villages on the west coast set back unexpectedly far from the shore.

[11] The Kvarken is a UNESCO World Natural Heritage Site, selected as a "type area" illustrating the effects of post-glacial rebound and the holocene glacial retreat.

For example, Oulunsalo "island of Oulujoki"[12] is a peninsula, with inland names such as Koivukari "Birch Rock", Santaniemi "Sandy Cape", and Salmioja "the brook of the Sound".

The "relative sea level data", which consists of height and age measurements of the ancient beaches around the world, tells us that glacial isostatic adjustment proceeded at a higher rate near the end of deglaciation than today.

[7] The fall in sea level also affects the circulation of ocean currents and thus has important impact on climate during the glacial maximum.

[20] Today, more than 6000 years after the last deglaciation terminated, the flow of mantle material back to the glaciated area causes the overall shape of the Earth to become less oblate.

[21] The changing gravity field can be detected by repeated land measurements with absolute gravimeters and recently by the GRACE satellite mission.

[23] The vertical datum is a reference surface for altitude measurement and plays vital roles in many human activities, including land surveying and construction of buildings and bridges.

Since postglacial rebound continuously deforms the crustal surface and the gravitational field, the vertical datum needs to be redefined repeatedly through time.

However, large earthquakes are found in intraplate environments like eastern Canada (up to M7) and northern Europe (up to M5) which are far away from present-day plate boundaries.

Thus, both postglacial rebound and past tectonics play important roles in today's intraplate earthquakes in eastern Canada and southeast US.

[9] The situation in northern Europe today is complicated by the current tectonic activities nearby and by coastal loading and weakening.

Increasing pressure due to the weight of the ice during glaciation may have suppressed melt generation and volcanic activities below Iceland and Greenland.

[27] Therefore, monitoring sea level rise and the mass balance of ice sheets and glaciers allows people to understand more about global warming.

Unusually rapid (up to 4.1 cm/year) present glacial isostatic rebound due to recent ice mass losses in the Amundsen Sea embayment region of Antarctica coupled with low regional mantle viscosity is predicted to provide a modest stabilizing influence on marine ice sheet instability in West Antarctica, but likely not to a sufficient degree to arrest it.

[31] The speed and amount of postglacial rebound is determined by two factors: the viscosity or rheology (i.e., the flow) of the mantle, and the ice loading and unloading histories on the surface of Earth.

Modelling of glacial isostatic adjustment addresses the question of how viscosity changes in the radial[7][32][33] and lateral directions[34] and whether the flow law is linear, nonlinear,[35] or composite rheology.

Finally, the heights of ancient beaches in the sea level data and observed land uplift rates (e.g. from GPS or VLBI) can be used to constrain local ice thickness.

[39] Glacial isostatic adjustment also plays an important role in understanding recent global warming and climate change.

The basic idea of the SLE dates back to 1888, when Woodward published his pioneering work on the form and position of mean sea level,[45] and only later has been refined by Platzman [46] and Farrell [47] in the context of the study of the ocean tides.

In the words of Wu and Peltier,[48] the solution of the SLE yields the space– and time–dependent change of ocean bathymetry which is required to keep the gravitational potential of the sea surface constant for a specific deglaciation chronology and viscoelastic earth model.

denote spatio-temporal convolutions over the ice- and ocean-covered regions, and the overbar indicates an average over the surface of the oceans that ensures mass conservation.