Is it possible to create new land?

Answer

The influence of global warming on sea level rise as suggested by the simulations and predictions of, among others, IPCC (Intergovernmental Panel on Climate Change) should be somewhat nuanced. It is not correct to simply convert the amount of ice melting into centimeters or decimeters of sea level rise and predict its impact on a particular coastal area based on this global rise.

It is also not correct to predict that low coastal areas will completely flood. The modelers only take into account the amount of ice that can melt and the expansion of the water due to higher temperature. However, there are more parameters that need to be taken into account in order to predict where and how much the sea level will rise. Although the oceans are all connected, the sea surface is not at the same level everywhere. One of the main factors causing this is the viscosity of the Earth’s mantle beneath the Earth’s crust. During the formation of land ice, the weight of the ice mass pushes the Earth’s crust down. When an ice sheet melts, the weight of the ice at this location decreases and so does the pressure on the Earth’s crust. This will cause this area to rise. On the other hand, areas outside the edge of the ice sheet will collapse as the mantle material flows slowly to the areas that have risen. Also the areas far away from ice sheets are subject to this bottom movement as a result of the ice melting because the weight of the melt water will put pressure on the ocean floor. As a result, the capacity of the ocean increases and the rise in sea level will not be equal to the amount of meltwater that has been added. The extra water that is added is not evenly distributed over the globe, but depends on where the melt water comes from. The coasts at the equator will experience a relative sea level drop with the melting of an ice sheet because the water there will flow to the areas beyond the edge of the ice sheet that are subject to subsidence. Also, the extra weight of meltwater on the continental shelf will cause an upward movement of the coast. The distribution of the melt water is much more important than the volume that is added.

Creating new land: huge amounts of sand are needed for this and they are certainly not available everywhere. The problem with artificially constructed areas is that very good prior knowledge is needed to find out how the natural processes (tides, currents, waves) will react to them. The question is therefore whether this does not simply correspond to shifting the problem.

Cecile Baeteman

Belgian Geological Survey

Royal Belgian Institute of Natural Sciences