Earth's sinking cities: Study reveals areas subsiding toward sea level

"Subsidence more than doubles the rate of sea level rise for some areas of the coastline. To make matters worse, researchers say that this affects the largest and most densely populated cities more than anywhere else. Between rising seas and sinking land, heavily urbanised areas of coast experience a relative sea level increase of about six millimetres per year on average. That is three times more than the global average for relative sea level rise, which stands at 2.1 millimetres per year."

"Likewise, land subsidence roughly doubles the absolute sea-level rise of 3.15 millimetres per year, which measures the actual increase in volume and height of the ocean. Lead researcher Dr Julius Oelsmann, of Technical University of Munich, says that this can 'significantly amplify the effects of climate-driven sea-level rise'. As the climate gets hotter, melting glaciers and the expansion of warming water are gradually raising the level of the world's oceans."

"However, Dr Oelsmann and his co-authors warn that the surface of the sea only tells half the story. 'If we want to understand sea-level rise along coastlines and respond effectively, we must not only observe the ocean but also the land itself,' Dr Oelsmann says. This is because a mixture of human activity and natural forces is combining to sink some of the world's biggest cities into the ocean."

"The biggest factors driving this subsidence are excessive groundwater and oil extraction, which remove underground resources that previously stabilised the surface. Dr Oelsmann points out that the 'sheer weight of cities' is also driving urban areas below sea level. As cities grow larger and taller, heavier buildings are"

Rising sea levels are increasing flooding risk, and land subsidence makes the danger greater in many coastal areas. Subsidence more than doubles the rate of sea level rise for some parts of the coastline. Relative sea level rise in heavily urbanised coastal areas averages about six millimetres per year, roughly three times the global average of 2.1 millimetres per year. Land subsidence roughly doubles absolute sea-level rise, measured as the actual increase in ocean height and volume, to about 3.15 millimetres per year. The combined effects of climate-driven ocean rise and sinking land significantly amplify flooding impacts, especially in the largest and most densely populated cities. Subsidence is driven by excessive groundwater and oil extraction and by the weight of expanding urban development.

Read at Mail Online