The rise in water levels in the world's oceans amid a changing climate is not a new phenomenon. A UN expert group is studying that issue and notes that the water rises by an average of 1.4 millimeters per year. Over the past 20 years, this figure has doubled. From 2005 to 2015, the water level rose by 3.6 millimeters per year. But is the rise in water levels around the world sustainable?
Katie McInnes, who is a Senior Fellow at the Commonwealth Scientific and Industrial Research Organization in Australia, says there are areas on the planet where water levels are decreasing.
There is no place on the planet that can somehow be protected from sea level changes. These changes depend on the climate, the rise in air temperature, and the melting of the planet's ice sheets. In Antarctica, warming oceans are the biggest contributor to the destruction of ice sheets. As they melt, the water level increases significantly.
The resulting water, which is conventionally called excess water, does not spread evenly throughout the world. There are two main factors: thermal expansion and gravitational pull of ice sheets. In the first case, ocean currents distribute heat by moving cold and warm water.
If there is less heat in one zone, and more in the other, then the winds in the atmosphere can lower and raise the oceans. As the planet warms, they can also change. Melting the ice sheets not only add water to the oceans, but also exert a gravitational pull on the sea around them, which makes sea levels higher in some places.
Thus, the sea level drops in places that are close to melting ice sheets. Processes such as pumping out groundwater, extracting fossil fuels and compaction of sediments also contribute to sea level rise. In some cities built in deltas, such as Tokyo and New Orleans, land is sinking and sea levels are rising.
The scientists believe that some of these deltas are actually sinking much faster than sea levels rise. It is a double whammy where the ground sinks and the sea level rises at the same time.