Climate research – continents lose water to the sea

The freshwater supplies in rivers, lakes and groundwater decrease worldwide. That is the result of an extensive Studywhich scientists from South Korea, China, Hong Kong, Australia and the USA recently presented in the journal “Science”. Accordingly, the water stored on land has declined by 2600 billion tons between 2000 and 2016. This corresponds to a water cube with an edge length of less than 14 kilometers or more than 50 times the content of Lake Constance. Particularly noteworthy: a little more than two thirds of the decline took place in the years 2000 to 2002, so very leap.

Determining this was not easy. While the water level in the seas can be determined comparatively easily from information about the topography of the pools and the height of the sea level and the water vapor content of the atmosphere results from the weather observations, the various freshwater reservoirs are much more confusing. However, modern weather forecast models are also a good help for this, as the new study shows. In addition to the precipitation, you can also simulate the drain in the rivers and the water balance of the soils as well as evaporation and transpiration through plants. Using older weather data, the water balance of the continents can also be subsequently determined in the past decades.

The procedure is called reanalysis, which could be called a complex extrapolation process. The measurement data are converted to a more or less close three -dimensional grid, which describes the condition of the atmosphere and the surface of the earth at a given time. Such data records generated are used wherever you need statements about longer periods, for example if information is required via the global water balance.

More than two thirds of the decline took place from 2000 to 2002.

The authors of the present study have therefore consulted such a reanalysis data set by the European Center for medium-term weather forecast (ECMWF). The ECMWF has been running extensive weather forecast and accompanying research on behalf of its 23 Member States from West, South and Southeast Europe on behalf of its 23 Member States from West, South and Southeast Europe.

The continental water balance, which results from this data, shows on the one hand the strong decrease in 2000 to 2002 – and further water loss in the following years until 2021. The Congo basin, the southwest of Brazil as well as adjacent regions in Paraguay and Argentina, parts of the USA, a strip from the Balkans to western Central Asia and a large region in northeastern China as well as the neighboring areas of Russia are particularly affected.

Different data records of a completely different kind confirm these observations regardless of the results of the weather models. The authors also used the data about the increase in sea level and deducted the well -known components from them, such as the loss of ice on Greenland and in Antarctic or the expansion of sea water due to warming. The result was that the sea level actually increased to the extent that the continental balance derived from the ECMWF data was expected.

The data of the pole movement, which the authors were also used and presented to them until 2016, confirm and confirm the dimensions and distribution of water loss on the continents. The redistribution of masses also leads to slight changes in the location of the rotation axis of our planet, especially if this is unevenly. Between 2005 and 2014, the axis has shifted by about 45 centimeters in the direction of the 90th Eastern Meridian, which is particularly pronounced at the time in parts of Eurasia, which runs through West Siberia.

However, such shifts are not necessarily unusual. Greater worries should worry that the freshwater loss on the continents appears to be a consequence of the climate changes and continues.