The calculation of variations in the sea level is relatively simple. It is by far more complicated to then determine the change in the water mass. A team of geodesists and oceanographers from the University of Bonn, as well as from the GFZ German Research Centre for Geosciences and the Alfred-Wegener Institute for Polar and Marine Sciences, two centres of the Helmholtz Association, have now, for the first time succeeded in doing this.
The researchers were able to observe short-term fluctuations in the spatial distribution of the ocean water masses. Their results are, amongst others, important for improved climate models.
In order to determine the ocean volume in a certain region, one only needs to know, in addition to the topography of the seabed, the height of the sea level. For this purpose, researchers have long been resorting to gauging stations and satellite altimetric procedures. The ocean mass depends, however, not only on the volume, but also on the temperature and on the salt content. Water expands when heated. Warm water, thus, weighs less than the same quantity of cold water.
For the calculation of the ocean mass it is, therefore, necessary to know the temperature and salt content profiles. However, this is not easy to quantify. "For our study we, therefore, combined different procedures so as to be able to judge changes in mass", explains Professor Dr. Juergen Kusche. The geodesist from Bonn is co-author of a scientific paper, which has just been published in the Journal of Geophysical Research.
On the one hand the researchers used data from the German-American satellite mission GRACE where the distance between two satellites (popularly known as Tom and Jerry as one chases the other in the same orbit ) are measured exactly to thousandths of millimetres. The larger the ocean mass at a certain point of the Earth, the stronger the gravitational strength. This influences the flight altitude of the satellites and thus the distance from each other. The gravitation and, hence, the mass distribution can be calculated from the change in distance between the two satellites.
The seabed bends under the weight of the water
In addition, the scientists put to use an effect which frequent book readers will have perceived. The ocean floor bends similarly to that of the shelves of an overfilled bookshelf. Thus, stationary GPS-gauging stations on land drop by up to one centimetre and move closer by a few millimetres. The heavier the water, the stronger is this movement.
"We combined these data with numerical models of the ocean" explains Kusche. "In this way we were able to prove, for the first time, that in particular in the higher latitudes, significant fluctuations of the water mass occur, and that this takes place within a time period of only one to two weeks".
So far one only knew that the mass of the world-wide ocean water varies seasonally by on average approximately three quadrillion kilogrammes (a quadrillion equals to 1 followed by 15 zeroes) - that implies a sea level variation of approx. seven to eight millimetres. This effect is brought about, among others, by variations in precipitation and evaporation as well as by the storage of water as snow. But, also, the melting of the glaciers and the ice masses in Greenland and in the Antarctic play a role.
By comparing the variation in volume and in mass the researchers want to determine changes in the amount of heat stored in the ocean. Therefore, in the near future, the long term changes are to be examined. The results will contribute to improved climatic models.
An urgent wish of the scientists is the realisation of a punctual follow-up mission for the satellite tandem GRACE. Otherwise the valuable information, particular in the registration of trends in the Earth system, obtained through GRACE, cannot be used to its full potential for Earth System and climate research.
The work is financed by the German Research Council (DFG) within the priority programme "Mass transport and mass distributions in the System Earth. The programme is coordinated at the Institute for Geodesy and Geoinformation at the University of BonnContact:
F. Ossing | EurekAlert!
As sea level rises, much of Honolulu and Waikiki vulnerable to groundwater inundation
29.03.2017 | University of Hawaii at Manoa
Researchers discover dust plays prominent role in nutrients of mountain forest ecoystems
29.03.2017 | University of Wyoming
The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.
To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
29.03.2017 | Materials Sciences
29.03.2017 | Physics and Astronomy
29.03.2017 | Earth Sciences