14 DAY TRIAL // A collaboration of German researchers has recently taken on one of the most difficult sets of measurements possible in nature, namely to determine the mass of an ocean. Unlike calculating variations in sea levels, which is relatively simple, finding out the mass of the water is far more complex, as a large number of factors contribute to changes in this number. Additionally, the oceans are not static, as in ideal models, so the number varies considerably over short time frames.
Regardless of these obstacles, scientists at the Helmholtz Association's GFZ German Research Center for Geosciences and the Alfred-Wegener Institute for Polar and Marine Sciences, working together with colleagues from the University of Bonn, set out to uncover the ocean's mass. Their calculations were so precise, in a true German fashion, that they observed even short-term fluctuations in the spatial distribution of water masses inside the body of water.
“For our study we, therefore, combined different procedures so as to be able to judge changes in mass,” Professor Dr. Juergen Kusche explains. The scientist is a geodesist at the University of Bonn, and also a coauthor of a new scientific paper detailing the findings, which appears in the latest issue of the respected Journal of Geophysical Research. The two main elements that a scientist needs to know in order to calculate the mass of the ocean are the topography of its bottom and also the height of the sea level. There are, however, other elements at work as well.
For example, the salinity level of the water is another factor that influences mass measurements, as is the temperature of the water. Among physicists and chemists, it's a widely known fact that a volume of hot water weighs less than the same volume of cold water. For the conclusions, data from the German-American satellite mission GRACE and knowledge on the “bookshelf effect” were used. “We combined these data with numerical models of the ocean. 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,” Kusche says.