*"Rising and falling sea levels over relatively short periods do not indicate long-term trends. An assessment of hundreds and thousands of years shows that what seems an irregular phenomenon today is in fact nothing new," explains Dr. Dorit Sivan, who supervised the research.*
The sea level in Israel has been rising and falling over the past 2,500 years, with a one-meter difference between the highest and lowest levels, most of the time below the present-day level. This has been shown in a new study supervised by Dr. Dorit Sivan, Head of the Department of Maritime Civilizations at the University of Haifa. "Rises and falls in sea level over relatively short periods do not testify to a long-term trend. It is early yet to conclude from the short-term increases in sea level that this is a set course that will not take a change in direction," explains Dr. Sivan.
The rising sea level is one of the phenomena that have most influence on humankind: the rising sea not only floods the littoral regions but also causes underground water salinisation, flooded effluents, accelerated coastal destruction, and other damage.
According to Dr. Sivan, the changing sea level can be attributed to three main causes: the global cause – the volume of water in the ocean, which mirrors the mass of ice sheets and is related to global warming or cooling; the regional cause – vertical movement of the earth's surface, which is usually related to the pressure placed on the surface by the ice; and the local cause – vertical tectonic activity. Seeing as Israel is not close to former ice caps and the tectonic activity along the Mediterranean coast is negligible over these periods, it can be concluded that drastic changes in Israel's sea levels are mainly related to changes in the volume of water.
In the present study, in light of earlier studies, research student Ayelet Toker and Dr. Sivan, set out to examine Israel's sea level over the past 2,500 years, based on data deduced from many coastal archaeological findings. They made a careful selection of findings that have been reliably and accurately dated, and first focused on findings that were excavated by the Antiquities Authority in Acre of the Crusader period. These revealed that the sea level during the Crusader period – just 800 years ago – was some 50-90 centimeters lower than the present sea level. Findings from the same period at Caesarea and Atlit reinforced this conclusion. When additional sites were examined from periods before and after the Crusader period, it was revealed that there have been significant fluctuations in sea level: During the Hellenistic period, the sea level was about 1.6 meters lower than its present level; during the Roman era the level was almost similar to today's; the level began to drop again during the ancient Muslim period, and continued dropping to reach the same level as it was during the Crusader period; but within about 500 years it rose again, and reached some 25 centimeters lower than today's level at the beginning of the 18th century.
"Over the past century, we have witnessed the sea level in Israel fluctuating with almost 19 centimeters between the highest and lowest levels. Over the past 50 years Israel's mean sea level rise is 5.5 centimeters, but there have also been periods when it rose by 10 centimeters over 10 years. That said, even acute ups and downs over short periods do not testify to long-term trends. An observation of the sea levels over hundreds and thousands of years shows that what seems a phenomenon today is as a matter of fact "nothing new under the sun", Dr. Sivan concludes.
Amir Gilat | University of Haifa
Water - as the underlying driver of the Earth’s carbon cycle
17.01.2017 | Max-Planck-Institut für Biogeochemie
Modeling magma to find copper
13.01.2017 | Université de Genève
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
18.01.2017 | Power and Electrical Engineering
18.01.2017 | Materials Sciences
18.01.2017 | Life Sciences