An alliance to address the Red Sea's record of past global climate and earthquakes

点击翻译按钮获取中文摘要

Evaporation in the desert climate causes the Red Sea to lose the isotope O-16 preferentially over O-18 and as a result Red Sea waters tend to be enriched in O-18. This tendency is particularly enhanced at times when global sea-levels were lower because the connection of the Red Sea with the Indian Ocean is very small (at Bab el Mandeb Strait). The sediments formed of the shells of pelagic organisms record this oxygen isotope signal. Researchers have used this, with the help of oceanographic models, to work out how sea-level has fluctuated for the past 500 thousand years. Meanwhile, other information (seismic reflection images) has revealed that the sediments within the Red Sea were being moved around by currents in the Pliocene, a period extending back to 5.3 million years. This generally does not happen today, as the Red Sea deep waters are very slow moving.A new partnership with Prof. Kaminski will allow us to date the sediments in legacy cores collected in the 1970s by the Deep Sea Drilling Project and left unused since then. We will measure oxygen isotopes where shells have not been badly altered, work out if the shells record information on the varying currents and measure the sizes of finer particles originating from the continents, also a potential measure of current speeds. Oxygen isotopes will be used to help evaluate the variability of sea-level in the Pliocene and earlier Pleistocene. The work with Prof. Kaminiski will be essential for working out the timing of these changes, as well as the use of shells to determine currents.Changes of sea-level also affect the strength of the sediments on the bed of the Red Sea because more extreme salinity tends to lead to aragonite (a form of calcium carbonate) precipitating directly from the water. With Prof. Jonsson, we will exploit this tendency to date the layering in seismic reflection images due to be collected with a device that is towed deeply near the seabed (towing deeply allows the device to collect much sharper images than we would normally get by collecting them from the sea surface). This will allow us, for the first time, evaluate the extent to which giant faults underlying the bed of the Red Sea are presently active and/or when they last slipped. This is important, as many coastal cities lie close to major active faults that present a threat to their populations, another focus of Prof. Jonsson's work with satellite methods. If we could work out the frequency with which earthquakes occur, this could help with disaster planning. Demonstrating the method in the Red Sea could create interest in using it in some of these other locations and thus be of broader benefit.