RBR loggers deployed in the Cretan Sea (Eastern Mediterranean Sea) to monitor climatic change impact on the marine environment

RBRconcerto³ CTD on top of rope

In February 2021, two deep-sea moorings were deployed in the west Cretan Sea strait (south Aegean Sea) between Crete and Antikythira. The moorings were equipped with two RBRconcerto3 deep-sea loggers, including pressure, temperature, conductivity, and RBRcoda T.ODO dissolved oxygen sensors. The RBR loggers were deployed both at the strait bottom (~900 m) and at intermediate depth (300 m), paired with current meters and sediment traps. The expedition was carried out by R/V AEGAEO of the Hellenic Centre for Marine Research – Greece (HCMR), with the collaboration of the National Observatory of Athens – Greece (NOA) in a joint action aiming at creating long time series of data related to the phenomenon of climate change and its impact on the marine ecosystem.

An integrated, multidisciplinary approach between the complicated physical, biochemical and ecological processes in the ecosystem are indispensable for assessing oceanic processes. The continuous monitoring of the marine environment by permanent marine observatories at key-points of the ocean constitutes crucial tools that will enable a better understanding of this highly complex ecosystem’s functioning by providing scientific knowledge essential for both sustainable development and mitigation of environmental pressures. Understanding and assessing climate change is not possible without the creation of long time series. Such time series are rather rare in the eastern Mediterranean Sea, one of the most climate-sensitive regions in the world. In every enclosed sea basin surrounded by densely populated coastal areas with strong economic activity such as the Mediterranean Sea, knowledge about the marine ecosystem functioning and the climatic change effects is directly linked to societal needs and the economy. This increasing demand for long-term oceanic observations has been widely acknowledged by the international community in both political, societal and scientific level.

Over the past few decades, the study of time series at key areas of the eastern Mediterranean Sea has revealed increasing water mass temperature and salinity trends at much faster rates than those observed in other parts of the world ocean. The Aegean Sea is one of the most important eastern Mediterranean sub-basins. During the early ‘90s the Aegean Sea has produced large amounts of very dense waters that have altered the whole deep thermohaline circulation of the eastern Mediterranean in an abrupt event known as the Eastern Mediterranean Transient. The best way to study the response of the Aegean Sea to climate change and to detect any variability in water mass properties and flows between the Aegean Sea and the eastern Mediterranean Sea is no other than the creation of long time series of marine data at specific choke points. These are the straits connecting the Cretan Sea (south Aegean Sea) to the open eastern Mediterranean basin since any water mass exchange between the two basins takes place through these straits. The deployment of the above mentioned instrument moorings at the west Cretan Straits aims precisely at monitoring the interannual variability of the hydrological properties of the exchanged water masses along with the quantification of biochemical fluxes. The latter will be pursued by the creation of time series of particulate matter flux that characterizes the carbon cycle response, which is found at the epicenter of the global biogeochemical cycles and climate change studies.

The project is supported by the Action entitled “National Νetwork on Climate Change and its Impacts – CLIMPACT”, funded by the Public Investment Program of Greece, General Secretary of Research and Innovation – Ministry of Development and Investments.