Investigation of long-term, basin-scale thermohaline trends in Qatar's marine region in response to environmental and climatic change

The Arabian Gulf, an economically and geopolitically important marine area, is a semi-enclosed and shallow basin with an average depth 36 m. The Gulf is one of the seasonally warmest (i.e., in summer) and most saline marine regions, which naturally experiences extreme seasonal heating, cooling, and evaporation cycles. Recent economic development and industrialization along with climate change also have introduced significant anthropogenic pressures on this naturally-stressed marine environment. Due to its semi-enclosed, shallow morphology and unique climatic setting, the impacts of environmental pressures are increasingly manifested in the hydrography and biogeochemistry of the Gulf. Oceanographic data collected within the exclusive economic zone (EEZ) of Qatar, although limited in space and time, indicate that physical and biogeochemical properties exhibit high spatial and temporal variability. Previous observational and numerical studies of the region conclude that increased field observation activity is required to better investigate the physical and biogeochemical dynamics of the Gulf. Long-term, continuous, and integrated monitoring of the marine environment, therefore, is essential to understand the status and seasonal/interannual variability of marine physical and biogeochemical dynamics as well as to predict any significant future changes in water column and ecological properties in response to environmental pressures and climatic changes. In this study, basin-scale oceanographic data collected in Qatar's marine region in the recent years are comparatively analyzed with available historical observations to assess thermohaline trends in water column structure and continental shelf circulation, to identify spatial and temporal data gaps, and to provide recommendations regarding optimal time and space coverage for future observational studies.qscienc

Prospects for climate-scale regional numerical modelling for the Arabian Gulf and Qatar's marine region

Physical oceanographic studies at the Environmental Science Center (ESC) entail observational and numerical aspects. The main objective of observational studies is to build a reference time series for Qatar's marine exclusive economic zone (EEZ), in which prominent spatial and temporal gaps in physical oceanographic knowledge exist due to scarcity of historical observational data. Numerical modelling studies are conducted to counteract the sparse nature of available marine observational data by complementing this space with simulated output. Numerical modelling of ocean circulation along with coupled atmosphere and marine ecosystem components involve high performance computational tools and model coupling interfaces. A high-resolution, multi-component regional numerical model capable of producing short and long-term data products for the Arabian Gulf and Qatar's EEZ is currently being implemented. The model system features a lower trophic level ecosystem module (nutrient-phytoplankton-zooplankton-detritus - NPZD) coupled to dynamical downscaling models of regional marine and atmosphere circulation. The output from this study is expected to: (i) provide a simulated picture of the present situation of Qatar's EEZ, as validated by historical and recent observational data; (ii) provide insight on the interaction among various components of the marine environment (i.e., atmosphere, ocean, ecosystem); (iii) predict regional marine physical-biogeochemical status as forced by forecasted natural and anthropogenic drivers; and (iv) assess and forecast marine resource availability for food, water, and renewable energy.qscienc

Seasonal variability of hydrography off the east coast of Qatar, central Arabian Gulf

Seasonal variability of hydrography along a nearshore-offshore transect in the eastern part of the EEZ of Qatar has been analyzed using in situ measurements carried out during 5 different months. The study reveals distinct features in temperature, salinity, density, dissolved oxygen (DO), and chlorophyll fluorescence. The sea surface temperature (SST) varies from nearshore to offshore with a positive gradient during January, June, and August, of the order of 1.0–2.0 °C, and with a negative gradient during October and April, of the order of 1.0 °C. Thermal stratification began in June, reached a well-defined thermocline with a vertical difference in temperature of about 10 °C during August, and started to de-stratify during October. The low salinity and low-density inflow of IOSW is evident in the surface layer of the middle of the transect during August, which has enriched the DO in the surface layer up to 20 m depth, while hypoxia prevailed below 50 m depth. The lowest chlorophyll fluorescence was measured in April 2013 (~ 1.0 μg l−1), moderate in June 2013 (~ 1.5 μg l−1), and relatively high in August 2013 (~ 6.0 μg l−1).This work has been supported by the QAFCO project (Grant no. QUEX-ESC-QAFCO-20/21-2

Sources of the Levantine Intermediate Water in Winter 2019

International audienceClimatic changes and interannual variability in the Mediterranean overturning circulation are crucially linked to dense water formation in the Levantine Sea, namely the Levantine Intermediate Water whose formation zone, comprising multiple and intermittent sources, extends over fluctuating pathways. To probe into the variability of this water formation and spreading, a unique dataset was collected during the winter of 2019 in the western Levantine Sea, via oceanographic cruises, profiling floats and a glider, at a spatio-temporal distribution suited to resolve mesoscale circulation features and intermittent convection events. This study highlights the competition between two source regions, the Cretan Sea and the Rhodes Cyclonic Gyre, to supply the Mediterranean overturning circulation in Levantine Intermediate Water. The Cretan source was estimated as the most abundant, supported by increasingly saltier water masses coming from the Levantine Sea under the pumping effect of a water deficit caused by strong western outflow toward the Ionian Sea