Oceanography

Prof. Steve Brenner | Prof. Yishai Weinstein

The Earth is often referred to as the water planet, although water accounts for only 0.023% of the mass of the planet. Nevertheless, water is found mainly at or near the surface and in the atmosphere and therefore is a very prominent planetary feature when viewed from space. Water as a substance appears in the solid, liquid, and gaseous phases. Liquid water is found in the hydrosphere which includes the oceans, marginal seas, lakes, and rivers. The oceans cover approximately 70% of the surface of the Earth, with an average depth of ~4 km. The specific heat capacity of water is nearly four times that of air and therefore the oceans serve as a major heat reservoir and regulator of the climate system. Furthermore ocean currents are responsible for more than one third of the heat transport from the equator to the poles and therefore affect the horizontal temperature gradients in the atmosphere which are closely linked to the development of major weather systems on various temporal and spatial scales. The oceans also serve as a major source of food and natural resources (e.g., natural gas and oil) and are important for commerce and transportation. For hundreds and perhaps even thousands of years, mariners intuitively understood some of the salient features of the surface circulation in the most highly traversed parts of the ocean. Yet despite the interest in and the importance of the oceans, oceanography as a formal science is relatively young, being only slightly more than a century old. Part of the rapid development of this science has been driven by the notable appearance of the cumulative effects of anthropogenic impacts on the oceans through processes such as the introduction and dispersion of land based pollutants in the coastal seas or the disturbance of the natural coastline due to the construction of various structures. The two main sub-disciplines of oceanography that are currently investigated in the department are: physical oceanography and marine geochemistry.

Physical Oceanography

Understanding the physical structure and the circulation of the oceans is of paramount importance due to its influence on all other aspects of the marine environment such as the ecosystem, the dispersion of tracers and pollutants, and its influence on the climate system. From a dynamical perspective the oceans consist of a thin layer fluid heated from above and located on a rapidly spinning sphere. Thus the combined effects of thermal stratification and the Earth's rotation play central roles in shaping the circulation on a wide range of spatial and temporal scales. Physical oceanographic investigations have three major goals: (1) describing the physical and dynamical structure of the oceans and it variability; (2) understanding the basic physical processes that control this structure and its variability; and (3) development of mathematical methods for simulating and predicting the system. Considering the geographical location of Israel, our research focuses mainly on the Mediterranean Sea, the Gulf of Eilat, and the Dead Sea. Some examples of our recent and ongoing research include:

• the development of an ocean forecasting system for the Mediterranean Sea
• the potential influence of climate change on the circulation of the Mediterranean Sea
• modeling the impact of riverine nutrient input on the southeastern Levantine planktonic ecology
• the environmental consequences of the proposed Red Sea – Dead Sea Water Conveyance Project for the Gulf of Eilat and the Dead Sea.

Marine Geochemistry

Understanding the geochemical structure of the oceans is central importance for addressing environmental issues related to the sea in general and coastal regions in particular. Exchange of water between the sea and the sediments on the seafloor has implications for the massive natural gas reserves that are stored beneath the oceans. Many studies have investigated the process of the release of this natural gas to the water column as well as the potential influence of global warming on these reserves along the margins of the Pacific Ocean and the Gulf of Mexico. Some of our recent and ongoing research includes:

• Submarine groundwater discharge (SDG) along the Mediterranean coast of Israel.