Artificial Ocean Upwelling on the Israel Shore of the Mediterranean Sea

The upper ocean is an important component of climate and climate change. The heat capacity of only a few meters of the ocean water is equivalent to the heat capacity of the entire atmosphere. (Solar radiation and infrared balance in the atmosphere are major factors as well.) An artificial upwelling system utilizing the energy of surface waves can help to mitigate extreme local climates (Soloviev 2016). Artificial upwelling devices using the energy of surface waves, similar to those developed by Vershinskiy et al. (1987), can bring cold water from below the thermocline to the sea surface. Their wave-inertia pump consisted of a vertical tube, a valve, and a buoy to keep the device afloat. The device operates by using the energy of surface waves to create an upward flow of water in the tube. An outlet valve at the top of the unit synchronizes the operation of the device with surface waves and prevents back-splashing. A single device with a 100 m long and 1.2 m diameter tube is able to produce up to 1 m³s^-1 flow of deep water to the surface. With a 10^oC temperature difference over 100 m depth, the negative heat supply rate to the sea surface is 42 MW, which is equivalent to a 42 Wm^-2 heat flux, if distributed over 1 km² area. Such flux is comparable to the average net air-sea flux. Following the suggestion of Dr. Singer (private communication), we consider installation of a wave-driven artificial upwelling system on the Israel shore of the Mediterranean Sea. The cold deep water brought to the surface from below the thermocline by the artificial upwelling system will slightly warm during the daytime by solar radiation and mix with the warmer upper layers before plunging back to deeper layers (below the thermocline). Reduced sea surface temperature also reduces sensible and latent heat fluxes, and effective long-wave radiation, resulting in less loss of heat from the sea to the atmosphere and additional heat accumulation in the water column during summer time. Although the mixed layer and, thus, sea surface temperature will drop due to mixing with the cold water, the total ocean heat content (from the surface to the bottom) on the Israel coast will be gradually increasing during summer months. During winter storms, the mixed layer deepens and entrains water from deeper layers. Tsvetkov and Assaf (1980) found statistically significant correlation between the heat content of the coastal Mediterranean accumulated during summer time and the precipitation for the corresponding period of time from November-December to March-April for Jerusalem. We expect dual beneficial effect of the artificial upwelling system: mild climate on the Israel coast during summer time and the winter rains brining more fresh water to the Levant. Other potential applications of the system, in other marine environments around the world, include developing offshore fisheries, preserving coral reefs from bleaching, and mitigating hurricane damage in the tropics. There are engineering, oceanographic, and environmental issues, which have to be addressed before the system can be implemented. Numerical experiments and field tests are expected to help in the development of a prototype system.

References:

Soloviev, A.V., 2016: Ocean Upwelling System Utilizing Energy of Surface Waves. Tech-Ocean 2016, Kobe, Japan, 6-8 October 2016.

Tzvetkov, T., and Assaf, G., 1980: The Mediterranean Heat Storage and Israeli Precipitation. Water Resources Research (18), 1036-1040.

Vershinsky, N.V., Pshenichnyy, and A.V. Soloviev, 1987: Artificial upwelling using the energy of surface waves. Oceanology 27(3), 400-402.