The effect of geothermal heating on the East Eea circualtion

Abstract

The magnitude of geothermal heating in the East Sea is about 100 mW/m2 , twice that of the open ocean average. On the other hand, bottom stratification in the East Sea is much smaller than that typical of the open ocean. Thus geothermal heating could have more prominent effects in the East Sea and we investigated this using numerical modeling. With less than 100 mW/m2 bottom heat flux, we were able to reproduce bottom mixed layers that are thicker than ~1000 m, as in the observations. Previously no numerical model has been successful in reproducing the bottom mixed layers. Geothermal heating intensifies the bottom flows but the simulated flows are not as strong as the observed ones, suggesting we are still missing important factors. Over the northern part of the East Sea, reduction in deep stratification strengthens deep water mass formation, intensifying cyclonic circulations located over this area so the effects of the heating extend to the surface. As the cyclonic circulation becomes stronger, the water at the center of the gyre is trapped and more exposed to cold air, so it becomes cooler, and colder deep water is produced. When the geothermal heating is strong enough, the surface cooling effect dominates the bottom heating and the deep layer becomes cooler, showing that the effects of geothermal heating are far reaching and cannot be assessed using a simple local heat budget estimati heating could have more prominent effects in the East Sea and we investigated this using numerical modeling. With less than 100 mW/m2 bottom heat flux, we were able to reproduce bottom mixed layers that are thicker than ~1000 m, as in the observations. Previously no numerical model has been successful in reproducing the bottom mixed layers. Geothermal heating intensifies the bottom flows but the simulated flows are not as strong as the observed ones, suggesting we are still missing important factors. Over the northern part of the East Sea,