Modelling Deep Ocean Circulation in the Panama Basin Driven by Geothermal Heating

Previous global modelling studies have applied conductive geothermal heat fluxes at the seabed and shown differences in circulation compared to cases which neglected heat from the Earth in their boundary conditions. The results show increases of up to one third in the meridional overturning, and an increase of global abyssal temperature by up to 0.4 ˚C. We are interested in investigating this phenomenon at a regional scale, where higher resolution can be given to the model and impacts of the geothermal heating can be seen with greater detail. We have chosen the Panama Basin in the equatorial East Pacific as our study area. The Panama Basin has a geothermal heat flux of 2.5 times the global average, due in part to a high amount of hydrothermal activity along spreading ridges on the seabed. The basin is entirely enclosed below about 2300 m except for one deeper channel along the South American coastline, known as the Ecuador Trench. The importance of geothermal heating on the circulation in the region has been theorised based on observational data. We are using the Hybrid Coordinate Ocean Model (HYCOM) to simulate long-term circulation in the Panama Basin, in both a control run with no geothermal heating and in simulations with heat sources at the seabed. We compare the data from these simulations with each other to determine what differences a geothermal input makes to the abyssal circulation, and compare with observations to assess to what extent this is actually occurring within the Panama Basin. Water from the Pacific flows through the Ecuador Trench into the abyssal Panama Basin, where geothermal heat causes upwelling and mixing to occur at greater rates. This drives a decrease in the renewal period of the abyssal waters in the basin, exemplifying the importance of including interactions with the solid earth in ocean modelling. This research is part of a major interdisciplinary NERC-funded collaboration entitled: Oceanographic and Seismic Characterisation of heat dissipation and alteration by hydrothermal fluids at an Axial Ridge (OSCAR).