Physical and Biogeochemical Controls on the Equatorial Pacific Carbon Cycle at the Mesoscale

Ocean physics, biology, and chemistry interact in a complex manner in the equatorial Pacific Ocean. One important example of these interactions is the large outgassing of CO2 from this part of the ocean. It is the largest source of natural ocean carbon to the atmosphere. One explanation for this CO2 outgassing is that the winds bring up carbon-rich waters from the ocean’s depth to the surface. However, recent studies suggest that smaller scale circulation patterns including “eddies” may also bring up carbon to the surface. At the same time, the smaller scale circulation may act to suppress CO2 outgassing by bringing up nutrients from depth and promoting biological production. How these opposing effects balance out is not understood well. This project attempts to provide a better understanding of these effects by using a suite of dynamical ocean models and various autonomous observations. This project combines existing observations from autonomous observing platforms, moorings, and satellites, with new high resolution model simulations of ocean circulation and biogeochemistry to characterize the effects of vertical and lateral transport, biological feedbacks, and their net balance on carbon outgassing and cycling at 10-500km scales in the eastern and central equatorial Pacific. A guiding hypothesis is that regional scale phenomena such as Tropical Instability Waves can have regionally distinct effects on carbon fluxes and drawdown. This project is expected to advance our currently poor understanding of the role of regional circulation in the ocean carbon cycle. It is also expect to guide observing strategies in the equatorial Pacific and inform the development of the next generation climate models. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.