John Marshall

Cecil and Ida Green Professor of Oceanography, MIT

Mesoscale modulation of air-sea CO2 flux in Drake Passage

Mesoscale modulation of air-sea CO2 flux in Drake Passage.

(Song, H., Marshall, J., Munro, D., Dutkiewicz, S., Sweeney, C., McGillicuddy Jr., D.J., Hausmann, U.), Journal of Geophysical Researach, vol. 121, 2016.

Abstract

We investigate the role of mesoscale eddies in modulating air-sea CO2 flux and associated biogeochemical fields in Drake Passage using in situ observations and an eddy-resolving numerical model. Both observations and model show a negative correlation between temperature and partial pressure of CO2 (pCO2) anomalies at the sea surface in austral summer, indicating that warm/cold anticyclonic/cyclonic eddies take up more/less CO2. In austral winter, in contrast, relationships are reversed: warm/cold anticyclonic/cyclonic eddies are characterized by a positive/negative pCO2 anomaly and more/less CO2 outgassing. It is argued that DIC-driven effects on pCO2 are greater than temperature effects in austral summer, leading to a negative correlation. In austral winter, however, the reverse is true. An eddy-centric analysis of the model solution reveals that nitrate and iron respond differently to the same vertical mixing: vertical mixing has a greater impact on iron because its normalized vertical gradient at the base of the surface mixed layer is an order of magnitude greater than that of nitrate.

doi = 10.1002/2016JC011714