Ha-jun Song

The Pacific sardine ( Sardinops sagax ) showed significant differences in spawning habitat area, spawning habitat quality and availability of survivor habitat as the Pacific Ocean went through the La Niña state in April 2002 to a weak El Niño in April 2003. During another El Niño/Southern Oscillation transition period in 2006–2007 when the El Niño state retreated and the La Niña returned, a similar pattern in spawning habitat quality was seen. The coupling between the atmospheric forcing, the ph

Abstract The Antarctic Circumpolar Current has highly energetic mesoscale phenomena, but their impacts on phytoplankton biomass, productivity, and biogeochemical cycling are not understood well. We analyze satellite observations and an eddy‐rich ocean model to show that they drive chlorophyll anomalies of opposite sign in winter versus summer. In winter, deeper mixed layers in positive sea surface height (SSH) anomalies reduce light availability, leading to anomalously low chlorophyll concentrat

Abstract We investigate the role of mesoscale eddies in modulating air‐sea CO 2 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 CO 2 ( p CO 2 ) anomalies at the sea surface in austral summer, indicating that warm/cold anticyclonic/cyclonic eddies take up more/less CO 2 . In austral winter, in contrast, relationships are r

Abstract Momentum input from westerly winds blowing over the Southern Ocean can be modulated by mesoscale surface currents and result in changes in large‐scale ocean circulation. Here, using an eddy‐resolving 1/20 degree ocean model configured near Drake Passage, we evaluate the impact of current‐wind interaction on vertical processes. We find a reduction in momentum input from the wind, reduced eddy kinetic energy, and a modification of Ekman pumping rates. Wind stress curl resulting from curre

Abstract A new approach is proposed to address the background covariance limitations arising from undersampled ensembles and unaccounted model errors in the ensemble Kalman filter (EnKF). The method enhances the representativeness of the EnKF ensemble by augmenting it with new members chosen adaptively to add missing information that prevents the EnKF from fully fitting the data to the ensemble. The vectors to be added are obtained by back projecting the residuals of the observation misfits from

Abstract We diagnose the ocean’s residual overturning circulation of the Arabian Gulf in a high-resolution model and interpret it in terms of water-mass transformation processes mediated by air–sea buoyancy fluxes and interior mixing. We attempt to rationalize the complex three-dimensional flow in terms of the superposition of a zonal (roughly along axis) and meridional (transverse) overturning pattern. Rates of overturning and the seasonal cycle of air–sea fluxes sustaining them are quantified

Abstract We report the significant impact of near‐inertial waves (NIWs) on vertical mixing and air‐sea carbon dioxide (CO 2 ) fluxes in the Southern Ocean using a biogeochemical model coupled to an eddy‐rich ocean circulation model. The effects of high‐frequency processes are quantified by comparing the fully coupled solution (ONLINE) to two offline simulations based on 5‐day‐averaged output of the ONLINE simulation: one that uses vertical mixing archived from the ONLINE model (CTRL) and another

Abstract A new hybrid ensemble Kalman filter/four-dimensional variational data assimilation (EnKF/4D-VAR) approach is introduced to mitigate background covariance limitations in the EnKF. The work is based on the adaptive EnKF (AEnKF) method, which bears a strong resemblance to the hybrid EnKF/three-dimensional variational data assimilation (3D-VAR) method. In the AEnKF, the representativeness of the EnKF ensemble is regularly enhanced with new members generated after back projection of the EnKF

Abstract The role of mesoscale eddies in the uptake of anthropogenic chlorofluorocarbon‐11 (CFC‐11) gas is investigated with a 1/20° eddy‐resolving numerical ocean model of a region of the Southern Ocean. With a relatively fast air‐sea equilibrium time scale (about a month), the air‐sea CFC‐11 flux quickly responds to the changes in the mixed layer CFC‐11 partial pressure ( p CFC‐11). At the mesoscale, significant correlations are observed between p CFC‐11 anomaly, anomalies in sea surface tempe