Research Projects

Annual heat and freshwater flux estimates on a global scale from Argo (2014)

The global pattern of annual heat and freshwater fluxes at the ocean surface is estimated using Argo temperature and salinity profile data for the period 2004 to 2012. Temperature or salinity changes are calculated in a volume of water above an isopycnal that is below the mixed layer and not subject to mixed-layer entrainment. Horizontal advection components from geostrophic velocity and from Ekman transport, based on wind stress, are also included. The annual heat or freshwater flux at the ocean surface is estimated as the sum of advective and time tendency contributions. The air-sea flux estimates from Argo are described in global maps and basin-wide zonal averages, in comparison to atmospheric reanalysis data and to air-sea flux products based on marine meteorological observations. This ocean-based estimate of surface fluxes can improve our understanding of errors in the large scale patterns inferred from sparse direct observations or remotely sensed data, and ensures that estimated fluxes are consistent with property variations in the subsurface ocean.

Understanding the annual cycle in global steric height (2013)

I have studied the wind-driven annual cycle in Ekman convergence, and hence in vertical advection at the base of the Ekman layer and compared it with vertical advection estimated from observed isopycnal displacement in the global collection of Argo profile data. My work is the first global study of its kind and demonstrates (i) that good agreement between the wind estimate and the observed vertical displacement extends to all oceans and to higher latitudes as well as the tropics and (ii) that the annual vertical advection extends deep into the water column and is consistent with subsurface steric height changes.

Wind-Driven Variability of the Subtropical North Pacific Ocean (2012)

I have studied the wind-driven interannual variability of the subtropical gyre in the North Pacific. I analysed the extensive subsurface Argo dataset to show for the first time that the North Pacific gyre varies in the strength of its interior circulation and in its spatial orientation, on interannual timescales. Also, satellite altimetry showed variations in sea surface height that were consistent with Argo steric height changes, and enabled a temporal extension of the 2004-2011 Argo study back to 1993. The observed gyre-scale circulation variability was also shown to be consistent with regional anomalies in wind-forcing through a time-dependant Sverdrup balance.