Integrated and Consistent Ocean Variables for Improved Satellite-based Air-Sea Flux Estimates

Exchanges of mass and energy between the ocean and atmosphere play a crucial role in the Earth’s energy and mass balance.

Quantifying air-sea fluxes of e.g. sensible and latent heat, and carbon dioxide (CO2), is essential for understanding oceanic and atmospheric processes, monitoring climate change and improving weather predictions. Moreover, the ocean takes up about a third of anthropogenic CO2 emissions. Thus, monitoring air-sea fluxes of CO2 is important for understanding the carbon cycle and ocean biochemistry.

Despite being crucial for constraining the atmospheric and oceanic models and essential in understanding the climate, air-sea fluxes are poorly quantified. In situ air-sea flux measurements are localised and sparse.

Over large spatial scales,  air-sea fluxes are estimated using bulk formulas and air-sea variables derived from satellites, which provide global coverage, but with low spatial resolution.

This project aims to fill the gap between local and sparse, and global and low resolution estimates of air-sea fluxes using observations from spaceborne synthetic aperture radar (SAR).

SAR is an all-weather day-night high resolution sensor, which is very sensitive to ocean surface dynamics, and thus offers a potential tool to observe the submesoscale ocean processes such as fronts and eddies, and waves. Hence the possibility to study the effect of these processes on the air-sea interaction.

These high resolution observations are particularly relevant in coastal regions, shelf seas and marginal ice zones.

One of the major sources of error in the estimation of air-sea fluxes are inaccurate parameterisations and ocean variables.

The parameterisations are based on empirical relationships, which can be associated with large biases and uncertainties.

The variables are usually derived independently from different sensors and at different temporal and spatial scales, hence the potential for inconsistency.

The uncertainty due to inconsistent variables and to the effect of sea state, submesoscale currents and wave-current interaction on the parameterisations are poorly understood and quantified due to the lack of co-located observations of ocean variables. This represents a major gap in our understanding of ocean-atmosphere exchange.

The overall aim of this project is to quantify the role of the submesoscale ocean currents and waves in the ocean-atmosphere exchange with the driving goal of improving air-sea flux estimates.

This project will 1) Resolve the spatial scales relevant to the submesoscale ocean processes using high spatial resolution ocean variables derived from SAR data combined with other observations, 3) Retrieve multiscale,  integrated and consistent ocean variables for air-sea flux estimation by optimally combining variables derived from different spaceborne sensors with model outputs, 4) Quantify wave and current induced uncertainty in the flux estimates, and 5) Develop wave-and-current-dependent parameterisation to reduce the uncertainty.