Oceanic budgets and transports
The ocean plays a central role in the climate system by redistributing heat, freshwater, and other properties around the globe. In particular, ocean currents transport large amounts of heat from low to high latitudes, thereby shaping regional climates and influencing the exchange of energy between the ocean and atmosphere. In the Atlantic, this redistribution is closely linked to the Atlantic Meridional Overturning Circulation (AMOC), with important implications for climate variability from the tropics to the Arctic.
Our group investigates ocean transports and their variability using direct observations, ocean reanalyses, and indirect estimates derived from the Earth's energy budget. By combining these complementary approaches, we aim to better understand changes in ocean circulation and heat transport and their role in the climate system.
Global meridional ocean heat transport. The ocean transports heat from low towards high latitudes in both hemispheres. Estimates from an ensemble of ocean reanalyses (red) are compared with estimates inferred from the Earth's energy budget (black); shading indicates their respective spread.
Observing and Estimating Ocean Transports
Direct observations of ocean transports are limited to a relatively small number of sustained observing systems and hydrographic sections. While these provide invaluable information on ocean circulation and its variability, their spatial coverage is sparse and many observational records are still relatively short.
To obtain a more complete picture, we complement these observations with ocean reanalyses, which combine ocean models with available observations to provide spatially and temporally continuous estimates of the evolving ocean state.
For the analysis of ocean reanalyses, our group has developed StraitFlux, a Python framework for consistently calculating ocean transports across arbitrary sections and model grids. At locations where sustained observations are available, such as the RAPID and Overturning in the Subpolar North Atlantic Program (OSNAP) arrays in the Atlantic Ocean, these transport estimates can be directly evaluated against observations, allowing us to assess their ability to represent the magnitude and variability of ocean circulation and heat transport.
Mean ocean velocity across Fram Strait and the Barents Sea Opening from the ORAS5 ocean reanalysis. Shading indicates flow into (red) and out of (blue) the Arctic region. The inset shows the location of the two sections.
Inferring Ocean Heat Transport from the Energy Budget
Alternatively, ocean heat transports can be estimated indirectly from the ocean heat budget. Changes in ocean heat content are governed by the exchange of energy with the atmosphere and the convergence or divergence of heat transported by ocean currents. Combining observations of ocean heat storage with estimates of surface heat fluxes therefore allows us to infer how much heat is transported between different regions of the ocean. This provides a complementary, observationally constrained approach to estimating ocean heat transports and offers a largely independent benchmark for evaluating transport estimates from ocean reanalyses and direct observations.