Grant: Discovery Grants Program - Individual

Surface currents are one of the essential ocean variables identified by the Global Ocean Observing System (GOOS). Essential ocean variables are those that are critical to measure "to be able to deliver ocean forecasts and early warnings, climate projections and assessments and protect ocean health and its benefits" (GOOS). Observations and predictions of surface currents are critical for many societal applications such as search and rescue operations, oil spill mitigation, or tracking of marine plastic debris. Surface currents and waves also play a crucial role in air-sea interactions, which drive the ocean circulation and regulate the earth climate. Yet the few centimetres below the ocean surface have been an observational blind spot until recent advances in remote-sensing measurement techniques, which have revealed that currents change rapidly with depth within centimetres below the ocean surface. The long-term objective of the proposed research program is to improve our understanding of the dynamics and structure of currents very near the ocean surface, by developing and testing new in-situ and remote-sensing approaches to measure currents with minimal flow disruption. To attain this objective, the following questions will be investigated in the next 5 years: 1) What is the vertical structure of horizontal currents near the sea surface, especially within one meter from the surface, which is usually not resolved by ocean circulation models? What processes are responsible for this structure? Can they be parameterized from near-surface wind and waves? 2) How does the drift and dispersion of floating particles (such as oil films and emulsions and marine debris) differ from those of neutrally-buoyant particles in the surface mixed layer? 3) Search and rescue operations rely on predictions of trajectories of floating objects, as well as their uncertainties, which are usually obtained by adding random variations to the surface currents predicted by ocean numerical models or measured by instruments. What processes do these random variations represent? Can they be parameterized? The proposed research activities will help test and improve representations of these unresolved processes in numerical ocean circulation models, which will in turn improve operational and climate predictions.