Assessing the role of eddies in exchanging nutrients across the European Shelf

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The ocean is full of time-varying, swirling circulations, called eddies. These eddies transfer heat, nutrients and carbon from one region to another, affecting the local store of each of these properties. This eddy exchange potentially becomes important across strong flows, such as boundary currents, jets and slope currents. However, while eddies are seen to occur throughout the ocean (such as remotely sensed observations), there have been very few systematic, repeated observations revealing how eddies transfer properties in the horizontal, particularly below the surface. Instead we have to rely on a combination of model and theoretical studies to understand the role of eddies in the ocean, often drawing parallels with how weather systems behave in the atmosphere.In this study, we wish to use the new glider technology to identify how eddies transfer nutrients in the horizontal. We wish to investigate this eddy transfer on the European Shelf at three different sites, drawing on the support of an existing programme, FASTNET, examining the physical exchange across the shelf break. Our aim is to include nutrient sensors in two gliders, one supported under FASTNET and the other supported via this call. Together with nutrient data from FASTNET cruises, we aim to use the glider data to estimate the eddy flux of nutrients in these three different sites between the open ocean and shelf seas. Our hypothesis is that the eddies provide a flux of inorganic nutrients from the open ocean to the shelf seas, across the shelf break, as well as a return flux of dissolved organic nutrients from the shelf seas to the open ocean.The eddy fluxes of nutrients onto the shelf are potentially important in sustaining biological productivity, there are particularly high rates of photosynthesis here, sustaining fishing activity and providing a biological drawdown of atmospheric carbon dioxide.In the longer term, the glider technology has the potential to provide the repeated observations needed to quantify eddies fluxes throughout the ocean. This step is necessary to really understand how heat, nutrients and carbon are transferred throughout the ocean, as well as the wider goal of how the ocean operates in the climate system.