Marine plants contribute about half of the global net primary production and thus sustain fisheries and world food supplies. Current climate change caused by anthropogenic greenhouse gas emissions is likely to affect this production through changes in temperature, ocean circulation, pH, nutrient and light availability. Understanding what drives production is therefore a key problem of marine science.In this pilot study involving “Orca”, one of UEA's three ocean gliders, we aim to improve our understanding by observing the physical, chemical and biological processes driving production in the Iberian upwelling region, off the coast of Spain, on a wide range of temporal and spatial scales. You can follow the progress of this study on the UEA glider mission website.
Wind-induced upwelling pumps nutrient-rich deep waters to the surface and often fuels intense phytoplankton (marine plants) blooms. Mixing between upwelled and surface water is usually not homogeneous, but occurs over a wide range of spatial scales. Often, smaller-scale processes contribute significantly, e.g., wind/turbulence interactions at the mesoscale (10-100 km) and submesoscale (1-10 km).
Resolving these small-scale processes through traditional ship-board surveys is expensive and technically challenging. Recently developed autonomous platforms and sensors can significantly enhance traditional ship-based work. For example, a fleet of >3000 Argo floats now take regular temperature and salinity profiles of the upper 2 km of the world's oceans and help improve our understanding of oceanic heat budgets and circulation.
However, floats can only move vertically in the water column and are otherwise drifting passively. Gliders have been developed to partly overcome the limited manoeuvrability of floats. These autonomous vehicles can be interactively piloted in the vertical as well as horizontal direction and acquire depth profiles of marine physical and biogeochemical parameters with high resolution in space and time. They can "see" where satellites cannot penetrate the surface, work for months at a time and are much cheaper than traditional oceanographic cruises.
Biological and chemical sensors add further dimensions to these technologies. In particular, oxygen sensors can measure net community production, i.e. the balance between oxygen-producing photosynthesis and oxygen-consuming respiration. Continuous measurements of key parameters and processes have thus become possible on a global scale.
This project is funded through the Natural Environment Research Council (NERC), Grant NE/G019509/1.