OMEGA has three main objectives; to determine the three-dimensional ageostrophic circulation at mesoscale (10-100 km) fronts and eddies and quantitatively estimate the vertical velocity, to evaluate the impact of the ageostrophic vertical motion on the biogeochemical properties in the upper 400 m, and to provide the scientific community with a standardised tool for the computation of vertical motions from routine CTD and ADCP data. Vertical motion couples the deep ocean with the near surface layers, providing an enhanced transport route for heat, nutrients and biomass. The distribution of primary production patchiness is driven by mesoscale physics. At these scales, successful research requires interdisciplinary observational strategies.
OMEGA is a comprehensive project combining an observational strategy of remote sensing and in-situ high resolution physical, biological and meteorological measurement with a numerical modelling/data assimilation strategy to quantify the errors involved in the diagnostic analysis of the observational data and make prognostic simulations of mesoscale features. Mesoscale eddies are ubiquitous in the ocean and the conclusions from OMEGA will be relevant to all ocean regions. However, the Alboran Sea and Almeria-Oran Front have been selected as the experimental area because of favourable environmental conditions and convenience for EC member countries. No one country or organisation could undertake OMEGA on its own.
Data and results will be shared and discussed by the OMEGA team using email, ftp and 6 monthly progress meetings and workshops. Analysed results, conclusions, datasets, new algorithms and software will be disseminated to Europe and worldwide through reports, scientific papers, a CD-ROM OMEGA atlas and an OMEGA World Wide Web server.
The three main objectives of this project are expanded below. They have been divided into several specific sub-objectives. Detailed information on the resourses required and the contribution of each organisation is given in section 3.
1 Three-dimensional ageostrophic circulation: to determine the three-dimensional ageostrophic circulation within an intense mesoscale upper ocean front (upper 300 m) and quantitatively estimate the vertical velocity.
1.1 To measure the short term three-dimensional spatial variability of the density field using quasi-synoptic sampling (CTD and SeaSoar) and to obtain the associated ageostrophic velocity distribution.
1.2 To determine the short term (order of 1 week) three-dimensional spatial and temporal variability of the density field and the associated ageostrophic velocity distribution using repeated sampling and data assimilation into a primitive equations (P.E.) numerical model.
1.3 To monitor the larger scale temporal variations in the current systems using the surface geostrophic velocity and hence the geoid along satellite tracks and also using prognostic P.E. computations.
1.4 To measure the three-dimensional ageostrophic flow using Lagrangian floats at different depths.
2.1 To investigate and assess the impact of mesoscale vertical motion on biogeochemical fluxes and biomass.
2.2 To improve our understanding of the relationship between remotely-sensed surface signatures (SST, surface height, SAR and ocean colour) and sub-surface structures in the water column.
2.3 To validate new optical satellite sensors to be launched between now and the scheduling of cruises related to this proposal.
3.1. To analyse and integrate all the different estimates of the three-dimensional ageostrophic flow, with emphasis on the vertical velocity and net transport.
3.2. To establish a methodology for routine computation of vertical velocities from CTD and ADCP data.