Oceans: studying the past to better understand the future

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A unique opportunity to investigate the natural variability of the ocean while highlighting its dynamics and processes: a simulation of a global eddying ocean is presented. The model realistically represents the ocean variability at upper and intermediate depths, the position and strength of the surface circulation, and exchanges of mass through key passages. Sea ice properties are close to satellite observations.
A study by CMCC Foundation reaching exceptional resolutions in ocean modelling and opens the way for the development of a new, operational short-term ocean forecast system meant to serve as the backbone for downscaling coastal and regional applications and realizing services for the global coastal ocean. Useful tools required by operational oceanography and its different applications such as services for marine management and protection, maritime security, fishery, search and rescue, oil spills, etc.

Today one of the most challenging issue of oceanographic research is to develop high resolution models and simulations that are capable to describe and realistically represent the ocean dynamics and processes that are occurring at smaller scales, that is at mesoscale. Many of the weather phenomena that most directly impact human activities occur on the mesoscale. Resolving eddies means adequately describes mesoscale variability and is currently the main goal of general circulation models in order to develop ocean forecasting systems.
“The global ocean is a highly turbulent system over a wide range of space and timescales. We can observe vortices, fluxes and energy exchanges, turbulence processes that are responsible for the distribution of nutrients, gases and heat in the water column. Both satellite and in situ data show that mesoscale eddies pervade the ocean at all latitude bands”, Dr Masina, Director of ODA – Ocean modelling and Data Assimilation Division at CMCC Foundation, explains.
“Those processes occurring at smaller scales, eddies and meandering currents with typical spatial scales between 10 and 100 km, play a substantial role in the dynamics of the global ocean, e.g. transporting and mixing temperature and salinity, exchanging energy and momentum with the mean flow, controlling the mechanisms of deep water spreading and deep convection preconditioning, and modulating air-sea interactions.”
Operational oceanography and its different applications such as marine and weather forecast, search and rescue, fisheries, oil spill etc. require global ocean forecasting systems to reach kilometric scales in coastal areas. A challenging demand fostered by the continuous increase of resolution in numerical weather prediction models and the design of next-generation satellites to better capture the ocean variability at smaller scales: thanks to progress in ocean modelling and the advances in high performance computing resources over the last decade, numerical simulations at higher resolution are now a realistic choice to bring new insights into the oceanic physical processes and to find application in ocean modelling and forecasting.

The system that ODA Division is currently developing uses NEMO (Nucleus for European Modelling of the Ocean), a state-of-the-art modeling framework for oceanographic research, operational oceanography seasonal forecast and climate studies, an open source, large community model that CMCC Foundation is both user and developer of.
In a study recently published on Geoscientific Model Development (among the authors, CMCC researchers D. Iovino, S. Masina, A. Storto and A. Cipollone from ODA Division) a new implementation of the NEMO model, hereafter called GLOB16, was used to realize a global eddying-resolving simulation of the global sea ice-ocean system. So far, GLOB16 represents the NEMO global configuration of the ocean and sea ice system having the highest horizontal resolution and is a foothold that opens the way for the development of a new, operational real-time ocean forecast system meant to serve as the backbone for downscaling coastal and regional applications to develop services for the global coastal ocean.

Watch the video:

Surface current speed performed with NEMO ocean model at 1/16° resolution (~ 6/7 Km) for one year of simulation (2015). The video was realized by ODA researchers and continued the running of the model described in the aforementioned study.

Dr. Iovino, lead author of the study, says “Our model has 1/16° horizontal resolution at the Equator (corresponding to  6.9 Km) that increases poleward. The highest spatial resolution is reached in the Arctic Ocean (~ 2 km). The vertical system consists of 98 vertical levels. The first simulation ran for the period 2003-2013 and results were compared and verified with observational data; moreover, the gain due to increased resolution was evident when compared to a coarser-resolution version of the model. The model adequately describes and capture the ocean mesoscale variability over almost the entire global domain. We think that GLOB16 represents a significant modelling improvement over the previous configurations of the CMCC global ocean/sea ice models at coarser resolutions.”
GLOB16 is now coupled to an ocean/sea ice data assimilation system, and constitutes the base of the CMCC global eddying analysis and short-term forecast system.

At the moment the running of the model and the development of the forecasting chain are run at the CMCC Supercomputing Center based in Lecce. “The model has been validated and is now ready to use for forecasting”, states Iovino. “It has been coupled to a data assimilation system to set up a real-time, global ocean forecasting system (GOFS16, that is, a global ocean forecasting system with the same spatial resolution of the model). Thanks to this higher resolution, the CMCC is at the cutting edge of ocean modelling and forecasting”.


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