This week’s Imaggeo on Mondays is no ordinary image; it’s a snapshot of surface ocean speeds and the extent of ice cover in the North Atlantic. It was produced using a high resolution model of ocean eddies – high resolution here means that details are simplified into grids 3 km across, or one 20th of a degree. Three kilometres may sound like a pretty large area, but in oceanographic modelling, this is considered to be a fine mesh and is important for resolving small-scale processes like mesoscale eddy formation.
Mesoscale eddies are 10-250 km in diameter – again the idea that this is a small-scale process does seem a little far-fetched, but when you consider the size of the Atlantic Ocean, which covers an area over 100 million square-kilometres, the size of these eddies pale in comparison. “There are plenty of these eddies in ocean, especially in regions of high ocean currents, where the current gets unstable like in the Gulf Stream, North Atlantic Current and in the West Greenland Current”, Erik Behrens explains.
“Surface currents in the North Atlantic” by Erik Behrens. The red colours indicate speeds of about 1.5 m/s, yellow around 0.7 m/s and green 0.3 m/s. Lower speeds become transparent, and you only see the ocean floor below (dark blue). The image is intended for the public and is distributed by the EGU under a Creative Commons licence.
These eddies are not well captured in present climate models, but have an important role in ocean transport processes, deep ocean convection and ocean-atmospheric exchange. In order to better understand their effects, oceanographers like Behrens perform global ocean simulations, where key regions are modelled in much more detail (in this case the North Atlantic Ocean). “This simulation captures the oceanic condition quite realistically, and is therefore used for many comparisons with observations in the North Atlantic”, Behrens adds, meaning the impact of eddies both locally and on the global ocean can be studied in more detail.
The model used to produce this image is known as VIKING20, which used a data set going back to 1948. Models like this one allow marine scientists to make better interpretations of the data they’re collecting today.
Imaggeo is the EGU’s open access geosciences image repository. A new and improved Imaggeo site will be launching soon, so you will be able to peruse an even better database of visually stunning geoscience images. Photos uploaded to Imaggeo can be used by scientists, the press and the public provided the original author is credited. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. You can submit your photos here.
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