| Summary: | Sharp fronts and eddies that are ubiquitous in the world ocean, as well as features such as shelf seas and under-ice-shelf cavities, are not captured in climate projections. Such small-scale processes can play a key role in how the large-scale ocean and cryosphere evolve under climate change, posing a challenge to climate models. There is much debate about what scales of motion need to be represented explicitly ('resolved') in models in order to produce robust climate projections. By contrast to atmospheric jet streams, mid-latitude weather systems and squall lines, the oceanic equivalents (boundary currents such as the Gulf Stream, mesoscale eddies and submesoscale eddies) are roughly ten times smaller in scale. The ocean also has boundaries (coastlines) and sub-surface orography (bathymetry) that constrain the circulation pathways, and shallower shelf regions where tides become more important. Determining the scales that need to be explicitly resolved in the ocean is challenging as small-scale processes can have a substantial impact on high-impact, low-likelihood events.
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