EarthRef.org Digital Archive (ERDA) -- Ocean Circulation - Transport and Mixing at Seamounts and Biological Consequences

Description
Oceanic seamounts are commonly considered as offshore hotspots of marine life unifying a wide range of biological processes and phenomena at a comparatively small spatial scale. These include aggregations of biomass, locally enhanced biodiversity and increased levels of primary and secondary production. In this SEAMOUNTS'09 keynote Christian Mohn explains that the classical view is that bio-physical coupling mechanisms (e.g. Taylor caps, anti-cyclonic circulation cells, upwelling, increased vertical mixing) may promote extended particle residence times to ultimately support aggregation and retention of biological material. However, there is little direct evidence that such an idealized situation really exists and that it can be maintained over a longer period. Previous studies have shown that the existence and stability of local seamount regimes are highly sensitive to changes in the physical environment: Their retention potential strongly depends on the relative importance of a number of parameters such as forcing amplitude, ambient stratification and seamount height. In addition, the definition of seamount effects should not be restricted to local and small-scale implications. It has to embrace a wider spectrum of biological phenomena associated with the potential influence of seamounts on the larger surrounding ocean on a scale of hundreds of kilometers. In this keynote, we review the major characteristics and basic dynamical concepts of the flow at isolated topography. We also present the sensitivity of the flow at seamounts to changing environmental conditions as well as factors influencing particle residence and patchiness development.