Improved Bathymetry Leads to 4000 New Seamount Predictions in the Global Ocean
Yesson, C., Letessier, T., Nimmo-Smith, A., Hosegood, P., Brierley, A., Harouin, M. and Proud, R. (2020) Improved bathymetry leads to 4000 new seamount predictions in the global ocean. UCL Open: Environment.
Seamounts are important marine habitats that are hotspots of species diversity. Relatively shallow peaks increased productivity and offshore locations make seamounts vulnerable to human impact and difficult to protect. Present estimates of seamount numbers vary from barely 10000 to more than 60000), because locating and identifying them remotely can be difficult. Seamount locations can be estimated by extracting conical shaped features from bathymetry grids. These predicted amounts are a useful reference for marine researchers and can help direct exploratory surveys. However, these predictions dependent on the quality of the surveys underpinning the bathymetry. Historically, quality has been patchy but is improving as mapping efforts step up towards the target of complete seabed coverage by 2030. This study presents an update of seamount predictions based on the most recent SRTM30 global bathymetry. This update was prompted by a seamount survey in the British Indian Ocean Territory, where locations of two putative seamounts, based on several previous global seamount predictions, were visited, but no such features were detected during echosounder surveys. An examination of Admiralty charts for the area showed that the summits of these putative features had soundings reporting no bottom detected at this depth where this depth was similar to the seabed reported from the bathymetry grids: we suspect that these features likely resulted from an initial misreading of the charts. We show that perhaps 15phantom seamount features, derived from a misinterpretation of no-bottom sounding data, persist in current global bathymetry grids and updated seamount predictions. Overall, we predict 37,889 seamounts, an increase of 4,437 from the previous prediction derived from an older global bathymetry grid. This increase is due to greater detail in newer bathymetry grids as acoustic mapping of the seabed expands.