Every couple of years UN Environment takes the global environmental temperature.
For the analysis the global shelf was divided into 551 reporting blocks, each approximately 500 km in along-shelf length. Eight shelf morphotypes were defined by multivariate analysis of the 11 input variables, and they can be grouped into four broad categories: narrow-shallow shelves; wide-flat shelves; intermediate shelves; and deep-glaciated shelves. There is a negative correlation between shelf width and active plate margins, although there are examples of most shelf morphotypes occurring on both active and passive margins.
Glaciation plays a major role in determining shelf geomorphology and characterizes around 21 % of the global shelf. In particular, we find a very strong correlation between mean shelf depth and the percentage area of glacial troughs, indicative of the role played by glaciation and glacial erosion in shaping the global shelf. Coral reef growth is an important factor for one morphotype, which covers 427,000 km2 or about 1.3 % of all continental shelves. The hypsometric curve for mean shelf depth exhibits a peak at a depth of 40 m that coincides with a persistent position of sea level during the last 500,000 years based on one published sea level curve.
The geomorphic characterization and classification of the continental shelf at a global scale could be advanced using predictive modeling tools (for tidal sand banks, for example) but is otherwise dependent upon improved resolution bathymetric data becoming available.
Type: Staff Publications
Year of publication: 2016