Resemblance of the global depth distribution of internal-tide generation and cold-water coral occurrences
van der Kaaden, A.-S.; van Oevelen, D.; Mohn, C.; Soetaert, K.; Rietkerk, M.; van de Koppel, J.; Gerkema, T. (2024). Resemblance of the global depth distribution of internal-tide generation and cold-water coral occurrences. Ocean Science Journal 20(2): 569-587. https://dx.doi.org/10.5194/os-20-569-2024 In: Ocean Science Journal. Springer: Ansan. ISSN 1738-5261; e-ISSN 2005-7172, more |   |
| Authors | | Top | - van der Kaaden, A.-S., more
- van Oevelen, D., more
- Mohn, C.
- Soetaert, K., more
| - Rietkerk, M.
- van de Koppel, J., more
- Gerkema, T., more
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| Abstract | Internal tides are known to be an important source of mixing in the oceans, especially in the bottom boundary layer. The depth of internal-tide generation therefore seems important for benthic life and the formation of cold-water coral mounds, but internal-tide conversion is generally investigated in a depth-integrated sense. Using both idealized and realistic simulations on continental slopes, we found that the depth of internal-tide generation increases with increasing slope steepness and decreases with intensified shallow stratification. The depth of internal-tide generation also shows a typical latitudinal dependency related to Coriolis effects. Using a global database of cold-water corals, we found that, especially in Northern Hemisphere autumn and winter, the global depth pattern of internal-tide generation correlates (rautumn = 0.70, rwinter = 0.65, p < 0.01) with that of cold-water corals: shallowest near the poles and deepest around the Equator, with a decrease in depth around 25° S and N, and shallower north of the Equator than south.We further found that cold-water corals are situated significantly more often on topography that is steeper than the internal-tide beam (i.e. where supercritical reflection of internal tides occurs) than would be expected from a random distribution: in our study, in 66.9 % of all cases, cold-water corals occurred on a topography that is supercritical to the M2 tide whereas globally only 9.4 % of all topography is supercritical. Our findings underline internal-tide generation and the occurrence of supercritical reflection of internal tides as globally important for cold-water coral growth. The energetic dynamics associated with internal-tide generation and the supercritical reflection of internal tides likely increase the food supply towards the reefs in food-limited winter months. With climate change, stratification is expected to increase. Based on our results, this would decrease the depth of internal-tide generation, possibly creating new suitable habitat for cold-water corals shallower on continental slopes. |
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