Observations of upwelling events in the Petacalco submarine canyon
Abstract
The head of the Petacalco canyon is located in the Petacalco Bay, in the Pacific Ocean (ca. 18N and 102W). The bathymetry of this submarine canyon, close to the head, shows steep slopes from the crests to the bottom and an average along axis slope of 6% within the studied region. The extension of this canyon goes as far as 110 km offshore, reaching the Central America Trench at 4600 m depth. The importance of the canyon in the region is mainly noticeable by the high fishing activity. Besides the windriven upwelling due to Ekman transport near coastal regions, the presence of the canyon enhances the upwelling of deep water from the adjacent oceanic region bringing the nutrients, which are injected into the bay, enhancing primary productivity, very much desire by fishery activities. During, at least six CTD surveys in the area, strong upwelling has been noticed, based on those observations a later survey was designed covering the Petacalco canyon with much larger spatial resolution. Along with those measurements, two thermistor arrays were deployed on the SW crest of the canyon at depths of approximately 60 [m], two ADCP current meters were deployed at 20 [m] depth on the opposite sides of the canyon's axis close to the head of the canyon. Figure 1 shows the CTD stations network and the location of all the instruments. The observations, from the thermistor arrays, show that temperature variations, at a given depth, could span ranges from 28 to 14 Celsius (during the fall period of September 2010). This variations, suggest the presence of internal waves; submarine canyons act as regions of enhanced mixing with focusing and amplification of internal waves. Individual profiles of potential density in the water column show, just below the thermocline, the existence of overturns just over the rim of the canyon suggesting turbulent mixing processes due to possible breakage of internal waves.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFMOS21A1602R
- Keywords:
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- 4546 OCEANOGRAPHY: PHYSICAL / Nearshore processes