Search

According to the typical thermal structure of the ocean, the water column can be divided into three layers: the mixing layer, the thermocline and the deep layer. In this study, we provide a new methodology, based on a function adjustment on the temperature profile, to locate the minimum and maximum depths of the thermocline, and therefore its thickness, to separate the water column into layers. We first validated our methodology by comparing the mixed layer depth obtained with the method proposed here with that of two previous studies. Since we found a very good agreement between the three methods we used the function adjustment to compute the monthly climatologies of the mixed layer depth, the maximum depth of the thermocline and the thermocline thickness, throughout the ocean. We also provide an assessment of the regions of the ocean where our adjustment is valid, and consequently the regions where the thermal structure of the ocean follows the three-layer structure. However, there are ocean regions where the water column cannot be separated into three layers due to the dynamic processes that alter it and the major contribution of salinity to stratification. This assessment highlights the limitations of the existing methods to accurately determine the mixed layer depth and the thermocline in oceanic regions that are particularly turbulent as the Southern Ocean and the northern North Atlantic, among others. The method proposed here has shown to be robust and easy to apply, and it can be used in both local and global studies.

Data from an autonomous ARGO float launched on December 26, 2016, south of the entrance of the Gulf of California, reveal variations in the distribution of water masses in the tropical-subtropical convergence off Mexico. The float trajectory drifted through three areas of distinct characteristics: i) the southern Gulf of California in January 2017, ii) south of Cabo San Lucas from February 2017 to January 2018, when the float crossed an eddy, and iii) off Cabo Corrientes from February 2018 to April 2021. During the sampling, the vertical distribution of the water masses showed for the first time with “in situ” data a semiannual variability mainly in the salinity as response to poleward propagating semiannual Kelvin wave. The surface water masses had potential densities <26 kg m−3. A shallow salinity minimum (<34.6 g kg−1) observed at ∼ 70 m depth south of Cabo San Lucas provided a proxy for the California Current Water distribution, which had its maximum southern extension during winter. The Tropical Surface Water was observed off Cabo Corrientes mainly above 50 m depth and had maximum northern extension during summer. The Gulf of California Water was scarcely evident in the float trajectory in the southern Gulf. The Transitional Water was located above ∼ 50 m depth and was dominant southwest of Cabo San Lucas during winter and spring, when the California Current Water extended furthest south. The Subtropical Subsurface Water, in spite of its high density (>25 kg m−3) at times extended up to only 20 m below surface in the three areas around the summer as part of a semiannual cycle. The intermittent presence of this oxygen-deficient water close to the surface (∼ 20 m depth) is consistent with the on-going expansion of the shallow oxygen minimum zone. Wavelet analysis highlighted a bimonthly spectral frequency in the StSsW lower limit when the float crossed the eddy in the south of Cabo San Lucas, showing the influence of the mesoscale features of the area, and theref

According to the typical thermal structure of the ocean, the water column can be divided into three layers: the mixing layer, the thermocline and the deep layer. In this study, we provide a new methodology, based on a function adjustment on the temperature profile, to locate the minimum and maximum depths of the thermocline, and therefore its thickness, to separate the water column into layers. We first validated our methodology by comparing the mixed layer depth obtained with the method proposed here with that of two previous studies. Since we found a very good agreement between the three methods we used the function adjustment to compute the monthly climatologies of the mixed layer depth, the maximum depth of the thermocline and the thermocline thickness, throughout the ocean. We also provide an assessment of the regions of the ocean where our adjustment is valid, and consequently the regions where the thermal structure of the ocean follows the three-layer structure. However, there are ocean regions where the water column cannot be separated into three layers due to the dynamic processes that alter it and the major contribution of salinity to stratification. This assessment highlights the limitations of the existing methods to accurately determine the mixed layer depth and the thermocline in oceanic regions that are particularly turbulent as the Southern Ocean and the northern North Atlantic, among others. The method proposed here has shown to be robust and easy to apply, and it can be used in both local and global studies.

The Gulf of California and adjacent Pacific have passed through a prolonged warming period that affects the Humboldt squid D. gigas life cycle, which was the third largest fishery in Mexico until its total collapse after 2010. The aims of the present study were (i) to characterize the nursery habitat of paralarvae of the complex Sthenoteuthis oualaniensis–Dosidicus gigas (SD complex) on the basis of 1112 paralarvae collected from zooplankton trawls carried out during ten oceanographic cruises off northwestern Mexico between 2010 and 2017; and (ii) to model the seasonal and interannual variability of the nursery habitat, applying a generalized additive model (GAM) using a regional long-term (1922–2017) hydrographic database. The GAM showed significant relationships of paralarvae abundance with the seasonal average of thermocline depth, absolute salinity, and conservative temperature. The potential nursery habitat of the SD complex paralarvae showed its maximum expected abundance in the entrance of the Gulf of California during spring, when the thermocline depth was shallowest (<30 m). During summer the nursery habitat moved northward along the Pacific west coast of the peninsula. Autumn and winter were less suitable seasons for paralarvae nursery because the thermocline was deep throughout the area of study. Potential nursery habitat did not change interannually in location during La Niña conditions, but did increase the expected abundance in its southern extension. El Niño events contracted the nursery habitat near Cabo San Lucas, and caused the habitat to move northwards over both coasts of the Baja California peninsula. Despite seasonal and interannual climatic variability, two regions remained suitable habitats almost throughout the year. One was associated with coastal upwelling regions (Cabo Corrientes) and the second comprised the oceanic region of high mesoscale kinetic energy located south of Cabo San Lucas. We conclude that the potential nursery habitat of

La construcción del nuevo Centro Comercial El Ensueño en la localidad de Ciudad Bolívar, al sur de la ciudad de Bogotá, representa una oportunidad de negocio para la empresa Bodytech, que con el propósito de expansión de la marca en un sector que ha venido creciendo demográficamente. El proyecto presentado en este trabajo de grado abarca la formulación de la oportunidad de negocio, el estudio técnico, estudio financiero y el plan de gestión del proyecto desarrollando las áreas de conocimiento establecidas por la Guía del PMBOK (6 Ed.), The construction of the new El Ensueño Shopping Center in the town of Ciudad Bolívar, south of the city of Bogotá, represents a business opportunity for the Bodytech company, which with the purpose of expanding the brand in a sector that has been growing demographically. The project presented includes the formulation of the business opportunity, the technical study, the financial study, and the project management plan, developing the knowledge areas established by the PMBOK Guide (6 Ed.)

The changes in temperature and dissolved oxygen concentration in the Pacific Ocean in the northern region of the shallow oxygen minimum zone (OMZ) off Mexico were analyzed on the basis of the Word Ocean Database and a series of oceanographic cruises (LEGOZ-Mex). In order to test the changes in both parameters between two similar oceanographic scenarios according to the Pacific Decadal Oscillation (PDO), a comparison was made between the last two cool PDO phases of 1962–1974 and 2002–2012 when conditions might be expected to be relatively similar. Results show that the surface layer (upper layer of 50 m depth) has been warming significantly in two of the three areas included in this study: 1) the southern end of the California Current (0.8 °C; p < 0.001), 2) the southern Gulf of California (0.49 °C; p < 0.001), and 3) the Tropical Transitional Pacific (0.4 °C). Simultaneously, the water column has been deoxygenating significantly (p < 0.001), not only in the subsurface shallow OMZ layer (~ 100 to 300 m depth) in the Tropical Transitional area (− 45%), as has been recorded previously, but from 300 to 1000 m depth (by between −38% and - 57%). The exception was the California Current area at the northern limit of the shallow OMZ, where the deoxygenation was only significant (p < 0.001) from 300 to 1000 m depth (~ − 20%). We conclude that the significant warming of the surface layer in the Pacific OMZ off Mexico has increased the stratification of the water column and contributed to the deoxygenation of the interior ocean, at least between the last two cool phases of the PDO. These changes may be significantly affecting the marine biota that inhabit the shallow OMZs

In this study, we explored the changes in the vertical distribution and abundance of copepod nauplii and ichthyoplankton every hour in three different depth strata during a period of strong internal tides, which have been shown to accumulate and transport plankters. In the deeper stratum, the abundance of copepod nauplii was significantly greater, significantly increased during the cold phase of the internal tide, and was significantly correlated with both total and baroclinic current flows in the direction of internal tide propagation. On the other hand, ichthyoplankton abundance was generally low, with no stratification in vertical distribution, no significant changes across the two phases of the internal tide, and no correlation at any depth with any current flows. The cold phases of the internal tide were characterized by a shallow thermocline, a cooler water column, and a significant increase in the abundance of copepod nauplii in the bottom stratum. On the other hand, the warm phases of the internal tide were characterized by abrupt warming in surface waters, a depression of the thermocline, and a significant decrease of copepod nauplii in the bottom stratum. The depth distribution and buoyancy of the different groups of larvae may be responsible for the differences found.