Simulation and future projection of the mixed layer depth and subduction process in the subtropical Southeast Pacific

2021 ◽  
Author(s):  
Ruibin Xia ◽  
Yijun He ◽  
Tingting Yang
Keyword(s):  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Layer Depth ◽  
Future Projection ◽  
Southeast Pacific

scholarly journals Environmental Gradients and Spatial Patterns of Calanoid Copepods in the Southeast Pacific

2020 ◽  
Vol 8 ◽  
Author(s):  
Carolina E. González ◽  
Johanna Medellín-Mora ◽  
Rubén Escribano
Keyword(s):  
Species Richness ◽  
Surface Temperature ◽  
Spatial Patterns ◽  
Mixed Layer ◽  
Coastal Upwelling ◽  
Mixed Layer Depth ◽  
Additive Models ◽  
Calanoid Copepods ◽  
Layer Depth ◽  
Southeast Pacific

Understanding the mechanisms maintaining the biodiversity of plankton communities in marine ecosystems subject to a strongly variable ocean has become a critical issue for modern oceanography. Here, we used data on distribution of calanoid copepods in the upper layer of the ocean (0–500 m), a widely distributed taxonomic group in the pelagic realm, to assess the effects of changing oceanographic conditions on their diversity patterns and family and species richness. Copepods abundance and occurrence were evaluated from 2002 to 2015 covering the region extended between the coastal upwelling zone (CUP-Z) and the offshore region of Chile at subtropical and temperate areas. We used spatial analyses of community structure descriptors, such as abundance and diversity (family and species richness), multivariate analysis and General Additive Models (GAMS) in order to study the effect of surface temperature and its gradients, mixed layer depth, salinity and Chlorophyll-a on copepod diversity. Seventeen families were identified comprising 151 species distributed in 3 predefined zones in the onshore-offshore gradient covering the coastal upwelling, the coastal transition and the oligotrophic zones, whereas over the alongshore gradient, same families were majorly linked to the northern and southern portions of the sampled area (20–40°S). Families and species were significantly structured over the zonal gradient, revealing the dominant habitat for each of the families. Spatial patterns revealed the presence of transitional zones comprised by mixed taxa. Over the alongshore gradient this transition zone was linked to the subtropical convergence (30°S). The spatial variation of sea surface temperature (SST) revealed strong environmental zonation of temperature gradients across onshore-offshore and alongshore dimensions. Mean SST combined with mean mixed layer depth explained about 40% and about 29% of variation in family and species richness, respectively over the onshore-offshore axis. We thus conclude that the environmental zonation imposed by SST and its spatial gradients, considered as ecological barriers, is the key driver for maintaining diversity of copepods in the southeast Pacific.

scholarly journals Seasonal-to-Interannual Response of Southern Ocean Mixed Layer Depth to the Southern Annular Mode from a Global 1/10° Ocean Model

2019 ◽  
Vol 32 (18) ◽  
pp. 6177-6195 ◽  
Author(s):  
Qian Li ◽  
Sukyoung Lee ◽  
Matthew H. England ◽  
Julie L. McClean
Keyword(s):  
Southern Ocean ◽  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Southern Annular Mode ◽  
Ocean Model ◽  
Ocean Mixed Layer ◽  
Layer Depth ◽  
Southeast Pacific ◽  
Mixed Layers ◽  
Ocean Mixed Layer Depth

Abstract The relationship between the southern annular mode (SAM) and Southern Ocean mixed layer depth (MLD) is investigated using a global 0.1° resolution ocean model. The SAM index is defined as the principal component time series of the leading empirical orthogonal function of extratropical sea level pressure from September to December, when the zonally symmetric SAM feature is most prominent. Following positive phases of the SAM, anomalous deep mixed layers occur in the subsequent fall season, starting in May, particularly in the southeast Pacific. Composite analyses reveal that for positive SAM phases enhanced surface cooling caused by anomalously strong westerlies weakens the stratification of the water column, leading to deeper mixed layers during spring when the SAM signal is at its strongest. During the subsequent summer, the surface warms and the mixed layer shoals. However, beneath the warm surface layer, anomalously weak stratification persists throughout the summer and into fall. When the surface cools again during fall, the mixed layer readily deepens due to this weak interior stratification, a legacy from the previous springtime conditions. Therefore, the spring SAM–fall MLD relationship is interpreted here as a manifestation of reemergence of interior water mass anomalies. The opposite occurs after negative phases of the SAM, with anomalously shallow mixed layers resulting. Additional analyses reveal that for the MLD region in the southeast Pacific, the effects of salinity variations and Ekman heat advection are negligible, although Ekman heat transport may play an important role in other regions where mode water is formed, such as south of Australia and in the Indian Ocean.

Interannual variability of the Tropical Indian Ocean mixed layer depth

2012 ◽  
Vol 40 (3-4) ◽  
pp. 743-759 ◽  
Author(s):  
M. G. Keerthi ◽  
M. Lengaigne ◽  
J. Vialard ◽  
C. de Boyer Montégut ◽  
P. M. Muraleedharan
Keyword(s):  
Indian Ocean ◽  
Interannual Variability ◽  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Tropical Indian Ocean ◽  
Ocean Mixed Layer ◽  
Layer Depth ◽  
Ocean Mixed Layer Depth

scholarly journals Summertime increases in upper-ocean stratification and mixed-layer depth

Nature ◽  
2021 ◽  
Vol 591 (7851) ◽  
pp. 592-598
Author(s):  
Jean-Baptiste Sallée ◽  
Violaine Pellichero ◽  
Camille Akhoudas ◽  
Etienne Pauthenet ◽  
Lucie Vignes ◽  
...  
Keyword(s):  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Upper Ocean ◽  
Layer Depth ◽  
Ocean Stratification

scholarly journals Global sensitivity analysis of the Indian monsoon during the Pleistocene

2015 ◽  
Vol 11 (1) ◽  
pp. 45-61 ◽  
Author(s):  
P. A. Araya-Melo ◽  
M. Crucifix ◽  
N. Bounceur
Keyword(s):  
Sensitivity Analysis ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Mixed Layer ◽  
Global Sensitivity Analysis ◽  
Indian Monsoon ◽  
Mixed Layer Depth ◽  
Sea Surface ◽  
Layer Depth ◽  
Global Sensitivity

Abstract. The sensitivity of the Indian monsoon to the full spectrum of climatic conditions experienced during the Pleistocene is estimated using the climate model HadCM3. The methodology follows a global sensitivity analysis based on the emulator approach of Oakley and O'Hagan (2004) implemented following a three-step strategy: (1) development of an experiment plan, designed to efficiently sample a five-dimensional input space spanning Pleistocene astronomical configurations (three parameters), CO2 concentration and a Northern Hemisphere glaciation index; (2) development, calibration and validation of an emulator of HadCM3 in order to estimate the response of the Indian monsoon over the full input space spanned by the experiment design; and (3) estimation and interpreting of sensitivity diagnostics, including sensitivity measures, in order to synthesise the relative importance of input factors on monsoon dynamics, estimate the phase of the monsoon intensity response with respect to that of insolation, and detect potential non-linear phenomena. By focusing on surface temperature, precipitation, mixed-layer depth and sea-surface temperature over the monsoon region during the summer season (June-July-August-September), we show that precession controls the response of four variables: continental temperature in phase with June to July insolation, high glaciation favouring a late-phase response, sea-surface temperature in phase with May insolation, continental precipitation in phase with July insolation, and mixed-layer depth in antiphase with the latter. CO2 variations control temperature variance with an amplitude similar to that of precession. The effect of glaciation is dominated by the albedo forcing, and its effect on precipitation competes with that of precession. Obliquity is a secondary effect, negligible on most variables except sea-surface temperature. It is also shown that orography forcing reduces the glacial cooling, and even has a positive effect on precipitation. As regards the general methodology, it is shown that the emulator provides a powerful approach, not only to express model sensitivity but also to estimate internal variability and detect anomalous simulations.

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