The effects of temporal variability of mixed layer depth on primary productivity around Bermuda

Ocean primary production is an important factor for determining the ocean's role in global carbon cycle. In recent years, much more chlorophyll-a concentration data in the euphotic layer were derived from the satellite ocean color sensors. The primary productivity algorithms have been proposed based on satellite chlorophyll measurements (Piatt, 1988; Morel, 1991) and other environmental parameters such as sea surface temperature or mixed layer depth (Behrenfeld and Falkowski, 1997; Esaias, 1996; Asanuma, 2002). In order to estimate integrated primary productivity in the whole water column, the vertical distribution of chlorophyll concentration below the sea surface should be reconstructed based on satellite data. In this paper, the vertical profile data of chlorophyll-a (Chl-a) measured around Japan Islands from 1974 to 1994 were reanalyzed based on the shifted-Gaussian shape proposed by Piatt et al (1988). Using this statistical model (neural network) and the photosynthesis irradiance parameters from Asanuma (2002), the distribution of primary productivity and its seasonal variation around Japan islands were estimated from SeaWiFS data, and the results were compared with in situ data and the other two models estimated from VGPM and mixed layer depth model. Keywords: ocean color, primary productivity, chlorophyll profile, artificial neural network

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Satellite Observed Spatial And Temporal Variability Of The Mixed Layer Depth In The Sargasso Sea

10.1109/igarss.1989.567247 ◽

2005 ◽

Author(s):

Xiao-Hai Yan ◽

M.J. Bowman ◽

J.R. Schubel

Keyword(s):

Mixed Layer ◽

Temporal Variability ◽

Mixed Layer Depth ◽

Spatial And Temporal Variability ◽

Sargasso Sea ◽

Layer Depth

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Temporal variability of chlorophyll distribution in the Gulf of Mexico: bio-optical data from profiling floats

Biogeosciences ◽

10.5194/bg-14-5647-2017 ◽

2017 ◽

Vol 14 (24) ◽

pp. 5647-5662 ◽

Cited By ~ 7

Author(s):

Orens Pasqueron de Fommervault ◽

Paula Perez-Brunius ◽

Pierre Damien ◽

Victor F. Camacho-Ibar ◽

Julio Sheinbaum

Keyword(s):

Gulf Of Mexico ◽

Mixed Layer ◽

Temporal Variability ◽

Mixed Layer Depth ◽

Chlorophyll Concentration ◽

Optical Data ◽

Layer Depth ◽

Basin Scale ◽

In Situ Experiments ◽

Surface Increase

Abstract. Chlorophyll concentration is a key oceanic biogeochemical variable. In the Gulf of Mexico (GOM), its distribution, which is mainly obtained from satellite surface observations and scarce in situ experiments, is still poorly understood. In 2011–2012, eight profiling floats equipped with biogeochemical sensors were deployed for the first time in the GOM and generated an unprecedented dataset that significantly increased the number of chlorophyll vertical distribution measurements in the region. The analysis of these data, once calibrated, permits us to reconsider the spatial and temporal variability of the chlorophyll concentration in the water column. At a seasonal scale, results confirm the surface signal seen by satellites, presenting maximum concentrations in winter and low values in summer. It is shown that the deepening of the mixed layer is the primary factor triggering the chlorophyll surface increase in winter. In the GOM, a possible interpretation is that this surface increase corresponds to a biomass increase. However, the present dataset suggests that the basin-scale climatological surface increase in chlorophyll content results from a vertical redistribution of subsurface chlorophyll and/or photoacclimation processes, rather than a net increase of biomass. One plausible explanation for this is the decoupling between the mixed-layer depth and the deep nutrient reservoir since mixed-layer depth only reaches the nitracline in sporadic events in the observations. Float measurements also provide evidence that the depth and the magnitude of the deep chlorophyll maximum is strongly controlled by the mesoscale variability, with higher chlorophyll biomass generally observed in cyclones rather than anticyclones.

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Spatial And Temporal Variability Of Mixed-Layer Depth And Entrainment Zone Thickness

Boundary-Layer Meteorology ◽

10.1023/a:1002790424133 ◽

2000 ◽

Vol 97 (1) ◽

pp. 47-71 ◽

Cited By ~ 65

Author(s):

P. Hägeli ◽

D. G. Steyn ◽

K. B. Strawbridge

Keyword(s):

Mixed Layer ◽

Temporal Variability ◽

Mixed Layer Depth ◽

Spatial And Temporal Variability ◽

Layer Depth ◽

Entrainment Zone

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Temporal variability of chlorophyll distribution in the Gulf of Mexico: bio-optical data from profiling floats

10.5194/bg-2017-201 ◽

2017 ◽

Cited By ~ 1

Author(s):

Orens Pasqueron de Fommervault ◽

Paula Perez-Brunius ◽

Pierre Damien ◽

Julio Sheinbaum

Keyword(s):

Gulf Of Mexico ◽

Mixed Layer ◽

Temporal Variability ◽

Mixed Layer Depth ◽

Chlorophyll Concentration ◽

Optical Data ◽

Spatial And Temporal Variability ◽

Layer Depth ◽

In Situ Experiments ◽

Surface Increase

Abstract. Chlorophyll concentration is a key oceanic biogeochemical variable. In the Gulf of Mexico (GOM), its distribution, which is mainly obtained from satellite surface observations and scarce in situ experiments, is still poorly understood. In 2011–2012, eight profiling floats equipped with biogeochemical sensors were deployed for the first time in the GOM and generated an unprecedented dataset that significantly increased the number of chlorophyll vertical distribution measurements in the region. The analysis of these data, once calibrated, permits us to reconsider the spatial and temporal variability of the chlorophyll concentration in the water column. At a seasonal scale, results confirm the surface signal seen by satellites, presenting maximum concentrations in winter and low values in summer. It is shown that the deepening of the mixed layer depth is the primary factor triggering the chlorophyll surface increase in winter. In the GOM, current belief is that this surface increase corresponds to a biomass increase. However, the present dataset reveals a vertically integrated content of chlorophyll which remains constant throughout the year, suggesting that the surface increase results from a vertical redistribution of subsurface chlorophyll or photoacclimation processes, rather than a net increase of primary productivity. One plausible explanation for this is the decoupling between the mixed layer depth and the deep nutrient reservoir since mixed layer depth only reaches the nitracline in sporadic events in the observations. Float measurements also provide evidence that the depth and the magnitude of the deep chlorophyll maximum is strongly controlled by the mesoscale variability, with higher chlorophyll biomass generally observed in cyclones rather than anticyclones.

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