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Multi-disciplinary approach: |
This lecture includes the following topics:
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Multi-disciplinary approach: |
This lecture includes the following topics:
3. Spring bloom in Southern California Bight resulting from coastal upwelling
Multi-disciplinary approach implies that the simultaneous measurements of distribution of phytoplankton and physical environment enable the studies of physical factors, which determine the distribution of phytoplankton.
SeaWiFS surface chlorophyll and AVHRR Sea Surface
Temperature
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Phytoplankton, the main contributor to ocean color:
Passive tracer and active growing biomass
Phytoplankton is both a passive tracer transported by water circulation and an active biomass growing under favorable conditions (light, nutrients, etc.). It is important to distinguish between these two processes.
Horizontal circulation transports phytoplankton in horizontal direction, resulting in its redistribution.
Vertical stratification of water column regulates the growth of phytoplankton biomass.
So, the mesoscale variability of phytoplankton visible at satellite images
results from both passive transport and active growth.
2. Horizontal transport of phytoplankton and pollutants offshore in the Black Sea and Southern California Bight
The illustrative example of mesoscale variability of phytoplankton is the Black Sea located in southeastern Europe.
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The abyssal plain of depth more than 2000 m is separated
from the margins by steep continental slopes, excluding the shallow northwestern
part. The wide northwestern continental shelf (mean depth about 50 m)
occupies the region between the Crimean peninsula and the west coast. |
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A basin scale cyclonic boundary Rim Current
is the main feature of the Black Sea general circulation. The Rim
Current is <75 km wide and has an average speed of 20 cm s-1.
Along the coastal lines anticyclonic vorticity arises due to the Rim Current
meandering, resulting in anticyclonic eddies in coastal zones. |
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High-resolution AVHRR images enabled studies of the formation and evolution of the cyclonic and near-shore anticyclonic eddies along the coast and their influence on distribution of remote-sensed chlorophyll.
These AVHRR images illustrate the dynamics of the cyclonic eddies (C-1, C-2) and near-shore anticyclonic eddies (NAE-1, NAE-2, etc.) during the autumn 1997.
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The propagation of the near-shore anticyclonic eddies resulted
in change of the direction of currents over the continental slope. |
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Hydrographical observations support upwelling in the cyclonic
eddies and downwelling in the anticyclonic eddies. |
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Torrential rains in the beginning of October 1997 resulted in increased freshwater discharge and accumulation of phytoplankton and pollutants in the near-shore anticyclonic eddies. |
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The concentration of chlorophyll increased in the cyclonic
eddies and decreased in the anticyclonic eddies of the
open sea. Near-shore anticyclonic eddies accumulated
high concentrations of chlorophyll. |
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The process of transport of phytoplankton from productive shelf region to the open sea was observed during summer 1998 over the continental slope in the northwestern part of the Black Sea.
Anticyclonic eddies slowly moved southwestward along the continental slope.
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The largest anticyclone with diameter of 90 km displaced
during three months southwestward with mean speed of about 3 cm/s. |
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The eddies transported chlorophyll-reach coastal waters to the deep basin. |
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Circulation in the Southern California Bight
is cyclonic, resulting from the interaction between California
Current and Southern California Countercurrent. |
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Mesoscale eddies transport offshore the rainstorm plumes with high suspended
sediment and chlorophyll concentration.
3. Spring bloom in Southern California Bight resulting from coastal upwelling
Strong alongshore wind results in upwelling and phytoplankton bloom.
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