Applied and Computational Mathematics Seminar

Seminar Details

Speaker:
Alejandro Orfila
Affiliation:
Spanish National Research Council and the University of the Balearic Islands
Time:
2PM Thursday, 4 April 2019
Location:
H2.32, O'Brien Centre for Science (Hub)

Effect of small scale transport processes on phytoplankton distribution in coastal seas

Coastal ocean ecosystems are major contributors to the global biogeochemical cycles and biological productivity. Physical factors induced by the turbulent flow play a crucial role in regulating marine ecosystems. However, while large-scale open-ocean dynamics is well described by geostrophy, the role of multiscale transport processes in coastal regions is still poorly understood due to the lack of continuous high-resolution observations. Here, the influence of small-scale dynamics (O(3.5–25) km, i.e. spanning upper submesoscale and mesoscale processes) on surface phytoplankton derived from satellite chlorophyll-a (Chl-a) is studied using Lagrangian metrics computed from High-Frequency Radar currents. The combination of complementary Lagrangian diagnostics, including the Lagrangian divergence along fluid trajectories, provides an improved description of the 3D flow geometry which facilitates the interpretation of two non-exclusive physical mechanisms affecting phytoplankton dynamics and patchiness.

Extreme waves and climatic patterns of variability in North Atlantic Ocean and Mediterranean Sea

The spatial and temporal variability of extreme wave climate in the North Atlantic Ocean and the Mediterranean Sea is assessed using 3-hour output of wave model during a period of 31 years (1979-2009). The seasonality accounts for a 50% of the extreme wave height in the North Atlantic Ocean and for a 85\% in the Mediterranean Sea. Once removed the seasonality, the North Atlantic Oscillation and the Scandinavian Index mainly control the interannual variability of extreme waves during winters. To a lesser extent, the East Atlantic Oscillation also modulates extreme waves in some areas. In the Mediterranean Sea, the dominant modes regarding extreme waves, correspond to the East Atlantic and East Atlantic/Western Russia modes both in their negative phases.

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