Physical dynamics and biological implications of a mesoscale eddy in the lee of Hawai’i: Cyclone Opal observations during E-Flux III

Sensitivity study of the generation of mesoscale eddies in a numerical model of Hawaii islands

“…In this way we can both (i) estimate the position of the eddy center, as the location where the components of the horizontal velocity are very small and (ii) calculate the eddy radius, as the maximum distance until which, starting at the center, the intensity of the barotropic velocity increases linearly (corresponding to the solid body rotation, e.g. Nencioli et al, 2008). This latter distance allows us to also check the previous evaluation of the eddy extent.…”

“…11. We have chosen this depth for a comparison with in situ measurements performed by Nencioli et al (2008) inside the cyclone Opal.…”

Mesoscale physical–biological–biogeochemical linkages in the open ocean: An introduction to the results of the E-Flux and EDDIES programs

“…It is likely due to a combination of variations in the magnitude, timing, and duration of nutrient input caused by differences in eddy formation, intensity, age, and movement as shown in this volume and previously (Bibby et al, 2008;Brown et al, 2008;McGillicuddy et al, 1999;Nencioli et al, 2008;Olaizola et al, 1993;Sweeney et al, 2003). For example, Hawaiian lee cyclones (and anticyclones) appear to be wind-driven, formed by a combination of strong northeasterly winds and island topography (Chavanne et al, 2002;Lumpkin, 1998;Patzert, 1969), whereas midocean eddies in the Sargasso Sea are formed by instability processes that feed on the larger scale flow (Robinson, 1983).…”

“…Cyclone Opal was characterized by very large isopycnal displacements of over 100 m at the eddy core relative to surrounding waters (Table 1) and was less than 6 weeks in age Nencioli et al, 2008). The only other Hawaiian cyclone studied to date to have similarly large displacements in isopycnal surfaces was Cyclone Haulani, a month older (Table 1, and see Figure 2, Vaillancourt et al, 2003), yet no increase in diatom biomass was observed.…”

“…Cyclone Noah, a 2.5-month-old mature feature when sampled, was characterized by relatively modest perturbations in chlorophyll and phytoplankton composition with respect to ambient conditions Rii et al, 2008). In contrast, younger and stronger Cyclone Opal contained a substantial diatom bloom that decayed during the nine days over which it was sampled (Brown et al, 2008;Landry et al, 2008b;Nencioli et al, 2008;Rii et al, 2008). Within the deep chlorophyll maximum (DCM) at Opal's center, photosynthetically active (high F v /F m ) diatoms, such as the chain-forming Chaetoceros spp.…”