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SUMMARY:How unsteady winds can fuel phytoplankton blooms at fronts in the 
 upper ocean - Dr. Dan Whitt\, University of Cambridge
DTSTART:20160608T130000Z
DTEND:20160608T140000Z
UID:TALK62026@talks.cam.ac.uk
CONTACT:Dr Dave Munday
DESCRIPTION:Observations and models suggest that upper-ocean density front
 s sometimes exhibit higher chlorophyll\, more biomass and/or different pla
 nkton community composition at and/or below the surface in a narrow region
  localized to the front. However\, the dynamics that lead to biogeochemica
 l anomalies at fronts are not fully understood.\n\nIn this talk\, I will b
 riefly review observations of anomalous biogeochemistry at fronts in the u
 pper ocean. Then\, I will present some results from an ongoing numerical p
 rocess study of how the unsteady part of the wind stress frequency spectru
 m can sustain higher upward nutrient fluxes and plankton biomass at geostr
 ophic fronts. In particular\, I will use experiments with a wind-forced pr
 imitive-equation model of an idealized geostrophic front coupled to a four
 -component ecosystem model to illustrate a synergistic interaction between
  stronger low frequency (sub-inertial) and weaker high frequency (near-ine
 rtial) parts of the wind stress. In this scenario\, the addition of a weak
  high-frequency stress to a strong low-frequency stress leads to a qualita
 tive change from deep biomass maximum to surface bloom and a large increas
 e in the depth-integrated biomass at the front. I will discuss the physics
  that lead to this biogeochemical sensitivity and the potential implicatio
 ns for other ocean biogeochemical models with different levels of the high
 -frequency wind stress variance and/or mesoscale-submesoscale geostrophic 
 kinetic energy.\n
LOCATION:British Antarctic Survey\, Room 330B
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