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Seasonal cycle of surface chlorophyll in the North Pacific and Atlantic subtropical gyres

In RESEARCH/PROJECTS/MARINE_BIOLOGY/SUBMESOSCALE_PROCESSES/OFES, prepare av_surf_CHL_OFES_obs.m to compute annual and seasonal mean surface chlorophyll for one year and over the North Pacific and North Atlantic subtropical gyres. It also computes annual and seasonal mean surface zonal geostrophic flow and geostrophic eddy kinetic energy. It needs more years (at least 3 as in Oschlies 2002b) as the averages for chlorophyll are noisy, especially in the Atlantic. It needs also to add the observational component (MODIS and SSH). Conclusions so far using 2004 alone:
  • more Chl in Atlantic than Pacific
  • strange maximum of Chl in the western Atlantic
  • tongue of Chl maximum extending westward and northward from the eastern tropical Pacific, especially in Fall. This tongue seems to be related to the 10N thermocline and nutricline ridge (Pennington et al. 2006; see also Fiedler and Talley 2006) with Ekman upwelling enhanced in Fall (Pennington et al. 2006; their Fig. 9). The tongue is also seen in the satellite data (Pennington et al. 2006).

Figure 1: Seasonal surface chlorophyll in OFES during 2004.

  • Not clear how to compute primary production: Is it the term J in equation (10) of Oschlies and Garcon (1999)? To compute this, I need nitrogen as well as the short-wave radiation used in the model. The ratio C:N=6.6 is then used to convert the primary production from moles of nitrogen into moles of carbon.