Impact of fronts on phytoplankton from satellite imagery

Gulf Stream meanders from space (MODIS data). Chlorophyll-a (top) and SST (bottom).

I am aiming at quantifying the effects of sub-mesoscale dynamics (~0.1-10km) on phytoplankton productivity and biodiversity. To that end I use satellite Sea Surface Temperature (SST) to detect fronts, in which I quantify the amount of Chlorophyll-a, also obtained from satellite. I am conducting this study in the North Atlantic, around the Gulf Stream.

So far I have been able to quantify an increase of Chlorophyll in fronts, related to the local upwelling of nutrients. The Chlorophyll increase is more intense for stronger fronts than weak fronts, however because they are much more scarce the overall effect on the Chlorophyll budget is less important for strong fronts.

I have also been able to detect a spring bloom onset that is a few days earlier in fronts than in the background. This can be explained by the restratification effect of sub-mesoscale fronts. The bloom is also longer in fronts by a few days.

We are planning to extend this study to the phytoplankton composition, and to other study regions.

You can find all the code used for this study here: Gitlab (IN2P3).

Other projects

Below are some tools I developped that you may find useful.


  This package allows to find files from their filename structure. Useful when dealing with databases composed from many files with varying dates or parameters. The structure of filenames is indicated with a simple but powerful syntax. Parts of the filenames varying from file to file can be indicated with format strings or regular expressions, or with pre-defined defaults (mainly for dates).


 This package allows to compute histograms from XArray data, taking advantage of its label and dimensions management. It relies on the Boost Histogram library for the computations, giving more features and better performances than numpy functions !


  A package which supplies color schemes for lines and maps, all color-blind safe. They were designed by Paul Tol, I merely made it available on PyPi to make it easier to install and use.


 A simple bash command to create lists of dates. Useful for operations on sets of dates.