Climate drivers that contribute to phytoplankton production along Chilean coasts

Abstract:

The Chilean coast is one of the most productive zones for fisheries. The base of this production is the phytoplankton that can be measured by satellite images (MODIS-a) that detect its Chl. The Chl concentration depends on specific parameters like precipitation, SST, or wind directions (UW, VW). These parameters are forced by cyclic climate drivers (e.g. ENSO, AAO, SPSA and PDO). Therefore, climate drivers affect Chl at different time and space scales. This work aims to determine which are the main climate drivers that could have an impact on climate variables, and consequently, Chl patterns.

The climate drivers indices data were obtained from NOAA. Linear regressions were used to determine how these influence each other and which had a significant role off Chile. To understand the climate drivers’ influence on the different parameters, composites were created using the years selected where the climate drivers were either strongly positive or negative. An extensive time period of the climatological parameters (provided by ECMWF) was used from 1979 until 2018.

The Chl is only available from 2003 until now. The Chl dataset from the long pre-MODIS period of 1979 to 2003 was reconstructed using Canonical Correlation Analysis. In this technique, another parameter is used to forecast the Chl. The variables tested were UW, VW and SST. Chl prediction had a better result using SST with a mean absolute error (MAE) of 0.69 standard units.

This analysis concludes that AAO and ENSO are the predominant climate drivers in Chile. The Chl’s impact during ENSO was significant, mostly in the southern zone, especially from November to December, while the AAO showed a Chl variation in the northern zone from December to May but mainly in the open ocean.