Hurricane Forcing of Phytoplankton Biomass in the Sargasso Sea

Phytoplankton is responsible for half of the world’s oxygen and plays an important role in carbon sequestration. Satellite ocean color sensors provide estimates of chlorophyll-a concentration [chl-a] from phytoplankton pigments. This study examines and quantifies the physical (ocean-atmosphere) variables that trigger an increase in [chl-a] signal due to the passage of hurricanes near the Sargasso Sea region over a 10-year period. Ocean color satellite products derived from Moderate Resolution Imaging Spectroradiometer (MODIS) and Sea Wide Field-of-view Sensor (SeaWiFS) were used to analyze changes in [chl-a] and sea surface temperatures (SST) along each storm track. Data from the Hurricane Research Division (HRD) were gathered to examine the path of 40 hurricanes that crossed the study region along with other physical parameters including: wind speed, hurricane size, barometric pressure, and transit speed in an attempt to correlate one or more of these variables with post [chl-a] increases. National Center for Atmospheric Research (NCAR) composites images of vector wind, sea level pressure, and precipitation rate were evaluated in order to get a better insight for the selected hurricane case studies. The study revealed that 78% of the storms (2000-2010) events exhibited a post increase in [chl-a] and 95% presented a decrease in SST. Generalized [chl-a] increases where better explained by determining the ratio between each storm average transit speed (negatively correlated with [chl-a] increases) to each average wind speed(positive correlation with [chl-a] increases).