A data fusion study on the impacts of the 2011 Japan tsunami on the marine environment of Sendai Bay

Abstract

Visible and thermal data retrieved by Moderate Resolution Imaging Spectroradiometer-Aqua (MODIS) were analysed using an image and data fusion approach to understand the marine environment changes associated with the 2011 Japan tsunami, with special emphasis on elucidating changes in the bio-optical and thermal variables. Two days after the tsunami, the MODIS visible sensor observed the increase in phytoplankton biomass (chlorophyll-a concentration [Chl-a]) 10 times (3.3 mg m−3) pre-tsunami Chl-a. The large increases in the MODIS Chl-a in the coastal and offshore waters were likely to be, respectively, more associated with high suspended sediment and gelbstoff/detritus loaded from the land by backwash. An intense phytoplankton growth due to horizontal and vertical nutrient fluxes could not be the only mechanism underlying the Chl-a increase, as sea surface temperature was relatively low and stable during the period of study. Hence, using a data fusion approach, we found the two different mechanisms underlying Chl-a enhancements after the Japan tsunami. The image and data fusion techniques can provide valuable preliminary information for further studies dealing with environmental changes due to the tsunami.