하계 북동 멕시코만에서 다중채널 원격탐사 자료를 이용하여 외해의 저염분수 추적 연구

Abstract

To trace offshore surface low-salinity water (LSW) in the northeastern Gulf of Mexico, a proxy was developed using a surface beam attenuation coefficient (cp), and salinity and bottle-sampled particulate matter (PM) and particulate organic carbon (POC) from three annual summer cruises from July 1998 to August 2000. The proxy was then matched with synchronous SeaWiFS remote sensing data. As expected, spatial patterns of salinity show that LSW (salinity <33) with high cp is connected to the mouth of the Mississippi River Delta and extends to the east-southeast. Saline water (salinity >33) with lower cp is confined to the shelf and upper slope in the eastern part of the study area. To vastly improve the limited spatial and temporal resolution of surface salinity distribution obtained by shipboard sampling, a two-step empirical approach was used to enable satellite remote sensing. First, the relationship between in situ salinity and cp was regressed (R2=0.83, N=210). Second, in situ cp was matched with SeaWiFS multi-spectral radiance using the radiance ratio of all available blue-to-green wavelengths, and an empirical correlation was calculated (R2=0.94, N=29). Finally, satellite-derived surface salinity was directly determined by combining the two empirical relationships, providing a robust estimate over a wide range of salinities. The empirical relationships were used to map satellit