Evaluation on 2002-2021 CHL-A Concentrations in the Sea of Marmara with GEE Enhancement of Satellite Data

Abstract

Remote sensing data, especially satellite observations make available large databases related to marine biosphere. This tremendous amount of the data causes a difficulty to acquisition, processing and evaluation processes. Google Earth Engine (GEE) platform make possible to overcome this difficulty by its state of art structure. Thus, GEE platform was included to study to process and evaluate the chlorophyll-a data for the sea of Marmara. The Sea of Marmara was considered in 2 main parts as North and South Marmara. These parts also divided into 6 sub-regions and analyzed as 12 different regions in total. MODIS (Moderate Resolution Imaging Spectroradiometer)-Aqua data were acquired between the years 2003-2021 with the GEE platform for all examined sub-regions and make them available for analysis. Approximately 19 years of arranged chl-a concentration data were visualized and evaluated by grouping them according to sub-regions, months and years. As expected, the highest concentration of chl-a was observed in the Sea of Marmara in square KM6, which includes the Gulf of Izmit and has limited regeneration The lowest concentration values throughout the years were found in the areal average values of the KM4 square under the influence of the jet stream formed by the upper water from the Black Sea. When the monthly data are examined, it can be said that the primary production in general takes place intensively in the whole of the Marmara Sea in the spring season. In the context of this study, the accuracy of the division of the Sea of Marmara in two main axes as North and South is clearly seen in the analyzes within the time series. We evaluate that the similarity of chl-a concentrations in the Marmara Sea to the period before 2007 and 2020 requires a special attention as evidence of a repetitive process rather than an ecological coincidence.