Marine Oil Pollution in an Area of High Economic Use: Statistical Analyses of SAR Data from the Western Java Sea

Veronika Mohr,Martin Gade

doi:10.3390/rs14040880

Abstract

In this paper, we analyze more than 2000 Synthetic Aperture Radar (SAR) images of the Western Java Sea acquired by Sentinel-1 SAR-C and ENVISAT ASAR, with the aim to generate oil pollution statistics for a sea region of high economic use. The spatial distributions show that most oil pollution occurs along the major shipping routes and at oil production sites in that area. The majority of the spills have sizes of less than 1 km2 and an axial ratio smaller than 10. For two sets of SAR images, we compared the results obtained by different operators, who analyzed the same images. While more than 50% of the spills were not found by both operators, the overall spatial patterns derived from their results are the same. Our results indicate that the observed differences are mainly due to lookalikes, which can easily be confused with oil spills, but also due to small oil spills that were overseen by one of the operators. These assumptions are supported by the fact that the percentage of spills jointly found by both operators increased when only oil spills were considered that were found on SAR images acquired at higher mean wind speeds.

Highlights

Pollution by oil spills affects the marine environment, and to sensitive environments such as Marine Protected Areas (MPA) it poses a major threat
Two major oil production sites are located in the area, off the coasts of western Java and southern Sumatra, and some major shipping routes lead through the Java Sea, connecting the economic centers in China and Japan with Europe, Africa, Australia, and the Persian Gulf
By raising the lower wind speed limit from 2 m/s to 5 m/s, we reduced the risk that biogenic surface films were mistaken for oil spills, because the latter are more likely to be disrupted at higher wind speeds than oil spills [30,37]

Summary

Introduction

Pollution by oil spills affects the marine environment, and to sensitive environments such as Marine Protected Areas (MPA) it poses a major threat. Oil pollution affects coastal communities, due to impacts on health, fishing industries and tourism [1]. While oil pollution caused by major accidents on platforms or ships is more often reported on by public media, smaller spills resulting from operating platforms or ships are very common, and because of their frequent occurrence, they introduce more oil into the marine ecosystem [2]. Among the multiple sources of operational oil pollution are routine operations on ships and vessels, primarily the release of waste, bilge water or ballast water used in tankers. Oil is frequently released into the environment during service operations. Though international regulations for the discharge of oil from ships and platforms exist, they do not prohibit oil discharge completely, if certain conditions are met

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Results

Discussion

Conclusion