Characterizing the surface layers of Arabian Sea using Argo profiling float data

Abstract

The upper ocean is the most variable and dynamically active part of the marine environment that couples the underlying ocean to the atmosphere above through the transfer of mass, momentum and energy. The oceanic surface layer assumes many shapes and forms. More common among others are, inversion layers, mixed layers, sonic layers, and barrier layers. The thickness of mixed layer is an important parameter in determining the quantity of heat that is available for exchange with atmosphere which is capable of triggering several ocean-atmosphere coupled processes. Mixed layer also plays an important role in determining the chlorophyll biomass and biological productivity of the upper ocean. Also ocean being almost opaque to electromagnetic radiation, sound is the only means to probe the ocean interior. Further, acoustic system plays a very important role in many civilian and military strategic applications. The depth of sonic layer plays an important role in refraction of sound rays traveling in the ocean, which in turn affects the sonar detection ranges. The present work is an attempt to study basin-scale variability of the mixed layer and sonic layer in the Arabian Sea, their inter relationship and factors responsible for it. In literature though sonic layer is considered almost equal to mixed layer, in this thesis a study is made, to understand how tightly these two are coupled during different seasons. After the introduction in Chapter 1 of the thesis, various data set and methodologies used for the work in this thesis is presented in Chapter 2. Data for the proposed work mainly comprises of in situ temperature and salinity profile data from the Argo floats acquired during the period 2002 2008. From the above source 15585 profiles of temperature and salinity were extracted. All the profiles were quality controlled by passing them through 18 quality control checks as per the guide lines implemented by the International Argo Data Management Team.