Ocean Science is the study of the physical, chemical, and biological properties of the ocean. The ocean and its organisms play a critical role in elemental cycling processes—such as those of carbon (C) and oxygen (O)—acting as both a sink and source for greenhouse gases. Examining distribution and trends of these gases, as well as using proxy methods (e.g. isotopic signatures), can illuminate past and present climate and guide understanding of oceanic and atmospheric processes. Sampling methods include ship or air-based methods, SCUBA diving, remotely or autonomously operated underwater vehicles, and satellite observations.