General Characteristics of the World's Oceans

By Seema Gupta
Scientist advisor: William Russell

This paper was written as a reference to provide scientific background to aid the Oceans team in their research.

Introduction

The bathymetry of the ocean is like the topography of land. It is ocean depth with respect to sea level. The image below shows how the ocean bottom, just like land, is not flat. The deepest ocean areas are indicated by pink while shallower areas are shown by light blue.

World Topography/Bathymetry. Image: Xingjian Jiang

According to a widely accepted theory, less than five billion years ago there were many volcanic eruptions which released carbon dioxide and water vapor. As the Earth started to cool off, the water vapor condensed and accumulated to form the world's first oceans. This formation of oceans further helped in the Earth's cooling due to the high heat capacity and latent heat of vaporization of water. However, recent theories suggest that large comets made of ice frequently bombarded the earth's atmosphere and vaporized above the earth's surface. It is believed that such comet-like "rain" could have supplied all of the earth's water, or at least its inital water mass, as well as many of the basic compounds necessary for the origin of life. Such compounds include methanol, formaldehyde, carbon monoxide, hydroden cyanide, hydrogen sulfide, and other molecules rich in carbon. Perhaps the primary water provided by these comets allowed for "recycling". Recycling occurs when the water bearing oceanic crustal plate collides with the continental crustal plate, causing the oceanic plate to be pushed down into the interior of the earth where it is melted and lifted back up by volcanic eruptions. It is due to water that life on our planet is possible.

The reason why studying the oceans is so important is that 70.8% of the world's surface consists of oceans: 96.5% of which is water. Water plays a significant role in the climate of our planet. This is because of its many unique properties (described later), and its capabilities in transporting energy. Because temperature and salinity are the driving forces of currents, we must better comprehend them to understand heat transfer. Since heat transfer is one of the major controls of climate, its understanding is vital in studying climate change. A Conductivity-Temperature-Depth (CTD) device is utilized for measuring the temperature and salinity of the ocean at different depths. The photo on the left shows the rosette of the device. A rosette collects water at the depth specified by the oceanographer. The data collected by this device is used to compare ocean composition at different longitudes and latitudes. Several rosettes are mounted on a scaffolding frame and are lowered into the ocean by a strong metal cable that can be as long as 15,000 feet.

on to Ocean Temperature >>

Seema Gupta was a student at the Bronx High School of Science at the time this paper was written. Her scientist advisors at GISS were Ron Miller, William Russell, and Xingjian Jiang, and her faculty mentor was Mitch Fox. (July 1997).