How has sea level changed over time How has sea level changed over time? Do Now: Name some of the cases of climate change go over workbook from Friday HW: rainfall worksheet due Wednesday

Data Collection and Analysis Oceanography is the scientific study of Earth’s oceans. Technologies such as sonar, floats, satellites, submersibles, and computers have become central to the continuing exploration of the ocean. Copyright © McGraw-Hill Education An Overview of Oceans

Data Collection and Analysis At the surface Sonar, which stands for sound navigation and ranging, is used by oceanographers to learn more about the topography of the ocean floor. Large portions of the seafloor have been mapped using side-scan sonar, a technique that directs sound waves at an angle to the seafloor, so that the sides of underwater hills and other topographic features can be mapped. An Overview of Oceans Copyright © McGraw-Hill Education

Origin of the Oceans Where did the water come from? Scientists hypothesize that Earth’s water originated from either a remote source or a local source, or both. Comets and meteorites are two remote sources that could have contributed to the accumulation of water on Earth. If early Earth contained the same percentage of water as meteorites, 0.5 percent, it would have been sufficient to form early oceans. An Overview of Oceans Copyright © McGraw-Hill Education

Origin of the Oceans Volcanism An episode of volcanism released large quantities of water vapor and other gases into the atmosphere. The water vapor eventually condensed into oceans. An Overview of Oceans Copyright © McGraw-Hill Education

Distribution of Earth’s Water The oceans contain 97 percent of the water found on Earth. Another 3 percent is freshwater located in the frozen ice caps of Greenland and Antarctica and in rivers, lakes, and underground sources. An Overview of Oceans Copyright © McGraw-Hill Education

Distribution of Earth’s Water The blue planet The northern hemisphere is covered by slightly more water than land. The southern hemisphere, however, is almost completely covered by water. An Overview of Oceans Copyright © McGraw-Hill Education

Distribution of Earth’s Water Sea level Global sea level, which is the level of the oceans’ surfaces, has risen and fallen by hundreds of meters in response to melting ice during warm periods and expanding glaciers during ice ages. Sea level is also affected by tectonic forces that lift or lower portions of Earth’s crust. An Overview of Oceans Copyright © McGraw-Hill Education

Distribution of Earth’s Water Ocean and atmospheric interaction Oceans provide moisture and heat to the atmosphere and influence large-scale circulation patterns. Oceans are also a vast reservoir of carbon dioxide. An Overview of Oceans Copyright © McGraw-Hill Education

Chemical Properties of Seawater Salinity The measure of the amount of dissolved salts in seawater is salinity. Oceanographers express salinity as grams of salt per kilogram of water, or parts per thousand (ppt). Seawater Copyright © McGraw-Hill Education

Chemical Properties of Seawater Variations in salinity The lowest salinity often occurs where large rivers empty into the oceans, creating areas of water called estuaries. Even though salinity varies, the relative proportion of major types of sea salts is constant because all ocean water continually intermingles throughout Earth’s oceans. Seawater Copyright © McGraw-Hill Education

Chemical Properties of Seawater Removal of sea salt In arid coastal regions, water evaporates from seawater and leaves solid salt behind. Winds can pick up salty droplets from breaking waves and deposit the salt further inland. Seawater Copyright © McGraw-Hill Education

Physical Properties of Seawater Density Seawater is more dense than freshwater, and its density increases with salinity. Temperature also affects density—cold water is more dense than warm water. Because of salinity and temperature variations, the density of seawater ranges from about 1.02 g/cm3 to 1.03 g/cm3. Freezing point Variations in salinity also cause the freezing point of seawater (–2°C) to be somewhat lower than that of freshwater (0°C). Seawater Copyright © McGraw-Hill Education

Physical Properties of Seawater Absorption of light Water absorbs light, which gives rise to another physical property of oceans—darkness. In general, light penetrates only the upper 100 m of seawater. Seawater Copyright © McGraw-Hill Education

Ocean Layering Temperature profiles This figure shows typical ocean temperature profiles, which plot changing water temperatures against depth. Such profiles vary, depending on location and season. Seawater Copyright © McGraw-Hill Education

It is characterized by temperatures that decrease rapidly with depth. Ocean Layering Temperature profiles The thermocline is the transitional ocean layer that lies between the relatively warm, sunlit surface layer and the colder, dark, dense bottom layer. It is characterized by temperatures that decrease rapidly with depth. Seawater Copyright © McGraw-Hill Education

Water Masses Deepwater masses Dense polar water sinks, producing a deepwater mass. Seawater Copyright © McGraw-Hill Education

Water Masses Intermediate water masses Antarctic Intermediate Water is warmer and less dense, and thus it overrides the other two deepwater masses. Seawater Copyright © McGraw-Hill Education