Most people don't realize that the ocean's surface is not flat, and that sea level changes at different rates across the globe. Sea level responds to a variety of conditions, from chemistry to temperature to changes in the shape of the ocean's basins.
Begin your exploration of sea level rise with this video interview of NASA oceanographers discussing the impact of climate change on the ocean. As you watch, consider the following:
- Why are satellites so important in NASA's study of the oceans?
- As our planet heats up where does most of the trapped heat go?
- What are some consequences of the trapped heat?
Next, examine a scientific visualization of changes in sea level from NASA's Science Update Story page. Click on "Click here to view this .mpg animation" in the text. In this visualization, sea level changes measured from space are shown using data from TOPEX/Poseidon and Jason satellites. How does sea surface height show us the amount of heat stored in the ocean?
The Earth's sea levels are dynamic, and rise and fall in response to changes in climate. Read "Sea Level Rise, After the Ice Melted and Today" from NASA to put sea level change in historical perspective. As you read, consider how the study of past sea level fluctuations provides us with a longer-term geologic context to help us better understand and anticipate future trends.
Global sea level rose about 17 centimeters in the last century. Over the past decade, sea levels have risen at twice the rate of the preceding century. Currently, the rate of rise is a little more than 3 millimeters a year. There are two main factors responsible for sea level rise, and both are related to our warming climate: the melting of land-based glaciers and ice sheets, and the thermal expansion of the upper ocean caused by warming surface waters.
Melting ice contributes to the volume of water in the ocean, but not all of Earth's ice contributes to sea level rise. Examine the "Ice Shelf and Ice Sheet Simulation," which explores the role of sea ice and land ice in sea level rise. As you watch the simulation, consider why the two ice masses have different effects on the level of water in the aquarium when they melt.
How do we know what part of observed sea level rise is the result of thermal expansion of water due to rising sea temperatures, and what part is because of an increase in ocean volume due to melting land ice? The GRACE satellite detects small changes in ocean mass reflected in ocean bottom pressure. This satellite helps scientists answer ongoing questions about sea level and climate change. It clarifies, for example, just how much of sea level change is due to differences in ocean mass, the result of evaporation, precipitation, melting land ice, or river run-off, and how much is due to temperature and salinity.