Melting ice is causing sea levels to rise substantially. In addition, carbon dioxide emissions are altering the chemistry of the world’s oceans, posing a risk to marine species.
Sea Levels Have Been Rising
Average sea level around the world has been rising and is projected to continue to rise. As glaciers and ice sheets melt, water that would have been contained in these ice formations instead flows into the ocean. In addition, climate change is causing the oceans to become warmer, which causes water to expand and contributes to rising sea levels.
Sea level has increased along most of the U.S. coast over the past 50 years, with some areas along the Atlantic and Gulf coasts experiencing increases of more than 8 inches (20 cm). Local sea level depends on changes in the global ocean, changes in local winds, and localized sinking or rising of the land.
Data from Church, J. and N. White (2011), Sea-level rise from the late 19th to the early 21st century. Surveys in geophysics, 1573-0956. DOI: 10.1007/s10712-011-9119-1. Source
This video, based on a National Research Council report, looks at how sea-level rise is likely to impact the west coast of the United States.
Video based on Sea-Level Rise for the Coasts of California, Oregon, and Washington: Past, Present, and Future, National Research Council, 2012. Source
By 2100, average sea level is projected to rise 1.6-3.3 feet (0.5-1.0 m). Some studies suggest a rise of nearly 6 feet (2 m). Animations from the U.S. Geological Survey demonstrate how such increases would affect the coastlines of Delaware and Florida (animations launch in separate tabs).
Oceans Have Been Increasing in Acidity
In addition to contributing to the greenhouse effect, high carbon dioxide emissions since the Industrial Revolution have caused the world’s oceans to become more acidic.
Seawater absorbs about one-quarter of the carbon dioxide currently released by human activities. Most of that carbon dioxide combines with water to form carbonic acid, increasing the acidity of the ocean.
National Research Council, Ocean Acidification: Starting with the Science. Source
Ocean acidity has increased roughly 30% since preindustrial times. Rising ocean acidity poses major risks for marine organisms because it makes it more difficult to grow shells, among other effects.
Phytoplankton (microscopic plant-like organisms vital to marine life) are at risk from ocean acidification. Projected levels of acidity would erode their calcium carbonate shells.
Images courtesy of Ulf Riebesell, IFM-GEOMAR. Source
Many other organisms, such as these sea snails, form an important component of marine food webs but are threatened by ocean acidification. (Pictured snails are healthy.)
Images courtesy of Russell Hopcroft, University of Alaska Fairbanks (UAF) and Census of Marine Life (CoML). Source
Additional Resources from the National Academies
This 20-page booklet describes the chemistry of ocean acidification. A podcast, report summaries, and other resources accompany the booklet.