RISING OCEAN LEVELS Over the past century, our ocean levels have been rising at a steady rate, recently ocean levels have began to rise at an increased rate.

Glossary

  • Meltwater- the water that flows off of or collects on glaciers after the ice melts.
  • Thermal Expansion- When water heats up, its mass increases due to the added amount of kinetic energy the water contains. Water particles begin to move more and occupy more space when it has more kinetic energy.
  • GMSL- an acronym that stands for Global Mean Sea Level. This is a number that indicates what the average sea level is.
  • Oceanographer- Someone that studies the science behind how our oceans work. They map out currents, depths, temperatures, and they work on maintaining marine wildlife.
  • Disproportionately- this means to not be done equally and at the same rate.
  • Gigatonne- Measurement of mass equaling one billion tons.

How much have our oceans risen already?

According to the article “Sea Level Rise” published by National Geographic, “Over the past century, the Global Mean Sea Level (GMSL) has risen by 4 to 8 inches (10 to 20 centimeters). However, the annual rate of rise over the past 20 years has been 0.13 inches (3.2 millimeters) a year, roughly twice the average speed of the preceding 80 years.” This information shows that although the GMSL has been rising for a longer period of time, recently it has been rising at an increased rate. So the oceans might have only risen 4-8 inches in the past 100 years, but the rate at which they are increasing is also increasing. One reason that our oceans are rising faster than normal is because of the amount the ice caps are melting due to global warming. In an article published by Deutsche Welle, Germany’s international broadcaster, “Dark meltwater pools absorb warmth from the sun which white ice would reflect back into space.” When water melts on the ice caps, they form dark pools of meltwater that absorb heat from the sun, therefore increasing the rate at which the ice caps melt. With an increased rate of melting, more water will pour into our oceans and therefore cause the sea levels to rise. The reason we know so much is because we have many oceanographers working hard to learn more about our ocean.

How are we gathering data about ocean levels?

One way oceanographers are collecting data is through the Argo project. According to Guatam Naik, a reporter for the Wall Street Journal, “Data [is] collected from the Argo Project, which consists of about 3,500 torpedo-like devices that zoom around in the ocean measuring temperature and salinity.” These devices are used to measure thermal expansion in the ocean and how quickly its temperature is changing. Another way oceanographers are obtaining data about ocean levels is through a network of satellites in the earth's orbit. This program is called GRACE. Through GRACE we are able to find the mass of the ice that is being lost from our ice sheets and moving into our oceans. According to NASA, “The continent of Antarctica has been losing about 118 gigatonnes of ice per year since 2002, while the Greenland ice sheet has been losing an estimated 281 gigatonnes per year.” Having the GRACE project helps us know more about what is happening around us. Although we know more about how much ice is melting, we still need to prepare ourselves for how much the oceans will rise.

How high will our oceans rise?

Measuring how high our oceans will rise is an inexact science and it is impossible to accurately determine how much the sea level will rise; however, According to Maureen Raymo, a world-renowned climate scientist at the Lamont-Doherty Earth Observatory at Columbia University, “Temperatures in the Pliocene are estimated to have been 2 to 3C warmer than pre-industrial values, which means that they were 1 to 2C warmer than today.” This is problematic for us because sea levels in the Pliocene era were approximately 10-40 meters higher than the sea levels we have today. Robert Kopp, a climate scientist at Rutgers University and the lead author of the study says “the last two decades have seen global sea level rise more than twice as fast as it did in the 20th Century”. Because our oceans are expanding so fast in sync with global temperatures, stating that our sea levels will become close to the levels that were seen during the Pliocene era would not be an outrageous statement. Global warming is the largest cause of ocean levels rising.

What is the role of global warming in the rising ocean levels?

Global warming plays a huge role in the ocean levels rising. One reason for this is thermal expansion. According to John Krasting, a physical scientist at the US National Oceanic and Atmospheric Administration’s Geophysical Fluid Dynamics Laboratory, “Thermal expansion through warmer ocean waters was the largest contributor to global sea level rise over the past century.” When water heats up, its volume increases due to the increase of kinetic energy in the molecules. Due to this property of water, as the atmospheric temperature goes up due to global warming, so does the the temperature of our oceans, causing volume of the water in our oceans to increase. Another way global warming affects ocean levels rising is the melting ice caps. According to marine geophysicist Robin Bell of Columbia University’s Earth Institute, “Sea levels rise by about 1/16” for every 150 cubic miles of ice that melts off one of the poles.” Although this seems like it won't change the oceans levels that much because it's only 1/16”, but if the entire Antarctic ice sheet melted, sea levels would rise by almost 200 feet. An ocean rise of only a fraction of this magnitude would have drastic effects on our society.

How does sea level rising affect us?

Sea level rising has a huge impact on our coastal communities. According to Josh Willis of NASA, because the slope of our beaches is about 100:1, for every centimeter the ocean rises, we lose about 3 feet of beach area. This is a large impact on us because since 1992, global sea levels have risen 8 centimeters. Coastal cities will be greatly affected by the decrease of beach area. Shanika Gunaratna, a writer for CBS News, states, “In the mildest projected scenario, global sea levels will rise by about one foot by the end of this century. In the worst-case scenario, global sea levels will rise by 8.2 feet…. researchers have estimated that a lower rise of six feet would be enough swallow up the homes of about six million Americans.” As you can see, rising sea levels can have devastating effects on our society if it continues to rise as is expected.

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If all the ice on the ice caps melted, more than 25% of the human population would lose their homes and have to relocate. Sun rays that would normally be reflected by the ice sheets would now be absorbed by the ocean, causing the oceans temperature to rise even more. The addition of that amount of fresh water to our oceans would offset the oceans current due to the change of salinity in the water.

Citations

"Are Arctic Sea Ice Melts Causing Sea Levels to Rise?" Scientific American. Scientific American, 13 June 2008. Web.

Church, John. “The evidence shows sea levels are rising: let’s not be caught out.” ECOS. CSIRO, 17 March 2014.

Cumming, Vivien. "This is how far seas could rise thanks to climate change." BBC News. BBC, n.d. Web.

Deutsche Welle. "Polar ice sheets melting faster than ever | DW Environment | DW.COM | 04.02.2013." DW.COM. Deutsch Welle, n.d. Web.

"EDITORIAL: Warming ocean waters demand our attention." The Packet. N.p., n.d. Web. 25 Jan. 2017.

Gunaratna, Shanika. "Sea level rise will disproportionately hit U.S. this century, NOAA warns." CBS News. CBS Interactive, 24 Jan. 2017. Web. 25 Jan. 2017.

Naik, Guatam. "World News: Faster Melt Behind Rising Sea Levels." The Wall Street Journal Asia. N.p., 3 June 2013. Web. 26 Jan. 2017.

“Nasa: sea levels rising as a result of human-caused climate change.” theguardian, commentary by Josh Willis, NASA, 27 Aug. 2015,

"Sea Level Rise." National Geographic. N.p., 21 Jan. 2017. Web. 24 Jan. 2017.

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Mitchell Nadeau
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