Sea Level Rise due to Global Climate Change: What's Next?

 Nicki Richmond and Scott Barker



       Introduction: Climate change and global warming may walk hand in hand and contribute to a fatal future for some of us: the consequence of sea level rise.  The burning of fossil fuels increases the amount of greenhouse gases in our atmosphere.  These threatening greenhouse gases blanket the earth, trapping in heat and warming earth’s surface. The average temperature of the earth has risen about .5-.7 degrees C in the last century, and the last decade of the twentieth century resulted in the warmest temperatures on record for centuries.  Sea level rise is due to increased temperatures that are causing thermal expansion of the oceans and the melting of polar ice caps.



The beauty of ice.  Melting of ice contributes to about 20% of sea level rise. Image provided by Microsoft Millennium Edition Software.


    Currently, the average rate of sea level rise is 2-3 mm/yr, with some places experiencing a higher rate of about 6 mm/yr (Douglas et al., 2001). 

This concurs with data we have compiled through both PSMSL and University of Hawaii Sea Level Data at a rate of 2.3 mm/year.  Relative sea-level rise measurements have been recorded since the early 1800’s, including U.S. data back to 1854 at San Francisco, California (Douglas et al., 2001).   Since 1880, sea level  has risen significantly.  The cause of this rise is mainly attributed to thermal expansion, which is the biggest catalyst in sea level rise. 

    Warming of the earth’s surface, both land and sea, can also affect atmospheric pressure.  If the atmospheric pressure decreases one millibar, the sea level rises 10 millimeters (Sherif, 1999).  Therefore, the lowering of atmospheric pressure could have a significant impact on water levels in the future. The objective of this project was to determine if sea level really is rising.  In particular we focused on the following questions: 1) How much will the sea level rise based on current relative and absolute sea level data?   2) Are any of the oceans rising at different rates?  3) What are some of the consequences of predicted sea level rise?  4) Who will be affected the most?


Why should we care?  Understanding sea level rise is interesting and imperative because everyone will most likely be negatively affected in some way.  Seventy-five percent of the U.S. population lives within 50 miles of shoreline.  Thirteen of the the world twenty largest cities are located along the shoreline.  Will cities be rebuilt? Manhattan Island will be underwater, Florida coasts will be underwater: Where will all these people go?  Will we have more problems with overpopulation?  How will our freshwater reservoirs be affected?  Will agriculture be destroyed?  Will storms be more damaging to shorelines?  If barrier islands are buried, how will erosion increase on beaches?  These are just a few of the many questions people will be forced to deal with in perhaps the not so distant future. 

     Sea level rise will have a significant impact on shoreline erosion.  An increase in sea level could erode

shorelines at a rate 50-200 times faster than present erosions rates.  Image taken from EPA Reports.


    Sea level has an enormous impact on ecosystems and habitats in coastal regions.  About 100 million people live within one meter of present day mean sea level (Douglas et al, 2001). An increase in sea level could erode shorelines at a rate 50-200 times faster than  today (Douglas et al, 2001).  The physical effects of sea level rise are: erosion of bluffs and beaches, increased flooding, saltwater intrusion in coastal aquifers, and storm damage.  Not only will beaches shrink, islands alone may be swept away, wiping away generations of culture and traditions.  Already there have been disappearances of small islands in Chesapeake Bay (Douglas et al, 2001), along with several Pacific island nations voicing concern over an observed rise.  This makes sea level rise not only a scientific question, but an ethical question. What will happen to future generations of the earth due to our careless ways of burning excessive fossil fuels and polluting the planet? Sea level rise will have the potential to wipe out generations of traditions and cultures, like the Pacific islanders. 

    Based on oxygen isotope dating and geologic evidence scientists have been able to model how sea level has fluctuated in the past.  Oxygen isotope records for foraminifera from deep-sea sediments provide significant evidence of the earth’s climate due to orbital changes (Broecker, 1989).

This graph shows different cycles of the earth based on eccentricity with corresponding isotope data.


    The oxygen isotopes studied are d18O and d16O.   Colder ocean temperatures and larger ice volume are affiliated with higher signatures of d18O in benthic foraminifera (Broecker, 1989).  The drilling of coral reefs has been another means that has provided a continuous and detailed record of sea level (Fairbanks, 1989).  Due to global cycling patterns, cooler temperatures have induced extensive glaciation and resulted in a drop in sea level.  Approximately 18,000 years ago the sea level is inferred to be 121 meters below what mean sea level is today (Wright, 1993).  Interglacial periods of increasing temperature and consequent ice melt have resulted in sea level rise.  There is evidence, in various places in the world such as raised beaches on the Florida panhandle, that indicates sea level was 6 meters above present mean sea level (MSL) about 125,000 years ago. Geological

evidence has been well documented:
        - geomorphic features
        - transgressive sequences
        - biological indicators
        - archeological data
        - intertidal deposits (coastal marshes)
A combination of these data will allow for a better reconstruction of sea level history (Douglas et al.).


    We are currently living in an interglacial period and naturally global temperatures should be rising. However, the rate at which the temperature is rising is alarming.  Scientists predict sea level to rise faster due to thermal expansion of the oceans and polar ice caps melting due to warmer temperatures.  The Intergovernmental Panel of Climate Change predicts that sea level may rise 15-95 cm by the year 2100, with an overall ‘best’ estimate of at least 50 cm by 2100 (Frederick, 1997).  

    Sea level rise is a consequence of global climate change.  Therefore, we also have to consider the reasons why temperatures are rising.  Is global climate change a natural phenomenon or are we contributing significantly to greenhouse gases that trap heat on the earth?  The biggest question to ask is: Is there a problem and what are we doing about it?  Would decreasing carbon dioxide and other greenhouse gases lower the risk of sea level rise?  How are we going to protect the innocent island nations of the West Pacific if sea level does continually increase?   What will be in store for the United States?   


Materials and Methods:

    We have collected resources from the library and the World Wide Web to gain valuable information from.  Currently, there is an abundant amount of research materials available dealing with issues of global climate change.  We have gathered tidal gauge data from the following websites: University of Hawaii Sea Level Data and PSMSL Tidal Data.  Today, satellites have become an important tool in measuring absolute global sea level (Douglas & Peltier, 2001).  For our purposes, however, we used tidal gauge data because we found it to be more available.  We were also able to take data from different regions of the world to aid in answering our questions of who will be affected the most and will different oceans be rising at similar rates.  We have discovered that recent compilations of articles in books dedicated to sea level rise have been fairly knowledgeable.  Please go to our folder to view the spreadsheets, graphs, and images we have collected thus far.  We used Excel and StatView to analyze the data we have collected. 



 From our data that we collected from the PSMSL website, we have compiled the following graphs that show a representative of sea level rise around the world.  The average global sea level rise we calculated was 2.3 mm/year for the worlds oceans. 



The average sea level rise for New York, New York is 2.8 mm/year.


The average sea level rise for Wilmington, North Carolina is 2.2 mm/year.


The average sea level decrease (!) for the US Aleutian Islands is -.6 mm/year. 

This negative relationship may be due to tectonic activity in that region.



The average sea level rise for Genova Italy is 1.2 mm/year.


The average sea level rise for Portland Maine is 1.9 mm/year.


The average sea level rise for Key West, Florida is 2.4 mm/year.



The average sea level rise for the North Sea in Germany is about 4.8 mm/year. 


The average sea level rise for the Mediterranean Sea from Spain is about 6.8 mm/year.


The average sea level rise for Australia is about .48 mm/year. 

It is important to show that not all of our data had consistent data.


    The U.S. has information back to 1854, from the Pacific Ocean in San Francisco, California.  It is important to note that only Europe and the U.S. have been consistent in collecting data. 


Each ocean appears to be rising at a different rate.  Our results show that the Atlantic is rising at a rate of 2.47 mm/year, and the Pacific is rising at a rate of 1.84 mm/year.  This was evident in the ANOVA test we ran on our mean sea level data comparing each ocean (shown below). Based on the P-values from the statistical analysis, the oceans are indeed rising at different rates. 




    Global sea level rise is definitely a problem that we will have to face in the future.  Our study has indicated that sea level is rising at approximately 2.3 mm/year.  If sea level continues to rise at the current rate, we can expect profound economic and social burden.  The consequences of sea level rise include:  increase in floods and storm surges, saltwater intrusion on freshwater resources, economic setbacks, destruction of wetland and marsh ecology, bleaching of coral reefs,  and the drowning of small island nations. 

According to Douglas et al. (2001) coastal areas would become more vulnerable to flooding for four reasons:
1) An increase in sea level can increase the impact of storms on low-lying coastal areas.
2) Beach erosion would leave particular properties more vulnerable to storm waves.
3) Higher water levels would increase flooding due to rainstorms by reducing coastal drainage
4) A rise in sea level would raise water tables and lead to salt water intrusion in coastal aquifers (affecting groundwater).

Global climate change will have an impact on the hydrologic cycle.  As mentioned above, coastal aquifers will experience salt water intrusion.  The intrusion of salt water into could affect domestic, industrial, and agricultural users (Sherif and Singh, 1999).  For example, the Sacramento-San Joaquin Delta in California, is already experiencing problems.  Not only is the Delta experiencing freshwater shortages, the saltwater poses a threat to numerous species of fish in the area (Frederick and Major, 1997). 

Picture of a house on the Virginia coast affected by flooding due to hurricane Floyd.  Picture taken from the NOAA site.

The U.S. Economy could potentially be destroyed by sea level rise.  Many U.S. economic powerhouses will be affected either directly or indirectly. It is estimated that as little as a one meter rise (predicted by the year 2100) will cost the U.S. anywhere from $200-$475 billion dollars (Douglas et. al, 2001).  An increase in sea level, leads to greater erosion of beaches, which will in fact be devastating to the United States biggest tourist destination: sandy beaches. 


Coastal wetlands, such as the Florida Everglades, have already been affected by human impacts, and now even more by the onslaught of sea level rise.  The Florida Everglades is a fragile ecological system and an increase in saltwater could be hazardous.  Deltaic coasts, such as southern Louisiana, will have to deal with a subsiding coastline, flooding, saltwater intrusion, which will throw off the delicate balances these places have established between society and nature (Douglas et al., 2001).  In a recent article, April 2002, the EPA announced that only 56% of the estuary areas in the U.S. are available for both human and wildlife use due to salt water intrusion.

Examples of ecosystems that could be affected by sea level rise.  Taken from Florida Everglades Website.

The warming of oceans and the rise in sea level in the tropics are causing the coral to “bleach” where the corals turn white and lose their polyps. Coral reefs are fragile ecosystems that contain great diversity; close to one million species inhabit these underwater rainforests.  Only .2 percent of the ocean is covered by coral reefs and atolls. 

Examples of the great diversity of life found in coral reef ecosystems. 

One of the most devastating effects of sea level rise is the drowning of small island nations.  This is specifically alarming in the West Pacific, where effects of sea level rise are already apparent.  Sea walls are built to decrease beach erosion and flooding.  These sea walls are sometimes built out of American garbage such as school buses and tires.  These islands could disappear with the slightest change in sea level.  This could require a relocation of millions.  Currently, the economy in the West Pacific Islands ranges from subsistence farming to a booming tourism industry, both which will be negatively affected by sea level rise.  According to the book Sea-Level Changes and Their Effects, by Noye and Grzechnik, 2001, currently the islands are doing the following to increase awareness of sea level rise:

  • Educating people: how to adapt to changes, disease
  • Establishment of early warning systems (ENSO)
  • Coastal zone management strategies for the next 20-50 years
  • Long-term policy changes dealing with global climate and sea level rise

If sea level rises as predicted, future generations of island nations in the West Pacific could face losing their unique cultures and traditions.


What if there was a rapid rise?


If the sea level would rise 100 meters, this is a possible image of the future terrestrial landmass. Anything pictured in light blue will be under water. 


According to the a recent article on the Environmental News Service, sea level could rise up to 7 m if the West Antarctic Ice Sheet collapsed (April 2, 2002).  In addition, if the more robust, East Antartic Ice Sheet collapsed, this could trigger a sea level rise up to 66 meters higher than today!  Researchers such as Paul Blanchon and John Shaw of the University of Alberta, Canada, believe that there have been three catastrophic sea level rise events in the past 18,000 years of deglaciation (1995).  They have looked at the deep sea cores for Acropora reefs.  Acropora palmata are good indicators of sea level due to the fact that they form a 'monospecific reef framework in waters less than 5 meters' and they cannot grow in water depths greater than about 10 meters.  Based on this evidence, Blanchon and Shaw have concluded that there were rises of 13.5 meters, 7.5 meters, and 6.5 meters, at 14.2 ka, 11.5 ka, and 7.6 ka respectively (1995).  This may have been due to a combination of factors-a rapid change in atmospheric circulation, ocean temperatures, and ice-sheet response, although no simple relationship between climate change and ice sheets exist (1995).  If such rises occurred today, flooding of coastal regions could cause massive loss of property and lives, and possibly a breakdown of social order (Douglas et al, 2001).

In conclusion, it is evident that everyone will be negatively impacted by the smallest level of sea rise.  At the current rate of sea level rise we calculated, we can expect at least a 23. 5 cm rise by 2100.  However, if the Antarctic or Greenland Ice Sheets would become unstable, could we experience a catastrophic sea level rise?  What would this do to our society?  Do you have any answers?  What are YOU doing to prevent it?  I think what we have learned the most is: the more research we continue to do, the more questions result, and the less we really know.  Any individual efforts for saving our Earth are appreciated!  LEARN MORE AND EDUCATE OTHERS!  Start recycling programs where you live! Conserve natural resources including water! Turn off the lights!  Drive smaller cars, even better, carpool, bike, use public transportation, or walk!  Support local farmers!  Hug trees...okay, enough hippie, tree-huggin' stuff! 




NOAA Web Site

PSMSL Tidal Data

Long term sea level change

Milankovitch cycles

Potential Impact

Out There News

EPA Reports

Global sea level change

CNN Site

Pacific Monitoring

Sea Level Rise Probability

Environmental News Network




Books/Journal References:


Blanchon, P. and Shaw, J. Reef drowning during the last deglaciation: Evidence for catastrophic sea-level rise and ice-sheet collapse, 1995. Geology, 23 No.1: 4-8.

This is a scientific paper that attempts to explain what led to rapid deglaciation and consequent sea level rise, and helps link ice-sheet collapse, with Acropora palmata evidence and climate.


Broecker, W.S. and Denton, G.H.  The role of ocean-atmosphere reorganizations in glacial cycles, 1989.  Geochimica et Cosmochimica Acta, 53: 2465-2501.

This paper is helpful because it correlates changes in the Earth’s orbital patterns to variations of ice levels on Earth.  It explains sea surface records of the past based on oxygen isotope records. 


Douglas, B.C., Kearney, M.S., et. al.  Sea Level Rise: History and Consequences. Academic Press, New York 2001.

This book surveys the history of sea level change. It covers topics such as sea level measuring techniques and consequences of sea level rise.


Douglas, B.C., Peltier, W.R., The Puzzle of Global Sea-Level Rise, 2002.  Physics Today Vol. 55 No. 3: 35-40.

This article address the discrepancies found in global sea level rise data and discusses how sea level is measured.


Earth Pulse Climate: Rising Tide of Concern. National Geographic Magazine, Feb. 2001.

This brief article shows a dramatic diagram of what could happen if sea level would rise. 


Fairbanks, R.G.  A 17,000 year glacio-eustatic sea level record: influence of glacial melting rates on the Younger Dryas event and deep-ocean circulation, 1989.  Nature 342: 637-642.   

This article provides evidence of past sea level rise through cores and coral reefs off the coast of Barbados.


Frederick, K.D. and Major, D.C.  Climate Change and Water Resources, 1997.  Climatic Change 37: 7-23.

This article is based on recent reports from the IPCC and focuses on a wide array of water problems that may result due to global climate change.


Grzechnik, M. and Noye, J. Sea Level Changes and Their Effects. World Scientific, New Jersey, 2001.

This book is a conglomeration of articles mainly dealing with the West Pacific Islands that will be greatly impacted if sea level rises.


Pinet, P.R. Invitation to Oceanography 2nd Ed.  Jones and Bartlett Publishers, Maryland, 1999.

This is an introductory oceanography textbook contains helpful diagrams and basic descriptions of global climate change and how it will affect the future of sea level.


Sherif, M.M. and Singh, V.P. Effect of Climate Change on Sea Water Intrusion in Coastal Aquifers, 1999.  Hydrological Processes 13: 1277-1287.

This scientific article explains how the saltwater-freshwater interface would change if sea level were to rise. 


Wright, H.E. et. al. Global Climates since the Last Glacial Maximum.  University Minnesota Press, Minnesota, 1993.

This mainly focuses on the last 14,000 years, but it has some really great articles on different methods of determining paleoclimates-tree ring evidence, oxygen isotope studies from foraminifera, ice cores, etc.



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