Baxter Miatke
HCOL 185-Climate Change
December 14, 2012
Rising Sea Level Rising Concerns
Millions of people are crowded together and attracted to coastal areas worldwide because
of port access for transportation, fishing, fertile land, and recreation. This attraction to the
coastline has caused coastal development to grow and it continues to accelerate with the
assumption that the stable sea levels of the past millennia will continue. This assumption is
dangerous however, because sea level rise is becoming a reality. Our society needs to consider
global sea-level rise caused by global climate change and its effects if we continue business as
usual. “Since 1900, the global sea level has risen by approximately 20 cm” and future projections
show it is going to rise even more (ScienceDaily 2012). Global sea level rise over the next
century will have a disastrous effect on Earth’s coastal ecosystems and human civilization.
Before describing the causes behind sea level rise, it is helpful to explain what sea level
actually means. Sea level is the average height of the sea with respect to a reference surface. A
common misconception is that sea level is at the 0.0-foot elevation. Sea level is actually
referenced to a standardized point known as a “geodetic datum” (Pilkey and Young 2009). This
means that the surveyed elevation of sea level is never really 0 feet as many people may think it
is. It will vary from place to place depending on the geodetic height rather than just the height
above the earth’s surface. While sea level does vary short term due to tides, winds, and seasons,
this paper will focus on the long term change in sea level and what will cause the sea level to rise
in the years to come.
A long term change in sea level rise comes from global climate change and its effects on
glaciers and the oceans. Global climate change and warming temperatures are causing glaciers
around the world to disappear at an alarming rate. The Greenland Ice Sheet, for example, “was
measured at a movement of 9 miles per year” (Journey 2009). The increase in movement is due
to higher temperatures causing melt lakes to form in the glaciers at higher elevations. These melt
lakes send water straight down through crevasses and lubricates the ice sheet, thus making it
move faster along the ground. As glaciers and ice sheets melt, the albedo rises due to less light
being reflected and thus a positive feedback loop is created. When the ice sheet hits the ocean, it
contributes to sea level rise, similar to dropping ice cubes in a full glass of water making the
water overflow the glass. It was estimated that “1/3 of global sea level rise comes from the
Greenland Ice Sheet alone” (Journey 2009). In addition to Greenland, there are another 300,000
glaciers around the world that are having similar
scenarios as at the Greenland Ice Sheet. An assessment
by scientists of the University of Innsbruck shows that
“between 1902 and 2009, melting glaciers contributed
to a total of 11 cm to sea level rise” (ScienceDaily
2012). The figure to the right, made by the IPCC,
shows the cumulative total mass of glaciers decreasing
over time. Scientists measure the volume of glaciers in
"mm SLE", the amount that sea levels would rise if the
ice melted.. This illustrates that melting glaciers are
therefore one of the most important causes of sea level
rise.
Another important cause of sea level rise is ocean temperature. The oceans are a central
component of the climate system, storing and transporting vast amounts of heat. As oceans warm
due to a warming climate, they expand and the sea level rises. “A 1000-m column of sea water
expands by about 1-2cm for every 0.1◦C of warming” (Church 2010). Ocean thermal expansion
was a major contributor to 20th century sea-level rise along with melting glaciers, and it is
projected to continue during the 21st century. Both melting glaciers and higher ocean
temperatures are direct effects of global climate change. Global climate change and sea level rise
are therefore closely interconnected.
(Source: Penn State https://www.e-education.psu.edu/geog438w/node/261)
Most scientists agree that rising global sea level is likely to accelerate throughout the 21st
century. “A total rise in the range of 18-60cm has been projected by the Intergovernmental Panel
on Climate Change” (Church 2010). To put sea level in perspective, the figure above shows
observed sea level change and predictions from 3 different sources. The height of the average
person is also included in the figure adding further perspective to the amount of projected sea
level rise. It can be seen that the IPCC has rather “conservative” predictions in comparison to the
other scientists. In fact, many other scientists, including NASA climatologist James Hansen,
argue that sea level rise in this century will be at least 1m (Pilkey and Young 2009). Most
experts think the Rahmstorf projections are the most likely to occur, based on his precise
methods and the changing climate that we are currently experiencing. It is clear that many other
scientists’ predictions are higher than the IPCC’s rather conservative estimates. This suggests
that either the IPCC made low estimates purposefully in order to not worry the public or to
ignore the costs of what it will take to defend against or prevent sea level rise. The words of
Neils Bohr Nobel Prize winning physicist and could possibly explain the predictions the best
when he said, “prediction is very difficult, especially if it is about the future” (Pilkey and Young
2009). It may not be possible to predict the exact sea level rise unanimously among the scientific
community, but it is agreed upon that the sea level is on the rise, it isn’t a distant abstract fear.
When analyzing the sea level rise, it is fundamental to understand the difference between
global (eustatic) and relative (isostatic) sea level rise. The relative sea level changes as results of
large scale changes in sea levels on a global scale. This means that relative sea-level rise is a
response to both climate change and other factors causing it to vary from place to place. While
the global sea level may rise, some places will actual experience relative sea level fall due to
local climate, coastline features, and other factors that cause the local lithosphere to move up and
down. Global sea level rise is still a problem despite the relative sea level fall. “Currently,
eustatic (global) sea level is rising at a rate of 3mm/year over the last fifteen years” (Pilkey and
Young 2009). The rate of this global sea level rise is accelerating in response to modern day
global warming. Skeptics will attempt to use global and relative sea level to argue that projected
global sea level rise will not be a problem. This is a poor argument though, because relative sea
level varies from place to place and it is inevitable that many different areas will be affected by
the global sea level rise we are experiencing. This inevitability to global sea level rising far
beyond the 21st century is known as the “commitment to sea-level rise” (Church 2010). Society
has made its commitment to sea-level rise and its ignorance to this problem will cause a wide
spread of impacts around the world.
The impacts of sea level rise and can be fundamentally separated between ecology and
humans. Neither impact is more important than the other since both are interconnected. When the
shoreline moves due to rising sea levels, coastal ecosystems associated with that shoreline must
also move with it, or perish. Coastal wetlands such as marshes, mangrove forests, and coral reefs
are biological living communities that are directly influenced by sea level rise. “The fact that
these [coastal] ecosystems have survived two million years of sea level fluctuation is a testament
to their robustness and adaptability” (Pilkey and Young 2009). In that two million years, coastal
ecosystem never had to face its greatest foe it faces now; humans. Sea level rise is now a
problem for these ecosystems because of modern coastal expansion and human activities. The
environmental impacts of sea level rise include inundation, surge, wetland loss, coral destruction,
invasive species, erosion, saltwater intrusion, rising water tables, and the list continues on.
“Globally, up to three million species of marine organisms live in, on, or very near the coast”
(Pilkey and Young 2009). Coastal ecosystems play a large part in our planet’s biodiversity, and
damage from sea level rise will have unimaginable impacts.
The rising sea will also have disastrous impacts for human-kind. Sea level rise will
impact land use of every sort such as parks, subways, communications, sewers, roads, railroads,
and buildings by the thousands. It will affect whole towns and even nations, making some of
them completely disappear in the worst case scenarios. Humans are drawn to these coastline
areas for leisure, business, and natural beauty. A huge part of the world’s population lives near
coastlines. In regards to rising sea level, “over 180 million people are exposed to full-range
impacts from a 1-m global rise in sea level (by 2100) and no protection” (Church 2010). That
means a 1-m sea level rise, the most likely predicted rise as mentioned before, will create over
180 million refugees. These environmental refugees will be forcibly displaced from their homes
due to sea level rise causing greater population density elsewhere. Growth of coastal population
has particularly exploded in the U.S. and elsewhere in the Western world. It was determined that
“53 percent of U.S. population growth is occurring in coastal regions that account for only 17%
of land area” (Kelley and Pilkey 2009). The image below shows that the threat of sea level rise
does not prevent our society from taking advantage of all the coast has to offer with high
populations in areas under 1 meter. As the population in coastal regions increase, the number of
people affected by sea level rise will continue to increase as well.
Source: Strauss et al 2012
Global costs of sea level rise and economic effects will be disastrous if we continue
business as usual. Global estimates of upgrading defense infrastructure suggest that the costs are
lower than the cost of the expected damage that will result from sea level rise. “Defending
against a 1-m sea level rise is estimated at US$500 billon” (Barth 1984). If $500 billion is lower
than the cost of the expected damage from sea level rise, than it is clear that rising sea level will
devastate the economy worldwide, from India to U.S. This may explain why the IPCC estimates
were so conservative in the previous observations and predictions graph.
Even though there are catastrophic impacts of rising sea level, there are responses to sea
level rise as well to combat the negative impacts. The two potential responses to sea level rise are
mitigation and adaptation. Mitigation can slow the global rise in sea level and reduce its impacts.
It has an important effect of stabilizing the rate of global sea-level rise as opposed to stabilizing
sea level itself. “The fundamental goal of mitigation is to reduce the risk of passing irreversible
thresholds and constrain the commitment to sea level rise to a rate which can be adapted to”
(Church 2010). Adaptation is then broken down into three generic approaches as defined by
IPCC; planned retreat, accommodation, or protection. The figure on the following page
illustrates the three different approaches. Planned retreat involves pulling back from the cost
using land use planning and development control. Accommodation involves adjusting human use
of the coastal zone using flood resilience, warning systems, and insurance. Protection involves
engineering solutions reducing human impacts in the coastal zone otherwise impacted without
protection. The most popular adaptation method used is protection because of its lower cost and
feasibility.
Source: Church 2010
Significant engineering projects have been undertaken during the past few centuries in
order to adapt to rising sea level. The different adaptation solutions to rising sea level include
bulkheads and seawalls, groins, revetments, beach nourishment, offshore breakwaters, storm
surge barriers, perched beaches, and other devices used for beach erosion control. “The
performance and effectiveness of different types of coastal structures and protective techniques
are affected by rising relative sea level” (Committee on Engineering Implications 1987). We
must therefore learn to adapt and respond to the sea level problem on hand. One engineering case
study uses Miami Beach, Florida as an example for successful adaptation. Between 1976 and
1980, a large beach nourishment and flood protection project was constructed by the U.S. Army
Corps of Engineers at Miami Beach and cost $64 million. The nourishment project added 300
feet of beach and while it retreated about 100 feet at, it remained stable afterwards and met the
needs of the coastal cities located behind the fill (Committee on Engineering Implications 1987).
This is just one example of successful engineering solutions for protection against sea level rise.
The problem with all protection adaptation solutions, however, is that the risk of failure increases
as sea level rises. How high will levees have to be in 2100 to still protect New Orleans? How
much more sand will have to be dredged and filled in to beaches like Miami Beach? What is the
best decision to make in regards to rising sea level?
The decision facing coastal communities is very difficult because there are a number of
factors that go into determining the best decision in regards to rising sea level. There are
economic factors including the long-term cost and maintenance cost, social factors including the
degree of risk and population density, and environmental factors. And when coastal cities are
threatened by rising sea level, will natural ecosystems even have high enough priority in order to
assure their survival. The decision making process is dynamic taking into account multiple
factors, but for the most part it is mostly done on local or state levels. In 2008, the EPA released
a document in order to set the stage for the nation’s response to sea level rise, but the stated goal
in the report was to add to the nation’s prosperity while still responding to sea level rise (Pilkey
and Young 2009). As the saying goes, you can’t have your cake and eat it too. The U.S. needs to
understand that the response to sea level rise will have to involve economic sacrifice. This
supports the fact that action on sea level rise occurs mostly on a local scale. This creates different
decision making, such as some states refusing to use seawalls while others pour money into
maintaining their seawalls. Some states invest heavily in marshland habitats, while other build
revetments causing greater erosion of marshlands. Other countries like Spain made it illegal to
build within 100 meters of its 3100 mile coastline, while other countries like the United
Kingdom recommended abandonment and retreat of the flat low elevation Norfolk Broads
(Pilkey and Young 2009). Still the most widely used method presently is protection of some sort
whether it is surge floodgates, bulkheads, or seawalls. Deciding on the best response to sea level
rise could still take communities many years, but the sea level continues to rise right now.
In conclusion, global climate change, melting glaciers, and thermal expansion are all
causing a global sea level rise. It is most likely that the sea level will rise by 1-m by 2100
according to Rahmstorf and Hansen. This will cause many changes to our environment and
coastal communities and require important decision making in how to respond to the many
negative impacts from sea level rise. These changes do not have to end the coastal economy as
we know it. In order to preserve our coastal resources, insightful and long-term planning as a
nation and as a worldwide community will be required. Global climate change and rising sea
level has become a reality, but there is still hope because the future is what we make of it.
References
“Journey to planet Earth- The state of the planet's oceans” [DVD] / producer, Marilyn Weiner ;
director-writer, Hal Weiner; a Screenscope production, in association with South
Carolina ETV (2009).
Church, John. “Understanding Sea-Level Rise and Variability”, Chichester, West Sussex;
Hoboken, NJ : Wiley-Blackwell (2010).
National Research Council (U.S.) Committee on Engineering Implications of Changes in
Relative Mean Sea Level, “Responding to Changes in Sea Level Engineering
Implications” Washington, D.C. : National Academy Press (1987).
Pilkey, Orrin & Young, Rob. “The Rising Sea”, Washington, DC : Island Press /Shearwater
Books (2009).
Barth, Michael & Titus, James. “Greenhouse Effect and Sea Level Rise”, New York : Van
Nostrand Reinhold (1984).
Kelley, Joseph & Pilkey, Orrin & Cooper, Andrew (Editors). “America’s Most Vulnerable
Coastal Communities”, Boulder, Colo. : Geological Society of America (2009).
University of Innsbruck. "Melting glaciers raise sea level." ScienceDaily, 14 Nov. 2012. Web. 2
Dec. 2012.
Benjamin H Strauss et al 2012 Environ. Res. Lett. 2012 IOP Publishing Ltd. Web. 2 Dec. 2012