Sea Level

Photo Credit: Fred Fullerton

Waders are the New Uggs

By now everyone has heard the stories about how low-lying islands will disappear and waterfronts will be washed away by the year 2100 due to sea level rise. The team of international experts that made that projection back in 2004 now look conservative in their predictions. Scientists now tell us that the impacts of sea level rise are probably going to be much worse than we thought.

How Does It Happen?

Sea level rise occurs on both global and local scales. Two major processes cause global sea level rise: melting land-based ice sheets, and thermal expansion of water. Melting of land-based ice sheets simply raises sea level by adding water that had previously been located on land to the oceans. Thermal expansion is an effect that works something like giving candy to a room full of children. The sugar in the candy gives each child more energy, causes them to move around more, and the children take up more space in the room. Heat adds energy to water molecules, causing them to move more and occupy more space.

Thousands of Scientists from Around the World Speak Out

The Intergovernmental Panel on Climate Change (IPCC) is the leading international organization that assesses climate change. The IPCC is a scientific body composed of thousands of climate change researchers from around the world and they all agree: climate change is happening, it is serious, and we can take action now to slow down future impacts.

The first IPCC assessment was completed in 1990 and in the 23 years since then there have been four additional assessments and numerous special reports. A draft of the fifth IPCC assessment was released in the fall of 2013 with the final draft expected in early 2014, and it contains the most cutting edge research and sophisticated projections to date.

While climate change research has been around for decades and scientists with specialties in disciplines relevant to climate change have come and gone, the message remains the same: the climate is changing at an unprecedented rate and both big and small actions by all people are needed to protect the environment, human health, and our economy.

Local sea level change is the change observed at a particular location, and it can be very different from the global average in sea level depending on where you live. Local sea level changes can be caused by land subsidence, or downward movement of the terrain relative to sea level, due to the earth’s response to ice or sediment loading, or the extraction of water or oil. The contribution of land subsidence to sea level rise varies at regional and local scales. (Anyone who has ever had a potted plant has observed subsidence as the soil in the pot appears to shrink.)

There is evidence that the coastline from Cape Cod to New Jersey is subsiding, but the exact rate is uncertain. When subsidence is taken into account, Rhode Island’s historic rate of relative sea level rise as observed in Newport is thought to be greater than the average around the globe.

Hans Brinker and the Pearly Gates

Projections versus Predictions

Projections are not predictions. Projections are based on a sequence of hard data that shows trends, whereas the word predictions is more readily associated with crystal ball gazers or local TV forecasters, whose accuracy is usually as reliable as a race track tout’s picks.

But if climatologists have erred in any way in their projections, it is increasingly evident that they have been conservative in their expectations. It is worth repeating: the amount of sea level rise that the Intergovernmental Panel on Climate Change (IPCC) scientists projected would occur by 2100 has already been deemed to be far too low, and those predicted rates of encroaching waters would likely be exceeded. Jokers in the pack such as large amounts of melting ice in Greenland and Ice is Nice
A Coastal Cabaret
Antarctica have now thrown a very ugly monkey wrench into the works, and we can count ourselves lucky if we only experience the relatively low increases in sea levels originally projected by the IPCC in 2007.

Sea Level Projections

Global

Regional

Rhode Island

OK, by now you probably fear drowning in numbers more than sea level rise. Just take a look at these maps that really bring home the picture of sea level rise from the most conservative to the more extreme estimates.

Click on the maps to see them larger

Map: What if All the Polar Ice Melted?

Credit: Paul Jordon, RI DEM

Six Meter Rise: Implications for Providence

Credit: Jim Lucht and Haidee Janak, The Providence Plan

“The rate of sea level rise will likely double or triple in the next hundred years...”

“Extremely rapid sea level rise — especially when coupled with decreased sediment supply — can inundate islands causing them to break up and disappear.”

- Goddard Space Flight Center


News


Factoids

Average global sea level has increased by 7 inches since 1900, which threatens coastal communities. Since 1930, sea level in Rhode Island has increased by an average of 1 inch per decade.

Over the past half century, sea levels in the Northeast have been increasing 3-4 times faster than the global average rate, resulting in a 6-inch rise between 1970 and 2012.

Sea level is projected to increase by 3 to 5 feet above 1990 levels in Rhode Island by 2100.

Over 55,000 homes in New England are situated less than 3 feet above sea level and will be at risk of inundation by 2100.


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