Transcript Mapping Sea-Level Rise

Stephen Young,
Department of Geography
Center for Economic Development and Sustainability
Salem State College
Many people want to know:
How high will the ocean be in 2020 or 2050?
And…. Where will flooding occur in my town?
I can’t tell you exactly, but……
It is possible to determine a potential range
of future sea-level rise and to map out the
vulnerable areas of your town.
Today I want to leave you with an
understanding of two basic issues:
1) How sea-level is rising and the scientific
uncertainties around how fast it is rising.
1) How sea-level is rising and the scientific uncertainties around how
fast it is rising.
2) How we go about mapping the
vulnerability of our coastal environment.
The good news first -
The Northeast is one of the least vulnerable
coastal areas of the US.
However, we are still vulnerable and need
to prepare.
Is the sea rising?
And if so how fast?
“Global sea level is rising, and there is
evidence that the rate is accelerating.”
Sea-level rise is caused by three factors:
1) Thermal Expansion of the ocean as the waters warm.
2) Addition of Water by the melting of land-based ice
sheets, ice caps, and glaciers.
3) Relative sea-level rise due to the changing elevation
of the adjacent land (subsidence & rebound).
How fast is it rising?
East Coast US, 20th Century: 3 to 4 mm per year (1.2 to
1.5 inches per decade).
In the 20th Century Massachusetts saw about a 10 to 11
inch increase in sea-level.
Concerning the melting of global ice – it
has rapidly increased and some scientists
now estimate that added water is now the
main cause of sea-level rise
(which has been thermal expansion).
Arctic Climate Research – University of Illinios
Journal: Skeptical Science
Ice mass loss in Greenland as observed by satellite
Grace in cubic kilometers per year. NASA/JPL/University
of Colorado
Mean size measured on 30 glaciers in 9 mountain ranges.
From: World Glacier Monitoring Service
Fresh Water - where it is
Second, how we map the vulnerability of
our coastal environment.
To understand how we map the
vulnerability of coasts, we need to
understand the potential harm
caused by rising sea levels.
These include:
1) Inundation from a rising sea-level.
2) Flooding from storm activity, especially storm surges on
top of a higher sea level.
3) Inland flooding from storms partly caused by altered
drainage patterns due to the rising sea-level.
4) New erosion patterns due to changing water flow and
sea level.
5) Inability of natural ecosystems to change with rising sea
levels.
Today rising sea levels are eroding beaches,
submerging low-lying areas, converting wetlands to
open water, increasing storm flood activity and
increasing the salinity of estuaries and freshwater
aquifers.
Some natural areas are able to adjust to the changes by
shifting upward and landward with the rising waters,
but areas confined by development are more
vulnerable and are not able to adjust.
Once we understand the potential
consequences in our town we can begin to
develop a mapping strategy.
1) Determine a range of future sea-level rises.
2) Get accurate geo-referenced elevation and coastal
image data as well as infrastructure and social data.
3) Characterize the coast’s geomorphology.
4) Run various simulations based on different sea-level
rises and different storm activity.
5) Produce static maps of potential damage.
1) Determine a range of future sea-level rises.
Intergovernmental Panel on Climate Change (IPCC) ,
2007, project that in the 21st century global sea-level
will rise between 7 and 23 inches.
Right now, March 2009 there is a major climate
change conference in Copenhagen and most scientists
are now estimating a rise of 1 meter (39 inches) or
more – about double the high end of the IPCC, 2007
report.
2) Get accurate geo-referenced elevation and coastal
image data as well as infrastructure and social data.
Elevation data is the most important data to
determine the influence of sea-level rise, and it is
critical to understand the accuracy of the data.
There are existing national standards for
quantifying and reporting elevation data
accuracy.
For most current elevation data sets, the
accuracy error is greater than the high-end of
potential sea-level rise (1 meter).
High-quality LIDAR elevation data should be
the base data for sea-level rise maps.
These data sets also need to be field checked.
High-resolution coastal LIDAR data is now
becoming available at NOAA
(http://maps.csc.noaa.gov/TCM/).
3) Characterize the coast’s geomorphology.
This needs to be done through field work.
In some areas the extent of inundation is controlled
largely by the slope of the land with gentle slopes
being the most vulnerable.
Also barrier island migration and wetland accretion
and shoreline erosion will alter inundation.
4) Run various simulations based on different
sea-level rises and different storm activity.
This can be done with various GIS software.
5) Produce static maps of potential damage.
Again this can be done with various GIS
software.
Despite the dearth of quality elevation data, some
crude modeling can be done now to provide some
broad patterns of potential change.
For example MASS GIS now has some Digital
Elevation Model (DEM) data which can be used for
modeling, but with the understanding of its
internal errors.
“This map is based on modeled elevations, not
actual surveys or the precise data necessary to
estimate elevations at specific locations.”
J.G.Titus and C.Richman, 2000, “Maps of Lands
Vulnerable to Sea Level Rise: Modeled Elevations Along the U.S.
Atlantic and Gulf
Coasts.” Climate Research