U.S. vulnerability to sea level rise
In the last century, sea level rose 5 - 6 inches (13 - 15 cm) more than the global average of 7 inches (18 cm) along the U.S. Mid-Atlantic and Gulf Coasts, because coastal lands there are sinking. Over 50% of the U.S. coastline is vulnerable or highly vulnerable to sea level rise, according to the Coastal Vulnerability Index (CVI) developed by the United States Geological Survey (USGS). In the U.S., relative sea level rise (the combined effects of global sea level rise plus the fact the land is sinking) is highest along the Mississippi River Delta in Louisiana, where relative sea level rises of 3.2 ft (.98 meters) have been observed during the 20th century. This is one of the highest relative sea level rises in the world. According to the NOAA Tides and Currents sea level rise interactive tool, the U.S. tide gauges that have shown the highest rates of sea level rise over the past century are at Grand Island, LA (1.8 ft rise since 1947), Galveston, TX (1.1 ft since 1957), and Chesapeake Bay, VA (0.6 feet since 1975). Alaska and some areas along the Pacific Northwest coast are at low risk of sea level rise, because the relative sea level is actually falling at present. Land in these regions is rising as it recovers from removal of the weight of the great ice sheets that covered much of North America during the last Ice Age. For example, relative sea level at Kodiak Island, Alaska has fallen by 1.1 feet since 1975, despite the fact global sea level has been increasing.
Figure 1. Twentieth century annual relative sea-level rise rates in mm/year along the U.S. coast. The higher rates for Louisiana (9.85 millimeters [mm] per year, about 3.3 ft/century) and the mid-Atlantic region (1.75 to 4.42 mm per year, 0.6 - 1.4 ft/century) are due to land subsidence. Sea level is stable or dropping relative to the land in the Pacific Northwest, as indicated by the negative values, where the land is tectonically active or rebounding upward in response to the melting of ice sheets since the last Ice Age. Image credit: Coastal Sensitivity to Sea-Level Rise: A Focus on the Mid-Atlantic Region (data from Zervas, 2001).
U.S. Coastal Vulnerability
The Coastal Vulnerability Index (CVI) takes into account six factors:
1) The geology of the coast. Barrier islands, river deltas, and marshes are the most vulnerable to erosion and sea level rise, while steep, rocky cliff shores are the least. Sheltered bays like Galveston Bay and Tampa Bay are less vulnerable than the exposed coasts. (Note, however, that hurricane storm surges are typically higher in sheltered bays, at least for slow-moving storms).
2) How steep the land near the coast is. Gently sloping lands are the most vulnerable. In the Gulf Coast region, the slope variable has the highest risk ranking along the Louisiana coast, the Texas coast north of Corpus Christi, and the southwest Florida coast.
3) The local rate of sea level rise. The sea level is rising faster along the western Gulf of Mexico than the eastern Gulf. The highest rates of sea-level rise in the Gulf of Mexico (and in the United States) are in the Mississippi delta region (10 mm/yr, or 1 inch/2.5 years).
4) The amount of shoreline erosion going on. Most of the U.S. coast is moderately or severely eroding, and very few areas are gaining (Figure 2).
5) The mean tidal range. Shores that have a large difference between low and high tide are less likely to get a significant storm tide--the height above mean sea level of the sum of the storm surge plus the tide. For example, in a region like Maine, which has a 12 ft range between low and high tide, a storm having a 9 ft storm surge will have a storm tide below local high tide for a quarter of a tidal cycle. Shores with a very narrow tidal range (e.g., the 2 ft tidal range common along the Texas and Louisiana Gulf Coast) will get a storm tide of 8 - 10 feet with the 9 ft storm surge in the above example. Shorelines with a narrow tidal range always get high storm tides regardless of when the storm surge hits.
6) How high the waves at shore are. Obviously, shores that experience higher wave heights are at greater risk. In the Gulf of Mexico, wave energy is highest along sections of the Texas coast and on the southern tip of the Mississippi delta.
Figure 2. Shoreline change around the United States based on surveys over the past century. All 30 coastal states are experiencing overall erosion due to natural processes (e.g., storms, sea-level rise) and human activity. If the shoreline is uncolored, no data was available. Image credit: USGS, 1985, and taken from Coastal Sensitivity to Sea-Level Rise: A Focus on the Mid-Atlantic Region).
The Coastal Vulnerability Index (CVI) web page gives detailed maps of each section of the U.S. coast, along with specific reasons why each portion of the coast was assigned the ranking it got. A brief summary:
The Gulf Coast
The Gulf Coast has 55% of its length in the "very high" or "high" vulnerability range. Fully 41% of the coast falls in the "very high" range, far more than the 28% in that category along the Pacific coast and 23% along the Atlantic coast. The region around New Orleans is the most vulnerable region of the entire U.S. coast. The Florida Panhandle, as well as the West Florida coast, are at low to moderate risk because the land is not sinking much, wave heights are lower, and the slope of the land is relatively steep near the coast. The Texas coast is considered to be at a high to very high risk because of the relatively high mean wave height, sinking land, and shallow coastal slope.
The East Coast
The East Coast has 50% of its length in the "very high" or "high" vulnerability range. The highest vulnerability areas are typically high-energy coastlines where the regional coastal slope is low and where the major landform type is a barrier island. A significant exception to this is found in the lower Chesapeake Bay. Here, the low coastal slope, vulnerable landform type (salt marsh) and high rate of relative sea-level rise combine for a high CVI value. The coastline of northern New England, particularly Maine, shows a relatively low vulnerability to future sea-level rise. This is primarily due to the steep coastal slopes and rocky shoreline characteristic of the region, as well as the large tidal range.
The Pacific Coast
The Pacific Coast has 50% of its length in the "very high" or "high" vulnerability range. Areas of very high vulnerability include the San Francisco - Monterey Bay coast and in southern California from San Luis Obispo to San Diego, where the coast is most highly populated. The highest vulnerability areas are typically lower-lying beach areas. The low risk, least vulnerable areas generally occur at rocky headlands along cliffed coasts where the coastal slope is steep, relative sea-level is falling, tide range is large, and wave energy is lower. Examples of these areas are the northern coast of Washington, Monterey, and Cape Mendocino, California.
Figure 3. The Coast Vulnerability Index (CVI) for the U.S.
References
Coastal Sensitivity to Sea-Level Rise: A Focus on the Mid-Atlantic Region.
National Assessment of Coastal Vulnerability to Sea-Level Rise: Preliminary Results for the U.S. Gulf of Mexico Coast (USGS, 2000).
Jeff Masters
Reader Comments
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June 24th, 2009 at 11:19 pm
Looking at the newest CFS…moderate to strong El Nino probs look even better…
This from the Tallahassee discussion...
"AFTER SUN...SYNOPTIC SCALE FORCES GAIN GREATER INFLUENCE OVER OUR WX
THAT THE SEA BREEZE. AS THE SRN NEW ENGLAND TROUGH LIFTS NEWD...
ENERGY OVER THE UPPER GREAT LAKES WILL SWING INTO THE ERN LAKES NEAR
SRN ONTARIO/UPSTATE NY. THIS WILL RESULT IN A MEAN LONG WAVE TROUGH
AXIS OVER THE ERN U.S. THIS TROUGHING WILL HELP ANOTHER FRONT TO
SETTLE INTO THE DEEP S...ATYPICAL FOR THIS TIME OF YEAR FOR SURE...
BUT THEN WHAT HAS BEEN TYPICAL ABOUT 2009. THIS FRONT WILL BE
APPROACHING OUR NRN ZONES ON MON AND BE IN THE VICINITY ON TUE. THE
PRESENCE OF THE FRONT AND DEEP LAYER MOISTURE (WITH PW WELL OVER 2
INCHES) WILL RESULT IN AT OR ABOVE CLIMO POPS. AS THE BOUNDARY
SETTLES S OF THE AREA ON WED AND THU...NRN AREAS WILL BEGIN TO DRY
OUT AND POPS WILL BE LOWERED ACCORDINGLY. TEMPS THROUGH THE PERIOD
WILL BE AT OR SLIGHTLY ABOVE NORMAL...EXCEPT FOR DAYTIME HIGHS ON
MON WHICH WILL BE SLIGHTLY COOLER THAN NORMAL DUE TO ABUNDANT CLOUD
COVER."
"BETTER RAIN CHANCES WILL COME INTO PLAY EARLY NEXT WEEK. AN UPPER
LEVEL TROUGH MOVING THROUGH CANADA WILL TRACK SEWD ACROSS THE
NORTHERN PLAINS. THIS TROUGH WILL STRENGTHEN AS IS MOVES INTO THE
GREAT LAKES REGION AND SEND A COLD FRONT SOUTHWARD. THIS BOUNDARY IS
EXPECTED TO STALL EITHER JUST NORTH OF THE AREA OR VERY CLOSE TO THE
GULF COAST. THE RESULT WILL BE INCREASED RAIN CHANCES MONDAY THROUGH
WEDNESDAY. HAVE CHNC POPS FOR NOW AND MAY HAVE TO INCREASE POPS EVEN
HIGHER."
No, the A/B high will be ridging in too much into the NW Caribbean.
Latest GFS has a track across the Yucatan into the western GOM.
Yes, the GFS has been really aggressive with the ridge lately. If one of the vigorous tropical waves off the African coast successfully coalesce into a tropical cyclone, it will likely not go out to sea. The long range GFS keeps the ridge strong, and even invigorates it at times.
I just wonder if it'll do the old Cape Verde Poof once it is fully over water.
Looks like the GFS likes that wave that is coming off the W coast of Africa
Still has a 1004 mb low in the NW Caribbean in the next 4 days or so.
Reflector site for those at work, which now also includes Weather456, daily updates
AOI #1
AOI #2
I second that. Way too early to even speculate.
Nothing like 100 degree weather and a garbage strike.. I hope it doesn't last more then a month or two :)
humidex 98f
one more day. The mercury will climb into the 31 to 34 degree range
by early afternoon, pushing humidex values to near or just over the
40 threshold.
Discussion of thunderstorm potential.
Today into this evening..There is a risk of severe thunderstorms
today in southern Ontario along and ahead of a slow-moving cold
front. Ample heat and humidity will almost ensure a few severe
thunderstorms will develop by early afternoon with damaging wind
gusts to 100 km/h, very large hail in excess of 3 centimetres,
torrential downpours giving over 50 mm of rain within an hour, and
frequent intense lightning. They may be particularly severe in areas
in and around the Golden Horseshoe. Isolated non-severe
Thunderstorms are expected in the northwest this morning spreading
into the northeast by this afternoon.
Yup lol
Anyways you have to wait a few more weeks. Right now...some waves that are going to start to come off the coast will look nice with a low-midlevel circulation... but will die out!..and unless 3 models support development with the GFS..aka ECMWF-Ukmet... I would give it under a 10% chance of developing east of 50W.
Pay more attention to home grown stuff this time of year for the next 2 weeks @ least.
Hurricane Bertha...all I have to say
I hope so, unless it is a very weak TS that just dumps about 6-10 inches of rain spread out over a few days.
i always follow this rule
what they say it will be and what it will be are two different things
Precisely: thats why i'm watching a little area off NC/SC coast
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