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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Scott doesn't that happen though everyday with the news and local weather I went to work and people talked about the lightning storm that occurred at 5am in the morning, that was not in a blog, I have not heard anyone say a hurricane will hit because Dr.M's blog said so.I suppose someone could say that, but a savvy person would check their weather station for that.
Your right there some great bloggers on here (456, StormW) are both watching these areas so it must have some chance.
Which by that definition, you cannot say it's wishcasting
In Chatham, an austere utopia yields to a relentless tide
Will it go poof? I have no idea.
Will it develop? I have no idea.
That's what makes watching the tropics fun.
WOW!!!!
First of all, I would suggest that there may be a bit more than 2% of the people posting in here who actually know what they're talking about.
But if you want to talk hype, let's talk the mainstream sources of information. One of my big problems has always been with bogus storm surge maps showing who will be underwater during which category of storm. When in reality, the storm surge wouldn't get anywhere close to those projections. Another thing is building up storms to be bigger and worse then they truly are, to try to convince people to leave a particular area. And yes, I know the consequences of not doing this, I live in SW FL and am well aware of what Charley did at the last minute. But if people are told a storm will be bad, and they need to evacuate, and they do, then the storm isn't bad, what are the chances of that person evacuating the next time a storm comes through? The mainstream outlets need to not hype the storms - just tell the truth. Why do you think I come here and not to the weather channel for info?
lol yeah I'm sure...a met wouldn't come onto a forum and cause trouble
Nice one! Lol.
KOTG, when do you expect a reprieve from the heat?
But really, guys, no one is right or wrong, and everyone can have an opinion. So play nice.
would just fit the pattern of no real pattern at all!
We use to have to prepare a lot more for storms before they were able to track as well as they can now. Our theory then, and still is today, is better to be wrong 9 times, and right once. We put our seat belts on every time we get in the car in case we have an accident - how often does it actually happen?
(click for full size)
Believe me, I fully understand the purpose behind the principle. But the difference is, when you put your seatbelt on, that's your choice. What if someone else told you you HAD to put your seatbelt on because if you didn't, you could die in a crash that COULD happen to you on this trip? And it didn't happen. How often would you listen to that person before you stopped listening - just in time for the REAL accident?
I completely agree there. I watch every wave, but I do my best to avoid hyping up anything to possibly form, unless it is very close to the US coast, and may be a "homegrown" system.
All that said... my apologies if I offended anyone by accusing them of wishcasting or anything like that. Its still morning here.
Geez, that's not funny! That had it right over my house. Glad that didn't actually materialize.
Let's see if this vorticity works its way over to the Nicaragua coast from the South Central Caribbean
John Wayne-Orange County, California
64 °F
Haze
South central Caribbean
I do indeed. We won't have long to wait to see how it plays out. The NAM has been developing a 1004 mb low in the NW Caribbean late this weekend for several runs now.
Not talking about that. Someone pointed out this plot with a lot less dust/dry air on it last week, as well.
One day's plot is not a season.
Shear is only 5-10 kts there too..
Certainly no offense here, jeffs. And if anyone needs some help keeping up with the waves-and they do get a little indistinct at times, these folks have been including a small section in their Monday through Friday discussion dedicated to analyzed tropical waves and forecasted movement out to 84 hrs.
Looks like this for yesterday: (if anybody knows how to paste text and keep the format-please advise lol).
EASTERLY/TROPICAL WAVES (INITIALIZED AT 12Z TODAY)
INITIAL F24 F36 F48 F60 F72 F84
50W (S/13N) 53W 57W 60W 63W 65W 69W
67W (SURGE) 71W 74W 76W 79W 81W 82W
78W (S/18N) 81W 83W 85W 88W 90W 92W
Caribbean Discussion-International Desk
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