Sea level rise: what has happened so far

By: Dr. Jeff Masters , 2:05 PM GMT on June 10, 2009

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Sea level has been rising globally since the late 1700s. This rise has accelerated in recent decades, thanks to increased melting of glaciers and ice sheets due to a warmer climate, plus the fact that warmer oceans are less dense and expand, further increasing sea level. Though sea level rise appears to have slowed over the past five years, it will significantly accelerate if the climate warms the 2 - 3°C it is expected to this century. If these forecasts of a warmer world prove accurate, higher sea levels will be a formidable challenge for millions of people world-wide during the last half of this century. Sea level rise represents one of my personal top two climate change concerns (drought is the other). I'll present a series of blog posts over the coming months focusing on at-risk areas in the U.S., Caribbean, and world-wide. Today, I focus on the observed sea level rise since the Ice Age.

What's at stake
Higher sea levels mean increased storm surge inundation, coastal erosion, loss of low-lying land areas, and salt water contamination of underground drinking water supplies. About 44% of the Earth's 6.7 billion people live within 150 km (93 miles) of the coast, and 600 million people live at an elevation less than ten meters (33 feet). Eight of the ten largest cities in the world are sited on the ocean coast. In the U.S., the coastal population has doubled over the past 50 years. Fourteen of the twenty largest urban centers are located within 100 km of the coast, and are less than ten meters above sea level (McGranahan et al., 2007). The population of many vulnerable coastal regions are expected to double by 2050, according to the U.S. Census Bureau.

Sea level rise since the Ice Age
Before the most recent Ice Age, sea level was about 4 - 6 meters (13 - 20 feet) higher than at present. Then, during the Ice Age, sea level dropped 120 meters (395 ft) as water evaporated from the oceans precipitated out onto the great land-based ice sheets. The former ocean water remained frozen in those ice sheets during the Ice Age, but began being released 12,000 - 15,000 years ago as the Ice Age ended and the climate warmed. Sea level increased about 115 meters over a several thousand year period, rising 40 mm/year (1.6"/yr) during one 500-year pulse of melting 14,600 years ago. The rate of sea level rise slowed to 11 mm/year (0.43"/yr) during the period 7,000 - 14,000 years ago (Bard et al., 1996), then further slowed to 0.5 mm/yr 6,000 - 3,000 years ago. About 2,000 - 3,000 years ago, the sea level stopped rising, and remained fairly steady until the late 1700s (IPCC 2007). One exception to this occurred during the Medieval Warm Period of 1100 - 1200 A.D., when warm conditions similar to today's climate caused the sea level to rise 5 - 8" (12 - 21 cm) higher than present (Grinsted et al., 2008). This was probably the highest the sea has been since the beginning of the Ice Age, 110,000 years ago. There is a fair bit of uncertainty in all these estimates, since we don't have direct measurements of the sea level.


Figure 1. Global sea level from 200 A.D. to 2000, as reconstructed from proxy records of sea level by Moberg et al. 2005. The thick black line is reconstructed sea level using tide gauges (Jevrejeva, 2006). The lightest gray shading shows the 5 - 95% uncertainty in the estimates, and the medium gray shading denotes the one standard deviation error estimate. The highest global sea level of the past 110,000 years likely occurred during the Medieval Warm Period of 1100 - 1200 A.D., when warm conditions similar to today's climate caused the sea level to rise 5 - 8" (12 - 21 cm) higher than present. Image credit: Grinsted, A., J.C. Moore, and S. Jevrejeva, 2009, "Reconstructing sea level from paleo and projected temperatures 200 to 2100 AD", Climate Dynamics, DOI 10.1007/s00382-008-0507-2, 06 January 2009.

Sea level rise over the past 300 years
Direct measurements of sea level using tide gauges began in Amsterdam in 1700. Additional tide gauges began recording data in Liverpool, England in 1768 and in Stockholm, Sweden in 1774. These gauges suggest that a steady acceleration of sea rise of 0.01 mm per year squared began in the late 1700s, resulting in a rise in sea level of 2.4" (6 cm, 0.6 mm/yr) during the 19th century and 7.5" (19 cm, 1.9 mm/yr) during the 20th century (Jevrejeva et al., 2008). There is considerable uncertainty in just how much sea level rise has occurred over the past few centuries, though. Measuring global average sea level rise is a very tricky business. For starters, one must account for the tides, which depend on the positions of the Earth and Moon on a cycle that repeats itself once every 18.6 years. Tide gauges are scattered, with varying lengths of record. The data must be corrected since land is sinking in some regions, due to pumping of ground water, oil and gas extraction, and natural compaction of sediments. Also, the land is rising in other regions, such as Northern Europe, where it is rebounding from the lost weight of the melted glaciers that covered the region during the last Ice Age. Ocean currents, precipitation, and evaporation can cause a 20 inch (50 cm) difference in sea level in different portions of the ocean. As a result of all this uncertainty, the 1996 Intergovernmental Panel on Climate Change (IPCC) report gave a range of 4 - 10" (10 - 25 cm) for the observed sea level rise of the 20th century. The 2007 IPCC report narrowed this range a bit, to 5 - 9" (12 - 22 cm), or 1.2 - 2.2 mm/year. Rates of sea level rise are much higher in many regions. In the U.S., the highest rates of sea-level rise are along the Mississippi Delta region--over 10 mm/yr, or 1 inch/2.5 years (USGS, 2006). This large relative rise is due, in large part, to the fact that the land is sinking.


Figure 2. Absolute sea level rise between 1955 and 2003 as computed from tide gauges and satellite imagery data. The data has been corrected for the rising or sinking of land due to crustal motions or subsidence of the land, so the relative sea level rise along the coast will be different than this. The total rise (in inches) for the 48-year period is given in the top scale, and the rate in mm/year is given in the bottom scale. The regional sea level variations shown here resulted not only from the input of additional water from melting of glaciers and ice caps, but also from changes in ocean temperature and density, as well as changes in precipitation, ocean currents, and river discharge. Image credit: IPCC, 2007

Sea level rise over the past 15 years
According to the Intergovernmental Panel on Climate Change (IPCC) 2007 report, sea level accelerated from the 1.2 - 2.2 mm/yr observed during the 20th century to 3.1 mm/year during the period 1993 - 2003. These estimates come from high resolution measurements from satellite radar altimeters, which began in 1992. Tide gauges showed a similar level of sea level rise during that ten-year period. The IPCC attributed more than half of this rise (1.6 mm/yr) to the fact that the ocean expanded in size due to increased temperatures. Another 1.2 mm/yr rise came from melting of Greenland, West Antarctica, and other land-based ice, and about 10% of the rise was unaccounted for. However, during the period 2003 - 2008, sea level rise slowed to 2.5 mm/year, according to measurements of Earth's gravity from the GRACE satellites (Cazenave et al., 2008). This reduction in sea level rise probably occurred because ocean sea surface temperatures have not warmed since 2003 (Figure 3). The authors concluded that sea level rise due to ocean warming decreased more than a factor of five from 2003 - 2008, compared to 1993 - 2003, contributing only 0.3 mm/yr vs. the 1.6 mm/yr previously.


Figure 3. Global average sea surface temperatures (SSTs) from 1990-2008. SSTs have not increased in the past seven years. Image credit: NASA/GISS.

For more information
The best source of information I found while compiling my sea level pages was the Coastal Sensitivity to Sea-Level Rise: A Focus on the Mid-Atlantic Region report by the U.S. Climate Science Program. It has a huge number of references to all the latest science being done on sea level rise.

References
Bard, E., et al., 1996, "Sea level record from Tahiti corals and the timing of deglacial meltwater discharge", Nature 382, pp241-244, doi:10.1038/382241a0.

Cazenave et al., 2008, "Sea level budget over 2003-2008: A reevaluation from satellite altimetry and Argo", Global and Planetary Change, 2008; DOI:10.1016/j.gloplacha.2008.10.004

Grinsted, A., J.C. Moore, and S. Jevrejeva, 2009, "Reconstructing sea level from paleo and projected temperatures 200 to 2100 AD", Climate Dynamics, DOI 10.1007/s00382-008-0507-2, 06 January 2009.

IPCC (Intergovernmental Panel on Climate Change), 2007: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor, and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, UK, and New York, 996 pp.

Jevrejeva, S., J.C. Moore, A. Grinsted,, and P.L. Woodworth, 2008, "Recent global sea level acceleration started over 200 years ago?", Geophysical Research Letters, 35, L08715, doi:10.1029/2008GL033611, 2008.

McGranahan, G., D. Balk, and B. Anderson, 2007, "The rising tide: assessing the risks of climate change and human settlements in low elevation coastal zones", Environment & Urbanization, 19(1), 17-37.

Moberg, A., et al., 2005, "Highly variable northern hemisphere temperature reconstructed from low- and high-resolution proxy data", Nature 433, pp613-617, doi:10.1038/nature03265.

United States Geological Survey (USGS), 2006, National Assessment of Coastal Vulnerability to Sea-Level Rise: Preliminary Results for the U.S. Gulf of Mexico Coast, U.S. Geological Survey Open-File Report 00-179.

Tropical update
The tropical Atlantic is quiet, and the only region worth watching is the Western Caribbean, which could see formation of a tropical disturbance with heavy thunderstorm activity this weekend.

Jeff Masters

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1432. Patrap
No doubt Levi..if the entity slips under the High and her engine is up and running,well the TCHP is there ..
Member Since: July 3, 2005 Posts: 423 Comments: 127807
Quoting StormFreakyisher:

Yes but what I am saying is if we ever got a hurricane make a direct hit here coming from the east coast.
Wilma was a horrific hurricane. Passed a couple hundred miles off Grand Cayman and we still had quite a bit of damage.
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Back from my run......WOW the Caribbean blob went poof real fast...
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1428. Levi32
18z GFS 200mb 96-hours.....the best time to look for a promising area of disturbed weather sitting underneath that anticyclone in the western Caribbean.

Member Since: November 24, 2005 Posts: 635 Comments: 26594
1426. Patrap
Wilma Local Landfall Radar Loop


Id say Wilma DIRECTLY Impacted that area,no doubt.
Member Since: July 3, 2005 Posts: 423 Comments: 127807
LOL...just reading some post's on the last page and someone doesn't think Wilma made a direct hit in West Palm Beach??

So the calm winds I experienced for about 30 minutes in between 100+ mph winds was just a break in the weather?
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1424. Patrap
Gentle ribbing is a form of endearment from me,anyone can post,..within the Community Standards.

Its not a club..its Dr. Masters Blog.

We all know its the most visible,..but if you never spend time in ones own House,you'll miss have the experience here.

Some of these young hard charging Bloggers have great potential,even a featured blog is attainable for some.

Maybe my Humor was lost in that,..and if so,.Im big nuff to apologize.
I meant no slight to anyone's talent or enthusiasm


Member Since: July 3, 2005 Posts: 423 Comments: 127807
Quoting Patrap:
NOAA only makes the NOAA Base Maps for Catastrophic Canes,..Ike and Rita are the 2 others I know of.

Rita NOAA Base Map

IKE NOAA Base Map

Okay thanks Patrap. I live in Wilmington, NC and was looking for a Fran(96) or Floyd(99) base map. Those were catastrophic hurricaneas as well. Thanks anyways.
Member Since: June 1, 2009 Posts: 0 Comments: 107
I live in Homestead,I rode out Andrew in 92. Went out in the eye..WOW!!! Then running room to room as the house came apart. It gave me a total respect for mother nature...




Quoting Patrap:
Andrew was bad storm,Horrific in it the eyewall,but very compact.
A Damage swath that one could drive thru in 45 minutes..
It Takes 3 Hours to drive the Damage swath from K..
Mobile Ala,to Houma, Louisiana.

Anyone who spends even 1 hour in a Hurricane eyewall has a very different view and respect for even a Small Cat-1...than those who havent.

Katrina was a Cat1 when she took Lives in Fla.

And Andrew Killed 4 in Louisiana from a F_4 Tornado she spawned in Laplace,La..west of NOLA.
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Quoting twhcracker:


whoops I'm sorry i hit send too soon! I just wondered if you might have any idea where in Florida it might be visible? I am in the panhandle, is there any way we could see at least a vapor trail here?


It will be very faint and distant. But yes, look to the SE on launch day and you might be able to see it, unless you have trees. I'd try an area with no trees what so ever.
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1419. Patrap
NOAA only makes the NOAA Base Maps for Catastrophic Canes,..Ike and Rita are the 2 others I know of.

Rita NOAA Base Map

IKE NOAA Base Map
Member Since: July 3, 2005 Posts: 423 Comments: 127807
1418. Levi32
18z GFS continuing to move everything out to the north way too fast before the upper low has a chance to retreat to the SW. On the surface map you can almost see the remnant surface circulation in the southern Caribbean, which is where the low should be on the model, while the surface trough races up near Cuba.

48-hour GFS surface:



48-hour GFS 200mb:

Member Since: November 24, 2005 Posts: 635 Comments: 26594
1417. Patrap
I rode out K on Bonnabel Blvd ..between Veterans Blvd and the Lake.

I mile west of the 17th Canal.

From Sept 12th after the Breech was sealed

Member Since: July 3, 2005 Posts: 423 Comments: 127807
Quoting TampaFLUSA:

Didn't you get hurricane force winds from Wilma?

Yes but what I am saying is if we ever got a hurricane make a direct hit here coming from the east coast.
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Quoting CybrTeddy:


Hey pat we got a shuttle going up here Saturday!
If any Floridians are early wakers on Saturday mornings at 7 AM you should be able to see it.


whoops I'm sorry i hit send too soon! I just wondered if you might have any idea where in Florida it might be visible? I am in the panhandle, is there any way we could see at least a vapor trail here?
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Quoting Patrap:
Impact counts,not cat size,wind Speeds,or Surge height.
Combined,and prolonged effects do the damage. Not any Man made scale or blogger's viewpoint.



NOAA Katrina Base Map Impact Page


Everything is relative to the observer.
Ones relative position to a Landfall,..is only one perspective.


Patrap can you get those images for other hurricanes as well?
Member Since: June 1, 2009 Posts: 0 Comments: 107
1413. Patrap
My VHS tape died at 5:15 AM CST the Morning of the 29th as the eyewall struck,1mile west of the 17th St Canal..and It didnt lay down to afte 3:30 Pm..

If you Look at the Radar Loop below/or above..you'll see the eye due west of NOLA at 9am,approx when the Levee's failed.

But we didnt know of the Breech till Tuesday afternoon,..and that sight is one Ill take to the grave.

The 12-14 days in the water blurs into one long dream,nightmare..I wouldnt wish on even a Enemy.
Member Since: July 3, 2005 Posts: 423 Comments: 127807
pat .. been meaning to ask. where were you in Nola that you were willing to ride out that sucker
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Quoting CybrTeddy:


Hey pat we got a shuttle going up here Saturday!
If any Floridians are early wakers on Saturday mornings at 7 AM you should be able to see it.
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1410. Patrap
The storm comes and goes in Hours,..then the real work begins in a Catastrophic one.
And if your not prepared,then you'll suffer along with the ones who didnt,..while those who left are watching it on TV safe .
And those who did prepare,..well,they take on the duty of helping each other out.,till en masse help arrives,which depending on the Impact,may take days
Seen it too many times now.
Member Since: July 3, 2005 Posts: 423 Comments: 127807
1409. Levi32
NASA high-resolution visible loop of the strong tropical wave along 53W. If you look closely you can see the sharp shift of the surface winds from SE to NE indicating a strong v-signature.
Member Since: November 24, 2005 Posts: 635 Comments: 26594
Pat - its nice of you to phrase it that way, but it stills an awful thought to think of you guys at some point of the eye for nine hours. I have been through a bunch of hurricanes, and for the most part they move fairly quickly. That's part of what you tell yourself as you listen to the winds.

I still think its amazing you went through that for such a length of time.
Member Since: August 13, 2007 Posts: 10 Comments: 4150
1407. Patrap

Band on the Run
Member Since: July 3, 2005 Posts: 423 Comments: 127807
1406. Ossqss
How true Pat, perhaps those who desire the canes would take a different perspective if they had the knowledge from being in one. Having seen the leftovers from Andrew and Charley soon after their impact, makes my hair stand up and knees shudder every time I think of it. I would prefer no canes, but Mother Nature has a different opinion.


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Quoting StormFreakyisher:
I'm surprised Boca Raton has not been affected by a hurricane in 3 years.We are part of the top 10 cities most affected by hurricanes and TS.Has Boca ever had a direct hit from the east coast.Katrina was almost direct but then it moved south.

Didn't you get hurricane force winds from Wilma?
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I'm surprised Boca Raton has not been affected by a hurricane in 3 years.We are part of the top 10 cities most affected by hurricanes and TS.Has Boca ever had a direct hit from the east coast.Katrina was almost direct but then it moved south.
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1402. Patrap
Impact counts,not cat size,wind Speeds,or Surge height.
Combined,and prolonged effects do the damage. Not any Man made scale or blogger's viewpoint.



NOAA Katrina Base Map Impact Page


Everything is relative to the observer.
Ones relative position to a Landfall,..is only one perspective.

Member Since: July 3, 2005 Posts: 423 Comments: 127807
1401. Drakoen
Quoting Patrap:
Wow..3 Bloggers all with their own respective Blogs,but all their posts are here.

Kinda like Blogcasting..High School Style


Way to stir the pot... and yet so subliminal
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1400. Patrap
Andrew was bad storm,Horrific in it the eyewall,but very compact.
A Damage swath that one could drive thru in 45 minutes..
It Takes 3 Hours to drive the Damage swath from K..
Mobile Ala,to Houma, Louisiana.

Anyone who spends even 1 hour in a Hurricane eyewall has a very different view and respect for even a Small Cat-1...than those who havent.

Katrina was a Cat1 when she took Lives in Fla.

And Andrew Killed 4 in Louisiana from a F_4 Tornado she spawned in Laplace,La..west of NOLA.
Member Since: July 3, 2005 Posts: 423 Comments: 127807
Glossary of NHC Terms

Direct Hit:

A close approach of a tropical cyclone to a particular location. For locations on the left-hand side of a tropical cyclone's track (looking in the direction of motion), a direct hit occurs when the cyclone passes to within a distance equal to the cyclone's radius of maximum wind. For locations on the right-hand side of the track, a direct hit occurs when the cyclone passes to within a distance equal to twice the radius of maximum wind. Compare indirect hit, strike.
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100mph winds is as close to a direct hit you will get, whether it came from one coast or another imo.....Tampa..Jacksonville...GA Coast..NYC, have not had a direct hit or Hurricane force winds in some time...
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Wilma hit a lot of places, we had no electric for 10 days, guess that counts as being hit.

Pat - 9 hours in the eyewall? That must be scary. Andrew from start to finish wasn't even nine hours. Difference in a fast moving storm, vs a slower moving storm. Can you imagine what would of happened to this area if it had taken 9 hours for Andrew to move through? That is a really scary thought.
Member Since: August 13, 2007 Posts: 10 Comments: 4150
Quoting Patrap:
Early morning Launches are best CT. A Nice CLimb to Orbit and sweet ET views from the on Board cam.


Yep, but I love launches that are right before sunrise/sunset.
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1392. Ossqss
Quoting Acemmett90:

For all i care it hit made it direct hit one the west coast and then made its exit through wpb that is not a direct hit



Her eye went right over WPB and traveled over a very warm swamp to get there with little obstruction. It is a direct as you can get from the gulf side to the east coast.


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1391. Patrap
Early morning Launches are best CT. A Nice CLimb to Orbit and sweet ET views from the on Board cam.
Member Since: July 3, 2005 Posts: 423 Comments: 127807
1390. Patrap
For any fool not thinking K didnt hit NOLA..should have spent the 9 Hours in the Eyewall with me,and the next 19days after
.
Such idiocy shows from such post.

And that's a fact for everyone who views here to see.
Nit-wit post without any merit are a Nickel a dozen.



Member Since: July 3, 2005 Posts: 423 Comments: 127807
1388. Michfan
Quoting extreme236:
You would think the grammar and such for a weather blog would be a bit better, but yet I still find myself having to sit there and reread some posts over and over again to determine what they are saying. Not trying to be a police about it but I mean come on its a bit annoying.


The day the internet and texting became prominent is the day that the english language got butchered to hell. Too many LOL's, BFF's, and ROFL's these days.
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Quoting Patrap:
During the active thrust ,Come Aug and Sept.
The flow will shift to necessary info.
Not wide scale speculation on, er.. BLobs.
A new endearing meteorological term.


Hey pat we got a shuttle going up here Saturday!
If any Floridians are early wakers on Saturday mornings at 7 AM you should be able to see it.
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Quoting extreme236:
You would think the grammar and such for a weather blog would be a bit better, but yet I still find myself having to sit there and reread some posts over and over again to determine what they are saying. Not trying to be a police about it but I mean come on its a bit annoying.


Kids...a few adults too though.
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1384. Levi32
ECMWF/GFS comparison, 8-10 day 500mb mean. Notice the big high centered over the north gulf coast and southern US. The area most likely to see tropical activity will be right under that high (by under I mean south of).

Member Since: November 24, 2005 Posts: 635 Comments: 26594
1383. Patrap
During the active thrust ,Come Aug and Sept.
The flow will shift to necessary info.
Not wide scale speculation on, er.. BLobs.
A new endearing meteorological term.
Member Since: July 3, 2005 Posts: 423 Comments: 127807
1382. gator23
Quoting Acemmett90:

For all i care it hit made it direct hit one the west coast and then made its exit through wpb that is not a direct hit


Katrina didnt make a direct hit on NO for that matter
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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