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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Quoting canesrule1:
really? i think AOI will become something (the one in caribbean) maybe a TD in the next 48 hours.


it could happen you never know
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Quoting beell:


Are they talking about the 2nd TUTT from 10N 60W to 30N 50W?


Believe so...A TUTT OVER THE CENTRAL ATLANTIC LIES TO THE SOUTH/SOUTHWEST TO JUST NORTH OF THE GUIANAS.
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1230. Michfan
Until the shear drops it is all a guessing game.
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really? i think AOI will become something (the one in caribbean) maybe a TD in the next 48 hours.
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Quoting CybrTeddy:


They're forecasted to die down.


CybrTeddy, what are your predictions on the two AOI? (The W. Carribean and the Atlantic ones)
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Quoting WeatherStudent:


Really Adrian? Despite conditions expected to become tremendously favorable in the Carib between 24-48-72 hours from now? Moreover, I'll take your feedback into consideration, since afterall, you do have a B.A. Degree in tropical meteorology, so that would lead me to believe that you must know a thing or two in regards to the tropics.


Tremendously favorable? Thats a slim chance.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting WeatherStudent:


Really Adrian? Despite conditions expected to become tremendously favorable in the Carib between 24-48-72 hours from now? Moreover, I'll take your feedback into consideration, since afterall, you do have a B.A. Degree in tropical meteorology, so that would lead me to believe that you must know a thing or two in regards to the tropics.


You should take the NHC into consideration, since they all have degrees and its their job, lol
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Quoting IKE:


I know who you are now....


I thought everyone knew I was HOG.
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Something to support the more negative view on this is the HPC's latest discussion on the Caribbean says this disturbance will be slow to development and doesn't really give forward guidance like yesterday.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1221. Levi32
Quoting hurricane23:
Chances are slim in my view.


I agree. Significant development is unlikely. It will have to be watched if it gets into the Gulf of Mexico though.
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Quoting canesrule1:
they really need to update the QuikSCAT.


Quikscat for what lol theres nothing out there with any kind of surface circulation.As in every june/july the caribbean is an area to watch for development but until those westerlys relax iam not seeing it.
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1219. beell
Quoting nrtiwlnvragn:
TROPICAL DISCUSSION - INTERNATIONAL DESKS

THE WAVE ALONG 52W AND THE ONE ALONG 56W...IN INTERACTION WITH THE TUTT...


Are they talking about the 2nd TUTT from 10N 60W to 30N 50W?
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Quoting canesrule1:
wow, you drink a lot of water, i know fiji, evian, voss, and acqua panna are expensive but i dont care because i know it will be plenty refreshing and very safe.
Fiji water tastes like the well water we have in Cayman.
Member Since: October 9, 2008 Posts: 0 Comments: 8392
If a center were to take hold, I dont see how it would make it to the Gulf,
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1216. hydrus
If you like water,mineral water from deep in the mountains of North Carolina will simply blow your mind.It is nothing short of incredible.
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If there was a center in the Carribbean its way down there just north of Panama, which is a lot farther south than what I thought.
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Quoting hurricane23:
Chances are slim in my view.
for what?
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Quoting hurricane23:
Dont see anything significant developing anytime soon as the westerlys are still quite strong down there.


They're forecasted to die down.
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Chances are slim in my view.
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they really need to update the QuikSCAT.
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TROPICAL DISCUSSION - INTERNATIONAL DESKS

THE WAVE ALONG 52W AND THE ONE ALONG 56W...IN INTERACTION WITH THE TUTT...WILL SUSTAIN A SURGE IN ITCZ RELATED CONVECTION OVER THE GUIANAS...WITH RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 20-40MM. AS THE WAVES INTERACTS/ MODULATES THE ATLANTIC ITCZ NORTH CONVECTION WILL SPREAD TO THE SOUTHERN WINDWARD ISLANDS/ORINOCO DELTA REGION IN VENEZUELA THROUGH 42-48 HRS...WITH MAXIMA OF 20-40MM. OVER THE LESSER ANTILLES IT WILL SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-35MM. OVER PUERTO RICO TO THE VIRGIN ISLANDS EXPECT ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF 25-50MM.
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Quoting kmanhurricaneman:
take look the rgb loop on the atlantic AOI its is looking impressive i believe we will soon see our first system shortly.
i agree it does look impressive i thin it will do a shift to the north and it will not make landfall in south america.
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1207. IKE
not much on the 12Z ECMWF
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Quoting hurricane23:
Dont see anything signifcant developing anytime soon as the westerlys are still quite strong down there.


Right now, yes
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Dont see anything significant developing anytime soon as the westerlys are still quite strong down there.
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1204. IKE
Quoting CaneWarning:


Yeah, was that with Fay? I can't remember. At least I was under a hurricane warning at the time.


I know who you are now....
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Quoting IKE:


I think he lives in Tampa, put up shutters last year and the winds never got over 15-20 mph.


Yeah, was that with Fay? I can't remember. At least I was under a hurricane warning at the time.
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take look the rgb loop on the atlantic AOI its is looking impressive i believe we will soon see our first system shortly.
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Quoting nrtiwlnvragn:


HouseGriffydor ?


That's me.
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Quoting jeffs713:

Nestle LifeWater = filtered tap water. Same thing with Dasani and Aquafina.

Fiji water is good, (I used to handle the imports of it.. it really is from Fiji), and it doesn't have *any* taste. But when you drink as much water as I do (I will go through 2x 32oz bottles at work, and another 2-3x 1/2 liter bottles at home)...

I generally get bottled, but in the largest containers I can find.
wow, you drink a lot of water, i know fiji, evian, voss, and acqua panna are expensive but i dont care because i know it will be plenty refreshing and very safe.
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Quoting kmanhurricaneman:
well i drink bottled water here i dont trust all the chemicals they put in our city water call paranoid but i feel better with bottled water nestles preferably.

Nestle LifeWater = filtered tap water. Same thing with Dasani and Aquafina.

Fiji water is good, (I used to handle the imports of it.. it really is from Fiji), and it doesn't have *any* taste. But when you drink as much water as I do (I will go through 2x 32oz bottles at work, and another 2-3x 1/2 liter bottles at home)...

I generally get bottled, but in the largest containers I can find.

Also, in the Houston area... you can taste the tap water, for sure. You can also see whats in it in your bathtub/shower/sink/anything that touches the tap water. Some days, its a white ring, some days its orangish... but definitely a chemical "flat" taste to it.
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1197. IKE
Quoting nrtiwlnvragn:


HouseGriffydor ?


I think he lives in Tampa, put up shutters last year and the winds never got over 15-20 mph.
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Quoting KEHCharleston:
Depends on where I am getting the tap water. Not at home, but my sister's water taste fine. Will probably fill some jugs from her house before any storm, but I am buying bottled water.
read what i wrote before, and i dont care if tap taste better i really do feel better drinking fiji and evian than drinking it straight out of the tap.
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1195. Levi32
Quoting Weather456:


To some extent yes. But tropical waves are very dynamic in changing the tropical atmopshere that is they are reffered to as "wave-like disturbance in the normal tropical airmass". So some level of instability will be created.



Ok that makes sense. This is also a stronger wave than the last one that didn't really generate much precip in the Caribbean. And I would think that Trinidad will get most of the rain due to day-time t-storms firing over mainland South America along the wave axis.
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Quoting kmanhurricaneman:
well i drink bottled water here i dont trust all the chemicals they put in our city water call paranoid but i feel better with bottled water nestles preferably.
i do agree with you (and even though tap tastes the best i will still continue to buy fiji) but sometimes tap cant be bad, and if you get sick, SUE, thats what i would do, :-)
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Just a heads up, you can stop by my blog during the off season for some interesting topics. They will not be daily but I have 3 definite topics that will be posted.

Relationship between hurricanes and other natural diasters: Earthquake

The 2009 Hurricane Season Forecast verification (April 2010)

Preliminary Outlook for 2010.

Gods Willing.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting canesrule1:
feel free to answer thanks, who here prefers bottled water over tap water?
Depends on where I am getting the tap water. Not at home, but my sister's water taste fine. Will probably fill some jugs from her house before any storm, but I am buying bottled water.
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Re: 1187. Eddye has been here at least once.

I prefer firewater myself. :-)
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well i drink bottled water here i dont trust all the chemicals they put in our city water call paranoid but i feel better with bottled water nestles preferably.
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Quoting IKE:
2009 missing bloggers....

eye(downcaster)
edie(school canceled blogger)


HouseGriffydor ?
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Quoting extreme236:


And you did this why?
because i wanted to do it.
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Quoting canesrule1:
well i live in miami and i have always drank bottled but yesterday i did a test blind folded with 4 types of water Voss, fiji, evian, and tap. to my surprise tap water was the best.
and there i stood thinking, damn man thousands of dollars down the drain because all i would buy was fiji water and now tap which is free is better!!!
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Strange.
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Quoting Levi32:


You're more familiar with tropical waves than I am, so correct me if I'm wrong, but I figured the area of upper convergence and subsidence currently over and SE of the windwards would limit shower activity as the wave passes through the islands?


To some extent yes. But tropical waves are very dynamic in changing the tropical atmopshere that is they are reffered to as "wave-like disturbance in the normal tropical airmass". So some level of instability will be created.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting canesrule1:
well i live in miami and i have always drank bottled but yesterday i did a test blind folded with 4 types of water Voss, fiji, evian, and tap. to my surprise tap water was the best.


And you did this why?
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting kmanhurricaneman:
bottled
well i live in miami and i have always drank bottled but yesterday i did a test blind folded with 4 types of water Voss, fiji, evian, and tap. to my surprise tap water was the best.
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roflmao
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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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