Sea level rise: what has happened so far

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

Share this Blog
4
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 682 - 632

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37Blog Index

Quoting Drakoen:


Never being wrong is a problem in itself lol


Never wrong... and seldom wrong
Different meanings
Member Since: Posts: Comments:
Quoting Orcasystems:
I think I would stick with 456, if you read his Blog every morning like I do... he is seldom wrong in his assessment.


Never being wrong is a problem in itself lol
Member Since: Posts: Comments:
Quoting StSimonsIslandGAGuy:
Perhaps Drakoen and Weather456 could collaborate.


Drak is good amateur.
I think 456 is actually a professional forecaster.

I could be wrong... god knows it wouldn't be the first or last time.
Member Since: Posts: Comments:
Quoting zoomiami:
Everyone is certainly entitled to have some time off.

W456 - based on the current steering patterns, which direction should the blob move for the next few days?

We actually have only a 20% chance of rain for the next 3 days, its kind of nice.


A shallow disturbance (which is most likely if anything develops) would move towards the northwest under the influence of low-mid level ridge north of the region. The deep layer is much different but I don't think we would get a system that deep.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
It was oppressively hot here today. Here's what's in store tomorrow:

THE AIRMASS THU WILL REMAIN RATHER SIMILAR TO WHAT WAS EXPERIENCED
WED...WITH RIDGING HOLDING FORT FROM THE SW WHILE AN INLAND LEE
SIDE TROUGH STAYS ANCHORED. THE MAIN FORCING WILL AGAIN BE THE
SEABREEZE...BUT ANOTHER STRONG CAP WITH HIGH CONVECTIVE TEMPS
SHOULD HOLD SHWR/TSTM DEVELOPMENT AT A MINIMUM THROUGH THE MRNG.
HOWEVER...THE MAIN DIFFERENCE WILL BE THAT A MIDLVL SHORTWAVE WILL
RIDE ALONG THE PERIPHERY OF THE RIDGE FROM GA INTO SC DURING THE
AFTN. THOUGH TIMING IS STILL IN QUESTION...THIS SHOULD INCREASE
THE COVERAGE OF SHWRS/TSTMS OVER THE PAST FEW DAYS SHOULD HAVE
INCREASED POPS TO THE 30/40 PERCENT RANGE...HIGHLIGHTING GREATEST
POPS N AND TRENDING LOWER GOING S. IN ADDITION...SEVERE CONVECTIVE
PARAMETERS WILL AGAIN RUN QUITE HIGH...MAKING FOR THE POTENTIAL OF
ISOLD STRONG/SEVERE TSTMS. MAX TEMPS WILL AGAIN RUN IN THE MID
90S...MAKING FOR HEAT INDEX VALUES CLOSE TO THE 100-DEGREE MARK.

Member Since: Posts: Comments:
Quoting StSimonsIslandGAGuy:
Perhaps Drakoen and Weather456 could collaborate.


LOL!
Member Since: Posts: Comments:
Quoting Weather456:
There's also an elongated and broad surface circulation in the SW Caribbean



Maybe the TWO Will mention it later today.
Member Since: July 8, 2005 Posts: 259 Comments: 24457

Quoting Drakoen:


He could let Drak do it. LOL!


Well normally I would agree but considering your post number I'll reconsider.
Member Since: Posts: Comments:
beleive me it won't be a blogger from here last time it was a forecaster from crown weather
Member Since: Posts: Comments:
I think I would stick with 456, if you read his Blog every morning like I do... he is seldom wrong in his assessment.
Member Since: Posts: Comments:
Quoting StSimonsIslandGAGuy:
Or better yet, me me me!


or JFV!!! I meant WeatherSutdent...PresidentialElection
Member Since: Posts: Comments:
Quoting Orcasystems:


I can't remember who it was... but he did have a stand in last year.

Hmmm let Weather 456 do it.



He could let Drak do it. LOL!
Member Since: Posts: Comments:
Everyone is certainly entitled to have some time off.

W456 - based on the current steering patterns, which direction should the blob move for the next few days?

We actually have only a 20% chance of rain for the next 3 days, its kind of nice.
Member Since: Posts: Comments:
okay so what do you judge my age mind wise?
Member Since: Posts: Comments:
Quoting Vortex95:
Are you sure that is not the perenial coloumbian low 456?


The Colombian low is much safer than a Colombian high...

Member Since: Posts: Comments:
Quoting Vortex95:
Orca why have you chosen to believe that I am elderly and infirm?


Just in mind buds... just your mind :)
Member Since: Posts: Comments:
Quoting Orcasystems:


I can't remember who it was... but he did have a stand in last year.

Hmmm let Weather 456 do it.



Read Dr Jeff's blog on Friday.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting zoomiami:


Normally either he will update from wherever he is, or he will have a guest blogger. Hasn't been an issue for the couple of years that I've been on.


He had one last year when he went into the canyon to hike.
Member Since: Posts: Comments:
Quoting Vortex95:
Are you sure that is not the perenial coloumbian low 456?


I was stating the facts not leaning towards an opinion, however it could be the climatological Colombian Low but that's a strange location for it. It's normally snuggled in the Gulf of Drien or stationed within the mosnoon trough over Colombia. The CL is also a heat low, which forms and sustain over land.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Orca why have you chosen to believe that I am elderly and infirm?
Member Since: Posts: Comments:
Quoting Vortex95:
Orca i am not certifiable I am INSANE!!! lol

anyway I am curious on who it would be.


I can't remember who it was... but he did have a stand in last year.

Hmmm let Weather 456 do it.

Member Since: Posts: Comments:
Quoting Vortex95:
Orca i am not certifiable I am INSANE!!! lol

anyway I am curious on who it would be.


Normally either he will update from wherever he is, or he will have a guest blogger. Hasn't been an issue for the couple of years that I've been on.
Member Since: Posts: Comments:
Quoting Vortex95:
Orca i am not certifiable I am INSANE!!! lol

anyway I am curious on who it would be.

well now that you admited you insane you are definly not getting to do it
Member Since: Posts: Comments:
Quoting weatherblog:


Just wondering, do you think you think we will have an active July like last year?


No I don't think July will be active; perhaps the later half will be somewhat interesting.
Member Since: Posts: Comments:
Does it make any sense at all that when we need to water you can't, and when there is plenty of rain, its ok?
Member Since: Posts: Comments:
Orca i am not certifiable I am INSANE!!! lol

anyway I am curious on who it would be.
Member Since: Posts: Comments:
649 -- its the dreaded blog disease.

Just reading an article where they are going to let us start watering again. Rather ironic, considering our issue this week is that there is so much water that lawn is turning to muck! Never a happy medium.
Member Since: Posts: Comments:
Quoting Vortex95:
Its a hoax no!!! it cannot be!!!

Doesn't look like one
Member Since: Posts: Comments:
Quoting zoomiami:
Hey Orca - see they are nominating you to take over for Dr. Masters...lol


THEY are only ONE.
And we know the ONE, is certifiable :)
Alzheimer's has obviously got a firmer hold on him then we actually thought.
Member Since: Posts: Comments:

blob
mark
15.5n/75.5w

2nd spin to dev at
mark
13.1n/79.9w

its going to be hard for something to fire but a window will open shortly after the next 24 hrs
Member Since: Posts: Comments:
Are you sure that is not the perenial coloumbian low 456?
Member Since: Posts: Comments:
456 - thanks for the graphics and the information.

Always like to read what you have to say.

Member Since: Posts: Comments:
Its a hoax no!!! it cannot be!!!
Member Since: Posts: Comments:
There's also an elongated and broad surface circulation in the SW Caribbean

Member Since: July 24, 2005 Posts: 407 Comments: 19076
641. Nothing there. :D
Member Since: Posts: Comments:
seriously the blob is being enhanced by the passing trough if I am sane.
Member Since: Posts: Comments:
Anyone notice a 1008 mb low in the SW Caribbean, from 1009 mb earlier.

1025 PM

Member Since: July 24, 2005 Posts: 407 Comments: 19076
Nice blob in the carribbean..Looks a lil okay.
Member Since: Posts: Comments:
June 12 Ana will form. For the record I posted before the 00z runs.
Member Since: Posts: Comments:
See new position of the low on the graphic as per my earlier post that it needed to be moved 5 degrees further east. Also, down to 1008.

See you tomorrow.

Member Since: August 19, 2006 Posts: 0 Comments: 15846
637. HadesGodWyvern (Mod)
Joint Typhoon Warning Center

Tropical Cyclone Formation Alert (0200z 11Jun)
===============================================
An area of convection near 11.5N 117.7W or 580 NM southwest of Socorro Island has persisted over the past 12 hours. Recent animated multispectral imagery shows deep convection with convective banding wrapping in from the northeast. Sea surface temperatures are very warm (greater than 30C) and the region is very moist throughout the column. Upper level analysis indicates the disturbance is located slightly south of the subtropical ridge axis in a favorable area of minimal vertical wind shear. Broad poleward and equatorward outflow is also evident in the animated multispectral imagery. Finally, a 2100z AMSU vertical cross section depicts improving warm anamaly aloft.

Maximum sustained winds near the center is 18-23 knots with a minimum sea level pressure of 1006 MB. The potential for this disturbance to form into a significant tropical cyclone within the next 24 hours is GOOD.
Member Since: Posts: Comments:
Hey Orca - see they are nominating you to take over for Dr. Masters...lol
Member Since: Posts: Comments:
Quoting stillwaiting:
Good night,see you in the morning everyone,remember shear w/be dropping quickly over the next 48-72hrs w/should have something to watch wondering into the GOM by the end of the weekend


TS guaranteed us a named storm before the 19th
Member Since: Posts: Comments:
The blob might have just form a CC
http://www.ssd.noaa.gov/goes/flt/t1/loop-rb.html
Member Since: Posts: Comments:
Goodnight
Member Since: Posts: Comments:

Viewing: 682 - 632

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

Local Weather

Overcast
48 °F
Overcast