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: 232 - 182

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

So I am about to start a weather company and I am trying to figure out which name that I want it to be..

I have came down to four names. Which do you all think is best?

  • Spark Weather

  • Star Weather

  • People Weather

  • iWeather Live
  • Dr. Masters best used word is "IF"--Warming is not a foregone conclusion!
    Member Since: Posts: Comments:
    Ain't those something like a Henry Box? Oh wait, they are Herbert Boxes right? I mean Hebert Boxes? They steer storms towards Florida right?

    Afternoon all ¿~)
    Member Since: Posts: Comments:
    those are heberts boxes...lol
    Member Since: Posts: Comments:
    Ahem...

    Excuse me, but someone is stirring the breeze in the wrong direction here in the Turks & Caicos (72 W x 22 N)... Light wind from the Southwest, veering to the West... that ain't right, who left which door open?

    CRS

    Member Since: Posts: Comments:
    Quoting Orcasystems:



    Don't you dare......


    Mind you.. if you did... it might get me off the hook for earlier.... so Ike... what do you think they are :)
    Member Since: Posts: Comments:
    Quoting IKE:


    Hey....what are those 2 boxes on that satellite? A glitch?



    Don't you dare......
    Member Since: Posts: Comments:
    224. IKE
    Quoting Orcasystems:


    Other then the South West Caribbean, it looks basically tranquil.


    Hey....what are those 2 boxes on that satellite? A glitch?
    Member Since: Posts: Comments:


    Other then the South West Caribbean, it looks basically tranquil.
    Member Since: Posts: Comments:


    Thank god for Shear :)
    Member Since: Posts: Comments:
    Quoting CybrTeddy:
    Alright guys, there are a thousand steps to go through and we are on number 8. you guys are talking about step 692.


    Hi Cybr that is something JP loved to say lol :)
    Member Since: Posts: Comments:
    Quoting IKE:
    12Z ECMWF


    Looks reasonable.
    Member Since: Posts: Comments:
    219. IKE
    12Z ECMWF
    Member Since: Posts: Comments:
    213 - Lets start with replacing that lawn mower. LoL L8R - back to the salt mines.

    Member Since: June 12, 2005 Posts: 6 Comments: 8185
    Teddy has it on the money.
    Member Since: Posts: Comments:
    Quoting CybrTeddy:
    Alright newer folks that its their first year, here's how it pretty much works for the blog and the tropical cyclone. From last year atleast and its showing this year.
    1) GFS predicts a system like 200+ hours out,
    2) After a few straight days of enduring the GFS some other models jump on board.
    3) A disturbance develops in the general area of the models predicting something to develop.
    4) The next day the NHC takes notice with usually a Low or sometimes a medium chance of development.
    5) The disturbance gets the snot beat out of it over night due to Durinal Cycles.
    6) The disturbance rebounds overnight and a lot of the times has -80C cloud tops.
    7) Declared an Invest 90L-99L.
    8) Invest recycles through step 5 and 6 for a few days,
    9) Finally the invest either dies out or becomes a Tropical Depression or some times straight to Tropical Storm and we go out from there,

    That is quite possibly the best plot synopsis I have seen of our local soap opera, "As the Blog Turns".
    Member Since: Posts: Comments:
    So the CMC finally joins. It's rather interesting how the models change like the blog tune when something turns around. :)
    Member Since: July 24, 2005 Posts: 407 Comments: 19076
    Quoting CybrTeddy:
    Alright newer folks that its their first year, here's how it pretty much works for the blog and the tropical cyclone. From last year atleast and its showing this year.
    1) GFS predicts a system like 200+ hours out,
    2) After a few straight days of enduring the GFS some other models jump on board.
    3) A disturbance develops in the general area of the models predicting something to develop.
    4) The next day the NHC takes notice with usually a Low or sometimes a medium chance of development.
    5) The disturbance gets the snot beat out of it over night due to Durinal Cycles.
    6) The disturbance rebounds overnight and a lot of the times has -80C cloud tops.
    7) Declared an Invest 90L-99L.
    8) Invest recycles through step 5 and 6 for a few days,
    9) Finally the invest either dies out or becomes a Tropical Depression or some times straight to Tropical Storm and we go out from there,


    That's the best way to sum it up
    Well sport..when the world began,..5000 years ago.
    or 4.9 Billion?

    Werent many coal burning dinosaurs nor 2 Billion Vehicles spewing out emission 24/7/365...even 5000 years ago

    But dont worry,those Methane,and Co2 Scrubbing Fairies come out every night and wave their Magic wands and POOF all those nasty GW emissions under the rug.

    Kinda like some Politicians...and Governments.

    Ever been to Beijing or Hong Kong at 5pm in August..?




    No worries mate.



    Hong Kong on a Good Day
    Member Since: Posts: Comments:
    Quoting CybrTeddy:
    The setup could be similar to Tropical Storm Arlene in 2005 or Tropical Storm Alberto in 2006.


    Alberto went over the Tallahassee area, and over my house, that Year....We dodged a potential bullet because it did not intensify, and only a few wind gusts and branches down, but the rain actually did some good and cooled things off.....Wouldn't actually mind some tropical moisture to bring down these 95 % temps right about next week...
    Member Since: Posts: Comments:
    208, if that is for me. I am only asking a question I don't have an answer for.
    Member Since: June 12, 2005 Posts: 6 Comments: 8185
    Alright guys, there are a thousand steps to go through and we are on number 8. you guys are talking about step 692.
    Member Since: July 8, 2005 Posts: 259 Comments: 23574
    Quoting Patrap:
    Jeff Masters,from reading the above..isnt spitting anything out but The scientific data collected by Scientists,..

    One has to read the data,before spewing thoughts into the great WWW void here.

    The Data is the Key..not one individual's view.
    The Warming occurs without ears to us or anyone.





    True, true, but you have to start the data when the world began.
    Member Since: Posts: Comments:
    Jeff Masters,from reading the above..isnt "spitting" anything out but The scientific data collected by Scientists,..

    One has to read the data,before spewing thoughts into the great WWW void here.

    The Data is the Key..not one individual's view.
    The Warming occurs without ears to us or anyone.



    Member Since: Posts: Comments:
    Alright newer folks that its their first year, here's how it pretty much works for the blog and the tropical cyclone. From last year atleast and its showing this year.
    1) GFS predicts a system like 200+ hours out,
    2) After a few straight days of enduring the GFS some other models jump on board.
    3) A disturbance develops in the general area of the models predicting something to develop.
    4) The next day the NHC takes notice with usually a Low or sometimes a medium chance of development.
    5) The disturbance gets the snot beat out of it over night due to Durinal Cycles.
    6) The disturbance rebounds overnight and a lot of the times has -80C cloud tops.
    7) Declared an Invest 90L-99L.
    8) Invest recycles through step 5 and 6 for a few days,
    9) Finally the invest either dies out or becomes a Tropical Depression or some times straight to Tropical Storm and we go out from there,
    Member Since: July 8, 2005 Posts: 259 Comments: 23574
    Gudentag, quite the exchange today on this subject.

    I hope there is someone lurking that can answer a simple question.

    What does all the reflected satellite energy to do the atmosphere? Like QuickSat for instance. That's powerful stuff to reach down and reflect wind speed readings far back up throught the atmosphere. Let's multiply that by (enter number here) or more since we don't know what many of secret satellites do. What does that slow steady injection of energy and excitement of particles in the atmosphere do to its temp?

    How many satellites are actually above the planet sending down energy at us? It seems hard to find a correct answer.

    Does Ice melt in a microwave?

    Just a skewed view that does not get much attention :)



    Link

    Link

    Link
    Member Since: June 12, 2005 Posts: 6 Comments: 8185
    Quoting Drakoen:


    I think it will stay west of 80W as well. The entire GOM needs to watch this lol. A lot of times these preliminary models will favor a deep layered ridge over the trough.


    Yeah it definitely bears watching. We'll have lots of time to track the area of disturbed weather before development occurs, if it occurs.

    Back later.
    Member Since: Posts: Comments:
    Drakeon bring the rain to TX! drought spreading like wild fire
    Member Since: Posts: Comments:
    Quoting Levi32:


    I agree. As the CMC shows I think it will stay west of 80W. I don't see it going any further east than that while it's south of 30N.


    I think it will stay west of 80W as well. The entire GOM needs to watch this lol. A lot of times these preliminary models will favor a deep layered ridge over the trough.
    Member Since: Posts: Comments:
    Dr. M spitting out more numbers again. Just like those Wall St folks, always wrong. Hell, scientists mapped the exact 4 corners states wrong by many miles and just now realized it!....maybe the same thing is happening with the sea level rise. Just a little miscalculation. Cant predict the future folks, Wall St can't, OPEC can't, and everybody else.
    Member Since: Posts: Comments:
    The setup could be similar to Tropical Storm Arlene in 2005 or Tropical Storm Alberto in 2006.
    Member Since: July 8, 2005 Posts: 259 Comments: 23574
    Quoting Drakoen:


    The 102hr is 4.25 days out. If the circulation remains small then the ridge will likely pull it out westward. If it gets larger I could see more poleward momentum. The 500mb vorticity on the CMC even hinted at that possibility.Link


    I agree. As the CMC shows I think it will stay west of 80W. I don't see it going any further east than that while it's south of 30N.
    Member Since: Posts: Comments:
    Quoting Levi32:


    It's not that hard to miss. We're not likely to see a rapidly-strengthening system in the NW Caribbean. What we're most likely to see is a slowly organizing area of low pressure moving near the coast of Honduras in 3-5 days. During that time the upper trough is going to be pulling out, and the GFS does have bias there in keeping the SW Atlantic ridge weak. The pattern is such that the west Caribbean and southern Gulf of Mexico are where to look. Recurvature into the trough is not impossible but I think it's less likely.


    The 102hr is 4.25 days out. If the circulation remains small then the ridge will likely pull it out westward. If it gets larger I could see more poleward momentum. The 500mb vorticity on the CMC even hinted at that possibility.Link
    Member Since: Posts: Comments:
    Criminals and Terrorists should be forced to cut Grass in NOLA at 1pm in This Heat and Humidity.


    Im ruined fer the day.
    Member Since: Posts: Comments:
    Quoting Drakoen:
    Don't see how any significant system misses this kind of 500mb trough


    It's not that hard to miss. We're not likely to see a rapidly-strengthening system in the NW Caribbean. What we're most likely to see is a slowly organizing area of low pressure moving near the coast of Honduras in 3-5 days. During that time the upper trough is going to be pulling out, and the GFS does have bias there in keeping the SW Atlantic ridge weak. The pattern is such that the west Caribbean and southern Gulf of Mexico are where to look. Recurvature into the trough is not impossible but I think it's less likely.
    Member Since: Posts: Comments:
    Ocean Levels - Fear of the unknown
    Member Since: October 13, 2005 Posts: 4 Comments: 2156
    If the GFS were showing something developing it would move to the northeast. It's showing the surface trough lifting northward into the Bahamas. The weakness is most pronounce on the GFS though that may be poleward bias.
    Member Since: Posts: Comments:
    Quoting Levi32:


    If by Atlantic you mean the Caribbean then yes it will.


    Sounds pretty good
    Quoting MeterologistDewon9:


    Will it drift into the Atlantic or stay in the Pacific?


    If by Atlantic you mean the Caribbean then yes it will.
    Member Since: Posts: Comments:
    Doesn't look like the UKMET wants to join the fun so all we have is the CMC and NOGAPS with a hint from the EMCWF.
    Member Since: Posts: Comments:
    Quoting Patrap:
    UNYSIS 10-day GFSx


    Is it just me, or does the GFSx take the Caribbean blob up near the keys, and then it disappears overnight on day 7?
    Member Since: Posts: Comments:
    Quoting Levi32:


    It's a broad area of low pressure that will be drifting northwestward over the next 5 days. Some models are forecasting development once the shear lowers but it remains to be seen.


    Will it drift into the Atlantic or stay in the Pacific?
    No floater on 91E but still code orange.
    Member Since: October 9, 2008 Posts: 0 Comments: 8268
    Quoting MeterologistDewon9:
    Guys, I am starting a weather website in a couple of weeks and I need the following and was hoping that you guys can help out;

    -4 Meteorologists for Tropical Weather
    -4 Meteorologists for Severe Weather

    You all don't have to be a real meteorologist, just let me know via mail if you want too!

    Also, what is the blob in central america near the Panamal?


    It's a broad area of low pressure that will be drifting northwestward over the next 5 days. Some models are forecasting development once the shear lowers but it remains to be seen.
    Member Since: Posts: Comments:
    Guys, I am starting a weather website in a couple of weeks and I need the following and was hoping that you guys can help out;

    -4 Meteorologists for Tropical Weather
    -4 Meteorologists for Severe Weather

    You all don't have to be a real meteorologist, just let me know via mail if you want too!

    Also, what is the blob in central america near the Panamal?
    Quoting tornadofan:

    BLEH! I don't like that. Why couldn't this just fizzle away, and give us all a full month of bickering and blob-watching?
    Member Since: Posts: Comments:

    Viewing: 232 - 182

    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
    70 °F
    Overcast