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: 632 - 582

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

Goodnight
Member Since: Posts: Comments:
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
Member Since: Posts: Comments:
we'll be waiting:)
Member Since: Posts: Comments:
Quoting stillwaiting:
however,its looking like shear in the west carib w/be falling quickly over the next 48hrs,imo


Thanks for the analysis. 'Noticed the shear as well but you're right too high now for anything of consequence. Happy watching.
Member Since: Posts: Comments:
so there's a ULL forming cutting off from the trough east of FL and w/be moving SW over the yucatan area????
Member Since: Posts: Comments:
however,its looking like shear in the west carib w/be falling quickly over the next 48hrs,imo
Member Since: Posts: Comments:
Quoting LightningCharmer:
615: The best evidence, I've seen so far. The IPC-whatever has got nothing on your findings here. LOL

Water Vapor Floater appears to show more organization to my rather untrained eye.

Atlantic and Caribbean Tropical Satellite Imagery


except for the 40-50kt UL winds over the area,the main reason for the wx,lol
Member Since: Posts: Comments:
Quoting Vortex95:
So was 1850 it was so quiet there is no record of it ;P.


Even if data during that year were available, it would be sketchy at best.

I'm sure you know this, but data prior to the satellite era is very limited and ambiguous.

In fact, I'd wager that a significant portion of tropical cyclones (either of tropical storm or hurricane intensity) went unnoticed during most of those years, which would indicate that those seasons were more active than is officially recorded.

I would also wager that the intensity of the storms that were recorded, were both grossly underestimated and overestimated during that time period.
Member Since: Posts: Comments:
Quoting Vortex95:
So was 1850 it was so quiet there is no record of it ;P.


Thats only because you didn't have a laptop :)
Member Since: Posts: Comments:
615

LOL - yep that just might be the cause
Member Since: Posts: Comments:
615: The best evidence, I've seen so far. The IPC-whatever has got nothing on your findings here. LOL

Water Vapor Floater appears to show more organization to my rather untrained eye.

Atlantic and Caribbean Tropical Satellite Imagery
Member Since: Posts: Comments:
Quoting Vortex95:
max 7 ?


Wave Height in feet
Member Since: Posts: Comments:
i'm going w/ june 22,I don't think this area w/get a name,less than 10% chance,IMO
Member Since: Posts: Comments:
Quoting StSimonsIslandGAGuy:
July 12 is the average date for the first tropical storm formation in the Atlantic. 4 years since 1960 have had the first storm form on August 15 or later.


1984 is a good reminder that, no matter how late a season starts, we can still see an active season.

That year, though relatively quiet in terms of landfalls (save for Category 4 Hurricane Diana, which fortunately had weakened to a Category 2 by the time of its North Carolina landfall), was very active, featuring 13 named storms, along with a December hurricane (Lili).

The first storm, Arthur, did not develop that year until August 28.
Member Since: Posts: Comments:
Quoting StSimonsIslandGAGuy:
July 12 is the average date for the first tropical storm formation in the Atlantic. 4 years since 1960 have had the first storm form on August 15 or later.


Yup, and since the more hyper-active tropical pattern began in 1995 there have been several seasons where the first tropical storm didn't form until after the date you mentioned.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Sea Levels - I think I found the problem...
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Navy NRL still has 91E listed as an invest, but has a Tropical Cyclone Formation Alert (TCFA) issued for it. I imagine we'll see a tropical depression out of this anytime within the next 12-24 hours.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
kman if you are still on I think I would rather get my updates from you instead of Sambula who doesn't sound like he knows too much and as for Jphn Foster he is a joke.
Member Since: October 9, 2008 Posts: 0 Comments: 8319
Quoting StSimonsIslandGAGuy:
We'll see. 4 days seems agressive to me--I really don't see much potential out there


Perhaps, but this system is supposed to begin evolving in about 60 hours or so with an initial disturbance forming in the Jamaica area.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting Drakoen:


My date already passed but if I had to put a date now I would pick Sunday June 14th


Just wondering, do you think you think we will have an active July like last year?
Member Since: Posts: Comments:
27th :P

Go Pens!

StSimonsIslandGAGuy,12,7,3,0,7-12

In the running !
Member Since: Posts: Comments:
Blog Update
Reflector site for those at work, which now also includes Weather456, daily updates


AOI #1

AOI #2

Member Since: Posts: Comments:
Quoting scottsvb:
You guys do know that this isnt a TD nor will be till probably Friday..right?? They will make this a invest on Thurs probably..then send a plane down there "if warrents" on Friday to maybe give us a call on this in the late afternoon.
The convection you see near Jamaica is just what you saw a few nights ago off Nicaragua..its being enhanced by the upper trough digging down to Cuba. This convection is "Far" away from the broad circulation thats developing around 11N and 78W... right now.. just give this time as it migrates NNW over the next day or 2.. probably has a 40% chance right now of developing since more models are picking up on this...but Dry air is in the GOM and forecasted to stay that way. Movement into the GOM or Yucitan is still over 3 days away..so we have time to see how the pattern evolves!



100%,great sypnosis...UL divergence is the mess SE of jamaica,the area to watch w/be south and west of jamaica,IMO and friday or sat. shear should be low enough for organization to occur as the feature moves towards the SE GOM over the NW tip of cuba by sat or sunday...
Member Since: Posts: Comments:


Upper Level WV/IR - North Atlantic - Latest Available - Large Scale
Member Since: Posts: Comments:
Quoting StSimonsIslandGAGuy:
Drakoen if you had to put up a date in a contest for the first named storm in the Atlantic this year, what date would you choose?


My date already passed but if I had to put a date now I would pick Sunday June 14th
Member Since: Posts: Comments:
Quoting Vortex95:
that blob is being enhanced anyways.


I love it when you use those highly Technical Meteorological terms.
Member Since: Posts: Comments:
Quoting Vortex95:
I think there was some confusion I think some where talking about a TD in the EPAC.


Don't think so. The post referred to sending a plane down to investigate it, something that is normal for the ATL basin but hardly likely for a system out in the EPAC.

Not that it matters much.

Good night all
Member Since: Posts: Comments:
Quoting scottsvb:
You guys do know that this isnt a TD nor will be till probably Friday..right?? They will make this a invest on Thurs probably..then send a plane down there "if warrents" on Friday to maybe give us a call on this in the late afternoon.
The convection you see near Jamaica is just what you saw a few nights ago off Nicaragua..its being enhanced by the upper trough digging down to Cuba. This convection is "Far" away from the broad circulation thats developing around 11N and 78W... right now.. just give this time as it migrates NNW over the next day or 2.. probably has a 40% chance right now of developing since more models are picking up on this...but Dry air is in the GOM and forecasted to stay that way. Movement into the GOM or Yucitan is still over 3 days away..so we have time to see how the pattern evolves!


The TD is referring to the storm in the Pacific. The High in the GOM doesnt spare the east coast or the Caribbean islands from a potential storm be it tropical or not.
Member Since: Posts: Comments:
with that latest Quikpass, the 00z models runs will finaly tell us what will happened with this long lasting disturbance.
Member Since: Posts: Comments:
587. scottsvb 2:18 AM GMT on June 11, 2009

TD ??. Who said that ??. I think Drak and I know a TD when we see one and also when we don't LOL
Member Since: Posts: Comments:
Quoting Vortex95:
577. Orca of course and he shall ban all who are insuborniate!!!! Anyways I remember someone steping in for him last year.


I think it was somebody under the name of suvillianweather i believe
Member Since: Posts: Comments:
Quoting Vortex95:
577. Orca of course and he shall ban all who are insuborniate!!!! Anyways I remember someone steping in for him last year.


???? umm what did I do this time?
Member Since: Posts: Comments:
Well I'm turning in for tonight. There won't be a lot new to see in the short term.

Catch you all tomorrow
Member Since: Posts: Comments:
You guys do know that this isnt a TD nor will be till probably Friday..right?? They will make this a invest on Thurs probably..then send a plane down there "if warrents" on Friday to maybe give us a call on this in the late afternoon.
The convection you see near Jamaica is just what you saw a few nights ago off Nicaragua..its being enhanced by the upper trough digging down to Cuba. This convection is "Far" away from the broad circulation thats developing around 11N and 78W... right now.. just give this time as it migrates NNW over the next day or 2.. probably has a 40% chance right now of developing since more models are picking up on this...but Dry air is in the GOM and forecasted to stay that way. Movement into the GOM or Yucitan is still over 3 days away..so we have time to see how the pattern evolves!
Member Since: Posts: Comments:
I see the blow up there. Seems like the High is pulling out to sea. Isnt there a lot of shear there as well? My last comment. Gotta hit the hay long day tomorrow.
Member Since: Posts: Comments:
Quoting Acemmett90:

based on the sat it should be td-1


Despite the presence of banding features, both on conventional satellite imagery as well as microwave imagery, I don't think the circulation is fully closed yet. We also haven't had a recent QuikSCAT pass to confirm it.
Member Since: Posts: Comments:
Same here. Just working a lot and doing the soocer thing with my oldest. Hoping for an active season with lots of fish storms, no damage, and good rainfall.
Member Since: Posts: Comments:
New Blog.
Member Since: Posts: Comments:

Viewing: 632 - 582

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
65 °F
Overcast