Sea level rise: what has happened so far
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
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most of those people have lost alot, getting a break on a trailer is probably not a bad thing,IMO
Wouldn't do much. Even if every person on earth used a 5 gallon bucket, that's only 30 billion gallons of water. The oceans hold ~ 326 million trillion gallons of water!
Not to mention all that water dumped inland would runoff back into the ocean.
If you purchase the trailer and become the owner,you waive all rights to Making a claim against the Gov,and Manufacturer to any and all Formaldehyde issues.
Ouch. I didn't notice that.
Did anyone just feel a sharp, stabbing pain in their back? :\
I still see a spin...now SW of Jamaica. I see clouds just south of the Caymans, going west. I see clouds SSW of Jamaica going east.
Huge problem...near 50 knots of shear in the area.
I know...it's suppose to drop, but it hasn't, yet.
Name 3 things that America Makes that aint worth a Dollar.
ULL formation???
Look at the blob of convection just off the NW coast of South America, it's very close to the area where the early post showed a surface low in the SW Carribean! One more blob to watch!
Also an area of lower shear, dropping south, toward south Florida and then Cuba....
Link
Wednesday June 10, 2009
The rainy season has just started in Tokyo, but residents in a small coastal town have reported a different phenomenon: tadpoles dropping out of the sky.
An office clerk in Nanao first noticed the anomaly when he heard a dull thud in a parking lot last week, news reports said.
Looking around, he saw about 100 dead tadpoles splattered on car windscreens and on the ground.
More reports followed from bewildered residents in Nanao.
"People speculate that a waterspout picked them up and dropped them from the air," an official at a local weather observatory said.
"But from a meteorological point of view, I have to say it is most unlikely.
"We have checked the weather conditions of last week, thinking gusts of wind might have hit the area but confirmed no damage.
"To be honest, I don't think it was anything caused by a weather condition."
Similar events have been reported around the world, with whirlwinds passing over water bodies and picking up frogs, jellyfish or other unfortunate animals before dumping them back to earth.
© ABC 2009
Local angler using dynamite at the nearest fishing hole?
Good Morning Ike
Remember there is a perennial low over that high terrain in Colombia that tends to create these big blow ups of convection. The thunderstorm mass then moves out over the open water but more often than not they do not develop into anything in the SW Caribbean. Typically they move off into the EPAC or dissipate.
I do not believe that what you are seeing there is the precursor of the potential low the NHC has on the forecast maps.
That is just what we need here in my area. A few streets over, we have a couple rows of mobile homes that were damaged by Ike. Everyone that was damaged, had a FEMA mobile stuffed in the "driveway" beside the damaged one.(their is about 20 of them with about three or four feet between each one.) I should mention it is a narrow road with open ditches so parking is a real nightmare in the area now.
I imagine the homeowners association in my neighborhood just put their heads in their laps and started to cry, especially since about half the folks had moved back into their normal home and are begging FEMA to come pick up the trailer.....
Man if I could jsut get one for the hunting camp....
Check out the cute "Twin Highs" in the GOMEX.
The models have not really handled the SW Caribbean well if you look at the last 7 days of runs. In particular, shear values have remained stubbornly high, thus preventing any development regardless of what the models have shown.
Shear has been on the rise for the past 24 hours in that area so we are at least 2 days or more away from any chance of something developing.
i think this season we may see the gulf a little more protected due to high pressure systems
Take a look.
My Blog
It would not appear to have anything to do with the SW Caribbean
A lot will depend on whether we have neutral or El Nino conditions. The jury is still out on that.
16:27 GMT le 10 juin 2009
Yes, I am leaving Sunday for my first-ever European vacation, a 2-week trip to London and Kefallonia Island, Greece. I trust there will be plenty of tropical action to follow during the time I'm gone! I'll post an last half-of-June outlook on Friday or Saturday before I go.
Jeff Masters
Thanks Dr. Masters!!! lol
Speaking of this issue, and I forgot when the "parking" occurs, but are we nearing the A-B high summer set up for the Atlantic & Gulf ridging yet (or does it set later in July)? If high pressure continues over the Gulf and SE US (the Devil's High I beleive) we could end up with an, albeit temporary one subject to trof erosion later in the season, bridge accross the area offering some protection for Florida and the Gulf...
Not yet but an earlier posted map showed one forecasted in that area in the near future. The convection there now could be the start of it is all I'm saying.
Quoting sporteguy03:
Dr.Masters,
Do you have any big vacations coming up? Then the tropics will heat up!
Yes, I am leaving Sunday for my first-ever European vacation, a 2-week trip to London and Kefallonia Island, Greece. I trust there will be plenty of tropical action to follow during the time I'm gone! I'll post an last half-of-June outlook on Friday or Saturday before I go.
Well as we all know, for sure there will be activity while doc is gone!!!! Where will it be?
2004
2005
see u later
1691. CycloneOz
"Through the night came the rains, soaking all things to be seen in the dim morning light. Life in the mountains, revitalized. One stares and wonders at nature's magnificence!"
1702. CycloneOz
"Bees are a buzz amongst the wildflowers that sing a new day with color. Rain moistened life, a steady pour has made green greener. The sounds of rejoicing fill the misty air."
1711. CycloneOz
"Puddle skippers at play shoo away bright birds that drank deeply. The high desert air softens. It rains without lightning, a sky-fed stream without thunder. Mountain morning comfort and contentment."
OK - OZ, don't let this go to your head, I still am against you playing chicken with a hurricane, but man can you write some kind of great poetry.
I must say, it happens all the time. As soon as he leaves he get a Tropical Depression or Storm.
Good punctuation there sir!
You sound like JFV with the "Sir"...Lol
That was my intention bud
Tropical Tidbit for June 10th
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