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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I wouldn't expect a direct movement over your area, but definatly nearby. It also depends on how soon, if at all, this system were to develop.
Link
The GFS has been out to lunch on this system for many many days now. All the other models take it slower and further south, which makes more sense. That's not a guarantee, but like I said to weatherwatcher12, even if it goes right over Jamaica the main impact will be rain. This isn't going to be a TS when it passes them. Only slow development, if any, is expected.
take it easy.....
As Tampa Spin indicated, maybe when it get's into the Central Caribbean. Even if it does clear SA, the notorious "Dead Zone" will keep it at bay.
Yes they run for invests.
as far as i know yes and dont forget hurricane lol
That thing east of the Antilles? Unlikely at the moment.
Your only a day late........LOL...its all good.
It will likely oscillate eastward over the north gulf coast when the TUTT lifts out in 4-5 days, and then back to the west a little bit.
COINCIDES WITH A DEEP MOISTURE MAXIMUM SEEN IN THE TOTAL
PRECIPITABLE WATER PRODUCT FROM CIMSS. SCATTERED MODERATE CONVECTION
IS E OF THE WAVE AXIS FROM 6N-12N BETWEEN 47W-53W.
Here is my Tropical Update from yesterday that if i had it to do today i would feel even more confident in!
Wouldn't surprise me.
Try to remember 2004. First named storm didn't come until the last day of July, and then 8 storms formed in one month, with 4 hurricanes hitting the same state in that season. It's way too early to call the season a bust. June only sees a named storm once every 3 years.
ABNT20 KNHC 111731
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT THU JUN 11 2009
FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...
TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE NEXT 48 HOURS.
$$
FORECASTER AVILA
A TROPICAL WAVE IS FROM 12N51W TO 3N54W MOVING W 15-20 KT. THE WAVE
COINCIDES WITH A DEEP MOISTURE MAXIMUM SEEN IN THE TOTAL
PRECIPITABLE WATER PRODUCT FROM CIMSS. SCATTERED MODERATE CONVECTION
IS E OF THE WAVE AXIS FROM 6N-12N BETWEEN 47W-53W.
A TROPICAL WAVE IS S OF 10N ALONG 89W MOVING W 15 KT. ASSOCIATED
CONVECTION IS NEAR THE S PORTION OF THE WAVE IN THE EASTERN PACIFIC.
FURTHER DISCUSSION OF THIS WAVE WILL NOW BE INCLUDED IN THE TWDEP.
CARIBBEAN SEA...
A STRONG SURFACE TROUGH OFF THE N COAST OF COLUMBIA IS FROM 15N74W
TO 9N77W. LOW LEVEL CONVERGENCE WITH THIS TROUGH ALONG WITH UPPER
LEVEL DIFFLUENCE BETWEEN AN UPPER TROUGH OVER THE WRN ATLC CENTERED
AROUND AN UPPER LOW OVER CUBA NEAR 22N77W AND A BROAD UPPER RIDGE
OVER THE ERN CARIBBEAN ARE SUPPORTING SCATTERED SHOWERS AND
THUNDERSTORMS ACROSS MUCH OF THE CENTRAL CARIBBEAN FROM 13N-20N
BETWEEN 70W-77W INCLUDING HAITI AND FAR E CUBA AS WELL AS OFF THE
COAST OF COSTA RICA AND PANAMA FROM 9N-13N BETWEEN 77W-83W. A
TROPICAL WAVE IS JUST INLAND OVER GUATEMALA AND BELIZE...SEE ABOVE
AND THE TWDEP. A SECOND WAVE WILL MOVE INTO THE E CARIBBEAN ON SAT.
ATLANTIC OCEAN...
A SURFACE TROUGH IS IN THE W ATLC EXTENDING FROM 30N67W TO 26N73W.
THIS IS BEING SUPPORTED BY AN UPPER LEVEL TROUGH LINKED WITH THE
AFOREMENTIONED UPPER LEVEL LOW OVER CENTRAL CUBA NEAR 22N77W.
SCATTERED SHOWERS AND THUNDERSTORMS ARE E OF THE TROUGH COVERING THE
SE BAHAMAS AND AN AREA FROM 21N-30N BETWEEN 63W-73W. THE REMAINEDER
OF THE ATLC IS DOMINATED BY SURFACE HIGH PRESSURE ANCHORED TO A 1026
MB HIGH NEAR 28N39W. UPPER LEVEL DIFFLUENCE BETWEEN A BROAD UPPER
TROUGH OVER THE CENTRAL ATLC AND UPPER LEVEL RIDGING LINKED TO AN
UPPER LEVEL HIGH NEAR 12N26W IS SUPPORTING ISOLATED SHOWERS FROM
20N-32N BETWEEN 26W-32W. A TROPICAL WAVE IS IN THE WRN TROPICAL
ATLC...SEE ABOVE.
No it looks sheared and probably will fizzle...something that just pops up and being considered a candidate for an invest is a bit too premature. If its around tomorrow, I'll change my mind.
Wow I just got on, and I don't think anyone
was seeing this one coming. Everyone was watching
the western caribbean and all of a sudden that pops up. It looks great compared to the caribbean disturbance and for being that far
south and close to south america
No, there is nothing imminent out there. Just two sheared areas of interest.
ABPZ20 KNHC 111732
TWOEP
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1100 AM PDT THU JUN 11 2009
FOR THE EASTERN NORTH PACIFIC...EAST OF 140 DEGREES WEST LONGITUDE..
VISIBLE SATELLITE IMAGES REVEALED THAT THE DISTURBANCE CENTERED
ABOUT 1000 MILES SOUTHWEST OF THE SOUTHERN TIP OF BAJA CALIFORNIA
IS LESS ORGANIZED THAN PREVIOUSLY THOUGHT...AND FURTHER DEVELOPMENT
INTO A TROPICAL DEPRESSION IS NOT IMMINENT. HOWEVER...THERE STILL
IS A HIGH CHANCE...GREATER THAN 50 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.
ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.
$$
FORECASTER AVILA
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