Sea level rise: what has happened so far

By: Dr. Jeff Masters , 14:05 GMT le 10 juin 2009

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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

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I think its about time for Dr.Masters to update his blog.
weren't you talking about a trough split a few days ago Levi?
Member Since: Posts: Comments:
Quoting canesrule1:
I like your forecast and i do have to agree with it, btw where do you see this Low located


Its not there, its just a broad spinning circulation
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1129. DDR
Quoting pottery:
LOL DDR.
Last wave that went past, I measured 13mm.
Did not do much for the garden at all.
Hope this one drops some more.

Yes,lets hope.
mOst likely we'll get more.
This dry weather sucks,you dont have pipe water by you?
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Quoting Vortex95:
speaking of DTV anyone in S Fla notice during this winter when it was in the 40's if many of their HD channels became unwatchable?
i did, i live in miami and few of my HD channels were unwatchable.
P*A*T*R*A*P

WU's dictionary.
Member Since: 19 juillet 2008 Posts: 43 Comments: 4051
1126. Patrap



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speaking of DTV anyone in S Fla notice during this winter when it was in the 40's if many of their HD channels became unwatchable?
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Quoting RitaEvac:
ok we got the spin going on at low levels, need a define cetner to form, shear has to relax so convection can form near that center, then the game begins on where this puppy will go.

Then how strong it gets, the shear factor and where high pressure is located down the road to steer it
I like your forecast and i do have to agree with it, btw where do you see this Low located
Quoting Levi32:


Not sure what you mean by that image lol.

One should note that the 850mb vort max does not indicate the center of the low in this case.


The image was posted not to negate your statement. The 850mb image shows that the main vorticity maxima is not located under the blob.
Member Since: 19 juillet 2008 Posts: 43 Comments: 4051
Good afternoon

From looking at the WV loop the ULL between Cuba and the Bahamas is starting to fill and appears to be retrograding very slowly. You can also see that moisture is now starting to wrap to the North of that feature which also signals a change in the make up of the trough.

The high from the GOM continues to bear down from the N of the ULL and seems to be driving a wedge between it and the N end of the trough, perhaps setting up a split scenario with a cut off low remaining to move out of the way.

It will be interesting to see how this plays out today.

WV Loop
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ok we got the spin going on at low levels, need a define cetner to form, shear has to relax so convection can form near that center, then the game begins on where this puppy will go.

Then how strong it gets, the shear factor and where high pressure is located down the road to steer it
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i have more belief in the one in the ATL than the carib, shear is still too high for any development at all any devel will be slow.
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Quoting Patrap:
e·quiv·o·cal (-kwv-kl)
adj.
1. Open to two or more interpretations and often intended to mislead; ambiguous. See Synonyms at ambiguous.
2. Of uncertain significance.
3. Of a doubtful or uncertain nature.


LOL!!!!
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1118. pottery
LOL DDR.
Last wave that went past, I measured 13mm.
Did not do much for the garden at all.
Hope this one drops some more.
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Quoting TampaSpin:
you can clearly see the blob separating from the big mess of clouds north of it. I'm beginning to see a Northeastward movement IMO.
1116. Patrap
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Quoting futuremet:


It is a big shift east compared to yesterday. The model forecasts are just too equivocal to believe any outcomes. One thing certain, TC development is likely over the next 72hrs.


Certainly, thanks for your feedback.
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1114. Ossqss
Non-weather update. Interesting read here on the DTV move from a recent publication. I think we will all have some suprises coming our way soon.

Digital TV Transition
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1113. Levi32
Quoting futuremet:




Not sure what you mean by that image lol.

One should note that the 850mb vort max does not indicate the center of the low in this case.
Member Since: 24 novembre 2005 Posts: 635 Comments: 26682
1112. hydrus
The NAM model shows a strong tropical low near the Yucatan in a few days.
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Quoting Levi32:


No....I'm not gonna argue with a dozen people about it lol. It's a broad area of low pressure but it is not a closed circulation. And FYI QuikSCAT does show it.

lol, sorry but i thought you were looking at the old quikscat from yesterday, and you can see the spinning on the visible imagery.
1110. DDR
Hey pal,all is well.It seems 'the tree',i dont know what to say,but that wave is fast approaching,so far i've got 25 mm of rain
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1109. Patrap
e·quiv·o·cal (-kwv-kl)
adj.
1. Open to two or more interpretations and often intended to mislead; ambiguous. See Synonyms at ambiguous.
2. Of uncertain significance.
3. Of a doubtful or uncertain nature.
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Member Since: 2 septembre 2007 Posts: 179 Comments: 20448
Quoting futuremet:


It is a big shift east compared to yesterday. The model forecasts are just too equivocal to believe any outcomes. One thing certain, TC development is likely over the next 72hrs.


the thing doesnt even exist so if the model shifts right or left makes no difference, it's crap shoot
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Quoting Levi32:


No....I'm not gonna argue with a dozen people about it lol. It's a broad area of low pressure but it is not a closed circulation. And FYI QuikSCAT does show it.



Member Since: 19 juillet 2008 Posts: 43 Comments: 4051
.
Blog Update
Reflector site for those at work, which now also includes Weather456, daily updates


AOI #1

AOI #2
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Quoting WeatherStudent:



Reliability dependency, FM.....slim, to zero, to none.


It is a big shift east compared to yesterday. The model forecasts are just too equivocal to believe any outcomes. One thing certain, TC development is likely over the next 72hrs.
Member Since: 19 juillet 2008 Posts: 43 Comments: 4051
1102. Levi32
Quoting canesrule1:
where did you get that Low location from??? if its from the QuikScat then you are wrong my friend.


No....I'm not gonna argue with a dozen people about it lol. It's a broad area of low pressure but it is not a closed circulation. And FYI QuikSCAT does show it.

Member Since: 24 novembre 2005 Posts: 635 Comments: 26682
1101. DDR
Quoting Levi32:


The area probably won't be completely void of showers, but they will be greatly reduced. You're right that you will probably get the most out of it, likely from day-time thunderstorms over South America enhanced by the wave axis.

Correct,we usually get 7 or 8 feet per year and high amounts falling in the islands NE and central interior.
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Quoting HobeSoundShudders:
re: puerto rico

http://earthquake.usgs.gov/eqcenter/recenteqsus/Maps/PR10/13.23.-71.-61_eqs.php

Earthquake List for Map Centered at 18°N, 66°W
MAG UTC DATE-TIME
y/m/d h:m:s LAT
deg LON
deg DEPTH
km LOCATION
MAP 3.4 2009/06/11 10:01:04 19.567 -66.342 10.6 122 km ( 76 mi) N of Breñas, PR

MAP 3.2 2009/06/11 05:05:15 19.025 -66.963 14.2 59 km ( 36 mi) N of Isabela, PR

MAP 1.7 2009/06/11 03:06:14 17.931 -65.919 15.5 9 km ( 5 mi) S of Palo Seco, PR


That would explain it, thanks for that info Hobe Sound.
re: puerto rico

http://earthquake.usgs.gov/eqcenter/recenteqsus/Maps/PR10/13.23.-71.-61_eqs.php

Earthquake List for Map Centered at 18°N, 66°W
MAG UTC DATE-TIME
y/m/d h:m:s LAT
deg LON
deg DEPTH
km LOCATION
MAP 3.4 2009/06/11 10:01:04 19.567 -66.342 10.6 122 km ( 76 mi) N of Breñas, PR

MAP 3.2 2009/06/11 05:05:15 19.025 -66.963 14.2 59 km ( 36 mi) N of Isabela, PR

MAP 1.7 2009/06/11 03:06:14 17.931 -65.919 15.5 9 km ( 5 mi) S of Palo Seco, PR
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Quoting extreme236:


Latest NHC surface maps dont even show a sfc low there anymore.


Look at visilbe and u can see it spinning
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1097. JRRP
Longitude 1.125 W
Latitude 18.375 N


24 hours (1 day ) of rainfall accumulation
225.42 mm 8.87 Inches

72 hours (3 days) of rainfall accumulation
225.42 mm 8.87 Inches

168 hours (1 week) of rainfall accumulation
225.42 mm 8.87 Inches
Member Since: 16 août 2007 Posts: 0 Comments: 6161
1096. pottery
DDR...and no signs of any new leaves on " the tree" LOL
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I see it the low is seen on the visible.
1094. Levi32
Quoting extreme236:


Latest NHC surface maps dont even show a sfc low there anymore.


It's still a broad area of low pressure.
Member Since: 24 novembre 2005 Posts: 635 Comments: 26682
1086. yep
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Pretty broad and thats not good, means big system to come
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Quoting futuremet:
According to 12z CMC, NOLA will get nailed.


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Quoting Levi32:
Just so everyone is understanding this correctly, the broad area of low pressure in the Caribbean is centered north of Panama, not under the biggest glob of convection.



Latest NHC surface maps dont even show a sfc low there anymore.
Member Since: 2 août 2007 Posts: 19 Comments: 19234
1089. Patrap
Yup..we got it now..Thanx

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You can see the circulatin on visible of where you circled the L
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Quoting TheCaneWhisperer:



Not really. That is a Tsunami station designed to detect a possible Tsunami. Something triggered it into event mode.
oh ok thought another Andrew was forming out there if the buoy thought there was a Tsunami.
1086. Levi32
Just so everyone is understanding this correctly, the broad area of low pressure in the Caribbean is centered north of Panama, not under the biggest glob of convection.

Member Since: 24 novembre 2005 Posts: 635 Comments: 26682
1085. pottery
Hi DDR. I would be glad for any rain at all.
Water is now Critical, and no sign that we will get any from WASA.
How have you been?
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it's headed for T&T, HMMM wnw into the carib mmmm got to watch this one.
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Quoting canesrule1:
holy cow, must be rough out there!!!


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

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