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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Reflector site for those at work, which now also includes Weather456, daily updates
AOI #1
AOI #2
I see that.
What are TAFS? They are a forecast for a 5 mile radius that something is either going to happen or not. You just look at the situation and make a decision. You do planners no good by saying there is a 50% chance something is going to happen. You make a call one way or another then pray you are right haha. Try it one day, track it and I bet your are right more times than wrong. Trust your skills.
June 10th, 2009 at 10:28 am
More on the El Nino front–all dynamical models now forecast El Nino conditions for next winter. The CFS ensemble–which is probably the best one out there–is currently forecasting an upper-end moderate event, with some individual ensemble members calling for a strong El Nino of 1982 or even 1997 magnitude. Still a lot of time to go between now and then, but there now appears to be at least the potential for a strong El Nino event in 2009-2010 winter season. It has been twelve years since the last big event, and there was a 14 year gap between the previous two. This seems to be approximately the right return period for major events. Stay tuned…I do expect that the Seasonal Outlook will call for above normal precipitation in SoCal for next winter and perhaps in NorCal as well. There also could be some impact on summer weather (which may already be being felt). More this weekend…
O_o wow
I'm not saying it's not possible, but I do recall the CFS forecasting that kind of a bomb in 2006, and it never verified.
Tornado just knocked down a 50 year old big tree in front of my house, power is out, fence is down, grill went flying across the yard.
Please say yes that you IM is fixs Please say yes it is
Glad to hear you are ok!
1996 El Nino was hell here in FL...so much rain.
Wow...glad you're ok!
Crap...
Too Funny, nothing like a good sense of humor!
Nov 2006
Link
Oct 2006
Link
Thanks for the well wishes..makes me wish to be back in Florida!!!
Thanks. That wasn't as big a forecast as this year's, but it still was way too big. I guess we'll see how it pans out.
ROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
500 PM PDT WED JUN 10 2009
FOR THE EASTERN NORTH PACIFIC...EAST OF 140 DEGREES WEST LONGITUDE..
1. SHOWER ACTIVITY ASSOCIATED WITH THE BROAD AREA OF LOW PRESSURE
LOCATED ABOUT 950 MILES SOUTHWEST OF THE SOUTHERN TIP OF BAJA
CALIFORNIA CONTINUES TO SHOW SIGNS OF ORGANIZATION. THIS SYSTEM HAS
THE POTENTIAL TO BECOME A TROPICAL DEPRESSION DURING THE NEXT
DAY OR SO. THERE IS A MEDIUM CHANCE...30 TO 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.
Thursday June 11, 2009
Frosty: Canberrans woke to sub-zero temperatures this morning. It was still 0 degrees at 9:00am.
Canberra has surprised weather forecasters by recording colder temperatures than surrounding rural regions this morning.
Sean Carson from the Bureau of Meteorology says temperatures in the ACT fell as low as minus 6 degrees celsius.
"When you look around this morning - Goulburn, Cooma(where my parents live), Braidwood, they're all only around minus 1C, minus 2C," he said.
"So it's very unusual for us to be colder than them."
Mr Carson says despite the cold start, Canberra should reach a top of 11 degrees today.
"A frost usually means clear skies, sunny days," he said.
"Only heading for 11C, it'll take a while to thaw out but a beautiful day with light winds. So get outside and enjoy it."
Mr Carson says the frosty conditions are expected to continue into the weekend.
© ABC 2009
It's not.
Wow TX2FL. Glad y'all made it through ok.
HPC estimated an area of low pressure to form within the next 54-60 hours with some possible slow development into a cyclone with favorable conditions. This was estimated to occur in the Cayman island/Jamaican area.
did t i say too say yes ??? LOL this kinding
well ok
Yet more die in hurricanes...
WHXX04 KWBC 082325
CHGQLM
ATTENTION...NATIONAL HURRICANE CENTER
NCEP COUPLED GFDL HURRICANE MODEL FORECAST MADE FOR
TROPICAL DEPRESSION INVEST 91E
INITIAL TIME 18Z JUN 8
DISCLAIMER ... THIS INFORMATION IS PROVIDED AS GUIDANCE. IT
REQUIRES INTERPRETATION BY HURRICANE SPECIALISTS AND SHOULD
NOT BE CONSIDERED AS A FINAL PRODUCT. PLEASE SEE THE TPC/NHC
OFFICIAL FORECAST.
FORECAST STORM POSITION
HOUR LATITUDE LONGITUDE HEADING/SPEED(KT)
0 10.8 116.4 285./ 7.0
6 10.2 117.6 246./12.5
12 11.0 117.7 350./ 7.2
18 11.4 118.4 303./ 7.8
STORM DISSIPATED AT 18 HRS AT THE ABOVE PSN.
WHXX01 KMIA 110047
CHGE77
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0047 UTC THU JUN 11 2009
DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.
EAST PACIFIC OBJECTIVE AIDS FOR
DISTURBANCE INVEST (EP912009) 20090611 0000 UTC
...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
090611 0000 090611 1200 090612 0000 090612 1200
LAT LON LAT LON LAT LON LAT LON
BAMS 11.5N 117.7W 12.7N 119.2W 14.0N 120.4W 15.2N 121.2W
BAMD 11.5N 117.7W 12.3N 119.3W 13.4N 120.7W 14.7N 121.6W
BAMM 11.5N 117.7W 12.4N 119.2W 13.5N 120.5W 14.6N 121.4W
LBAR 11.5N 117.7W 12.4N 118.9W 14.1N 120.3W 15.9N 121.4W
SHIP 25KTS 34KTS 42KTS 46KTS
DSHP 25KTS 34KTS 42KTS 46KTS
...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
090613 0000 090614 0000 090615 0000 090616 0000
LAT LON LAT LON LAT LON LAT LON
BAMS 16.5N 121.8W 19.4N 121.2W 21.4N 121.0W 23.0N 118.8W
BAMD 16.2N 121.9W 20.0N 121.6W 23.8N 119.6W 28.7N 112.3W
BAMM 15.9N 122.0W 18.9N 122.5W 21.4N 122.9W 24.0N 121.4W
LBAR 18.3N 122.1W 25.0N 119.8W 34.4N 106.8W 38.9N 88.8W
SHIP 47KTS 38KTS 21KTS 0KTS
DSHP 47KTS 38KTS 21KTS 0KTS
...INITIAL CONDITIONS...
LATCUR = 11.5N LONCUR = 117.7W DIRCUR = 320DEG SPDCUR = 5KT
LATM12 = 10.5N LONM12 = 117.0W DIRM12 = 330DEG SPDM12 = 3KT
LATM24 = 10.5N LONM24 = 117.0W
WNDCUR = 25KT RMAXWD = 50NM WNDM12 = 20KT
CENPRS = 1008MB OUTPRS = 1012MB OUTRAD = 200NM SDEPTH = M
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM
$$
NNNN
The existence of an area of low pressure already may mean one of two things. Either the low that was forecasted to develop has done so already OR the current stationary low is not the forecasted low that MAY produce a cyclone.
In any event the upper level environment is too hostile for tropical cyclone development in the near term.
http://www.spc.noaa.gov/climo/reports/today.html
Which is why they say the earliest this disturbance will form is 54-60 hours, with any development being gradual, but with conditions being favorable for convective organization.
Are you absolutely certain that our favorite topic wouldn't be covered if there was? I am not so sure, any more.
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