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USGS: Sea Level Rise Accelerating in U.S. Atlantic Coast

 

Rates of sea level rise are increasing three-to-four times faster along portions of the U.S. Atlantic Coast than globally, according to a new U.S. Geological Survey report published in Nature Climate Change.

Since about 1990, sea-level rise in the 600-mile stretch of coastal zone from Cape Hatteras, N.C. to north of Boston, Mass. — coined a “hotspot” by scientists — has increased 2 – 3.7 millimeters per year; the global increase over the same period was 0.6 – 1.0 millimeter per year.

Based on data and analyses included in the report, if global temperatures continue to rise, rates of sea level rise in this area are expected to continue increasing.

The report shows that the sea-level rise hotspot is consistent with the slowing of Atlantic Ocean circulation. Models show this change in circulation may be tied to changes in water temperature, salinity and density in the subpolar north Atlantic.

“Many people mistakenly think that the rate of sea level rise is the same everywhere as glaciers and ice caps melt, increasing the volume of ocean water, but other effects can be as large or larger than the so-called ‘eustatic’ rise,” said USGS Director Marcia McNutt. “As demonstrated in this study, regional oceanographic contributions must be taken into account in planning for what happens to coastal property.”

Though global sea level has been projected to rise roughly two-to-three feet or more by the end of the 21st century, it will not climb at the same rate at every location. Differences in land movements, strength of ocean currents, water temperatures, and salinity can cause regional and local highs and lows in sea level.

“Cities in the hotspot, like Norfolk, New York, and Boston already experience damaging floods during relatively low intensity storms,” said Dr. Asbury (Abby) Sallenger, USGS oceanographer and project lead. “Ongoing accelerated sea level rise in the hotspot will make coastal cities and surrounding areas increasingly vulnerable to flooding by adding to the height that storm surge and breaking waves reach on the coast.”

During the 21 st century, the increases in sea level rise rate that have already occurred in the hotspot will yield increases in sea level of 8 to 11.4 inches by 2100. This regional sea level increase would be in addition to components of global sea level rise.

To determine accelerations of sea level, USGS scientists analyzed tide gauge data throughout much of North America in a way that removed long-term (linear) trends associated with vertical land movements. This allowed them to focus on recent changes in rates of sea-level rise caused, for example, by changes in ocean circulation.

Note: The report, Hotspot of accelerated sea-level rise on the Atlantic coast of North America , was published in the journal Nature Climate Change.

 

5 Comments

  1. Fayjus Salehin says:

    Now we can hope that USA will take some drastic action to implement the Kyoto Protocol and all other international treaties regarding climate change, global warming, and Carbone emission. USA is getting some hands on experience regarding climate change and sea level rise right now. It will be better for the world and the USA as well.

  2. Shahzada Mohiuddin says:

    Sea level rise will be felt both through changes in mean sea level, and, perhaps more importantly, through changes in extreme sea level events. Even if there are no changes in extreme weather conditions (for example, increases in tropical cyclone intensity), sea level rise will result in extreme sea levels of a given value being exceeded more frequently. This change in the frequency of extreme events has already been observed at many locations. The increase in frequency of extreme events will depend on local conditions, but events that currently occur once every 100 years could occur as frequently as once every few years by 2100.

  3. Jahedi Rezaul Maksud says:

    Indian Ocean Sea-Level Rise Threatens Coastal Areas:_______

    Indian Ocean sea levels are rising unevenly and threatening residents in some densely populated coastal areas and islands, a new study concludes.

    The study, led by scientists at the University of Colorado at Boulder (CU) and the National Center for Atmospheric Research (NCAR) in Boulder, Colo., finds that the sea-level rise is at least partly a result of climate change.

    Sea-level rise is particularly high along the coastlines of the Bay of Bengal and the Arabian Sea, as well as the islands of Sri Lanka, Sumatra and Java, the authors found.

    The rise–which may aggravate monsoon flooding in Bangladesh and India–could have future impacts on both regional and global climate.

    The key player in the process is the Indo-Pacific warm pool, an enormous, bathtub-shaped area spanning a huge area of the tropical oceans stretching from the east coast of Africa east to the International Date Line in the Pacific.

    The warm pool has heated by about 1 degree Fahrenheit, or 0.5 degrees Celsius, in the past 50 years, primarily because of human-generated emissions in greenhouses gases.

    “Our results from this study imply that if future anthropogenic warming effects in the Indo-Pacific warm pool dominate natural variability, mid-ocean islands such as the Mascarenhas Archipelago, coasts of Indonesia, Sumatra and the north Indian Ocean may experience significantly more sea-level rise than the global average,” says scientist Weiqing Han of CU and lead author of a paper published this week in the journal Nature Geoscience.

    While several areas in the Indian Ocean region are experiencing sea-level rise, sea level is lowering in other areas. The study indicated that the Seychelles Islands and Zanzibar off Tanzania’s coastline show the largest sea level drop.

    “Global sea-level patterns are not geographically uniform,” says NCAR scientist Gerald Meehl, a co-author of the paper. “Sea-level rise in some areas correlates with sea-level fall in other areas.”

    Funding for the research came from the National Science Foundation (NSF), NCAR’s sponsor, as well as the Department of Energy and NASA.

    “This work is a step forward towards getting improved estimates of sea-level changes in one of the most heavily populated regions of the globe,” says Eric Itsweire, director of NSF’s physical oceanography program.

    “Quantifying the heat and fresh water balance, as well as the large-scale circulation changes, in the Indo-Pacific warm pool through the use of observations and numerical models is crucial to understanding the subtle sea-level changes occurring in that region,” Itsweire says.

    The patterns of sea-level change are driven by the combined enhancement of two primary atmospheric wind patterns known as the Hadley circulation and the Walker circulation.

    The Hadley circulation in the Indian Ocean is dominated by air currents rising above strongly heated tropical waters near the equator and flowing poleward at upper levels, then sinking to the ocean in the subtropics and causing surface air to flow back toward the equator.

    The Indian Ocean’s Walker circulation causes air to rise and flow westward at upper levels, sink to the surface and then flow eastward back toward the Indo-Pacific warm pool.

    “The combined enhancement of the Hadley and Walker circulation form a distinct surface wind pattern that drives specific sea-level patterns,” Han says.

    In their paper, the authors write that “our new results show that human-caused changes of atmospheric and oceanic circulation over the Indian Ocean region–which have not been studied previously–are the major cause for the regional variability of sea-level change.”

    The study indicates that in order to anticipate global sea-level change, researchers also need to know the specifics of regional sea-level changes.

    “It is important for us to understand the regional changes of the sea level, which will have effects on coastal and island regions,” says NCAR scientist Aixue Hu.

    The research team used several sophisticated ocean and climate models for the study, including the Parallel Ocean Program–the ocean component of the widely used Community Climate System Model, which is supported by NCAR and the U.S. Department of Energy (DOE).

    In addition, the team used a wind-driven, linear ocean model for the study.

    The complex circulation patterns in the Indian Ocean may also affect precipitation by forcing even more atmospheric air down to the surface in Indian Ocean subtropical regions than normal, Han speculates.

    “This may favor a weakening of atmospheric convection in subtropics, which may increase rainfall in the eastern tropical regions of the Indian Ocean and drought in the western equatorial Indian Ocean region, including east Africa,” Han says.

  4. Fayjus Salehin says:

    Rising sea level settles border dispute________

    In an unusual example of the effects of global climate change, rising sea levels in the Bay of Bengal have helped resolve a troublesome territorial dispute between two of the world’s most populated countries, a leading Indian oceanographer says.

    Sugata Hazra, the head of oceanography at Kolkata’s Jadavpur University, says a flat muddy patch of land known as South Talpatti in Bangladesh and New Moore Island in India has disappeared under the Bay of Bengal. The landmass had been claimed by both countries but Professor Hazra says satellite images prove it has gone.

    ”It is now a submerged landmass, not an island,” Professor Hazra told.
    ”Only small parts can be seen in very, very low tide conditions.”

    Sea-level rise caused by climate change was ”surely” a factor in the island’s inundation, Professor Hazra said.

    ”The rate of sea-level rise in this part of the northern Bay of Bengal is definitely attributable to climate change,” he said.

    ”There is a close correlation between the rate of sea-level rise and the sea surface temperature.”

    The island was once about 3.5 kilometres long and three kilometres wide and situated four kilometres from the mouth of the Hariabhanga River, the waterway that marks a stretch of the border between south-western Bangladesh and India.

    Scientists believe the disputed island was formed following a cyclone in the Bay of Bengal in 1970 and both countries laid claim to the land.

    Bilateral negotiations were inconclusive and in 1981 the Indian government sent gunboats to the island and members of its Border Security Forces planted an Indian flag there.
    The island was not inhabited but Bangladeshi fishermen were reportedly sighted there frequently during the dry season.

    ”This is a unique instance of how climate resolves a dispute,” said Professor Hazra.
    ”It also goes to show how climate can affect all of us beyond geographical boundaries.
    ”The Indian government had once sent ships with guns to guard the island.
    ”Now one will have to think of sending submarines to mount a vigil there.”

    Professor Hazra said sea-level rise, changes in monsoonal rain patterns which altered river flows and land subsidence were all contributing to the inundation of land in the northern Bay of Bengal.

    The low-lying delta region that makes up much of Bangladesh and the neighbouring Indian state of West Bengal are acutely vulnerable to climate change.
    The United Nations Intergovernmental Panel on Climate Change predicts rising sea levels will devour 17 per cent of Bangladesh by 2050, displacing at least 20 million people. More than 155 million people live in the country.

    The Bangladesh non-governmental organisation Coastal Watch says an average of 11 Bangladeshis are losing their homes to rising waters every hour.
    Professor Hazra predicts that 15 per cent of the Indian Sundarbans region on the northern shore of the Bay of Bengal will be submerged by 2020.
    ”A lot of other islands are eroding very fast,” he said.

    The cyclone-prone region is also likely to experience more frequent and extreme storms as the sea-water temperature in the Bay of Bengal rises due to global warming.

    Read more: http://www.smh.com.au/environment/climate-change/rising-sea-level-settles-border-dispute-20100324-qwum.html#ixzz20XM55VnL

  5. Fayjus Salehin says:

    Sea-level rise fastest in Pacific————

    Sea levels in the southwest Pacific started rising drastically in the 1880s, with a notable peak in the 1990s thought to be linked to human-induced climate change, according to a study.
    The research, which examined sediment core samples taken from salt marshes in southern Australia’s Tasmania island, used geochemistry to establish a chronology of sea level changes over the past 200 years.
    Patrick Moss, from the University of Queensland, said major environmental events which affected the ocean such as the introduction of unleaded gasoline and nuclear tests, showed up in the samples and were used for dating.
    The chronology revealed a major jump in sea levels around 1880 after 6,000 years of relative stability, Moss said, with peaks in the 1910s and 1990s – the latter of which appeared to be linked to human activity.
    “Overall, over the past 200 years or so, sea levels have increased by about 20 centimetres,” Moss said.
    The first peak coincided with an end to what was known as the Little Ice Age, “a 500 or so year period of slightly cooler conditions that ended roughly around 1850” and saw glaciers around the world retreat.
    Sea levels in the southwest Pacific rose at four times the average 20th-century rate between 1900 and 1950, according to the study.
    That was followed by a period of “relative quiet” broken by a second spike in 1990 which saw sea levels rise at a rate that defied projections.
    “The natural climatic factors seem to be not as apparent and anthropogenic [man-made] climate change seems to be the key possible culprit,” said Moss.
    The study, which also involved researchers from Britain and New Zealand and was published in the journal Earth and Planetary Science Letters, found that sea levels had risen much more in the southwest Pacific than elsewhere.
    Moss said a large ice melt was like a “fingerprint” which could be tracked across the Earth’s surface, and the study had determined that the water which had caused the rising Pacific sea levels had come from the northern hemisphere.
    The Arctic’s Greenland ice sheet looked to be the primary source, along with “mountain glaciers in Alaska, western North America and the Canadian Arctic,” he said.
    Most scientists have until now said the sea level rise in recent decades is due to thermal expansion, the expansion of water due to heating, and from glacier melt and there is much debate as to how much Greenland is melting.
    Some pro-melt research indicates the run-off is quite recent and probably contributes only about half of the current sea level rise, but Moss suggests the melt began long ago and began to affect sea levels as much as two decades ago.

    Read more: http://www.vancouversun.com/technology/level+rise+fastest+Pacific+report/6459807/story.html#ixzz20XQw5dJu

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