Sea Level Rise Due To Global Warming Poses Threat To New York City

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ScienceDaily (Mar. 16, 2009) — Global warming is expected to cause the sea level along the northeastern U.S. coast to rise almost twice as fast as global sea levels during this century, putting New York City at greater risk for damage from hurricanes and winter storm surge, according to a new study led by a Florida State University researcher.

Jianjun Yin, a climate modeler at the Center for Ocean-Atmospheric Prediction Studies (COAPS) at Florida State, said there is a better than 90 percent chance that the sea level rise along this heavily populated coast will exceed the mean global sea level rise by the year 2100. The rising waters in this region -- perhaps by as much as 18 inches or more -- can be attributed to thermal expansion and the slowing of the North Atlantic Ocean circulation because of warmer ocean surface temperatures.
Yin and colleagues Michael Schlesinger of the University of Illinois at Urbana-Champaign and Ronald Stouffer of Geophysical Fluid Dynamics Laboratory at Princeton University are the first to reach that conclusion after analyzing data from 10 state-of-the-art climate models, which have been used for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report. Yin's study is published in the journal Nature Geoscience.
"The northeast coast of the United States is among the most vulnerable regions to future changes in sea level and ocean circulation, especially when considering its population density and the potential socioeconomic consequences of such changes," Yin said. "The most populous states and cities of the United States and centers of economy, politics, culture and education are located along that coast."
The researchers found that the rapid sea-level rise occurred in all climate models whether they depicted low, medium or high rates of greenhouse-gas emissions. In a medium greenhouse-gas emission scenario, the New York City coastal area would see an additional rise of about 8.3 inches above the mean sea level rise that is expected around the globe because of human-induced climate change.
Thermal expansion and the melting of land ice, such as the Greenland ice sheet, are expected to cause the global sea-level rise. The researchers projected the global sea-level rise of 10.2 inches based on thermal expansion alone. The contribution from the land ice melting was not assessed in this study due to uncertainty.
Considering that much of the metropolitan region of New York City is less than 16 feet above the mean sea level, with some parts of lower Manhattan only about 5 feet above the mean sea level, a rise of 8.3 inches in addition to the global mean rise would pose a threat to this region, especially if a hurricane or winter storm surge occurs, Yin said.
Potential flooding is just one example of coastal hazards associated with sea-level rise, Yin said, but there are other concerns as well. The submersion of low-lying land, erosion of beaches, conversion of wetlands to open water and increase in the salinity of estuaries all can affect ecosystems and damage existing coastal development.
Although low-lying Florida and Western Europe are often considered the most vulnerable to sea level changes, the northeast U.S. coast is particularly vulnerable because the Atlantic meridional overturning circulation (AMOC) is susceptible to global warming. The AMOC is the giant circulation in the Atlantic with warm and salty seawater flowing northward in the upper ocean and cold seawater flowing southward at depth. Global warming could cause an ocean surface warming and freshening in the high-latitude North Atlantic, preventing the sinking of the surface water, which would slow the AMOC.
Journal reference:
Yin et al. Model projections of rapid sea-level rise on the northeast coast of the United States. Nature Geoscience, March 15, 2009; DOI: 10.1038/ngeo462
Adapted from materials provided by Florida State University, via EurekAlert!, a service of AAAS.

Researchers Study Cave’s 'Breathing' For Better Climate Clues

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ScienceDaily (Mar. 16, 2009) — A University of Arkansas researcher studying the way caves “breathe” is providing new insights into the process by which scientists study paleoclimates.

Katherine Knierim, a graduate student at the University of Arkansas, together with Phil Hays of the geosciences department and the U.S. Geological Survey and Erik Pollock of the University of Arkansas Stable Isotope Laboratory, are conducting close examinations of carbon cycling in an Ozark cave. Caves “breathe” in the sense that air flows in and out as air pressure changes.
The researchers have found that carbon dioxide pressures vary with external temperatures and ground cover, indicating a possible link between the carbon found in rock formations in the caves and seasonal changes. They presented their findings at a recent meeting of the American Geophysical Union.
The movement of carbon in cave systems is controlled by the concentration of carbon dioxide. When conditions are right, this carbon can be deposited as layers in stalagmites, stalactites and soda straws. These layers resemble the rings found in trees, except that they can date back millions of years, hold information about cave conditions.
“People have been using these formations as paleoclimate records,” Hays said. However, researchers make an assumption when they do so.
“The problem is that you have to assume you are getting even carbon and oxygen isotope exchange,” Knierim said. Isotopes, or atoms of the same type but with slightly different weights, are found in plants, animals, organic matter and rocks. Different types of material have unique “signatures,” or proportions of a particular atom at a particular atomic weight.
By looking at carbon isotope ratios in cave topsoils, the cave atmosphere and the stream within the cave, Knierim and her colleagues will be able to determine the different contributions of carbon sources to the formations. This will help scientists develop more accurate paleoclimate conditions from cave formations.
A greater knowledge of how carbon cycles through cave systems also will help scientists develop better methods for watershed management.
The researchers are in the geosciences department of the J. William Fulbright College of Arts and Sciences.
Adapted from materials provided by University of Arkansas, Fayetteville.

Ninth Warmest February For Globe, NOAA

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ScienceDaily (Mar. 16, 2009) — The combined global land and ocean surface average temperature for February 2009 was the ninth warmest since records began in 1880, according to an analysis by NOAA’s National Climatic Data Center in Asheville, N.C.

The analyses in NCDC’s global reports are based on preliminary data, which are subject to revision. Additional quality control is applied to the data when later reports are received several weeks after the end of the month and as increased scientific methods improve NCDC’s processing algorithms.
Temperature Highlights – February
The combined global land and ocean surface temperature for February was 54.80 degrees F, 0.90 degree F above the 20th century mean of 53.9 degrees F, ranking as the ninth warmest on record.
Separately, the global land surface temperature was 39.38 degrees F, 1.58 degrees F above the 20th century mean of 37.8 degrees F.
The global ocean surface temperature of 61.25 degrees F ranked as eighth warmest on record and was 0.65 degree F above the 20th century mean of 60.6 degrees F.
Temperature Highlights – Boreal (Meteorological) Winter
The combined global land and ocean surface temperature for boreal winter (December-February) was 54.72 degrees F, 0.92 degree F above the 20th century mean of 53.8 degrees F and ranking eighth warmest.
Separately, the global land surface temperature was 39.31 degrees F, 1.51 degrees F above the 20th century mean of 37.8 degrees F, ranking as ninth warmest on record.
The global ocean surface temperature of 61.20 degrees F ranked as seventh warmest on record and was 0.70 degree F above the 20th century mean of 60.5 degrees F.
Global Highlights for February
Based on NOAA satellite observations of snow cover extent, 10.7 million square miles (27.7 million square kilometers) of Eurasia (Europe and Asia) were covered by snow in February 2009, which is 0.4 million square miles (1.1 million square kilometers) below the 1966-2009 average of 11.1 million square miles (28.8 million square kilometers).
Satellite-based snow cover extent for the Northern Hemisphere was 17.4 million square miles (45.0 million square kilometers) in February, which is 0.3 million square miles (0.9 million square kilometers) below the 1966-2009 average of 17.7 million square miles (45.9 million square kilometers).
Arctic sea ice coverage during February 2009 was at its fourth lowest February extent since satellite records began in 1979, according to the National Snow and Ice Data Center. Average ice extent during February was 5.7 million square miles (14.8 million square kilometers). The Arctic sea ice pack usually expands during the cold season, reaching a maximum in March, then contracts during the warm season, reaching a minimum in September.
Very hot, dry conditions affected southern Australia during the end of January and beginning of February. An intense heat wave February 6-8 resulted in a high temperature of 119.8 degrees F at Hopetoun, Victoria, Feb. 7, surpassing the previous record of 117.0 degrees F set in January 1939. This is a state record and perhaps the highest temperature ever recorded for such a southerly latitude. The hot, dry conditions contributed to the development of Australia’s deadliest wildfires in history.
China declared its highest level of emergency for eight provinces that were suffering from their worst drought in 50 years. The drought conditions, which began in November 2008, affected more than 4 million people and more than 24 million acres of crops.
A strong winter storm brought heavy snow to parts of the United Kingdom on February 2, disrupting transportation and bringing London to a virtual standstill. The event, in which up to 12 inches of snow fell in southeastern England, was the UK’s most widespread snow in 18 years, according to the UK Met Office.
Adapted from materials provided by National Oceanic And Atmospheric Administration.

Silica Algae Reveal How Ecosystems React To Climate Changes

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ScienceDaily (Mar. 14, 2009) — A newly published dissertation by Linda Ampel from the Department of Physical Geography and Quaternary Geology at Stockholm University in Sweden examined how rapid climate changes during the most recent ice age affected ecosystems in an area in continental Europe.

Rapid and extensive climate changes have taken place on several occasions in the past. For example, the latest ice age (lasting from about 115,000 to 11,500 years ago) is characterized by several rapid and dramatic climate swings. These swings recurred in cycles of roughly 1,500 years and were originally discovered through studies of ice cores from Greenland in the early 1990s. These cycles started with an extremely rapid rise in temperatures, over just a few years or decades, of as much as 8-16o C over Greenland.
Linda Ampel studied how these rapid cycles in the climate affected ecosystems in an area in continental Europe. The study was based on analyses of sediment cores from an overgrown lake named Les Echets in eastern France and focuses on a time interval between 40,000 and 16,000 ago.
The findings are based on analyses of fossil silica algae, diatoms. Various species of diatoms prefer different water conditions relating to physical and chemical parameters such as temperature, salinity, access to nutrients, light, water depth, or available types of places to grow. These parameters, in turn, are affected by climate. Different species of diatoms can therefore indicate how the water environment changed as a consequence of the climate in the past.
Diatom analyses of the environmental archive from Les Echets, together with further analyses of chemical and biological parameters such as content of organic material and pollen grains from trees and other plants preserved in the lake, show that the ecosystems in the lake and its surroundings underwent marked changes during the latest ice age as a consequence of these 1,500-year cycles. The adaptation of the ecosystems prompted by the recurring warm periods took place as quickly as within 50 to 200 years.
“These findings show that ecosystems have changed rapidly in reaction to climate changes in the past, which indicates that quick adaptations could also take place in the future as a consequence of global warming, for instance,” says Linda Ampel.
Adapted from materials provided by Vetenskapsrådet (The Swedish Research Council), via AlphaGalileo.

Wind Shifts May Stir Carbon Dioxide From Antarctic Depths, Amplifying Global Warming

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ScienceDaily (Mar. 13, 2009) — Natural releases of carbon dioxide from the Southern Ocean due to shifting wind patterns could have amplified global warming at the end of the last ice age--and could be repeated as manmade warming proceeds, a new paper in the journal Science suggests.

Many scientists think that the end of the last ice age was triggered by a change in Earth's orbit that caused the northern part of the planet to warm. This partial climate shift was accompanied by rising levels of the greenhouse gas CO2, ice core records show, which could have intensified the warming around the globe. A team of scientists at Columbia University's Lamont-Doherty Earth Observatory now offers one explanation for the mysterious rise in CO2: the orbital shift triggered a southward displacement in westerly winds, which caused heavy mixing in the Southern Ocean around Antarctica, pumping dissolved carbon dioxide from the water into the air.
"The faster the ocean turns over, the more deep water rises to the surface to release CO2," said lead author Robert Anderson, a geochemist at Lamont-Doherty. "It's this rate of overturning that regulates CO2 in the atmosphere." In the last 40 years, the winds have shifted south much as they did 17,000 years ago, said Anderson. If they end up venting more CO2 into the air, manmade warming underway now could be intensified.
Scientists have been studying the oceans for more than 25 years to understand their influence on CO2 levels and the glacial cycles that have periodically heated and chilled the planet for more than 600,000 years. Ice cores show that the ends of other ice ages also were marked by rises in CO2.
Two years ago, J.R. Toggweiler, a scientist at the National Oceanic and Atmospheric Administration (NOAA), proposed that westerly winds in the Southern Ocean around Antarctica may have undergone a major shift at the end of the last ice age. This shift would have raised more CO2-rich deep water to the surface, and thus amplified warming already taking place due to the earth's new orbital position. Anderson and his colleagues are the first to test that theory by studying sediments from the bottom of the Southern Ocean to measure the rate of overturning.
The scientists say that changes in the westerlies may have been triggered by two competing events in the northern hemisphere about 17,000 years ago. The earth's orbit shifted, causing more sunlight to fall in the north, partially melting the ice sheets that then covered parts of the United States, Canada and Europe. Paradoxically, the melting may also have spurred sea-ice formation in the North Atlantic Ocean, creating a cooling effect there. Both events would have caused the westerly winds to shift south, toward the Southern Ocean. The winds simultaneously warmed Antarctica and stirred the waters around it. The resulting upwelling of CO2 would have caused the entire globe to heat.
Anderson and his colleagues measured the rate of upwelling by analyzing sediment cores from the Southern Ocean. When deep water is vented, it brings not only CO2 to the surface but nutrients. Phytoplankton consume the extra nutrients and multiply.
In the cores, Anderson and his colleagues say spikes in plankton growth between roughly 17,000 years ago and 10,000 years ago indicate added upwelling. By comparing those spikes with ice core records, the scientists realized the added upwelling coincided with hotter temperatures in Antarctica as well as rising CO2 levels.
In the same issue of Science, Toggweiler writes a column commenting on the work. "Now I think this really starts to lock up how the CO2 changed globally," he said in an interview. "Here's a mechanism that can explain the warming of Antarctica and the rise in CO2. It's being forced by the north, via this change in the winds."
At least one model supports the evidence. Richard Matear, a researcher at Australia's Commonwealth Scientific and Industrial Research Organisation, describes a scenario in which winds shift south and produce an increase in CO2 venting in the Southern Ocean. Plants, which incorporate CO2 during photosynthesis, are unable to absorb all the added nutrients, causing atmospheric CO2 to rise.
Some other climate models disagree. In those used by the Intergovernmental Panel on Climate Change, the westerly winds do not simply shift north-south. "It's more complicated than this," said Axel Timmermann, a climate modeler at the University of Hawaii. Even if the winds did shift south, Timmermann argues, upwelling in the Southern Ocean would not have raised CO2 levels in the air. Instead, he says, the intensification of the westerlies would have increased upwelling and plant growth in the Southeastern Pacific, and this would have absorbed enough atmospheric CO2 to compensate for the added upwelling in the Southern Ocean.
"Differences among model results illustrate a critical need for further research," said Anderson. These, include "measurements that document the ongoing physical and biogeochemical changes in the Southern Ocean, and improvements in the models used to simulate these processes and project their impact on atmospheric CO2 levels over the next century."
Anderson says that if his theory is correct, the impact of upwelling "will be dwarfed by the accelerating rate at which humans are burning fossil fuels." But, he said, "It could well be large enough to offset some of the mitigation strategies that are being proposed to counteract rising CO2, so it should not be neglected."
In addition to Anderson, the paper was coauthored by Simon Nielsen of Florida State University, and five Lamont-Doherty researchers: Shahla Ali, Louisa Bradtmiller, Martin Fleisher, Brenton Anderson and Lloyd Burckle. The study was funded by NOAA, the National Science Foundation, Norwegian Research Council and Norwegian Polar Institute.
Journal reference:
. Wind-Driven Upwelling in the Southern Ocean and the Deglacial Rise in Atmospheric CO2. Science, March 13, 2009
Adapted from materials provided by The Earth Institute at Columbia University, via EurekAlert!, a service of AAAS.

New Method For Monitoring Volcanoes

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ScienceDaily (Mar. 13, 2009) — Seventeen of the world’s most active volcanoes have been supplied with monitoring equipment from Chalmers University of Technology in Sweden to measure their emission of sulphur dioxide. The measurement results will be used to make it easier to predict volcano eruptions, and they can also be used to improve today’s climate models.

One of the Chalmers researchers who developed the monitoring equipment is Mattias Johansson, who recently defended his doctoral dissertation in the subject.
The most active volcanoes in the world have special observatories that monitor them in order to be able to sound the alarm and evacuate people in the vicinity if an eruption threatens. These observatories keep track of several parameters, primarily seismic activity. Now 17 observatories have received a new parameter that facilitates their work – the volcanoes’ emissions of sulphur dioxide.
“Increasing gas emissions may indicate that magma is rising inside the volcano,” says Mattias Johansson at the Department of Radio and Space Science at Chalmers. “If this information is added to the other parameters, better risk estimates can be made at the observatories.”
The equipment he has been working with measures the total amount of gas emitted, whereas most other methods for metering gas can only indicate the gas concentration at a particular point. This is made possible by placing two or more metering instruments in different places around the volcano and then aggregating the information they gather.
Much of the Chalmers researchers’ work has involved making the equipment sufficiently automatic, robust, and energy-efficient for use in the inhospitable environment surrounding volcanoes, in poor countries with weak infrastructure.
“I have primarily been working with the software required for processing and presenting the measurement results,” says Mattias Johansson. “Among other things, I have created a program that analyzes the data collected, calculates the outward flow of gas, and presents the information as a simple graph on a computer screen that the observatory staff need only glance at to find out how much sulphur dioxide the volcano is emitting at any particular time.”
He has also participated in the installation of the equipment on two of the volcanoes, Aetna in Italy and San Cristobal in Nicaragua. In Project Novac, which his research is part of, a total of 20 volcanoes will be provided with monitoring equipment from Chalmers.
It will also be possible to improve global climate models when the Chalmers researchers receive continuous reports about how much sulphur dioxide is emitted by the 20 most active volcanoes.
“Sulphur dioxide is converted in the atmosphere to sulphate particles, and these particles need to be factored into climate models if those models are to be accurate,” says Associate Professor Bo Galle, who directed the dissertation. “Volcanoes are an extremely important source of sulphur dioxide. Aetna alone, for instance, releases roughly ten times more sulphur dioxide than all of Sweden does.”
The methods that Mattias Johansson has devised can moreover be used to measure the total emissions of air pollutants from an entire city. China has already purchased equipment that they are now using to study the pollution situation in the megacity Beijing.
Adapted from materials provided by The Swedish Research Council, via AlphaGalileo.

Coral Reefs May Start Dissolving When Atmospheric Carbon Dioxide Doubles

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ScienceDaily (Mar. 10, 2009) — Rising carbon dioxide in the atmosphere and the resulting effects on ocean water are making it increasingly difficult for coral reefs to grow, say scientists. A study to be published online March 13, 2009 in Geophysical Research Letters by researchers at the Carnegie Institution and the Hebrew University of Jerusalem warns that if carbon dioxide reaches double pre-industrial levels, coral reefs can be expected to not just stop growing, but also to begin dissolving all over the world.

The impact on reefs is a consequence of both ocean acidification caused by the absorption of carbon dioxide into seawater and rising water temperatures. Previous studies have shown that rising carbon dioxide will slow coral growth, but this is the first study to show that coral reefs can be expected to start dissolving just about everywhere in just a few decades, unless carbon dioxide emissions are cut deeply and soon.
"Globally, each second, we dump over 1000 tons of carbon dioxide into the atmosphere and, each second, about 300 tons of that carbon dioxide is going into the oceans," said co-author Ken Caldeira of the Carnegie Institution's Department of Global Ecology, testifying to the U.S. House of Representatives Subcommittee on Insular Affairs, Oceans and Wildlife of the Committee on Natural Resources on February 25, 2009. "We can say with a high degree of certainty that all of this CO2 will make the oceans more acidic – that is simple chemistry taught to freshman college students."
The study was designed determine the impact of this acidification on coral reefs. The research team, consisting of Jacob Silverman, Caldeira, and Long Cao of the Carnegie Institution as well as Boaz Lazar and Jonathan Erez from The Hebrew University of Jerusalem, used field data from coral reefs to determine the effects of temperature and water chemistry on coral calcification rates. Armed with this information, they plugged the data into a computer model that calculated global seawater temperature and chemistry at different atmospheric levels of CO2 ranging from the pre-industrial value of 280 ppm (parts per million) to 750 ppm. The current atmospheric concentration is over 380 ppm, and is rapidly rising due to human-caused emissions, primarily through the burning of fossil fuels.
Based on the model results for more than 9,000 reef locations, the researchers determined that at the highest concentration studied, 750 ppm, acidification of seawater would reduce calcification rates of three quarters of the world's reefs to less than 20% of pre-industrial rates. Field studies suggest that at such low rates, coral growth would not be able to keep up with dissolution and other natural as well as manmade destructive processes attacking reefs.
Prospects for reefs are even gloomier when the effects of coral bleaching are included in the model. Coral bleaching refers to the loss of symbiotic algae that are essential for healthy growth of coral colonies. Bleaching is already a widespread problem, and high temperatures are among the factors known to promote bleaching. According to their model the researchers calculated that under present conditions 30% of reefs have already undergone bleaching and that at CO2 levels of 560 ppm (twice pre-industrial levels) the combined effects of acidification and bleaching will reduce the calcification rates of all the world's reefs by 80% or more. This lowered calcification rate will render all reefs vulnerable to dissolution, without even considering other threats to reefs, such as pollution.
"Our fossil-fueled lifestyle is killing off coral reefs," says Caldeira. "If we don't change our ways soon, in the next few decades we will destroy what took millions of years to create."
"Coral reefs may be the canary in the coal mine," he adds. "Other major pieces of our planet may be similarly threatened because we are using the atmosphere and oceans as dumps for our CO2 pollution. We can save the reefs if we decide to treat our planet with the care it deserves. We need to power our economy with technologies that do not dump carbon dioxide into the atmosphere or oceans."
Journal reference:
Silverman, J., B. Lazar, L. Cao, K. Caldeira, and J. Erez. Coral reefs may start dissolving when atmospheric CO2 doubles. Geophys. Res. Lett., 2009; DOI: 10.1029/2008GL036282
Adapted from materials provided by Carnegie Institution, via EurekAlert!, a service of AAAS.