Earth’s Polar Ice Sheets Vulnerable to Even Moderate Global Warming
Breakup of the northern section of the Larsen B ice shelf. A new analysis of the geological record of the Earth's sea level, carried out by scientists at Princeton and Harvard universities and published in the Dec. 16 issue of Nature, employs a novel statistical approach that reveals the planet's polar ice sheets are vulnerable to large-scale melting even under moderate global warming scenarios. Such melting would lead to a large and relatively rapid rise in global sea level. (Credit: NASA/GSFC/LaRC/JPL, MISR Team)
A new analysis of the geological record of the Earth’s sea level, carried out by scientists at Princeton and Harvard universities and published in the Dec. 16 issue of Nature, employs a novel statistical approach that reveals the planet’s polar ice sheets are vulnerable to large-scale melting even under moderate global warming scenarios. Such melting would lead to a large and relatively rapid rise in global sea level.
According to the analysis, an additional 2 degrees of global warming could commit the planet to 6 to 9 metres of long-term sea level rise. This rise would inundate low-lying coastal areas where hundreds of millions of people now reside. It would permanently submerge New Orleans and other parts of southern Louisiana, much of southern Florida and other parts of the U.S. East Coast, much of Bangladesh, and most of the Netherlands, unless unprecedented and expensive coastal protection were undertaken. And while the researchers’ findings indicate that such a rise would likely take centuries to complete, if emissions of greenhouse gases are not abated, the planet could be committed during this century to a level of warming sufficient to trigger this outcome.
As part of the study, the researchers compiled an extensive database of geological sea level indicators for a period known as the last interglacial stage (about 125,000 years ago). Polar temperatures during this stage were likely 3 to 5 degrees Celsius warmer than today, as is expected to occur in the future if temperatures reach about 2 to 3 degrees Celsius above pre-industrial levels.
Sea levels during the last interglacial stage are of interest to scientists and important to policymakers for several reasons. Most notably, the last interglacial stage is relatively recent by geological standards, making it feasible for climate scientists to develop a credible sea level record for the period, and is the most recent time period when average global temperatures and polar temperatures were somewhat higher than today. Because it was slightly warmer, the period can help scientists understand the stability of polar ice sheets and the future rate of sea level rise under low to moderate global warming scenarios. The findings indicate that sea level during the last interglacial stage rose for centuries at least two to three times faster than the recent rate, and that both the Greenland and West Antarctic ice sheet likely shrank significantly and made important contributions to sea level rise.
Sea Level Could Rise from 0.75 to 1.9 Meters This Century
Inundated areas (blue) in lower Manhattan, New York in a statistically typical one-hundred year storm event based on the present sea level. A sea-level rise of 1 metre would result in storm surges of this height approximately every four years. (Credit: Source: Rosenzweig and Solecki, 2001; data based on USGS, U.S. Army Corps of Engineers, Marquise McGraw, NASA GISS)
A new scientific study warns that sea level could rise much faster than previously expected. By the year 2100, global sea level could rise between 75 and 190 centimetres, according to a paper published in the Proceedings of the National Academy of Sciences.
The authors, Martin Vermeer of Helsinki University of Technology in Finland and Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research in Germany, based their analysis on measurements of sea level and temperature taken over the past 130 years. In those data they identified a strong link between the rate of sea level rise and global temperature.
“Since 1990 sea level has been rising at 3.4 millimetres per year, twice as fast as on average over the 20th Century,” says Stefan Rahmstorf. Even if that rate just remained steady, this would already lead to 34 centimetres rise in the 21st century. “But the data show us clearly: the warmer it gets, the faster sea level rises. If we want to prevent a galloping sea level rise, we should stop global warming as soon as possible,” adds Rahmstorf.
The link between the rate of sea level rise and global temperature was originally proposed by Rahmstorf in an article in the journal Science in 2007. The new study refines this idea. It adds a second term to the equation in order to capture the short-term response of sea level, leading to greater physical realism as well as a much greater precision. Vermeer and Rahmstorf also added the latest data sets, including satellite measurements up to 2008 and a correction for water storage in man-made reservoirs, which overall lowers global sea level by 3 centimetres.
Their results show that even for a relatively low greenhouse gas emissions scenario with just 2 degrees Celsius warming over the 21st century, sea level is likely to rise by more than one meter. Their highest scenario, with over 4 degrees Celsius warming over the 21st century, would lead to over 1.4 meters of sea level rise by 2100. When the full set of emissions scenarios and estimated uncertainties are considered, waters may rise by anything between 75 centimetres and 1.9 metres by the year 2100 — consistent with another recent estimate of an upper limit of 2 metres, based on consideration of ice sheet dynamics.
“More noteworthy even than the very high figures for sea level rise is the almost clockwork precision by which, on climatic time scales, temperature drives sea level rise,” says Martin Vermeer. The results of the study also demonstrate the quality of the existing sea level and temperature time series used, “painstakingly constructed from measurements at stations around the globe for well over a century,” Vermeer notes.
The projected rise is about three times as much as estimated in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change in 2007, which did not fully include the effects of ice loss from Greenland and Antarctica. To avoid such a large sea level rise, which would be an existential threat to many large coastal cities as well as a number of small island nations, drastic and rapid cuts in greenhouse gas emissions will be required.
The study finds that delays in emissions reductions will come at a high cost, since early emissions cuts are much more effective in limiting sea level rise than later cuts. The emissions reductions needed to keep sea level rise below 1 meter will likely be considerably more ambitious than those needed to limit global warming to 2 degrees Celsius, a policy goal now supported by many nations.
Hudson Canyon Shows Diverse Marine Ecosystem
The autonomous underwater vehicle Eagle Ray. (Credit: Peter Rona)
A series of newly discovered pits in the bottom of the Hudson Canyon, 100 miles southeast of New York Harbor, may be a key ingredient for the abundant and diverse marine ecosystem in and around the canyon, according to research by scientists from Rutgers University and the National Oceanic and Atmospheric Administration (NOAA).
Peter Rona, professor of marine science at Rutgers’ Institute of Marine and Coastal Sciences, and Vincent Guida, a research fisheries biologist at the NOAA Northeast Fisheries Science Center, led the cruise which found the pits up to hundreds of feet in diameter and tens of feet deep this summer. Their findings will be presented at the fall meeting of the American Geophysical Union, Dec. 14-18, in San Francisco.
“Finding these pits is new for this area,” Rona said. “They’ve been found in certain other places, such as the Gulf of Mexico. There, they’ve been related to the dissolution of gas hydrates in the sediments below the sea floor.”
When enough gas hydrates — methane gas frozen in ice crystals in muddy sediments beneath the seafloor- have dissolved, the sediments in which they’ve been trapped may collapse, forming pits. Rona suspects that may have happened in the Hudson Canyon. During their cruise on the NOAA Fisheries Survey Vessel Henry B. Bigelow in August, the researchers recovered water samples from the canyon. These samples, still being analyzed by Mary Scranton, professor of marine science at Stony Brook University, indicated abnormally high levels of methane in water taken from above at least one of those pits.
All this, Guida said, may benefit much of what lives and swims in the water column in the canyon, from bacteria to tilefish.
Methane is a source of energy that certain bacteria use to manufacture carbohydrates (sugars and starches) in order to nourish themselves. The bacteria, in turn, are consumed by other organisms like clams and worms.
They, in turn, may support the larger animals up the food chain, including golden tilefish, which are the focus of a major fishery, and therefore of Guida’s professional attention. Guida said he found what appear to be the burrows of tilefish in the canyon. Generation of methane may have direct environmental effects, too. It is not only important as a chemical energy source to enable bacteria to nourish themselves at the base of a food chain, but is also a potent greenhouse gas that can contribute to global warming. Net benefits or costs of methane release to the ecosystem depend on rates of production and consumption, which have yet to be measured.
Rona and Guida said their work was made possible by the use of a robotic free-swimming underwater vehicle, the Eagle Ray, provided by the National Institute for Undersea Science and Technology. The institute is a joint venture of NOAA, the University of Mississippi and the University of Southern Mississippi.
The Eagle Ray cruises about 50 meters (165 feet) above the ocean bottom, and automatically conforms its track to the contours of the bottom. Using sonar, the Eagle Ray produces maps of seafloor objects as small as 15 feet.
U.S. Navy to Use Marine Mammals to Protect Base
Last week, the U.S. Navy announced its decision to install a swimmer interdiction security system at Naval Base Kitsap in Bangor, Washington, that will employ teams of security personnel and specially-trained marine mammals to protect waterside assets and sailors. This action will enhance security capabilities to counter intruder threats from swimmers or divers and will be implemented in 2010.
The use of marine mammals to protect sensitive waterside areas has been proven to be reliable and effective. The Navy’s bottlenose dolphins and California sea lions are uniquely qualified for underwater sentry duty, mine clearance, and object recovery because of their exceptional sensory and diving capabilities.
An environmental impact statement (EIS) evaluated potential effects of several factors on the Navy’s dolphins and sea lions, including temperature, noise, water quality, toxins and the presence of other marine mammals in the NBK-Bangor environment. The EIS concluded that the Navy’s dolphins and sea lions are not expected to experience adverse environmentally-related effects from transfer to, and residence at Bangor.
The Navy’s decision concludes a multi-year process involving operational assessments, technical analysis, and environmental analysis under the National Environmental Policy Act. In addition to addressing public concerns, the Navy also consulted with state and federal regulatory agencies, including U.S. Fish and Wildlife Service, National Marine Fisheries Service, Army Corps of Engineers, Washington State Department of Ecology, and the Washington Department of Archaeology and Historic Preservation.
Greenland Ice Cap Losing Mass at an Accelerating Rate
Satellite observations and a state-of-the art regional atmospheric model have independently confirmed that the Greenland ice sheet is losing mass at an accelerating rate, reports a new study in Science.
This mass loss is equally distributed between increased iceberg production, driven by acceleration of Greenland’s fast-flowing outlet glaciers, and increased meltwater production at the ice sheet surface. Recent warm summers further accelerated the mass loss to 273 Gt per year (1 Gt is the mass of 1 cubic kilometre of water), in the period 2006-2008, which represents 0.75 mm of global sea level rise per year.
Professor Jonathan Bamber from the University of Bristol and an author on the paper said: “It is clear from these results that mass loss from Greenland has been accelerating since the late 1990s and the underlying causes suggest this trend is likely to continue in the near future. We have produced agreement between two totally independent estimates, giving us a lot of confidence in the numbers and our inferences about the processes”.
The Greenland ice sheet contains enough water to cause a global sea level rise of seven metres. Since 2000, the ice sheet has lost about 1500 Gt in total, representing on average a global sea level rise of about half a millimetre per year, or 5 mm since 2000.
At the same time that surface melting started to increase around 1996, snowfall on the ice sheet also increased at approximately the same rate, masking surface mass losses for nearly a decade. Moreover, a significant part of the additional meltwater refroze in the cold snowpack that covers the ice sheet. Without these moderating effects, post-1996 Greenland mass loss would have been double the amount of mass loss observed now.
This work was funded by the Natural Environment Research Council.
Climate Change Could Be Next Great Military Threat
Retired U.S. Vice Admiral Lee Gunn is warning that climate change could be the next great threat from the military perspective. In the October 20th edition of the Bulletin of Atomic Scientists he writes the article below. (For those interested in this topic we also highly recommend the National Bestseller Climate Wars by geopolitical analyst, Gwynne Dyer.)
Climate Change Could Be Next Great Military Threat
Article Highlights
- Although the United States has faced many threats over the last few decades, climate change may be the most ominous.
- Specifically, it will contribute to resource scarcity, state failure, increasingly mobile populations, and regional instability.
- The U.S. military may not be the best body to tackle climate change, but it still should be quick to reassess its global engagement strategy and be proactive in minimizing the effects of climate change on U.S. and international security.
The United States currently faces one of its greatest and most misunderstood threats: climate change. And as changing climate patterns affect the water supplies critical to human life and agriculture, as sea levels rise and threaten coastal communities, and as changes in the environment increasingly weaken marginal states, the implications for U.S. defense will only grow.
Specifically, instability and conflict abroad will affect three important dimensions of U.S. national security: how the United States chooses to use its power, how and where the U.S. military operates around the world, and with whom Washington will and will not ally itself.
How power is applied. As societies struggle to adapt to changing climate conditions, the U.S. military will be called on more frequently to provide assistance, support governments, fight extremism in weak states, and anticipate natural and human-made disasters. In short, Washington will have to consider carefully why U.S. defense forces fight.
Take Central and South Asia, for example. The region’s main water source–the Himalayan glaciers–continues to recede due to climate change. The trend will no doubt lead to a dramatic reduction in freshwater availability, particularly in Pakistan, India, Bangladesh, and parts of China. In fact, a 2007 U.S. Marine Corps report ranks Afghanistan, Pakistan, and India in the top 10 states at risk of instability and violent conflict over water.
A fight for resources among these states–which are already mired in violence and mutual suspicion–would be disastrous for U.S. security interests in the region, particularly since declining conditions among poor segments of the population would be a boon for terrorist and extremist groups’ recruitment. Climate-intensified conflict between mobile populations seeking fresh water amid wanton state instability may prompt future policy makers to deploy U.S. forces not only to combat extremism in the region, but also to provide aid to the hungry and displaced.
How and where the military operates. Climate change also will force a re-evaluation of how the United States operates its forces around the world. Facilities, logistics, and strategic planning will need to be reassessed. The British Indian Ocean Territory of Diego Garcia, for example, is home to a critical staging facility for U.S. and British naval and air forces operating in the Middle East and Central Asia. But this atoll sits just a few feet above sea level. If sea levels rise as projected, the facility could be lost, forcing the U.S. and British militaries to adapt and adjust their logistics and operations throughout the region.
Who will U.S. allies be? Changing climate conditions also will test traditional alliances and may even inspire unexpected new ones as states grapple with altered topographies, climate refugees, and changes in commercial and economic circumstances.
For instance, the U.S. Navy has been concerned about the loss of sea ice in the Arctic for nearly a decade. Specifically, it worries that as the fabled Northwest Passage opens, military and commercial activities there will increase. One need not look further than the 2007 Russian expedition that planted its flag on the seabed at the North Pole. Not surprisingly, Canada, Norway, Denmark, and the United States–all bordering the Arctic–reacted critically to Russia’s perceived act of encroachment.
In addition, the effects of climate change could strain U.S. relations with Mexico. As Latin American water and arable land resources decline, poverty and internal unrest are likely to spread in the region, leading to increased human migration northward–both legal and illegal. Mexico’s perceived inability to staunch the flow north would likely raise tensions with Washington, hampering U.S. collaboration in the fight against Mexico-based drug cartels.
Given all of this, the decision, therefore, isn’t whether U.S. planners and strategists should adapt and prepare, but how they should adapt and prepare. Looking ahead, China is predicting the loss of 5-10 percent of its wheat harvest by 2030 due to climate change. In southern Sudan and the Darfur region, existing conflicts will be severely exacerbated by increasingly scarce water, food, and arable land. Responding to these and myriad other climate-influenced changes presents great challenges for the United States and the international community–far beyond the specific capabilities of the U.S. military.
Thus, here’s how Washington should begin preparing for the consequences associated with climate change:
- Invest in capabilities within the U.S. government (including the Defense Department) to manage the humanitarian crises–such as a new flow of “climate refugees”–that may accompany climate change and subsequently overwhelm local governments and threaten critical U.S. interests;
- Prepare military officers and troops to address the security and humanitarian needs of resource-stressed populations and climate refugees;
- Expand global public health programs (e.g., malarial eradication);
- Negotiate an agreement with Canada and Mexico to govern the use of fresh water in North America;
- Lead the world in developing conflict-resolution mechanisms to mediate between climate change’s winners and losers.
If it doesn’t take these steps, the United States will be ill-equipped to face climate-induced threats when they’re most acute, forcing future generations to deal with a world full of conflict, disease, hunger, displacement, and extremism.
Changing Arctic Affecting Air, Ocean, And Everything In Between
Wide-spread melt ponds observed by NOAA's North Pole Web cam. (Credit: NOAA)
Despite the fact that summer 2009 had more sea ice than in 2007 or 2008, scientists are seeing drastic changes in the region from just five years ago and at rates faster than anticipated. The findings were presented October 22 in the annual update of the Arctic Report Card, a collaborative effort of 71 national and international scientists.
“The Arctic is a special and fragile place on this planet,” said Jane Lubchenco, Ph.D., under secretary for oceans and atmosphere and NOAA administrator. “Climate change is happening faster in the Arctic than any other place on Earth — and with wide-ranging consequences. When I visited the northern corners of Alaska’s Arctic region earlier this year, I saw an area abundant with natural resources, diverse wildlife, proud local and native peoples — and a most uncertain future. This year’s Arctic Report Card underscores the urgency of reducing greenhouse gas pollution and adapting to climate changes already under way.”
Among the changes highlighted in the 2009 update to the report card were:
- A change in large scale wind patterns affected by the loss of summer sea ice,
- The replacement of multi-year sea ice by first-year sea ice,
- Warmer and fresher water in the upper ocean linked to new ice-free areas,
- A continued loss of the Greenland ice sheet,
- Less snow in North America and increased runoff in Siberia, and
- The effect of the loss of sea ice on Arctic plant, animal, and fish species.
Scientific assessments are key to informing our understanding of climate — how and why it is changing and what the changing conditions mean to lives and livelihoods.
The Arctic Report Card established a baseline of conditions in the region at the beginning of the 21st century and the annual updates track and monitor the often quickly-changing conditions in the Arctic. Using a color-coding system of red to indicate consistent evidence of warming and yellow to indicate there are mixed signals about warming from climate indicators and species, the report card is updated annually in October and tracks Arctic data in six categories: atmosphere, sea ice, biology, ocean, land, and conditions in Greenland.
“The Arctic we see today is very different from the Arctic we saw even five years ago,” said Jackie Richter-Menge of the USACE Cold Regions Research and Engineering Laboratory in Hanover, N.H. and the report’s chief technical editor and contributing author. “It’s a warmer place with less thick and more mobile sea ice, warmer and fresher ocean water, and increased stress on caribou, reindeer, polar bears and walrus in some regions.”
The 2009 update to the report card reflects the contributions of an international team of 71 researchers from countries that include the United States of America, Canada, Belgium, China, Denmark, Japan, The Netherlands, Russia, and the United Kingdom.
The Report Card can be found at http://www.arctic.noaa.gov/reportcard
Arctic Surveillance Research Moves Ahead
A Twin Otter aircraft arrives during the summer with supplies for Camp Gascoyne, the Northern Watch base at Devon Island. (Dan Hutt/Defence Research and Development Canada Atlantic)
Military scientists are moving ahead with plans to monitor the approaches to the Northwest Passage as part of the federal Northern Watch program.
Northern Watch tests the surveillance devices used to watch for foreign vessels and other craft travelling through the Arctic waterway from the east.
The program was launched in 2008 but scaled back earlier this year because of logistical difficulties.
“We discovered that we needed to do some more planning and preparation,” Rick Williams, director general of science and technology operations with Defence Research and Development Canada, told CBC News.
Williams said he had to delay this year’s work on Northern Watch to bring the team back together, re-establish expectations and rebuild a base camp on Devon Island.
“There was mould on the inside of some of the buildings and at some of the washing facilities and some of the storage facilities,” he said.
The crew also had to find a new path leading to the main camp from a remote lookout site — on an outcrop 300 metres above water — because the existing route turned out to be dangerous.
“The weather conditions are pretty variable,” Williams said. “Things can change dramatically and [in a] very short amount of time.
“If someone gets hurt, we had to have plans in place to be able to do things like medical care, evacuations.”
Despite the logistical problems, Williams said, the team was able this past summer to install an underwater array of surveillance sensors that gathered data for about four weeks in Barrow Strait.
“We’ve got pictures of vessels that have actually gone by the test set-up over the course of this summer,” he said.
“The kind of information we gather, the kinds of pictures we can take from the shoreline — that demonstrates we’re getting smarter about how to do that channel surveillance.”
Some of the sensors had problems and had to be removed.
Still, Williams said the Northern Watch team will return in full force next summer, working on developing technology that can operate year-round in the High Arctic.
Williams said the program is important in the North, which is becoming a bigger priority for the military.
“I think we’re playing a key role to understand how we can bring all this high technology into the North and use it effectively,” he said.
Underwater Exploration: Autosub 6000 Dives To Depth Of 5.6 Kilometres
The Autosub 6000 is being readied for launch.
The United Kingdom’s deepest diving Autonomous Underwater Vehicle (AUV), Autosub 6000, has been put through its paces during extremely successful engineering trials from 27 September to 17 October 2009.
Autosub 6000 was working in regions of the Iberian Abyssal Plain in the North Atlantic deeper than 5600 metres and also around the steep and rugged terrain of the Casablanca Seamount, between Madeira and Morocco. The vehicle was designed and constructed by engineers at the Underwater Systems Laboratory in the National Oceanography Centre, Southampton.
Highlights:
- Operating at 5600 metres depth. Very few (if any) AUVs have ever operated autonomously at this depth.
- Survey at 3 metre altitude — paving the way for deep ocean photographic surveys.
- Terrain following at 10 metre altitude over very rough relief.
- Testing improved fault detection software so that the AUV can recover from hardware faults.
- Testing of recently fitted magnetometer, turbidity and precision salinity sensors
One of the main goals of the Autosub 6000 engineering trials was the demonstration of the accessibility of deep ocean regions approaching the 6000 metre design depth limit. On 3 October 2009, the AUV descended and reached its pre-programmed target depth of 5525 metres in 1.5 hours. At this point, a navigation update procedure was undertaken to update and correct for the Autosub 6000’s drift which was incurred as it descended through the moving water column.
After 2.5 hours from deployment, the Autosub 6000 was on station at a depth of 5600 metres, positioned to accuracies of a few metres, and ready to start collecting scientific data.
Autosub 6000 has been enhanced with a forward-looking vertically scanning obstacle-detection sonar and improved terrain-following control software, giving the AUV the ability to operate safely, closer to the seabed. This was demonstrated at low altitudes in the steep and rugged slopes of the Casablanca Seamount with a 10 metre altitude run starting at 3000 metres depth and rising up to 700 metres depth over a course of 7.5 kilometres.
The ability of Autosub 6000 to perform low-altitude colour photographic surveys was demonstrated on the more level summit regions of the Casablanca Seamount with low-speed surveys at altitudes of as low as 3 metres.
Steve McPhail, Autosub 6000 project leader, said, “Apart from the correct functioning of the vehicle during the trials at extreme depths, what particularly pleased me was that we have now developed the control and obstacle avoidance systems such that we have the confidence to send the AUV into a hostile and rugged terrain. This will lead to more challenging and interesting scientific campaigns in the future.”
Autosub 6000 is now being prepared for a cruise to the Caribbean Sea near the Cayman Islands in April 2010, where it will be used to search for deep hydrothermal vents.
Global Surface Temperature Was Second Warmest in September ‘09
Global surface temperature anomalies (degrees F) for the month of September 2009. (Credit: NOAA)
The combined global land and ocean surface temperature was the second warmest September on record, according to NOAA’s National Climatic Data Center (NCDC). Based on records going back to 1880, the monthly NCDC analysis is part of the suite of climate services NOAA provides. NCDC scientists also reported that the average land surface temperature for September was the second warmest on record, behind 2005.
The combined global land and ocean surface temperature was 1.12° F above the 20th century average of 59.0° F. Separately the global land surface temperature was 1.75°F above the 20th century average of 53.6°F.
Warmer-than-average temperatures engulfed most of the world’s land areas during the month. The greatest warmth occurred across Canada and the northern and western contiguous United States. Warmer-than-normal conditions also prevailed across Europe, most of Asia and Australia.
The worldwide ocean temperature tied with 2004 as the fifth warmest September on record, 0.90°F above the 20th century average of 61.1°F. The near-Antarctic southern ocean and the Gulf of Alaska featured notable cooler-than-average temperatures.
Arctic sea ice covered an average 2.1 million square miles in September – the third lowest for any September since records began in 1979. The coverage was 23.8 percent below the 1979-2000 average, and the 13th consecutive September with below-average Arctic sea ice extent.
