The Impending Deluge

Fifty thousand drowned, steamships aground with their bows among trees, cattle rolled head over heels by gigantic waves — stories of great sea surges from past centuries abound. Many of them cascaded ashore when coastlines were relatively stable, killing everyone in their path. Today, we live in a warming world of rising sea levels, where tens of millions of us live a few meters above the ocean. The potential for sudden cataclysm is greater than ever.

The record of history is sobering. On Jan. 16, 1362, a severe southwesterly storm swept across the British Isles. The wooden spire of Norwich cathedral in eastern England collapsed.

Hours later, the Grote Mandrenke, “The Great Killing of Men,” descended on the Low Countries at high tide. Huge waves carried everything before them. “An infinity of people perished,” fishing fleets became matchwood, entire herds of cattle and sheep perished in the raging waters. Three centuries later, in 1634, another cataclysmic storm surge brought sea levels four meters above normal to the Strand Islands off northern Germany. As many as 15,000 people and 50,000 livestock drowned.

These were but two of the savage attacks on the low-lying coasts of the North Sea, this from a patch of ocean that was largely dry land less than 8,000 years ago. The geologists call it Doggerland, a sunken landscape that once formed the North Sea. It was a land of sluggish rivers, lakes and extensive wetlands. A few thousand hunters thrived there, living off fish and small game, using antler-tipped spears.

We know this because a trawler dredged one from the seabed in 1932. Doggerland slowly vanished in the face of sea level rise caused by thawing ice sheets, an ever-changing world for those who lived there. By 5,500 B.C., Doggerland had disappeared under the chilly waters of the North Sea.

The inhabitants of the Low Countries have been battling the ocean ever since. For over a thousand years, they have tried to wall off the ocean. Today, millions of people live in densely occupied coastal landscapes behind great barriers. The Dutch government’s hideously expensive Delta Works was the culmination of centuries of defense work, but the authorities never relax in the face of a warming future with predictions of more extreme weather events. They are planning for at least 10,000-year storms in a world of rising sea levels.

It’s hard for us to imagine what the world was like at the end of the Ice Age, when sea levels were about 220 meters lower and the North Sea was dry land.

Take the Nile, which flowed into the Mediterranean through narrow gorges. As the ocean rose, the now silt-heavy Nile formed a fertile delta that became the granary of the pharaohs. All was well two thousand years ago, when Alexandria had only 300,000 inhabitants. Today, the Aswan Dam far upstream has drastically reduced silt flow. Nearly 10 million people live in Alexandria and Cairo. The delta is slowly vanishing under rising sea levels, its groundwater contaminated by saltwater, the soils depleted. The delta is no longer a balanced system. Perhaps 7 million people will suffer regularly from starvation by 2100.

The world’s sea levels have risen since the 1860s, with no end in sight. Skeptics argue that this is a long-term problem, measured in centuries rather than generations, that there is plenty of time to adapt to changing shorelines. But they forget about the more frequent extreme-weather events with their sea surges predicted for the future.

Hurricane Katrina in 2005 and Superstorm Sandy in 2012 were both wake-up calls for Americans living near sea level. Katrina devastated New Orleans, leaving 80 percent of the city underwater. Levees broke, over 1,500 people died, and thousands were stranded, especially poorer people. Sandy’s surge flooded Lower Manhattan and the New Jersey Shore. Subways flooded, thousands of houses became rubble. With $60 billion of damage, recovery will take years, while a debate over long-term solutions sputters along. Does one wall off New York, force people to build on higher ground, or restore protective mangrove swamps? The answers will be long in coming, but meanwhile, as cities like Miami grow, our vulnerability increases every year.

The threat is even more ominous elsewhere. Today, some 200 million people live within five meters of sea level, many of them in megacities like Shanghai. The Netherlands has the resources to wall off the sea, but what about other parts of the world? Small Pacific islands like Tuvalu, Alaska’s barrier island communities, and the Maldives in the Indian Ocean are seriously endangered and may even cease to exist.

Bangladesh, most of which is river delta country, lies at the head of the Bay of Bengal, where intense cyclones and their fast-moving storm surges have the potential to kill thousands. And kill they do, in a country with an exploding population, chronic poverty and a long coastline. Cyclone Bhola in 1970 killed over half a million people, at a time when the population was much smaller than today. To its credit, the government has developed early warning systems, erected refuge buildings, and created evacuation strategies that have saved many lives. But these do not answer the longer-term problem of fast-growing urban populations, threats to rice crops, seawater contaminated groundwater, and nowhere to move millions of people forced from their homes by rising seas. More

 

Earth's Mantle Affects Long-Term Sea-Level Rise Estimates

Equally compelling is the fact that the shoreline is not flat, as it should be, but is distorted, reflecting the pushing motion of Earth's mantle.

This is big news, says Moucha, for scientists who use the coastline to predict future sea-level rise. It's also a cautionary tale for those who rely almost exclusively on cycles of glacial advance and retreat to study sea-level changes.

"Three million years ago, the average global temperature was two to three degrees Celsius higher, while the amount of carbon dioxide in the atmosphere was comparable to that of today," says Moucha, who contributed to a paper on the subject in the May 15 issue of Science Express. "If we can estimate the height of the sea from 3 million years ago, we can then relate it to the amount of ice sheets that melted. This period also serves as a window into what we may expect in the future."

Moucha and his colleagues -- led by David Rowley, professor of geophysical sciences at the University of Chicago -- have been using computer modeling to pinpoint exactly what melted during this interglacial period, some 3 million years ago. So far, evidenced is stacked in favor of Greenland, West Antarctica and the sprawling East Antarctica ice sheet, but the new shoreline uplift implies that East Antarctica may have melted some or not at all. "It's less than previous estimates had implied," says Rowley, the article's lead author.

Moucha's findings show that the jagged shoreline may have been caused by the interplay between Earth's surface and its mantle -- a process known as dynamic topography. Advanced modeling suggests that the shoreline, referred to as the Orangeburg Scarp, may have shifted as much as 196 feet. Modeling also accounts for other effects, such as the buildup of offshore sediments and glacial retreats.

"Dynamic topography is a very important contributor to Earth's surface evolution," says Rowley. "With this work, we can demonstrate that even small-scale features, long considered outside the realm of mantle influence, are reflective of mantle contributions."

Building a case

Moucha's involvement with the project grew out of a series of papers he published as a postdoctoral fellow at the Canadian Institute for Advance Research in Montreal. In one paper from 2008, he drew on elements of the North American East Coast and African West Coast to build a case against the existence of stable continental platforms.

"The North American East Coast has always been thought of as a passive margin," says Moucha, referring to large areas usually bereft of tectonic activity. "[With Rowley], we've challenged the traditional view of passive margins by showing that through observations and numerical simulations, they are subject to long-term deformation, in response to mantle flow."

Central to Moucha's argument is the fact that viscous mantle flows everywhere, all the time. As a result, it's nearly impossible to find what he calls "stable reference points" on Earth's surface to accurately measure global sea-level rise. "If one incorrectly assumed that a particular margin is a stable reference frame when, in actuality, it has subsided, his or her assumption would lead to a sea-level rise and, ultimately, to an increase in ice-sheet melt," says Moucha, who joined SU's faculty in 2011.

Another consideration is the size of the ice sheet. Between periods of glacial activity (such as the one from 3 million years ago and the one we are in now), ice sheets are generally smaller. Jerry Mitrovica, professor of geophysics at Harvard University who also contributed to the paper, says the same mantle processes that drive plate tectonics also deform elevations of ancient shorelines. "You can't ignore this, or your estimate of the size of the ancient ice sheets will be wrong," he says.

Rise and fall

Moucha puts it this way: "Because ice sheets have mass and mass results in gravitational attraction, the sea level actually falls near the melting ice sheet and rises when it's further away. This variability has enabled us to unravel which ice sheet contributed to sea-level rise and how much of [the sheet] melted."

The SU geophysicist credits much of the group's success to state-of-the-art seismic tomography, a geological imaging technique led by Nathan Simmons at California's Lawrence Livermore National Laboratory. "Nathan, who co-authored the paper, provided me with seismic tomography data, from which I used high-performance computing to model mantle flow," says Moucha. "A few million years may have taken us a day to render, but a billion years may have taken several weeks or more."

Moucha and his colleagues hope to apply their East Coast model to the Appalachian Mountains, which are also considered a type of passive geology. Although they have been tectonically quiet for more than 200 million years, the Appalachians are beginning to show signs of wear and tear: rugged peaks, steep slopes, landslides, and waterfalls -- possible evidence of erosion, triggered by dynamic topography. More

 

Rising sea levels threaten survival of cities like Kolkata: Pachauri

Rising sea levels due to climate change are threatening the survival of big cities located near coastal areas like Kolkata, Shanghai and Dhaka, said Dr RK Pachauri, chairperson of the Intergovernmental Panel on Climate Change (IPCC).

“There is a very high risk in delta cities like Kolkata, Shanghai and Dhaka. They are very vulnerable to the impacts of climate change due to sea level rise and coastal flooding. Both people and property would be affected in such a scenario,” Pachauri told reporters.

Asking governments worldwide to start adaptation measures as soon as possible to counter the effects of climate change, the scientist said the matter has to be taken up in all seriousness.

“Scientific factors are evident. We cannot keep our eyes shut,” he said.

Earlier, delivering the convocation address at the Indian Institute of Management, Calcutta, last night, Pachauri said, “Partial loss of ice sheets on polar land could imply metres of sea level rise, major changes in coastline, and inundation of low lying area, with greatest effects in river deltas and low-lying areas.”

Such changes are projected to occur over millennial timescales, but more rapid sea level rise on century timescales cannot be excluded, he warned.

IPCC’s fourth assessment report on climate change had stated, “Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global sea average level.” More

 

Islands struggle to convince UN Security Council that climate change is a security threat

The Marshall Islands and other low-lying island nations appealed to the U.N. Security Council on Friday to recognize climate change as an international security threat that jeopardizes their very survival.

Tony deBrum, a minister and assistant to the Marshall Islands president, said the island nations are facing opposition from Security Council permanent members Russia and China and a group of more than 130 mainly developing nations, which argue that the U.N.'s most powerful body is the wrong place to address climate change.

DeBrum told reporters after a closed Security Council meeting on the "Security Dimensions of Climate Change," organized by Britain and Pakistan, that he hopes more council members will be convinced that "this is a security issue and not just an economic-political-social issue."

The low-lying islands, which are already being inundated with sea water, want the council to bring its "political weight" to the issue and help their countries survive, for example, by harnessing new technologies and ensuring alternative energy supplies, he said.

DeBrum said it was "ironic, bizarre perhaps" that 35 years after he went before the Security Council to seek the independence of the Marshall Islands he was back again "to appeal for the survival of my country."

He said climate change has already taken a toll on the Marshall Islands. Wells have filled with salt water, making drinking water scarce and in turn affecting food production. One small island in a lagoon is now under water, and coastlines are being eroded.

The impact of climate change is also causing migration to other islands, as well as to Australia and the United States, he said.

In an interview Friday with The Associated Press, Rachel Kyte, the World Bank's vice-president for sustainable development, said that since the council's last discussion of climate change "the sense of immediacy and urgency has increased."

"The question is: Do you want to keep on cataloguing all of the terrible things that are going to happen if we continue on a business as usual track, or are we actually going to start doing anything about it?" she said

Kyte said she explained to the council on Friday that "it is possible to stop the worst from happening but it will require real, concerted policy action globally at every country level." More

 

 

Fear of 'catastrophic' sea-level rise as ice sheets melt faster than predicted

Glaciologists fear they may have seriously underestimated the potential for melting ice sheets to contribute to catastrophic sea-level rises in coming decades which could see increases of a metre or more by 2100.

The ice sheets of Greenland and Antarctica contain about 99.5 per cent of the Earth's glacier ice and could raise sea levels by 65 metres if they melted completely – although experts think this is highly unlikely in the foreseeable future. However, a survey of the world's top 26 glaciologists found most believe melting of the ice sheets could be more rapid and severe than previously estimated. They believe that melting of the ice sheets alone this century would be likely to raise the average global sea level by 29cm, the poll found, but there is a five per cent chance of it increasing even further by a catastrophic 84cm.

This would take the total sea-level increase to well over a metre if other factors such as the thermal expansion of oceans and runoff from mountain glaciers are taken into account.

"Our analysis shows the biggest uncertainty when it comes to sea levels is the contribution from the ice sheets," said Professor Jonathan Bamber of Bristol University, lead author of the study published in the journal Nature Climate Change.

"It shows glaciologists believe there is a one-in-20 chance of sea levels rising by a metre or more by 2100, and a metre rise in sea level is really very serious.

"The impacts of sea-level rise of this magnitude are potentially severe, implying a conceivable risk of the forced displacement of up to 187 million people within this century."

Rising sea levels are one of the greatest uncertainties of climate change. A warmer world causes oceans to expand thermally but also leads to faster melting of mountain glaciers and some regions of the polar ice sheets. More

 

Scientists Seek Strategy to Convey Seriousness of Sea-Level Rise

LA JOLLA, Calif. — Sea-level rise threatens cities around the world, and academic leaders must talk about it differently to help people grasp the potential dangers and costs, climate experts said last week.

Researchers must detail effects at the local and regional levels, members of the Association of Pacific Rim Universities (APRU) Sustainability and Climate Change Program said as they met at the University of California, San Diego. They need to talk shorter time windows, mentioning impacts in 2050 as well as in 2100. And they should drive home to people that actions to limit climate change can help protect their children and grandchildren from huge economic and social impacts.

“Sea-level rise is not a problem that’s going away,” said Dan Cayan, a climate researcher at the Scripps Institution of Oceanography at UC San Diego. “In some sense, this is an important investment. This is a multigenerational issue.”

Climate researchers from around the world gathered for three days at UC San Diego to share information and formulate strategies. They discussed the importance of talking about sea-level rise and climate change as they brainstormed what advice they should give to university presidents. During that session, some of the APRU members urged more of an activist role, saying too much time already has been lost.

“People who don’t believe climate change is real, and sea-level rise is real, are really few and far between,” said Bernard Minster, a UC San Diego professor and Scripps researcher.

The conference took place just after sea-level rise and climate change happened to surface on the national stage. At the Republican National Convention, presidential nominee Mitt Romney in his acceptance speech derided President Obama’s position on the issues.

“President Obama promised to begin to slow the rise of the oceans,” Romney said as some in the audience snickered, “and to heal the planet. My promise is to help you and your family.”

Obama in his speech at the Democratic National Convention said that “climate change is not a hoax.”

“More droughts and floods and wildfires are not a joke. They are a threat to our children’s future. And in this election, you can do something about it.” More